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Uroradiology Text and Atlas

Uroradiology Text and Atlas

Suresh M Bakle

DMRD MD (Radiology)

Professor in Radiology Nijlingappa Medical College, Bagalkot Karnataka, India

Bipin V Daga

MD DNB (Radiology)

Lecturer in Radiology VM Govt Medical College, Solapur Maharashtra, India

®

JAYPEE BROTHERS MEDICAL PUBLISHERS (P) LTD St Louis (USA) • Panama City (Panama) • New Delhi • Ahmedabad • Bengaluru • Chennai Hyderabad • Kochi • Kolkata • Lucknow • Mumbai • Nagpur

Published by Jitendar P Vij Jaypee Brothers Medical Publishers (P) Ltd Corporate Office 4838/24 Ansari Road, Daryaganj, New Delhi - 110002, India, Phone: +91-11-43574357, Fax: +91-11-43574314 Registered Office B-3 EMCA House, 23/23B Ansari Road, Daryaganj, New Delhi - 110 002, India Phones: +91-11-23272143, +91-11-23272703, +91-11-23282021 +91-11-23245672, Rel: +91-11-32558559, Fax: +91-11-23276490, +91-11-23245683 e-mail: [email protected], Visit our website: www.jaypeebrothers.com Branches  2/B, Akruti Society, Jodhpur Gam Road Satellite Ahmedabad 380 015, Phones: +91-79-26926233, Rel: +91-79-32988717 Fax: +91-79-26927094, e-mail: [email protected]  202 Batavia Chambers, 8 Kumara Krupa Road, Kumara Park East Bengaluru 560 001, Phones: +91-80-22285971, +91-80-22382956, 91-80-22372664 Rel: +91-80-32714073, Fax: +91-80-22281761 e-mail: [email protected]  282 IIIrd Floor, Khaleel Shirazi Estate, Fountain Plaza, Pantheon Road Chennai 600 008, Phones: +91-44-28193265, +91-44-28194897 Rel: +91-44-32972089, Fax: +91-44-28193231 e-mail: [email protected]  4-2-1067/1-3, 1st Floor, Balaji Building, Ramkote Cross Road, Hyderabad 500 095, Phones: +91-40-66610020, +91-40-24758498, Rel:+91-40-32940929 Fax:+91-40-24758499, e-mail: [email protected]  No. 41/3098, B & B1, Kuruvi Building, St. Vincent Road Kochi 682 018, Kerala, Phones: +91-484-4036109, +91-484-2395739 +91-484-2395740 e-mail: [email protected]  1-A Indian Mirror Street, Wellington Square Kolkata 700 013, Phones: +91-33-22651926, +91-33-22276404, +91-33-22276415 Fax: +91-33-22656075, e-mail: [email protected]  Lekhraj Market III, B-2, Sector-4, Faizabad Road, Indira Nagar Lucknow 226 016 Phones: +91-522-3040553, +91-522-3040554 e-mail: [email protected]  106 Amit Industrial Estate, 61 Dr SS Rao Road, Near MGM Hospital, Parel Mumbai 400 012, Phones: +91-22-24124863, +91-22-24104532, Rel: +91-22-32926896, Fax: +91-22-24160828 e-mail: [email protected]  “KAMALPUSHPA” 38, Reshimbag, Opp. Mohota Science College, Umred Road Nagpur 440 009 (MS), Phone: Rel: +91-712-3245220, Fax: +91-712-2704275 e-mail: [email protected] North America Office 1745, Pheasant Run Drive, Maryland Heights (Missouri), MO 63043, USA Ph: 001-636-6279734 e-mail: [email protected], [email protected] Central America Office Jaypee-Highlights Medical Publishers Inc. City of Knowledge, Bld. 237, Clayton, Panama City, Panama Ph: 507-317-0160 Uroradiology: Text and Atlas © 2010, Jaypee Brothers Medical Publishers All rights reserved. No part of this publication should be reproduced, stored in a retrieval system, or transmitted in any form or by any means: electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the authors and the publisher. This book has been published in good faith that the material provided by authors is original. Every effort is made to ensure accuracy of material, but the publisher, printer and authors will not be held responsible for any inadvertent error(s). In case of any dispute, all legal matters are to be settled under Delhi jurisdiction only. First Edition: 2010 ISBN 978-81-8448-784-8 Typeset at JPBMP typesetting unit Printed at Gopsons Papers Ltd, A-14, Sector 60, Noida 201 301, India

Preface This book intends to present complex information on Uroradiology in easily accessible formats. The notes and images contained within this book have been structured to conform to the format needed for undergraduate and postgraduate examinations. In addition, the authors have, where relevant, not only tried to give complete material but also management aspect in an attempt to provide a useful acid memory for the students. The main use of this book as opposed to others is for pictorial review of all important cases of urology. Despite the concise nature of the material and the inevitable omission of some of more complicated issues, we believe that this book fulfills its purpose and will support the education of postgraduates apart from supporting the practitioners in the glorious art and science of uroradiology. The images in the book are unique and the most interesting part of this book mainly includes the common and classical uroradiology cases. Suresh M Bakle Bipin V Daga

Contents 1. Embryology ............................................................................................................................ 1 2. Anatomy and Normal Variants .............................................................................................. 3 3. Various Imaging Modalities and Techniques in Uroradiology ............................................... 7 4. Congenital Anomalies of Urorenal Tract ............................................................................. 27 5. Cystic Disease of Kidney .................................................................................................... 71 6. Calculus Diseases of Kidney ............................................................................................... 78 7. Obstructive Diseases of Kidney .......................................................................................... 92 8. Renal Infections ................................................................................................................ 103 9. Urorenal Trauma ................................................................................................................ 120 10. Urorenal Neoplasms .......................................................................................................... 140 11. Medical Renal Disease ...................................................................................................... 161 12. Renal Vascular Diseases ................................................................................................... 168 13. Radiology of Renal Transplant .......................................................................................... 182 14. Urethral Diseases .............................................................................................................. 192 15. Urinary Bladder Diseases .................................................................................................. 199 16. Diseases of Prostate .......................................................................................................... 212 17. Urorenal Interventions ....................................................................................................... 223 18. Miscellaneous Genitourinary Conditions ........................................................................... 225 19. Recent Advances in Uroradiology ..................................................................................... 231 20. Radiological Contrast Media ............................................................................................. 234

Bibliography ................................................................................................................................... 239 Index ............................................................................................................................................... 241

Introduction and Historical Aspect “Urology can be said to owe its existence as a specialty to inventing genius of Sir Thomas Edison and Sir Wilhem Conrad Roentgen. The roentgen rays provided a means whereby diagnostic studies of the entire genitourinary tract could be carried out.” — RM NESBITT (1956) MILESTONES IN URORADIOLOGY • In 1896, first preoperative radiograph of a calculus was reported by John McIntyre. • In 1897, French physician Theodore Tuffier introduced a metal stylet into a ureteral catheter to make the catheter radiopaque and outlined the ureter. • In 1903, Wittek first used air as a contrast agent. • In 1905, Voelcker and von Lichtenberg devised first liquid contrast using colloidal A. They also emphasized the value of lateral and oblique views. • In 1923, first clinical trial of 10% sodium iodide was done by Earl Osborn, which later became the basis of present-day IVU study. • In 1929, Swick first described IVU. • Smith (1994) first described the role of non-contrast spiral/helical CT in calculus disease. Uroradiology is a discipline involving imaging techniques like plain radiography, contrast radiography, ultrasound, computed tomography, radionuclide imaging and magnetic resonance imaging and in any given clinical situation, the relevant information can be obtained most rapidly and efficiently by using a specific order of radiological modalities for investigation and evaluation.

Abbreviations ADPKD ARPKD ATN CT CTA DRC (DIC) DSA IRC IVC IVU MCU MRI PUJ PUV UTI VUR MIBG RVT RLQ

Autosomal dominant polycystic kidney disease Autosomal recessive polycystic kidney disease Acute tubular necrosis Computed tomography CT angiography Direct radionuclide (isotope) cystogram Digital subtraction arteriography Indirect radionuclide cystogram Inferior vena cava Intravenous urogram Micturating cystourethrogram Magnetic resonance imaging Pelviureteric junction Posterior urethral valve Urinary tract infection Vesicoureteral reflux Meta-iodobenzyl guanidine Renal vein thrombosis Right lower quadrant

Embryology

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KIDNEY The development of the embryonic urinary system involves three separate stages (Figure 1.1): 1. Pronephros 2. Mesonephros and 3. Metanephros. 1. The earliest structure, the pronephros, forms at about 3 weeks in utero, never functions and is reabsorbed by the fourth week. Its caudal portion, however, plays a role in the development of the mesonephros. The longitudinal pronephric duct becomes the mesonephric or Wolffian duct, which is initially connected to the primitive cloaca. 2. Primitive excretory tubules and glomeruli develop symmetrically from this duct to comprise the mesonephros which regresses in the latter part of the second month. 3. The metanephros or permanent kidney. It then undergoes division into several small tubules, each of which becomes associated with a thin part contributed by the metanephric blastema. These caps differentiate into the mature excretory tubules or nephrons. The presence of the ureteric bud is believed necessary for the differentiation of tissues into mature renal parenchyma. The metanephros is initially located in the lower lumbar or sacral region and its shift to

FIGURE 1.1: Developmental sequence of urinary tract (For color version see Plate 1)

the more cranial position of the mature kidney is achieved through differential growth of the urinary tract relative to the trunk (Figure 1.2). BLADDER AND URETHRA The urogenital sinus is formed from the anterior part of the cloaca at the time of the descent of the urogenital septum. That portion of the urogenital sinus above the entrance of the mesonephric ducts is called the vesicourethral canal and this becomes the bladder. The portion which is inferior is termed the definitive urogenital sinus.

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Uroradiology: Text and Atlas

FIGURE 1.2: Development of collecting system of kidneys (For color version see Plate 1)

With further development, the distal mesonephric duct is absorbed into the urogenital sinus until the metanephric duct (now the ureteric bud) enters separately from, and superior to, the mesonephric duct. The latter will become the Wolffian duct, precursor to the ductus deferens in the male. At maturation it enters into that portion of the definitive urogenital sinus which will become the prostatic urethra. The development of the definitive urogenital sinus proceeds differently in the female. The elongation

FIGURE 1.3: Ascent of kidneys (For color version see Plate 1)

responsible for the development of the penile urethra of the male does not occur and, instead, a connection with the developing müllerian ducts gives rise to the lower urethra, a small portion of the vagina and the vestibule (Figure 1.3).

Anatomy and Normal Variants

NORMAL ANATOMY • Anatomy of retroperitoneum • Anatomy of kidney, ureter and bladder • Anatomy of prostate. ANATOMY OF RETROPERITONEUM

The transversalis fascia lines the inside of the abdominopelvic cavity, including the inferior aspect of the diaphragm, the posterior and medial surfaces of the anterior and lateral abdominal wall muscles respectively,

3

the anterior aspect of the spinal column, psoas and paraspinal muscles and the superior aspect of the pelvic diaphragm. The major organs and their associated fascia develop within the space defined by the transversalis fascia (Figure 2.1). During embryological development, as the kidneys ascend from the pelvis the surrounding (perinephric) fascia forms a cone, with its apex superiorly. The perinephric fascia anterior to the kidney is often referred to as Gerota’s fascia, the posterior fascia as Zuckerkandl’s

FIGURE 2.1: Schematic representation of retroperitoneal anatomy (For color version see Plate 2)

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Uroradiology: Text and Atlas

fascia and the enclosed space as the perinephric space. It contains the kidney, the suprarenal gland anteromedial to the kidney on the left, It superomedial to the kidney on the right the upper ureter and the perinephric fat. There is a small space between the posterior perinephric fascia and the adjacent transversalis fascia which contains only fat (the posterior pararenal space). This space is of interest to the interventional radiologist as a potential area in which to kink a guide-wire and mistakenly position a drain intended for the renal collecting system. There is a more substantial space anterior to the perinephric spaces between the anterior perinephric fascia and the posterior layer of the peritoneum, the anterior pararenal space. This contains the pancreas and duodenum centrally, with the ascending colon on the right and the descending on the left. These organs are therefore in direct contact with the anterior perinephric fascia. Laterally the anterior and posterior perirenal fasciae fuse with the lateroconal fascia at the fascial trifurcation. The lateroconal fascia continues laterally and anteriorly to fuse with the parietal perietal peritoneum. The retroperitoneum is a large space bounded anteriorly by the posterior parietal peritoneum, posteriorly by the transversalis fascia, and superiorly by the diaphragm. Inferiorly, it extends to the level of the pelvic brim. On either side, the retroperitoneum is divided into three compartments by coronally oriented anterior and posterior renal fasciae, which lie anterior and posterior to the kidneys, respectively. The anterior renal fascia is a thin layer of connective tissue, which is difficult to identify on images. The anterior and posterior renal fasciae fuse laterally to form the lateroconal fascia. The lateroconal fascia extends posterolaterally to the ascending and descending colon and fuses with the parietal peritoneum. Superiorly, both layers of renal fasciae blend with the diaphragmatic fascia, and inferiorly, this fuses with the iliac fascia and periureteric connective tissue at the level of the iliac crest. Medially, the anterior renal fascia blends with the connective tissue and fat that surround the great vessels, and the posterior renal fascia blends with the fascia of the psoas and quadratus lumborum muscles. Each perirenal space, which is situated between the anterior and posterior renal fasciae, contains a kidney,

adrenal gland, pelvocalyceal system, proximal ureter, and neurovascular and lymphatic structures. No potential communication exists between the 2 perirenal spaces. The anterior pararenal space is limited anteriorly by the posterior parietal peritoneum and posteriorly by the anterior renal fascia. The contents are the first, second, and third parts of the duodenum; the pancreas; the ascending colon; the descending colon; and the splenic, hepatic, and proximal superior mesenteric arteries. The anterior pararenal space communicates across the midline. The posterior pararenal space is bounded anteriorly by the posterior renal fascia and posteriorly by the transversalis fascia. The medial extent of this space is limited by the fusion of posterior renal fascia with the fasciae of the psoas and quadratus lumborum muscles; however, communication with the retrocrural space, and therefore the mediastinum, is possible. Laterally, the fat of the posterior pararenal space continues as the properitoneal fat stripe. The posterior pararenal space contains no organs. The anterior and posterior pararenal spaces communicate along their inferior margin. STRUCTURE OF THE KIDNEY, URETER AND BLADDER (FIGURE 2.2)

1. 2. 3. 4. 5. 6. 7. 8. 9.

Cortex Compound calyx Minor calyx Medullary pyramid Papilla Renal sinus Renal pelvis Infundibulum of major calyx Ureter. Ureter to the level of the ischial spine, from where it runs anteromedially until it enters the superolateral angle of the bladder base. The vas deferens crosses over the ureter, separating it from the bladder just before the ureters enter the bladder wall. The ureters run obliquely through the bladder wall for around 2 cm. A fibrous capsule is closely applied to the renal cortex over the entire kidney apart from the hilum. The kidney is surrounded by perinephric fat and lies within a space partly enclosed by layers of fascia, traditionally referred

Anatomy and Normal Variants

FIGURE 2.2: The vasculature of kidney: note the main renal artery, the hilar branches, the lobar branches, the segmental branches and finally the arcuate arteries (For color version see Plate 2)

to as the perinephric space (perirenal space). The perinephric space is one of a number of spaces within the abdomen and pelvis that are important determinants of the direction of disease spread. MR ANATOMY OF PROSTATE

The prostate and periprostatic tissue are visualized well using CT. On older generation CT scanners, neither the zonal anatomy nor the differentiation between the prostatic parenchyma and the prostatic capsule were visualized. With dynamic fast-scanning CT, the contrast resolution of CT has markedly improved and intraprostatic anatomy can be demonstrated. On sequential CT scans, prostatic volume can be measured by using the single parameters of length, width and AP diameter, or by summation of the prostatic volumes on each slice. On MRI, the ability to demonstrate the zonal anatomy of the prostate gland and the distinction between the gland and periprostatic tissue varies with the imaging planes and sequences used. On spin-echo (SE) T1-weighted images, regardless offield strength, the prostate shows an homogeneous intermediate signal intensity, and the zones cannot be differentiated. On T2-weighted images, the

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zonal anatomy is well delineated, with the prostatic urethra serving as the key reference point. On T2-weighted images, the peripheral zone demonstrates a higher signal intensity than either the central or the transition zones. The peripheral and central zones are consistently distinguishable in men under 35 years old and in 35% of older patients. The central and transition zones have similar lower signal intensity and can be differentiated from each other only by knowledge of their anatomical location. In young subjects, the transition zone has a uniformly low signal intensity, but it becomes heterogeneous with the development of BPH. The surgical pseudocapsule can be seen in older subjects at the interface between the transition and peripheral zones. The anterior fibromuscular band covering the anterolateral surface of the prostate gland demonstrates a low signal intensity, allowing distinction between the prostate and the anterior periprostatic space composed of vascular areolar tissue. On axial T2-weighted images, the shape of the peripheral zone changes from the base to the apex. At the base, the peripheral zone surrounds the posterolateral aspect of the central zone. The ejaculatory ducts can be visualized coursing through the central zone towards the verumontanum. At the apex, the peripheral zone is nearly concentric around the urethra (with the exception of the thin anterior fibromuscular band). The apical urethra is surrounded by muscular fibers giving low-intensity signals. The prostatic capsule is visualized as a thin rim giving a low-intensity signal, surrounding the peripheral zone. The NVB are seen as punctate signal voids posterolateral to the capsule at the 5 and 7 O’clock positions. The seminal vesicles look like grapes, and are well seen in any plane of section. Periprostatic structures can be differentiated from the prostatic parenchyma. The periprostatic venous plexus (PVP) is seen on the anterior and lateral aspects of the prostate gland. The levator ani muscles give a lower signal intensity than the peripheral zone, regardless of which spin-echo TR or TE is used, though the contrast between the peripheral zone and the levator ani muscle is enhanced on T2-weighted images. Unlike CT, MRI in all three planes enables the prostate to be differentiated from the surrounding levator ani muscle, bladder neck and lower rectum. In the assessment of prostate size using the formula, MR is more accurate than either USG or CT.

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Uroradiology: Text and Atlas

NORMAL VARIANTS (PSEUDOTUMORS) • Fetal lobulations • Dromedary or splenic hump • Column of Bertin (hypertrophied) Column of Bertin is an extension of normal renal cortex into the medulla, towards the hilum. It is a normal

variation in renal morphology and should not be confused with a mass. The column of Bertin anatomically and functionally resembles the rest of the renal cortex. The use of different imaging modalities to differentiate a column of Bertin from a renal tumor is listed below:

Modality

Column of Bertin

Renal neoplasm

1. Ultrasound 2. 99mTc DMSA 3. 99mTc DTPA 4. CT

Isoechoic to cortex Normal uptake Normal uptake Isodense to cortex Homogeneous contrast enhancement

5. MRI

Isointense to cortex

Hypo- or hyperechoic relative to cortex Photon deficient area Photon deficient area Hypodense, rarely hyperdense Decreased contrast enhancement Peripheral Increase Puddling Nonhomogeneous Hypo- or hyperintense Nonhomogeneous

Various Imaging Modalities and Techniques in Uroradiology

VARIOUS IMAGING MODALITIES AND TECHNIQUES • • • • • •

• • • • • • • •

Plain radiography (KUB film) Intravenous urography (IVU) Retrograde urography (RGP) Antegrade urography (AGP) Nephrotomography Cystography and cystourethrography a. With voiding urethrogram b. Retrograde urethrogram c. Cystogram d. With DC (air) e. Triple contrast (angiography plus pneumocystogram plus interstitial air in wall of UB) f. Chain urethrogram g. Choke urethrogram Ultrasound Color Doppler Computed tomography Non-contrast CT Contrast CT Magnetic resonance imaging (MRI) Radionuclide Imaging Arteriography

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Satisfactory bowel preparation is important prerequisite. • 90% radiopaque calculi (calcium oxalate phosphate, triple, cystine) • ‘Radiologists graveyard’ • Radiolucent calculi missed (uric acid, xanthine matrix, orotic acid stones) • Other radiopaque densities like pheloboliths, arterial calcifications, lymph nodes, masses may be misleading. THINGS TO BE SEEN ON KUBU FILM

1. 2. 3. 4. 5. 6.

Bowel preparation Visualized bones Properitoneal fat lines Renal outlines/shadows Psoas shadows Calcific density along kidney, ureter, bladder or urethra.

FEW ILLUSTRATIONS SHOWING DIAGNOSTIC USE OF KUB RADIOGRAPHS

See Figures 3.1 to 3.12.

PLAIN KUBU RADIOGRAPH

MIMICS OF RENAL COLIC (PLAIN KUBU FILM)

The main use of plain radiography is in calculus diseases.

See Figures 3.13 to 3.18

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Uroradiology: Text and Atlas

FIGURE 3.1: Ectopia vesicae

FIGURE 3.2: Prune belly syndrome

FIGURE 3.4: Nephrocalcinosis

FIGURE 3.5: Vesical calculus

RETROGRADE UROGRAPHY (RGP) Close attention to detail in performing a tailored IVU will usually result in a satisfactory demonstration of the pelvicaliceal systems and ureters and retrograde pyelography should rarely be necessary. The latter is indicated mainly in those patients suspected of having a urothelial tumour of the upper urinary tract and in whom excretion urography is normal. Bulb ureterography will

FIGURE 3.3: Right pyonephrosis with calculi

FIGURE 3.6: Multiple calculi in right kidney with DJ stent

give a good demonstration of the ureter, and the retrograde introduction of a catheter into the upper ureter or renal pelvis is the best method for demonstrating the pelvicaliceal system (Figure 3.18). Fluoroscopic guidance should be used and the study should include some oblique views of the kidney and ureter. The catheter may be left in a selective position for some hours to collect urine for cytological examination.

Various Imaging Modalities and Techniques in Uroradiology

FIGURE 3.7: Left putty kidney

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FIGURE 3.8: The lower poles of both kidneys—renal FIGURE 3.9: Seminal vesicle calcification shadows are seen approaching towards spine instead of divergent or laterally directed lower poles as should be seen normally—Horse-shoe kidney)

FIGURE 3.10: Bladder-wall calcification— schistosomiasis

FIGURE 3.11: Postoperative KUB film with some prosthesis in urinary bladder

INDICATIONS

ANTEGRADE UROGRAPHY (AGP)

• Mainly used for better visualization of lower ureter and pelvi-caliceal system • IVU not satisfactory • Contrast reaction render IVU hazardous • Renal failure • To delineate exact site of the Ureteric strictures • Filling defects like: tumors, sloughed papillae radiolucent calculus, are better seen on RGP.

Antegrade pyelography is an accurate method of demonstrating precisely the site of an obstruction to the upper urinary tract. The IVU with delayed films may outline the obstruction, but the concentration of contrast may be poor and the final diagnosis only made on a 24 hour film. Helical CT is a more rapid and accurate method of demonstrating the site (and possible cause) of obstruction.

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Uroradiology: Text and Atlas

FIGURE 3.12: Large calculus in a horse-shoe kidney on left side

FIGURE 3.13: Extensive pancreatic calcification

FIGURE 3.15: Colon studded with fecoliths

Ultrasound will rapidly confirm the presence of dilatation in the pelvicaliceal system and one can then proceed directly to antegrade pyelography. With the patient prone, a fine 20 or 22 gauge Chiba needle is inserted under ultrasound guidance or fluoroscopic control beneath the 12th rib into a lower pole calyx, under local anesthesia. As soon as the collecting system is punctured, trapped urine will escape through the needle. This should be aspirated and sent for culture and, if a urothelial tumor is suspected,

FIGURE 3.14: Worm infestation, as seen in right lower quadrant

FIGURE 3.16: Enteroliths

for cytology. Once some reduction of pressure has been achieved within the system, contrast medium is injected to outline the pelvis and ureter down to the level of obstruction and it may be necessary to tilt the patient into a semierect position to achieve this. INDICATIONS

It gives an opportunity to perform interventional procedures like:

Various Imaging Modalities and Techniques in Uroradiology

FIGURE 3.17: Ovarian dermoid with toothlike calcification

• • • •

Decompression of PUJ obstruction Drainage of pus in pyonephrosis PCNL-Stone removal and Stenting Biopsy and balloon occlusion.

ADVANTAGES OF AGP

• • • •

Direct site of obstruction shown (mid. 1/3 ureter) Ureteral stenting can be done Brush—Biopsy from suspected lesions can be obtained Stone manipulations can be attempted.

DISADVANTAGES OF AGP

• To assess the prognostic value of therapeutic intervention, urosurgeons demand IVU and the functional aspect of urinary system is always better commented and documented on IVU only • Invasive procedure. INTRAVENOUS UROGRAPHY (IVU) INTRODUCTION

• • • •

Widely used study Require bowel preparation IV contrast media required Indirect signs-delayed nephrogram urogram, hydronephrosis, hydroureter can be absent in acute, partial obstruction.

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FIGURE 3.18: Normal RGP

• Longer duration required • Radiation hazard. An Intravenous Urogram (IVU) is an X-ray examination of the kidneys, ureters and urinary bladder. Most people are familiar with X-ray images, which produce a still picture of the body’s interior by passing small, highly controlled amounts of radiation through the body and capturing the resulting shadows and reflections on film. An IVU study uses a contrast material (iodine) to enhance the X-ray images. The contrast material is injected into the patient’s system and its progress through the urinary tract is then recorded on a series of quickly captured images. The exam enables the radiologist to review the anatomy and the function of the kidneys and urinary tract. EXCRETORY UROGRAPHY (INTRAVENOUS UROGRAPHY, IVU, IVP) Since 1929, when the first intravenous contrast agent was developed by Swick, excretory urography has been the primary modality for imaging the urinary tract. This original agent, Uro-selectan, was the precursor of the numerous excellent contrast agents available at the present time. As early as 1937, Berger made several recommendations for improvement in technique that are still valid today. The elimination of the obscuring effect of abdominal gas has since been accomplished by

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Uroradiology: Text and Atlas

routine tomography. A greater renal concentration of contrast media has been facilitated by use of higher doses of the safer modern contrast agents, and ureteral compression, also advocated, is now widely practiced. State of the art urography is now such that with “tailoring” and proper attention to detail, the renal margins and parenchyma, as well as the entire collecting system including the ureters and bladder, can be visualized diagnostically. Techniques have also been described for evaluating the urethra as a final step in urography. This procedure has now attained a high degree of safety as well as efficacy. The mortality rate of 1 in 75,000 is similar to that expected from the parenteral administration of penicillin. PHYSIOLOGY OF RADIOGRAPHIC CONTRAST EXCRETION

Commercially available contrast agents that are approved for urography consist of ionic salts of benzoic acid derivatives containing three iodine atoms. The two anions used most widely in the United States are diatrizoate and iothalamate. Following injection, their distribution in the body and routes of excretion are identical, and their visualization in the kidneys is equal. Assuming normal renal function, their route of excretion is greater than 99% by glomerular filtration. Other commercially available anions are Iodamide and Metrizoate. Cations most commonly encountered are sodium and methylglucamine (meglumine) or a mixture of the two. After intravenous injection, whether by bolus or by infusion, these preparations leave the vascular system in two ways. First, rapid permeation of the capillary wall and equilibration with the extracellular fluid occurs. At the same time, contrast in the bloodstream undergoes glomerular filtration and subsequent excretion in the urine. As plasma contrast concentration falls as a result of ongoing renal excretion, there is a continual redistribution of the extracellular contrast into the vascular system. Meglumine is not metabolized and is excreted entirely by glomerular filtration. This results in a higher urinary solute output and a subsequent increase in urinary flow rate due to an osmotic diuresis. The final result is a lower concentration of urinary iodine with the meglumine salts

and yet the potential for greater distention of the collecting system. Conversely, sodium undergoes extensive reabsorption by the renal tubule. While the plasma halflife is relatively low for both meglumine and the contrast anions, that for sodium is longer because of reabsorption and subsequent refiltration. The delayed excretion of sodium due to reabsorption by the tubules leads to a decreased osmotic diuresis compared with that achieved with the meglumine salts and thus results in increased concentrations of iodine in the urine, purportedly providing higher contrast and hence better visualization. Facts such as these have led some investigators to recommend using only the sodium salts for urography because of the supposed increased contrast attainable. Others have recommended the meglumine salts because of the increased distention of the collecting system that may be encountered. In fact, McClennan and Becker showed that in a comparison of sodium and meglumine salts, films showed no reliable difference in a heterogeneous patient population or even in the same patient. The advantage of greater collecting system filling as may be seen with the meglumine salts can be achieved with any of the commercial preparations by application of adequate ureteral compression. Attempts to maximize the benefits of both cations have resulted in the production of preparations combining the two. The quality of the urogram depends on good pelvocaliceal concentration of contrast media as well as sufficient distention of the collecting system. All attempts to improve urographic quality are based on manipulation of these two variables. Elkin has found that as one goes from small to large doses of contrast media, the urine concentration of organic iodide increases. He also found, however, that there was an upper limit of such concentration, which, when exceeded, led to even greater diuresis and subsequent dilution of iodine in the urine. With the high doses of contrast now in common use, the production of urine with a very high concentration of iodine is not so much the main objective as is the duration of the high concentration of the contrast medium in the urine. Thus exposures have a greater likelihood of being obtained at a time of peak concentration, and there is also a prolongation of the interval during which optimal tomography can be performed. Talner states that

Various Imaging Modalities and Techniques in Uroradiology with large doses of contrast (30–42 g of iodine), urographic quality will be consistently good. With average doses (17–20 g of iodine), urographic quality can be just as good if one pays attention to details of technique. In a busy department in which many urograms are performed each day, large doses may be justifiable as routine simply because the radiologist may not have time to monitor each study carefully. There have been no reports of any increase in the incidence of side-effects with the use of larger contrast doses. INDICATIONS

By current standards of medical practice, almost anyone suspected of urologic disease will be recommended for an intravenous urogram, although this may vary from hospital to hospital because of the availability and acceptance of the newer imaging techniques. Another variable is the preference and experience of the referring clinician. Among the more common indications for urography, Friedland and co-workers list infections, acute genitourinary pain, hematuria (microscopic or gross), trauma, suspected neoplasm, renal transplantation, neurogenic bladder, congenital anomalies, and investigation of complications following a surgical procedure. These investigators further stated that urography often is not useful in the evaluation of acute pyelonephritis (unless obstruction is suspected), ureteral colic in which the calculus is clearly visible on the plain film, in the staging of lymphoma or testicular neoplasms, in cases of medical renal disease, in medical hematuria, in renal failure, and for the investigation of benign prostatic hypertrophy. However, clinical experience indicates that many patients with these diagnoses will eventually undergo urography at some stage of their diagnosis or treatment. There are several indications for immediate urography. These include trauma involving the genitourinary system, massive gross hematuria of unknown cause, a suspected vascular accident involving the kidneys, overwhelming sepsis that may possibly have its source in the urinary tract, and suspected ureteral calculus. In the past, indications for urography have included the evaluation of hypertension. The hypertensive urogram involves obtaining coned-down films of the

13

kidneys in a rapid sequence following bolus injection of contrast. The minimum series includes films at 1, 2, and 3 minutes post injection. The radiographic criteria for renovascular hypertension include delayed visualization of contrast in the collecting system on the affected side, decreased renal size, and delayed wash-out of contrast on the later films in the urogram. A secondary finding is that of notching of the proximal ureter on the involved side due to development of collateral flow via the periureteral plexus reconstituting the renal artery. Thornbury and co-workers have evaluated the hypertensive urogram with regard to its efficacy. They found the true-positive rate in 197 patients with renovascular hypertension to be only 60%. Furthermore the predictive value for favorable surgical outcome in hypertensive patients with positive hypertensive urograms was only 24%. They concluded that the examination is a nondiscriminatory test for renovascular hypertension. Their recommendation was that the suspicion of renovascular hypertension likely to be surgically correctable should prompt the clinician to select renal arteriography and assays of peripheral and renal venous renin activity. Recently, digital subtraction angiography has been claimed to provide good visualization of the renal arteries and may eventually become a satisfactory screening examination for renovascular hypertension. The present-day urogram is not a reliable test for either the presence or severity of functional impairment of the kidneys. Modern contrast media contain more iodine atoms per molecule than did the older agents and are of exceedingly low toxicity. The current use of high doses results in such high plasma concentration of contrast that even kidneys with significantly decreased function may produce diagnostic studies. Useful information can be gained with regard to the presence or absence of obstruction in many patients with renal failure, assuming tomography is used for better visualization of the poorly opacified collecting systems. A better modality for evaluating such patients, however, is renal ultrasound, which is an excellent screening examination for suspected urinary tract obstruction. Its usefulness is based on its ability to detect hydronephrosis. However, it must be realized that there exist a significant

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Uroradiology: Text and Atlas

number of conditions that can mimic or produce dilatation of the collecting system in the absence of obstruction. Renal sonography suggestive of hydronephrosis should be followed by additional diagnostic studies to confirm or exclude obstruction. CONTRAINDICATIONS

There are no absolute contraindications to urography. There are, however, several situations in which the potential risks must be weighed against the possible diagnostic benefits. These conditions; include combined renal and liver failure, multiple myeloma, pregnancy, previous reactions to contrast media, history of allergy, infancy, thyroid disease, renal failure, and diabetes mellitus. In patients with multiple myeloma or diabetes, proper hydration may prevent the possibility of renal damage from injected contrast. If it is essential to perform urography during pregnancy, minimal radiation exposure can be accomplished by obtaining a plain film and a 30 minutes postinjection film. In patients with a history of previous serious reactions to contrast, pretreatment with cortico-steroids and the use of a different type of contrast are recommended, although this is not a proven means of preventing another reaction. Major life-threatening reactions do not usually recur, whereas minor reactions tend to be repeated more often. During infancy, normal hydration will counteract the marked rise in plasma osmolarity that may occur following contrast injection. Urography should be avoided in patients with thyroid disease who are undergoing either diagnosis or treatment of their problem, since the iodine-containing contrast may block the thyroid uptake of radioisotopes of iodine. In renal failure, it must be accepted that in a very few cases renal function will decrease following urography. PATIENT PREPARATION

Dehydration

It has been well established that no significant dehydration (change in urine osmolality) occurs with the standard regimen of nothing by mouth (NPO) after midnight. Further, it has been shown that at least 22 hours of fluid restriction is required to reliably dehydrate human subjects. Effective fluid restriction may produce a slightly

detectable increase in urographic density, but the nephrogram is unaffected. Also to be remembered is that severe fluid restriction may occasionally result in inadvertent dehydration, which may be detrimental to the patient with multiple myeloma, diabetes, or renal failure who is undergoing urography. The purpose of maintaining the patient on an NPO basis for several hours prior to the examination has as its primary purpose the prevention of emesis with possible aspiration following injection of the contrast. BOWEL PREPARATION

In the past, enemas have been advocated before urography. However, water may be absorbed from the bowel, and in some cases large amounts of gas are actually introduced into the colon during the enema. Many bowel preparation kits are available commercially. Dulcolax tablets, two to four 5 mg tablets at bedtime prior to study, usually provide an adequate bowel preparation. They are useful in eliminating feces and gas. PSYCHOLOGICAL PREPARATION

Lalli has reported that anxiety appears to be a factor in the so-called idiosyncratic reactions (nausea and vomiting, urticaria) following contrast injection, although this is an unproven hypothesis. Certainly, every effort should be made to decrease patient anxiety during any procedure. A gentle, relaxed approach to the patient in an atmosphere of pleasant ambiance can do much toward putting the patient at ease. If possible, to minimize pain, larger rather than the smaller veins should be used for the injection. INFORMED CONSENT

The need for informed consent prior to urography is controversial at the present time. Certainly, the time required to inform the patient in detail of the possible complications from urography as well as to obtain his witnessed signature delays the completion of a heavy schedule. It is recommended that the patient be questioned regarding previous reactions to contrast and informed that he will likely feel a warm flushed feeling, a metallic taste in the mouth, and perhaps a mild wave of nausea during and following the injection.

Various Imaging Modalities and Techniques in Uroradiology EXPOSURE FACTORS (THE PHYSICS OF UROGRAPHY)

Both the plain film and the urogram should be exposed at 66 kV(p)–70 kV(p). In general, the mean energy of polychromatic radiation is between one third and one half of its peak energy. Thus, the mean energy of the recommended X-ray beam will be very close to the K-shell binding energy of iodine (33.2 keV). If the binding energy of iodine and the mean of the diagnostic X-ray beam are approximately the same, many interactions will occur at the K-shell level. This allows maximum attenuation of the beam, since attenuation is increased when the photoelectric effect predominates. As the radiation energy is increased, compton scattering comes more into play and cannot attenuate a beam as rapidly as the photoelectric effect. Another advantage of the diagnostic beam energy of 66 kV(p)–70 kV(p) is the increased ability to image calcium-containing structures. At lower beam energies, calcium structures have a higher linear attenuation coefficient than soft tissue, resulting in greater contrast. As the energy of the X-ray beam increases, differential attenuation between calcium structures and soft tissue is not nearly as large, resulting in reduction of image contrast. Therefore, small stones that are seen easily at 70 kV(p) are progressively more difficult to see as the voltage increases. At 100 kV(p) many small stones cannot be seen. Generally speaking, a medium-speed calcium tungstate screen/film combination is most desirable for urography. If this combination is assigned a speed of 1, screen/film systems in the speed range of 2 to 5 offer improvement in overall quality due to diminished respiratory motion at the cost of some loss of detail and increase in mottle. However, this trade-off is less significant if higher-output generators are used to minimize the exposure time. In tomography, the motion of the arm should be linear as the study progresses along the long axis of the kidney. A medium arc of 30º to 40º is thought to be preferable. There is an inverse relationship between the magnitude of the arc and the thickness of the cut obtained. The greater the arc, the thinner the section, resulting in sharpening of detail. However, more tomographic cuts may be needed, and, as section thickness decreases, as would occur with larger arcs, contrast may also decrease,

15

tending to cancel the sharper detail. Tube sweep times of less than 1 second require generation of very high current. A tube sweep time of greater than 2 seconds invites patient motion and tube sway or unsmoothness. PLAIN FILM OF THE ABDOMEN (SCOUT FILM; KIDNEYS, URETERS, BLADDER; PRELIMINARY FILM)

A preliminar y plain film of the abdomen is an indispensable adjunct to excretory urography (See Table 3.1). No attempt to interpret a urogram should be made if a scout film is not available. Otherwise, erroneous interpretations of areas of increased contrast density such as calculi may be made, and, conversely, when stones are present, they may be obscured by the contrast and thus missed entirely. The most common deficiency of the preliminary film is failure to demonstrate the upper poles of the kidney or the region of the prostate. It has been reported that the entire urinary tract is included on a single 14 × 17 inch film in only 17% of adult patients of average height. This figure seems somewhat high, but certainly, in a significant percentage of patients, coned plain views of the kidneys or pubic area may be necessary to complete the preliminary evaluation. The importance of visualizing the upper renal poles and adrenal areas is self-evident in that calcifications or a mass effect may be detected on the plain film. Similarly, evaluation of the prostatic area is necessary prior to administration of contrast to determine the presence or absence of calcifications that may suggest the diagnosis of prostatitis. In trauma patients, it is especially important to visualize the lower ribs and the entire bony pelvis for the evaluation of possible fractures that could affect the urinary system. If calcifications are seen on the plain film overlying the renal shadows, it becomes necessary to further study the patient with appropriate oblique views. A right posterior oblique is necessary for evaluation of calcifications questionably within the right kidney, and similarly, a left posterior oblique is obtained to evaluate left-sided calcifications. If, on the oblique views, the calcifications remain in constant relationship to the renal shadow, it can be stated with a reasonable degree of assurance that they are renal in origin. On the oblique views, calcifications anterior to the kidney will be projected lateral to the renal shadow and calcifications posterior

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Uroradiology: Text and Atlas Table 3.1: Intravenous urography

Radiography

Modification

Purpose

Plain films

Additional obliques or tomograms

To assist the location of potentially intrarenal opacities Rarely required; ultrasound and other imaging maneuver usually preferable

Nephrogram

Thick slice tomogram Omit alongwith the 5 min film and Take a solitary 3 min film

To improve definition of the renal outlines To reduce radiation dose

15 min film

Second injection of contrast

To improve opacification of the pelvicalyceal systems if inadequate

14 min compression film

Series of 1 cm thick tomograms

To differentiate between overlying shadows and filling defects within the collecting systems To delineate the renal outlines when inadequately seen (better done with ultrasound)

15 min release film

Additional bladder views

When the bladder is poorly filled on the release film (as is often the case) delayed films of the fuller bladder may be performed. When equivocal filling defects are seen in the bladder area oblique films may be performed The above additional bladder views are rarely indicated as they increase the radiation burden to the patient and the relevant clinical problems are better answered by ultrasound or cystoscopy. However, occasionally a small suspected calculus in the distal ureter may be confirmed with the appropriate oblique

Full length postmicturition film

Bladder area only

If the upper tracts have already been adequately imaged then imaging the bladder area alone with reduce the patient’s radiation burden

Omit

The preceding films may have already provided all the information required from the investigation

Prone full length film

Additional view

Where the renal pelvis is dilated, contrast may be slow to pass into the ureter; this can be accelerated by positioning the patient prone when the heavier contrast will run anteroinferiorly into the ureter, often to the level of the obstruction. Simply asking the patient to sit or stand for a few minutes first may improve the result.

Erect images

Additional radiograph or fluoroscopy

If it is difficult to determine whether or not there is a small ureteric calculus, an erect oblique radiograph of the ureter or screening the ureter in this position may be useful on rare occasions

Frusemide IVU

Administration of 20 mg of frusemide If suspected pelviureteric junction obstruction is being Intravenously after the 15 minute film investigated and there is no evidence of this on the With a further film 15 minutes later Standard IVU, this maneuver can be performed. It May provoke hydronephrosis and pain. It is rarely necessary if the patient is to be investigated with radionuclide renography, as is often the case in this situation.

to the kidney will be projected medial to the renal shadow. This allows more cogent comment as to their specific etiology. In children, careful coning of the films is necessary to minimize radiation exposure. The preliminary films should include the pubic symphysis to exclude exstrophy and the lumbosacral spine to exclude anomalies that

might suggest neurogenic dysfunction of the lower urinary tract. If the spine is not seen clearly, lateral views are recommended for better assessment of its integrity. If tomograms are planned following injection of contrast, a scout tomographic section should be obtained to ensure that the tomographic series will be adequate for evaluation of the renal outlines. The midpoint for tomographic

Various Imaging Modalities and Techniques in Uroradiology sections (distance from table top) is easily determined by multiplying the thickness of the abdomen in centimeters at the level of the lower costal margin by 0.4. The figure obtained is rounded to the nearest whole number and this becomes the middle of three cuts. The scout tomographic section should reveal a reasonably large portion of the renal outline as an indicator that the planned section levels will encompass the entire renal outline following injection of contrast. In accomplishing this, it should be remembered that the long axis of the kidney is slightly oblique to the long axis of the body, with the upper pole of the kidney lying more posterior and the lower pole more anterior. The limitations of tomography are such that the normal routine as described above permits visualization of the renal margins only when they are situated tangential to the X-ray beam. Distortions of the renal outline in other areas (anterior or posterior) may thus be missed. CONTRAST ADMINISTRATION BOLUS VERSUS INFUSION

The physiology of contrast excretion has been discussed in an earlier section. There are few if any indications for choice of a specific contrast agent other than personal preference and economic factors. In the past, there has been considerable controversy regarding the advantages of the bolus injection technique versus the infusion technique for administration of radiographic contrast agents. There are advantages to both. In most centers, the bolus technique is currently used. Its major advantage is that it allows the maximum plasma concentration of contrast media. An equivalent amount of iodine given by infusion over a period of 5 to 10 minutes does not allow as high a plasma level as can be obtained following the bolus injection. Infusion, on the other hand, is a somewhat more convenient way of administering the contrast material, from the point of view of both the physician and the patient. The unpleasant flushing sensation that often accompanies bolus injections of a large dose of contrast is minimized by the longer infusion. Furthermore, infusion achieves a diagnostically useful nephrogram over a longer time interval. This allows greater latitude in obtaining

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tomograms and other special views at a later point in the study. DOSAGE

The concept of a routine dose is important, since there are no useful body nomograms of weight and surface area for every patient from which to determine an ideal dose. As discussed above, doses in the range of 17 to 20 g of iodine for the average size adult will result in diagnostic studies if careful monitoring is performed. However, larger bolus doses of 28 to 40 g of iodine will more consistently provide diagnostic urographic studies in the busy radiology department. Thus, the doses in Table 3.4 reflect the larger dose of radiographic contrast material. Modification of these doses is recommended in patients with diabetes, multiple myeloma, renal failure, and congestive hear t failure. In such patients, approximately one half the recommended normal adult dose should be sufficient to gain significant diagnostic information about the urinary tract. In children, weight of the patient is a more prominent factor, and recommended doses are based on this parameter. Administration of contrast should take place through a 21 or 23 gauge scalp vein needle, whereas in the adult, a 19-gauge scalp vein needle is of adequate caliber for bolus injection or infusion technique. In the adult, the needle is often left in place for the major portion of the examination to allow a rapid access to the venous system should treatment of contrast reaction become necessary. This is frequently difficult in the younger agegroups. FILM SEQUENCING GENERAL CONSIDERATIONS

The preliminary film of the abdomen and scout tomographic section have been discussed above. If these are technically and anatomically adequate, the urogram can proceed following injection of contrast by whatever method has been selected. Picture of normal urogram can be seen in Figures 3.19 to 3.21. Table 3.2 lists a recommended sequence to be followed for both the pediatric and adult age-groups. In the infant, bowel gas may obscure the kidneys to a significant degree. The adverse effect of this gas can be minimized by allowing

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Uroradiology: Text and Atlas

the child to drink a commercial soft drink that contains carbon dioxide. This causes distention of the stomach and provides a window for visualization of the kidneys. Alternatively, prone filming for the early view of the kidneys will often act as a form of compression and displace colon and stomach gas away from the renal areas. In the adult, while abdominal bowel gas is somewhat bothersome, routine use of tomography should

allow adequate visualization of the renal outlines and parenchyma.

FIGURE 3.20: Normal IVU

FIGURE 3.19: Schematic diagram showing important renal structures 1. Renal cortex 2. Infundibulum 3. Minor calyx 4. Major calyx 5. Papilla 6. Infudibulopelvic junction 7. Renal pelvis 8. Infundibulum 9. Ureter Table 3.2: Recommended film sequence Pediatric urography 1. Plain film of abdomen-appropriate size and collimation 2. Postbolus injection 3. 1 minute full view 4. 10 minute full view Adult urography 1. Plain film of abdomen Full view Coned view as necessary to include kidneys or prostatic area Oblique views as necessary for calcifications over kidneys Scout tomogram –0.4 × body thickness at costal margin 2. Postbolus injection 3. 1-minute tomograms, 3–5 views as necessary 4. 5-minute full view 5. Apply compression 10-minute full view with compression in place Release compression Full view immediately after release of compression (“release,” “flush,” or “X” film) 6. Full view post voiding

FIGURE 3.21: IVU 1. Calyx 2. Infundibulum 3. Pelvis

As a general rule, all urographic exposures should be made with the patient in deep expiration. This allows the kidneys to reach the upward limit of their mobility with subsequent straightening of the ureter and minimizes

Various Imaging Modalities and Techniques in Uroradiology the possibilities of ureteral tortuosity or kinking. Furthermore, the patient should be instructed to void prior to the study to allow better opacification of the bladder on later films. It should be remembered that there is no single”best” method for sequencing of films on the standard urogram. Indeed, it would be rare to find two institutions performing exactly the same sequence of films. A ‘‘standard” urogram, as outlined in Table 3.3, can therefore be recommended only as a basic guide from which one may subsequently develop his own criteria and techniques. TOMOGRAPHY (ADULT)

The astute radiologist should consider using tomography in virtually every adult patient undergoing an initial standard intravenous urogram. It should be noted that tomography of the kidneys during intravenous urography does not bear the same connotation as the “nephrotomography” used in the past. This latter technique involved injection of very high doses of contrast through a large-bore needle with the timing of the tomographic sections based on previous determination of circulation time. With the high doses of contrast currently used, entirely adequate tomographic sections are obtained if exposed approximately 1 to 2 minutes following the bolus injection of contrast or after half of the contrast (150 ml) has been infused in the drip infusion technique. If tomography is not to be performed, good visualization of the renal outlines and full thickness of parenchyma can be obtained by exposing a coned view of the kidneys at 1 to 2 minutes following bolus injection of contrast. Table 3.3: Contraindications to compression Suspected or proven aortic aneurysm (check plain film for typical calcifications) Evidence of obstruction on early urogram films Recent abdominal surgery Urinary diversion Severe hypertension Abdominal pain on application of compression device Recent acute injury (trauma) Renal transplant Abdominal distention Bowel ostomies

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COMPRESSION

Following the 5 minute full view, many authorities recommend routine application of ureteral compression unless contraindicated (Table 3.3). The most significant of these contraindications is that of known or suspected aortic aneurysm. This presumes that the preliminary film of the abdomen will have been scrutinized carefully by the radiologist for calcifications in the aortic wall of configuration to suggest aneurysmal dilatation. While some radiographic tables have a built-in compression band that can be applied, this does not appear to be as effective as the Velcro belt device with inflatable balloons. The position of the balloons is critical in providing adequate compression of the ureter against the sacral promontory. The balloons should nearly touch in the midline when inflated, and their upper edges should parallel the upper level of the iliac crest. The key to success is a tight application of the belt while the patient is in deep expiration prior to inflating the balloons. This allows as much compression as possible to be obtained with the belt itself. Pain in the renal areas during or after application of compression usually indicates that there has been rupture of the collecting system with pyelosinus extravasation. Compression should then be released immediately. This minor complication is usually of no consequence. However, if the patient is known to have infected urine, appropriate antibiotic coverage is indicated. After the compression cuff has been in place for approximately 4 or 5 minutes, the 10 minutes full view is obtained. If compression has been adequately applied, there will be complete and adequate opacification of the upper ureters and entire intrarenal collecting system. Not infrequently there will be mild distention of the collecting system due to the minimal degree of obstruction caused by the compression cuff. Following release of compression, a full view is exposed immediately. This has been termed the ‘‘flush’’, ‘‘X’’, or ‘‘release” view and is designed to visualize the distal ureters as a result of the rapid distal passage of contrast from the distended upper systems.

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Uroradiology: Text and Atlas

FIGURE 3.22: IVU: Postvoid film 1. Sacrum 2. Ureter (distal) 3. VUJ 4. Bladder 5. Pubic symphysis

POSTVOID FILM (FIGURE 3.22)

The patient is requested to void in privacy and a full postvoiding view is obtained. It should be apparent that the environment in most radiology departments is not conducive to normal voiding. While comment should be made on the radiographic report concerning the presence and amount of postvoid residual urine, the only valid inference that can usually be drawn from a postvoiding film will be in those patients who demonstrate an empty bladder. TAILORING

If the study is being monitored after each exposure, significant abnormalities can be noted and appropriate deviations from the standard sequence requested. These may include oblique tomographic sections, coned oblique views of the kidneys, or full oblique or prone views to hopefully provide better filling of the distal ureters. If it becomes necessary to better visualize the ureterovesical junctions, the right posterior oblique coned view of the bladder will allow visualization of the left ureterovesical

junction and vice versa. Coned oblique views of the bladder are also useful for imaging filling defects in the bladder and irregularities of the bladder wall and for determining the presence of extravasation in the retrovesical region. A coned postvoid view of the bladder is a necessity when evaluating questionable filling defects. This view often enhances a persistent defect. Delayed films are essential when an obstructive nephrogram is seen on the routine early views. A recommended sequence for these delayed views is 30 minutes, 1 hour, 2 hours, 4 hours, 8 hours, and 24 hours. When obtaining delayed views, the patient should be instructed to void prior to exposure of the film so that a calculus at the level of the ureterovesical junction will not be obscured by the full bladder. Unless the degree of obstruction is extremely severe, at some point during this sequence of delayed films contrast can usually be seen columning in the ureter to the point of obstruction. If the degree of obstruction is such that there is no columning by 24 hours, further films are not indicated. In such patients further imaging modalities will be necessary to determine the anatomy of the obstructed system. These may include antegrade or retrograde pyelography. Routine full views obtained in both obliquities are a standard part of the urographic sequence at some institutions. This will depend on the personal preference of the radiologist. LIMITED UROGRAM

This study usually consists of a preliminary film of the abdomen followed by a single full view obtained 10 minutes after injection of a standard dose of contrast. Indications for such studies would include, for example, follow-up on a patient who has recently passed a ureteral calculus that was diagnosed by a standard urogram at an earlier date. In some institutions, the limited urogram is used in young female patients with signs and symptoms of acute pyelonephritis to exclude obstruction as a possible cause. Certainly, in children, a more limited study is indicated as is noted. Most reports in the literature and standard texts recommend a film shortly after injection followed by another full view at 5 or 10 minutes postinjection.

Various Imaging Modalities and Techniques in Uroradiology

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are pregnant. The effective radiation dose from this procedure is about 1.6 mSv, which is about the same as the average person receives from background radiation in six months. Radiation disadvantages are further minimized by: • The use of high-speed X-ray film that does not require much radiation to produce an optimal image • Technique standards established by national and international guidelines that have been designed and are continually reviewed by national and international radiology protection councils • Modern, state-of-the-art X-ray systems that have very tightly controlled X-ray beams with significant filtration and X-ray dose control methods. Thus, scatter or stray radiation is minimized and those parts of a patient’s body not being imaged receive minimal exposure. LIMITATIONS OF IVU FIGURE 3.23: Focal hydrocalicosis at right upper pole with ureteric strictures–tubercular

An IVU shows details of the inside of the urinary tract including the kidneys, ureters and bladder. CT or MRI may add valuable information about the functioning tissue of the kidneys and the surface and surrounding structures nearby the kidneys, ureters and bladder. IVU studies are not usually indicated for pregnant women. MODIFICATIONS OF IVU

FIGURE 3.24: Black or negative pyelogram on right side

An Abnormal Pyelogram

See Figures 3.23 and 3.24 DEMERITS OF IVU

• Contrast materials used in IVU studies can cause adverse reactions in some people • Women should always inform their doctor or X-ray technologist if there is any possibility that they

Modern non-ionic contrast agents do not provoke an osmotic diuresis and the degree of opacification is unlikely to be significantly altered by dehydration. Fluid restriction should therefore be avoided and if there is a risk that the patient is dehydrated before the IVU this should be corrected first. The classical series of plain films (immediate, 5 and 15 minute, full length release and postmicturition) is described, with mention of some of many potential modifications. A preliminary postmicturition plain film (KUB) is performed. This should be examined to check exposure factors, centring and obvious pathology, particularly urinary tract calcification. Intravenous contrast is given relatively rapidly by hand. The standard dose is 50 ml of 350–370 strength water-soluble contrast. Some understanding of the underlying structure of water-soluble contrast agents is desirable and a knowledge of potential adverse reactions and their treatment is imperative. These

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Uroradiology: Text and Atlas

issues are discussed under water-soluble contrast (p. 926). At this point it is worth emphasising some safety features. Although modern contrast medium is exceptionally safe, there is a small risk of serious reactions. The most dangerous of these are the anaphylactoid-type hypersensitivity reactions. CYSTOGRAPHY AND CYSTOURETHROGRAPHY a. b. c. d. e.

With voiding urethrogram Retrograde urethrogram Cystogram With DC (air) Triple contrast (angiography plus pneumocystogram plus interstitial air in wall of UB) f. Chain urethrogram g. Choke urethrogram MCU

The MCU is the most accurate method of demonstrating posterior urethra and VUR, and it is important in children with UTI and reflux nephropathy. It is a relatively uncomfortable investigation. The catheterization should be carried out gently but confidently with anesthetic jelly and an appropriately sized catheter, using a sterile non touch technique. Dilute watersoluble contrast medium (15–20%) should be used and the bladder filled to capacity. After removal of the catheter the patient is tilted with the table to the erect position and asked to empty the bladder into a plastic jug. Images during filling and during micturition should be obtained to document any vesicoureteric reflux. Micturating radiographs taken with the patient slightly oblique will demonstrate the posterior urethra. This part of the study is especially important in children suspected of having posterior urethral valves, which will only fill out and cause obstruction during micturition. Contrast medium injected retrogradely will fail to show valves. When catheterization is not possible because of a urethral stricture, the bladder can be filled in the retrograde manner using an ascending urethrogram.

distal sphincter mechanism. Water soluble contrast medium should be introduced by means of either a clamp and nozzle (Knutsson’s clamp) or a Foley balloon catheter gently inflated in the fossa naviculare just proximal to the urethral meatus. For a simple ascending urethrogram to demonstrate a penile or bulbar urethral stricture the clamp is easy and quick to use, the whole investigation taking just a few moments. As soon as the urethra is filled and contrast medium is seen to be trickling past the distal sphincter, films are taken in two oblique projections. COMBINED ASCENDING URETHROGRAM AND MCU

When both an ascending urethrogram and a descending (micturating) study are required to show the posterior urethra, the bladder can be filled slowly using a 50 ml syringe for repeated injections. After images of the anterior urethra have been obtained in the usual way, the clamp or catheter is removed, the patient tilted to the upright position, and oblique views during micturition obtained to exclude vesicoureteric reflux and to demonstrate the posterior urethra. This combined study is of particular importance in demonstrating the anatomy of strictures in the proximal and distal urethra after pelvic and perineal trauma. Films of the urethra obtained during micturition at the end of an IVU are inadequate, the concentration of contrast medium being insufficient for this purpose. ULTRASONOGRAPHY A normal kidney shows central echogenic sinus fat and pelvicalyseal system and peripheral sim of cortex (normal thickness of cortex is 1.8–2.0 cm) with distinct CM-differ entiation is corticomedullary differentiation as shown in Figure 3.25. ADVANTAGES

1. 2. 3. 4.

Widely used No hazard of ionizing radiation Easily available Multiplanner capability

ASCENDING URETHROGRAM

DISADVANTAGES

The ascending urethrogram gives excellent anatomical information concerning the distal urethra as far as the

1. Bowel gas obscures especially in mid ureter 2. Obese patients

Various Imaging Modalities and Techniques in Uroradiology

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ROLE OF MDCT IN UROLOGIC DISEASES INCLUDING THE IMAGING PROTOCOLS INTRODUCTION

CT imaging of the urinary system has essentially replaced conventional plain film excretory urography. CT scanning for stones, hematuria, or for evaluating renal masses are performed worldwide. The appropriate CT protocol will be selected by the radiologist based on the clinical history of the patient (see Table 3.4). INDICATIONS

FIGURE 3.25: Ultrasonography: A normal kidney

3. Calculus size cannot be evaluated 4. Operator dependent It is a very vital modality especially in pediatric urology practice and in screening for urorenal diseases in all age groups, e.g. in obstructive diseases: Signs of Obstruction Indirect signs: 1. Hydronephrosis 2. Hydroureter 3. Absent ureteric jets 4. Renomegaly 5. Renal blood flow changes—can be absent in early obstruction 6. Forniceal rupture, 7. Acute renal failure 8. Extrarenal pelvis. Direct Signs

1. Differentiating cyst from tumor when ultrasound equivocal 2. Staging renal tumor 3. Excluding small tumors in patient with hematuria and otherwise normal studies 4. Renal tumor 5. Retroperitoneal pathology affecting the upper urinary tract 6. Retroperitoneal fibrosis 7. Retroperitoneal tumor 8. Differentiating uric acid calculi from urothelial tumor 9. Filling defects in the pelvicaliceal system 10. Renal trauma 11. If IVU is abnormal will show extent of injury better than ultrasound 12. Lower tract tumor 13. Staging bladder, prostatic and testicular tumors Follow up after surgery, radiotherapy or chemotherapy 14. Calculus disease 15. Colic—emergency nonenhanced helical CT precise localization of stones before treatment.

Calculus itself as a cause may be seen. Table 3.4: Urinary tract imaging protocols Stone Protocol For detection of renal, ureteral, or bladder stones

Non-contrast CT imaging from kidney to bladder. (May be necessary infrequently to use iodinated contrast agent to distinguish between ureteral stones and phleboliths) Follow-up imaging with non-contrast plain film radiography

CT Urography (Hematuria Protocol) For evaluation for common causes of persistent hematuria, i.e. stones, urothelial tumors, renal tumors

Non-contrast followed by contrast CT imaging from kidney to bladder

Renal Mass Protocol For characterization of renal masses detected by other imaging studies, e.g. ultrasound, MRI

Non-contrast followed by contrast CT imaging of kidneys only

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STONE PROTOCOL

For detection of renal, ureteral, or bladder stones noncontrast CT imaging from kidney to bladder (May be necessary infrequently to use iodinated contrast agent to distinguish between ureteral stones and phleboliths). Follow-up imaging with non-contrast plain film radiography. Non-contrast followed by contrast CT imaging of kidneys only axial image from “stone protocol” CT showing left ureteral stone.

detection of stones on follow-up plain film radiographic images since the detection rate of stones increases from 45% identified on non-contrast radiographic films alone to 78% on films viewed together with 3-D reconstructions of the initial diagnostic CT images. Pregnant patients should be evaluated initially with ultrasound imaging, to avoid exposure to any unnecessary radiation, and MR urography is an alternative imaging technique for evaluating the renal system in pregnant women, children, and patients with contraindications to contrast agents.

Urolithiasis and Nephrolithiasis

Almost all ureteral and renal stones, including those containing uric acid, can be detected by non-contrast CT imaging. The accuracy of the technique in diagnosing urolithiasis in patients presenting with acute flank pain has been determined to be as high as 97%, with a sensitivity of 95% and specificity of 98%. This compares to sensitivities in the range of 45–58% for non-contrast plain film radiography and 64–87% for plain film excretory urography. However, it is occasionally difficult to distinguish between non-obstructing distal ureteral calculi and pelvic phleboliths on non-contrast CT images. In these cases, it may be necessary to use intravenous contrast agent, so that the relationship of the calculus to the opacified ureter can be determined. Another situation in which intravenous contrast can be helpful is in the detection of stones in HIV positive patients on protease inhibitors such as Indinovir. These calculi are typically non-radio opaque and may go undetected on stone protocol CT scans. The use of 3-D reconstruction techniques of contrast-enhanced pyelographic phase images can be helpful in all of these situations. The disadvantage of “stone protocol” CT is that the radiation dose is high (about 500 mrem) compared to that needed for plain film excretory urography (about 150–350 mrem) and non-contrast plain film radiography (about 13 mrem). This exposure is a significant concern, especially as urinary stones frequently affect young people. For this reason, it is better to avoid CT for follow up studies wherever possible and to use non-contrast plain film radiography instead. The initial CT scan and reconstruction images can be used to aid subsequent

CT UROGRAPHY (HEMATURIA PROTOCOL)

For evaluation for common causes of persistent hematuria, i.e. stones, urothelial tumors, renal tumors. Non-contrast followed by contrast CT imaging from kidney to bladder. RENAL MASS PROTOCOL

For characterization of renal masses detected by other imaging studies, e.g. ultrasound, MRI. Many renal lesions are incidentally detected on a variety of imaging tests, but cannot usually be characterized at the time of detection. Currently, at this institution “renal-mass protocol” CT is the gold standard for the characterization of renal masses. This protocol acquires thin section images of the kidneys before and after intravenous contrast administration to evaluate the important characteristic of solid lesions, the unequivocal demonstration of lesion enhancement post contrast. Lesions that demonstrate unequivocal enhancement require histologic diagnosis either by image-guided biopsy or by surgical resection ADVANTAGES OF MDCT

1. The advantages of multidetector CT urography over conventional plain film excretory urography (also known as IV urography) and ultrasound for the evaluation of the urinary tract are numerous. Dedicated CT protocols have been developed for these new high speed machines for different clinical indications including “stone protocol” for the evaluation of urinary tract calculi, CT urography for the evaluation of patients with hematuria and “renal

Various Imaging Modalities and Techniques in Uroradiology mass protocol” for the characterization of known renal masses. Multidetector CT scanning is fast, taking around 15 seconds for image acquisition from the kidneys to the bladder during a single breath-hold. The images have good spatial resolution, little misregistration due to respiratory movement, and the acquisition of multiple thin slices allows excellent twoand three-dimensional reconstructions of the abdominal anatomy, making it possible to detect pathologies outside the urinary tract as well as those within. Iodinated contrast agents are not usually required for the detection of renal stones, thus avoiding the risk of adverse reactions to these agents, but are routinely used in CT urography and the renal mass protocol. 2. In comparison to CT, plain film excretory urography offers excellent delineation of calyceal and papillary anatomy, the ureters and bladder, but it is inferior to multi detector CT for imaging of the kidney parenchyma. Both CT and plain film excretory urography are associated with a substantial radiation dose. Ultrasound is good for imaging the kidney parenchyma and for detecting hydronephrosis, does not require the administration of iodinated contrast, and avoids radiation exposure. However, ultrasound is not good for detecting urinary tract calculi, and does not adequately image the renal collecting system or ureters. For these reasons, multidetector CT imaging has become the gold standard for the diagnosis of urinary tract calculi, the investigation of hematuria, and the characterization of renal masses and has largely replaced both plain film excretory urography and ultrasound examinations for these purposes. 3. The main causes of hematuria are urinary tract calculi, renal tumors, urothelial tumors, and infection. CT urography is the best single diagnostic examination for diagnosing all of these pathologies, with the exception of infection, which is effectively diagnosed in most cases by microbiological analysis of the urine. 4. CT urography requires the use of contrast agent to opacify the collecting system, the ureters, and the bladder. In addition to optimal opacification, distension appears to be an important requirement

5.

6.

7.

8.

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for thorough evaluation of the renal collecting system and ureter. For this reason, intravenous saline is given at the same time as the contrast material to aid in the detection of subtle filling defects and the discrimination between urothelial neoplasms and other filling defects. Image reconstruction techniques are used to create images of the entire length of the urinary system from the kidneys to the bladder. Multiplanar 3-D reconstruction can provide the anatomic detail required to correlate the finding with retrograde ureterography or to perform an endoscopic evaluation. CT has been shown to detect parenchymal masses in the kidney with a sensitivity of 94%, compared to 67% for plain film excretory urography and 79% for ultrasound. Another potential advantage of CT is that reconstructed images can show tumors in a filled bladder opacified with contrast agent (“virtual cytoscopy”). In comparison to CT, plain film excretory urography offers excellent delineation of calyceal and papillary anatomy, the ureters and bladder, but it is inferior to multi detector CT for imaging of the kidney parenchyma. Both CT and plain film excretory. Three dimensional coronal reconstruction of CT urography image, showing contrast-enhanced renal collecting system, ureters, and bladder. Note duplicated system on left side. As Urography is associated with a substantial radiation dose, ultrasound is not good for detecting urinary tract calculi, and does not adequately image the renal collecting system or ureters, multidetector CT imaging has become the gold standard for the diagnosis of urinary tract calculi, the investigation of hematuria, and the characterization of renal masses and has largely replaced both plain film excretory urography and ultrasound examinations for these purposes.

DISADVANTAGES OF MODALITIES IN GENERAL

Conventional cytoscopy remains the “gold standard” for the detection of tumors of the bladder, as it will detect early mucosal lesions that do not deform the contour of the bladder wall. In addition, cytoscopy has the added capability of biopsy of suspicious lesions.

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MRI MRI has as yet less to offer than CT in the imaging of the upper urinary tract, although the detection of minor venous involvement by a renal cell carcinoma may be better shown by MR angiography and MRI plays an important role in the staging of pelvic malignancy. The initial results in the staging of prostatic carcinoma were disappointing but purpose-built, endorectal coils are producing excellent detail and may well be important in demonstrating breaks in the prostatic capsule by prostatic cancer. MR UROGRAPHY

MR urography is being used in the diagnosis of obstruction. The coronal images using FlSP, HASTE sequences rapidly portray a dilated collecting system and demonstrate the site of obstruction. It avoids irradiation of the patient; however, CT has the advantage of being able to show calculi which MR urography cannot accurately differentiate from other filling defects. RENAL SCINTIGRAPHY 1. Dynamic renal scan 2. Static renal scan DYNAMIC SCAN (I-123 HIPPURAN,

99M

Tc, DTPA, MAG3)

• Suspected obstruction • Evaluation of surgical treatment (indirect cystography and post-renal transplant) • With captopril for renovascular hypertension—a sensitive screening test. STATIC SCAN (DMSA)

• To locate ectopic kidney • To diagnose intra and extrarenal arterial abnormalities • In urinary incontinence to detect occult duplication when IVU and USG are normal • For renal scarring in Chronic Pyelonephritis or UTI with VUR • To estimate differential function. RENAL CORTICAL SCINTIGRAPHY

It is the most accurate evaluation for renal cortical scarring. DMSA is bound in the renal tubular cells and provides excellent visualization of the renal cortex. Maximal uptake is reached within 3 hours of radiotracer

administration. The typical dose is 5 mCi for adults. Delayed planar (and pinhole in children) imaging is acquired 2 hours after injection; in multiple projections. SPECT is more sensitive and may be helpful, but is usually not required. Split renal function as a percentage is typically calculated. The primary indication for a renal cortical scan is to assess for renal scarring or acute inflammatory changes. This technique is superior to both ultrasound and excretory urography in both instances. Pyelonephritis is demonstrated as a solitary defect involving one kidney, multiple focal defects or diffuse involvement of an entire kidney without volume loss (and sometimes with evidence of volume expansion). Decreased uptake of DMSA is associated with ischemia in the inflamed or scarred zones of renal parenchyma. An alternative hypothesis proposes failed tubular transport secondary to paralysis from granulocyte toxic by-products. Abnormalities resulting from infection are transient, whereas scars result in a permanent abnormality. Sequential scanning after a newly documented urinary tract infection in children should be performed 2–3 months after the initial diagnosis to assess for scarring. The presence of scarring is indicated by photopenia and cortical contraction (volume loss). Vesicoureteral reflux (VUR) is present in 25–50% of kidneys with new renal scarring but the majority of patients (63–75%) with acute inflammatory changes have pyelonephritis not associated with VUR. The kidney is most susceptible to scarring from reflux in the first year of life and a single instance of pyelonephritis may result in scarring. Renal scars rarely develop after age 5. Infection must be present as reflux alone has not been shown to result in renal scarring. Renal cortical scanning may also be used as a secondary means to provide information about renal tumors or after renal trauma. ARTERIOGRAPHY (INDICATIONS)

• Renovascular hypertension (gold standard) • Preceding conservative surgery for Wilms’ • In renal trauma with persistent hematuria, and hypertension • In suspected vasculitis (polyarteritis) • Prior to interventional procedures (like embolization of AVM, balloon dilatation of RA stenosis).

Congenital Anomalies of Urorenal Tract

INTRODUCTION Congenital anomalies of the kidneys are frequently encountered and probably related to its complex embryogenesis. Congenital anatomic anomalies of the GU tract are more common than those of any other organ system. Complications (e.g. urinary obstruction, stasis) may result in impaired renal function, infection and calculus formation, and sexual disability or infertility. Treatment is often surgical. ANOMALIES OF URORENAL TRACT • • • •

Kidney Ureter Bladder and Urethra

27

Agenesis: Bilateral renal agenesis (absence of both kidneys—Potter’s syndrome) is fatal. It is associated with oligohydramnios, pulmonary hypoplasia, and low-set ears. Unilateral renal agenesis is not uncommon and usually is accompanied by ureteral agenesis with absence of the ipsilateral trigone and ureteral orifice. Compensatory hypertrophy of the solitary kidney maintains normal renal function. SUPERNUMERARY KIDNEY It is extremely rare. Cleavage of the metanephric blastema has been suggested as the cause. Most supernumerary kidneys are caudally placed and are hypoplastic. A separate collecting system is generally present. ANOMALIES OF FUSION EMBRYOLOGY

KIDNEY

• • • •

Anomalies Anomalies Anomalies Anomalies

of of of of

number position fusion form

Anomalies of Number

1. Agenesis 2. Supernumerary kidney

The kidneys begin to form initially in the pelvis and then rise into the upper abdomen later in development. The so called ascent of the kidneys is caused by a diminution of the body curvature as well as by the growth of the body in the lumbar and sacral region. During this ascent they undergo a 90º lateral rotation about a vertical axis with the renal hilus changing from ventral to medial. As they ascend the kidneys pass through the arterial fork formed by the umbilical arteries. If one of them fails

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pass completely, it remains in the pelvis close to the common iliac artery and is a ‘pelvic kidney’. Sometimes both kidneys are pushed together during their passage through the arterial fork and the lower poles become fused, usually between the 4th and 8th week of fetal life. Fusion results in improper rotation and incomplete ascent.

When ureteropelvic junction obstruction is present, pyeloplasty is the treatment of choice (Figures 4.1 to 4.3). Fused pelvic kidney (pancake kidney) is a much less common fusion anomaly in which a pelvic renal mass is served by two collecting systems and ureters. If obstruction is present, reconstruction is indicated. Anomalies of Position

FUSED KIDNEYS ARE DIVIDED INTO THREE GROUPS DEPENDING ON THE RELATIVE HEIGHT AT THE TIME OF FUSION

1. Kidneys present on either side of the spine with an isthmus across the midline joining either upper or lower poles are horseshoe kidneys. A central isthmus is a disk kidney and a sigmoid is an upper of one fused to a lower of another. 2. Both kidneys fused as irregular masses near the sacral promontory, a clump kidney. 3. Both fused into one mass which lies on one side of the spine. Fusion anomalies (in which the kidneys are joined but the ureters still enter the bladder on each side) increase the risk of ureteropelvic junction obstruction, vesicoureteral reflux, multicystic renal dysplasia, and injury from anterior abdominal trauma. 1. Horseshoe kidney 2. Crossed fused renal ectopia 3. Fused pelvic kidney (pancake kidney) Horseshoe kidney is the most common fusion anomaly. Renal parenchyma on each side of the vertebral column is joined at the corresponding (usually the lower) poles, with an isthmus of renal parenchyma or fibrous tissue across the midline at the joined areas. The ureters course medially and anteriorly over this isthmus and generally drain well. Obstruction, if present, is usually secondary to high insertion of the ureter in the renal pelvis, not secondary to the isthmus. Pyeloplasty can be performed without resection of the isthmus. Crossed fused renal ectopia is the second most common fusion anomaly. The renal parenchyma (representing both kidneys) is on the same side of the vertebral column. One of the ureters crosses the midline and enters the bladder on the side opposite the kidneys.

1. Renal ectopia 2. Malrotation. Renal ectopia: Renal ectopia (abnormal renal location) results from a kidney that fails to ascend from its origin in the true pelvis or from a superiorly ascended (thoracic) kidney. There is an increased incidence of ureteropelvic junction obstruction, vesicoureteral reflux, and multicystic

FIGURE 4.1: Antenatal ultrasound scan crossfused ectopia

FIGURE 4.2: Ultrasound scan (postnatal)—Crossfused ectopia

Congenital Anomalies of Urorenal Tract

29

Duplex kidney (double kidney) consists of a single renal mass with more than one collecting system. An increased risk for ureteral ectopy with or without ureterocele exists in duplex systems; management depends on the anatomy and function of each separately drained segment. Surgery may be necessary to correct obstruction or vesicoureteral reflux. Renal dysplasias: These parenchymal abnormalities with consequent renal dysfunction may result from abnormal development of the renal vasculature, renal tubules, collecting ducts, or drainage apparatus. Biopsy may be necessary for diagnosis.

FIGURE 4.3: Computed tomography: Coronal reconstruction– Crossfused ectopia on left side

renal dysplasia in incompletely ascended kidneys, but not in superiorly ascended ones. Surgical correction is performed when indicated. Malrotation: This usually minor anomaly of the renal axis can appear abnormal on radiography of the collecting system. It should be differentiated from the effects of true obstruction or renal masses.

Multicystic dysplastic kidney: This nonfunctioning renal unit consists of noncommunicating cysts with intervening solid tissue composed of fibrosis, primitive tubules, and foci of cartilage. Usually, there is associated ureteral atresia. A low risk for tumor, infection, and hypertension exists; some advocate removing these kidneys, whereas others would observe the patient. Renal hypoplasia: An underdeveloped kidney is usually associated with inadequate branching of the ureteral bud. The kidney is small, with histologically normal nephrons. Hypertension can occur with segmental hypoplasia, and ablative surgery may be necessary (Figure 4.4).

Anomalies of Form

1. 2. 3. 4. 5. 6.

Duplication anomalies Calyceal diverticulum Renal dysplasias MCDK (Multicystic dysplastic kidney) Medullary sponge kidney Medullary cystic disease of kidney (Juvenile nephronopthesis) 7. Renal hypoplasia and Ask-up mark kidney 8. ARPKD 9. ADPKD. Duplication anomalies: Supernumerary collecting systems may be unilateral or bilateral and may involve the renal pelvis and ureters (accessory renal pelvis, double or triple pelvis and ureter), calyx, or ureteral orifice.

FIGURE 4.4: IVU: Small sized right kidney with smooth outline and small pelvicalyceal system → right renal hypoplasia

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Autosomal recessive polycystic kidney disease: Although rare (1/10,000 births), autosomal recessive polycystic kidney disease is the most common genetically determined childhood cystic disease of the kidneys (involving both kidneys and the liver) and frequently produces renal failure in childhood. Generally, patients presenting in early childhood show mainly renal-related symptoms; those presenting in adolescence show mainly hepatic-related symptoms. These differences probably reflect phenotypic variation of the same genetic disorder. Severely affected newborns commonly have pulmonary hypoplasia secondary to the in utero effects of renal dysfunction and associated oligohydramnios. Less severely affected newborns have a protuberant abdomen with huge, firm, smooth-surfaced, symmetric kidneys. The enlarged liver is abnormal with periportal fibrosis, bile duct proliferation, and rare cysts; the remainder of the hepatic parenchyma is normal. These pathologic findings are responsible for perisinusoidal portal hypertension with minimal or absent hepatic dysfunction. Ultrasonography is the best diagnostic tool and, in late pregnancy, usually allows presumptive in utero diagnosis. In patients aged 5 to 10 years, signs of portal hypertension appear, such as esophageal and gastric varices and hypersplenism (leukopenia, thrombocytopenia). If the patient presents in adolescence, nephromegaly is less marked. Renal insufficiency may be mild to moderate. The major symptoms are related to progressive hepatic fibrosis (portal hypertension, gastric and esophageal varices, hepatic insufficiency, hypersplenism). Diagnosis is difficult, especially without a positive family history. Ultrasonography may demonstrate renal or hepatic cysts; definitive diagnosis may require biopsy. Many newborns die in the first few days or weeks of life from pulmonary insufficiency. Most who survive the first few years have progressive renal failure. Those with less renal involvement develop progressive portal hypertension. Portacaval or splenorenal shunts reduce morbidity but not mortality. Experience with transplantation in these patients is limited. If transplantation is performed, hypersplenism must be controlled to prevent immunosuppression; otherwise, hypersplenism may induce leukopenia, increasing the risk of systemic

infection. Dialysis is used as for other children with chronic renal insufficiency. URETER

Ureteral anomalies frequently occur with renal anomalies but may occur independently. Complications include obstruction, infection, and sometimes calculus formation from urinary stasis, as well as urinary incontinence if the ureter bypasses the bladder and terminates in the urethra, perineum, or vagina in the female. 1. Peliv-ureteric Junction (PUJ) Obstruction 2. Duplication anomalies 3. Ectopic orifices 4. Ureteral stenosis 5. Ureterocele 6. VUR 7. Megapolycalicosis and megaureter 8. Retrocaval ureter. CONGENITAL PUJ OBSTRUCTION INTRODUCTION

It is the most common congenital anomaly of the urinary tract. It is also the most common cause of an abdominal mass in a neonate. INCIDENCE

Male to female ratio is 2:1. The left side is more commonly affected. Bilateral PUJ obstruction is present in 10–40% of cases. A familial tendency has been reported. PATHOPHYSIOLOGY

The intrinsic form is responsible for 80% of cases and it thought to be due to a defect in the circular muscle bundle of the renal pelvis that results in an inability to transmit normal peristalsis. The extrinsic form accounts for no more than 15–20% of cases and is usually caused by aberrant renal vessels that cross anterior to the pelvis or proximal ureter. Some authors have postulated less widely held views regarding the causation of the intrinsic form of PUJ obstruction, such as the presence of abnormal folds or a kink of the PUJ, or that the lesion represents an exaggerated from of extrarenal pelvis.

Congenital Anomalies of Urorenal Tract CLINICAL FEATURES

It may be clinically silent until adulthood, when symptoms of flank pain, fever or hypertension (rarely) may occur. However, increasingly, many cases are discovered prior to birth by obstetric ultrasound. In some cases, a sustained diuresis may be needed to provoke symptoms (“beerdrinker’s hydronephrosis”). Such cases may be due to a mild PUJ obstruction that is compensated in the absence of diuresis.

31

Also, percutaneous nephrostomy followed by balloon pyeloplasty or endoscopic endopyelotomy may be performed. These may also be performed as secondary procedures when surgery has failed. Success rates of 85% have been reported. The procedures should not be utilized in small infants. If obstruction secondary to an aberrant vessel is suspected, the above mentioned procedure should not be performed until the aberrant vessel has been excluded by prior angiography.

ROLE OF RADIOLOGY AND IMAGING

Urography demonstrates a dilated renal pelvis and calyces. Slow opacification of the affected side is seen. Delayed radiographs are needed to demonstrate that the PUJ is the point of obstruction. With high-grade/longstanding obstruction, the renal pelvis may be markedly dilated (>10 cm in diameter) with a ballooned appearance. The kidney may be virtually non-functional. If there is kinking of the PUJ, obstruction secondary to an aberrant vessel should be considered. A diuretic renogram or the Whitaker procedure performed after acute symptoms are brought on may be helpful to determine whether functionally significant obstruction is present, in patients with equivocal PUJ obstruction or if there is a discrepancy between clinical symptoms and radiologic findings. Antegrade or retrograde pyelography may help better define the ureter and thereby establish the diagnosis. The antegrade procedure may be performed by percutaneous nephrostomy. The retrograde procedure may be useful to confirm the diagnosis prior to surgery. A voiding cystourethrogram is recommended to exclude vesicoureteral reflux as the cause of the renal pelvic dilatation. Ultrasound will demonstrate a very dilated renal pelvis and caliectasis but will not be able to demonstrate a dilated ureter. DIFFERENTIAL DIAGNOSIS

A large extrarenal pelvis may be distinguished by the fact that the calyces are not dilated. TREATMENT

It may include pyeloplasty.

Duplication Anomalies

Duplication of PC system only with normal ureter is common and can otherwise be considered as a normal variant. Partial or complete duplication of one or both ureters may occur with duplication of the ipsilateral renal pelvis. The ureter from the upper pole of the kidney opens at a more caudal location than the orifice of the lower pole ureter. Ectopia or stenosis of one or both orifices, vesicoureteral reflux into the lower or both ureters, or ureterocele may occur. Surgery may be necessary to correct vesicoureteral reflux, obstruction, or urinary incontinence (Figures 4.5 and 4.6). Ectopic Orifices

These malpositioned openings of single or duplicated ureters may occur on the lateral bladder wall, distally along the trigone, in the bladder neck, in the female urethra distal to the sphincter (leading to continuous incontinence), in the genital system (prostate and seminal vesicle in the male, uterus or vagina in the female), or externally. Lateral ectopic orifices frequently are associated with vesicoureteral reflux, whereas distal ectopic orifices more often are associated with obstruction and incontinence. Surgery is indicated for obstruction and incontinence and is sometimes necessary for vesicoureteral reflux. Stenosis

Narrowing may occur at any location in the ureter, most commonly at the ureteropelvic junction and less commonly at the ureterovesical junction (primary megaureter). Stenoses often improve with time and growth, but ureteral tapering and reimplantation may be necessary when there is increasing dilatation and infection. Any obstruction is also an indication for surgery.

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FIGURE 4.5: Ultrasound scan: Bifid pelvicalyceal system

Ureterocele

Ballooning of the lower end of the ureter into the bladder may produce progressive obstructing dilatation, leading to ureterectasis, hydronephrosis, infection, occasional calculus formation, and potential loss of renal function. Treatment includes endoscopic transurethral incision or open repair. When a ureterocele involves the upper pole of duplex ureters, treatment may depend on function in that renal segment because of the significant incidence of renal dysplasia. Removal of the affected renal segment and the affected ureter may be preferable to repair of the obstruction if no segmental renal function is found or if significant renal dysplasia is suspected. Vesicoureteral Reflux

Reflux of urine from the bladder into the ureter may result in damage to the upper urinary tract by bacterial infection and occasionally by increased hydrostatic pressure. It most often is due to congenital anomalous development of the ureterovesical junction. Incomplete development of the intramural ureteral tunnel causes a failure of the flap valve action at the ureterovesical junction and permits backwash of bladder urine into the ureter and renal pelvis. Reflux can occur even in the presence of an ordinarily sufficient tunnel when there is bladder outlet obstruction with increased intravesical pressures or neurogenic vesical dysfunction.

FIGURE 4.6: CT scan: Coronal reconstruction—Bifid pelvicalyceal system on left side

Bacteria in the lower urinary tract can be easily transmitted by reflux to the upper tract, leading to parenchymal infection with potential scarring and loss of renal function. Chronically elevated bladder storage and emptying pressures (> 40 cm H2O) have resulted in progressive hydrostatic damage to the kidney in most patients, even without infection or reflux. Abdominal or flank pain, persistent or recurrent UTI, dysuria or flank pain with voiding, frequency and urgency, or signs of renal insufficiency may be secondary to vesicoureteral reflux. Pyuria, hematuria, proteinuria, and bacteriuria may be present. Filling and voiding cystourethrograms demonstrate reflux and are the preferred means to diagnose bladder outlet obstruction, which can be surgically repaired. IVU may show calyceal dilatation, ureteral “ribboning,” and ureterectasis with dilatation of the upper collecting system. Reflux may also be demonstrated by direct (catheter) radioisotope cystogram. Renal cortical involvement with acute infection or scarring is precisely delineated with succimer (dimercaptosuccinic acid) nuclear scans, when indicated. Vesicoureteral reflux is usually mild to moderate (with little or no calyceal dilatation) and often resolves spontaneously over months to several years while daily antibacterial prophylaxis is maintained. Infection despite

Congenital Anomalies of Urorenal Tract

33

prophylaxis, or significant and progressive renal scarring is best managed by ureteral reimplantation. When such reflux is accompanied by high-pressure storage or emptying of urine in the bladder, the approach is to lower bladder pressures by pharmacotherapy and/or behavioral means. Reflux may sometimes resolve with this management; if not, reimplantation would be appropriate. This approach almost always eliminates reflux and minimizes future pyelonephritis, with reduced morbidity and mortality from renal disease secondary to reflux and infection. Retrocaval Ureter

Anomalous development of the vena cava (pre-ureteric vena cava) allows the infrarenal vena cava to form anterior to the ureter. A retrocaval ureter on the left is seen only with persistence of the left cardinal vein system or with complete situs inversus. It can cause ureteral obstruction. For significant ureteral obstruction, surgery consists of division of the ureter with ureteroureteral anastomosis anterior to the vena cava or iliac vessel.

FIGURE 4.7: IVU: Pubic diastasis with small hypoplastic urinary bladder in a case of bladder exstrophy

fails to expand sufficiently or has sphincter insufficiency. Reconstruction of the genitalia is required (Figure 4.7).

BLADDER

Congenital Bladder Diverticula

Congenital anomalies of the urinary bladder include exstrophy; agenesis; duplication; persistent urachus; megacystis syndrome, which may be a primary myoneural defect and diverticula. 1. Exstrophy of bladder 2. Congenital bladder diverticuli.

Bladder diverticula predispose to UTI and may be associated with reflux. Diagnosis is made by cystography and cystoscopy. Surgical removal of diverticula and reconstruction of the bladder wall may be indicated. PENIS AND URETHRA

Exstrophy

In this easily detectable and serious major anomaly, the bladder is open (unroofed) in the suprapubic region with urine dripping from the ureteral orifices. The bladder mucosa is continuous with the abdominal skin, and the pubic bones are separated. The prognosis for maintenance of normal renal function is good. The bladder can almost always be reconstructed and returned to the pelvis, although vesicoureteral reflux is invariably present. Ureterosigmoidostomy or other types of continent urinary diversion may be used to treat a bladder reservoir that

The penis in the male and the urethra in the male or female may be congenitally absent. Other anomalies include hypospadias; epispadias; double penis; congenital penile curvature or malrotation; microphallus; urethral valves, stricture, stenosis, or duplication; meatal stenosis; and phimosis and paraphimosis. 1. Hypospadias 2. Epispadias 3. Congenital urethral stricture 4. Urethral meatal stenosis 5. Urethral diverticulum

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6. Duplication of urethra 7. Phimosis and paraphimosis. Hypospadias

A displaced urethral opening is caused by failure of tubularization and fusion of the urethral groove. In female hypospadias, the urethra opens into the vaginal introitus. In the male, the foreskin fails to become circumferential and appears as a dorsal hood. The urethral opening may be located on the underside of the penile shaft, at the penoscrotal junction, between the scrotal folds, or in the perineum. It is often associated with chordee (ventral curvature of the penis, most apparent on erection), caused by fibrous tissue along the usual course of the corpus spongiosum. Prognosis for functional and cosmetic correction is good. During the first year of life, the chordee can be repaired and a neourethra constructed using penile shaft skin or foreskin. Epispadias

This dorsal fusion defect of the urethra can be partial (in 15% of cases) or complete, the most severe form being associated with exstrophy of the urinary bladder. It is more common in males. In partial epispadias, urinary control can be satisfactory. Reconstruction of the penis alone may be associated with persistent incontinence. Bladder outlet reconstruction is often required to achieve complete urinary control. Posterior Urethral Valves

Congenital folds of the urethra act as valves that occur in the prostatic urethra (posterior urethral valves). Complications are due to obstruction, which may be severe and may lead to myogenic bladder malfunction, massive upper tract damage, and renal insufficiency. Symptoms and signs include weak and dribbling urinary stream, overflow incontinence, and UTI. Diagnosis is established by voiding cystourethrography. Initial treatment is endoscopy. Early surgery may prevent progressive renal deterioration. A different entity, diverticulum of the anterior urethra, may act as a valve (anterior urethral valve) and is also treated endoscopically.

Urethral Stricture

Although urethral stricture in the male is most commonly acquired, typically from a crush injury after straddle trauma, it may be congenital. Acquired stricture usually presents with postvoid bloody urethral discharge and may heal spontaneously or progress to true stricture. Initial management is endoscopic urethrotomy. Urethral Meatal Stenosis

Urethral meatal stenosis associated with hypospadias is the most common form of congenital urethral stenosis, although it is more commonly an acquired condition resulting from healed irritation of the meatus in boys who are circumcised while still in diapers. Meatotomy is indicated for a significantly deflected stream or for a pinpoint stream. Duplication of Urethra

It may be complete or incomplete. It occurs in sagittal plane. Three types known: 1. Epispadic (dorsal) type usually abortive 2. Hypospadic (Ventral) type is more functional 3. Other types: forked Perneal is a rare variant. Phimosis and Paraphimosis

Phimosis is congenital or acquired (inflammatory) constriction of the foreskin, which cannot be retracted. Paraphimosis is inability of the retracted constricting foreskin to be reduced distally over the glans. When either condition is present, surgical circumcision is indicated. A preliminary dorsal slit may be required. The prognosis is excellent. Few important anomalies are discussed in details in following pages. RENAL AGENESIS INTRODUCTION

True renal agenesis is defined as the complete congenital absence of renal tissue. Acquired forms of agenesis are characterized by the development of renal tissue which atrophies either during development or during childhood.

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INCIDENCE

It is between 1:500 and 1:1500 births. PATHOPHYSIOLOGY

Failure of formation of the ureteral bud or because of an inherent deficiency of the metanephric blastema. BILATERAL RENAL AGENESIS

This is extremely rare and is incompatible with life. Males are affected in three-fourths of cases. Infants demonstrate characteristic features of Potter’s syndrome including lowset ears and a prominent palpebral fold. Bilateral renal agenesis is uncommon and incompatible life. Newborns that die from chronic renal failure do so that the end of the first week of life and those who die in hours or day of life usually do so from respiratory. Bilateral renal agenesis is almost always accompanied by oligohydramnios and there is a high incidence of associate monary hypoplasia. Following delivery, many affected have a spontaneous pneumothorax or pneumomediastinum they also have a typical facies with low-set ears - the so~called ‘Potter facies’. ASSOCIATED ANOMALIES

The ipsilateral adrenal gland is absent in 8–10% of cases. Some investigators report a two-fold increase in the incidence of congenital anomalies of the contralateral kidney. Associated genital abnormalities in males may include cysts of the ipsilateral seminal vesicle, absence of the ipsilateral vas deferens, hypoplasia or agenesis of the testicle, and hypospadias. In females, unicornuate or bicornuate uterus, absence or hypoplasia of the uterus, and absence or aplasia of the vagina (Rokitansky-KusterHauser syndrome) may be present.

FIGURE 4.8: IVU: Left renal agenesis

RENAL ECTOPY INTRODUCTION

It refers to an abnormal position of the kidney. Renal ectopia (abnormal renal location) results from a kidney that fails to ascend from its origin in the true pelvis or from a superiorly ascended (thoracic) kidney. Most commonly, it takes the form of a pelvic kidney, in which the kidney is located in the true pelvis (pelvic kidney) or adjacent to the sacrum (sacral kidney). Occasionally, the kidney may lie at the level of the iliac crest (abdominal ectopy). Rarely (1:15,000 births), the kidney ascends to a position higher than the second lumbar vertebra, and enters the thorax, presumably via a diaphragmatic aperture (intrathoracic kidney). This anomaly is more common in males and on the left side. Blood supply to an intrathoracic kidney arises from the abdominal aorta in its normal location.

ROLE OF RADIOLOGY AND IMAGING

INCIDENCE

In true agenesis, a hemitrigone is found in the bladder on cystoscopy. No renal artery is present. The colon occupies the renal fossa on the affected side, and this may suggest the diagnosis on plain films or barium enema. IVU is helpful (Figure 4.8).

1:500 to 1:1200. PATHOPHYSIOLOGY

As the fetal kidneys ascend from their pelvic position to meet the adrenal glands, each kidney acquires blood

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supply from neighboring vessels. The initial supply from the external and internal iliac vessels is lost and blood supply is acquired directly from the aorta around the 8th week of development. Renal ectopy occurs if there is any abnormality in acquiring such blood supply or there is an associated abnormality of the spine which prevents such cephalic migration from occurring. Left-sided ectopia is more common, and men are affected three times more often than women. It is usually unilateral, but may be bilateral Thoracic kidney has been recognized prenatally, and it has also appeared after a previously normal chest radiograph. High ectopia is usually not associated with functional abnormality and is more commonly an incidental finding on chest X-ray, however, there is an increased incidence of ureteropelvic junction obstruction, vesicoureteral reflux, and multicystic renal dysplasia in incompletely ascended kidneys, but not in superiorly ascended ones. Malrotation may be present with the renal pelvis anterior to the kidney. The ureter is elongated. The origin of the renal artery can be at the level of the opposite renal artery, or it may be higher. The adrenal gland may accompany the kidney, and one instance in which ipsilateral superior splenic ectopia occurred has been reported.

If the ectopic kidney is small and no hydronephrosis is present, the kidney may be obscured by the bony pelvis. In such cases, tomography is useful (Figure 4.9). Ultrasound

It is the modality of choice to demonstrate a small ectopic kidney not visualized on urography. A reniform mass with a characteristic pattern of renal sinus echoes will be identified in the pelvis (Figure 4.10).

CLINICAL FEATURES

Often asymptomatic. In nearly 50% of cases, a pelvic kidney is associated with hydronephrosis or vesicoureteral reflux, leading to obstruction, infection and related pain.

FIGURE 4.9: IVU: Ectopic right kidney with bilateral VUR

ASSOCIATED ANOMALIES

Other GU malformations are commonly present in patients with pelvic kidneys. These include: Ureteropelvic junction obstruction; cryptorchidism; hypospadias (males); and absence of the vagina (females). Also, nonGU anomalies may be present, such as vertebral and rib (skeletal) anomalies; septal defects (heart anomalies); malrotation, imperforate anus (GI anomalies); and, in nearly 50% of patients with unilateral renal ectopy, an abnormality of the normally positioned kidney is also present. ROLE OF RADIOLOGY AND IMAGING

Urography

Findings depend on the degree of renal function in the pelvic kidney, and presence of associated anomalies.

FIGURE 4.10: Ultrasonography: Ectopic right kidney

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CT

A functional mass of renal parenchyma can usually be identified. Angiography

Prior to any surgical procedure contemplated on a pelvic kidney, angiography is performed to investigate the highly variable nature of its blood supply. INTRATHORACIC KIDNEY Thoracic kidney or superior renal ectopia is the rarest of the renal ectopies. The adrenal gland and the spleen may accompany the kidney. Simple chest film combined with sonography and confirmed by enhanced CT scan after or excretory urography readily allows differentiation from other masses in the chest thus avoiding unnecessary and even hazardous biopsy or surgery . There is no need to treat the malformation. If there is an associated diaphragmatic hernia or eventration containing bowel or stomach, the diaphragm is repaired. Intrathoracic kidneys have a reported prevalence of less than 1 in 10,000 and represent only 5% of ectopic kidneys. It is a rare form of renal ectopia. Four forms of intrathoracic ectopy have been reported. Most commonly, as was found in our patient, a thin membrane of diaphragm will cover the kidney, thus making it subdiaphragmatic yet intrathoracic in position. This is also referred to as a diaphragmatic eventration. The embryologic origin is debatable; various authors have proposed either an abnormality in pleuroperitoneal membrane fusion or abnormally high migration of the kidney due to delayed mesonephric involution. Traumatic rupture of the diaphragm, Bochdalek’s hernia, and supradiaphragmatic ectopic kidney without herniation are less common causes of an intrathoracic kidney. Anatomically, four features are commonly found: Rotational abnormality, in which the hilum is anterior; elongated ureter; high renal vessel origin; and medial deviation of the lower pole. The adrenal gland may or may not be ectopic. The possibility of an intrathoracic kidney exists with all chest masses, though its likelihood is low (Figures 4.11 to 4.13).

FIGURE 4.11: IVU: Bilateral intrathoracic kidneys

FIGURE 4.12: IVU: Left intrathoracic kidney-Retrocardiac opacity

FIGURE 4.13: CECT (Axial): Left intrathoracic kidney

CROSSED FUSED RENAL ECTOPIA (CFE) INTRODUCTION

It is the fusion of both kidneys, with at least one kidney on the side opposite its normal location. Originally, this condition was diagnosed at autopsy; currently, it is identified with various imaging studies. Crossed fused ectopia is seen in 1/1000 to 1/1500 autopsies. In 85–90% of patients with ectopic kidney will be fused. CFE is believed to occur when either there is a failure of nephrogenic cells to separate or fusion of 2 blastemas during abdominal ascent. Typically the lower kidney is malrotated and both pelves point toward midline. The ureter of the ectopic kidney crosses midline

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and enters the bladder on the contralateral side. There are no known congenital anomalies associated with CFE. Typically CFE is asymptomatic and is an incidental finding. There can be an higher risk of injury the ectopic kidney if it overlies the spine. PATHOPHYSIOLOGY

The fusion of the two kidneys is believed to result from either of the two events: 1. Failure of the primitive nephrogenic cell masses to separate or 2. Fusion of the two blastemas during their abdominal ascent. Either component of the fused kidneys can have associated renal abnormalities such as a Wilms’ tumor, hydronephrosis, multicystic dysplasia, and ectopic ureterocele. These abnormalities can occur in unfused nonectopic kidneys or in conjunction with renal ectopia. Crossed fused renal ectopia is not known to be associated with abnormalities of nongenitourinary systems. Incidence: Crossed fused ectopy occurs in approximately 1:1000 births. The anomaly is more common in males (2:1). Left-to-right ectopy is three times more common than right-to-left ectopy. Etiology: An abnormally situated umbilical artery prevents normal cephalic migration from occurring. As a consequence, the developing kidney takes the path of least resistance and crosses to the opposite side, where cephalic migration resumes. An alternative hypothesis postulates that the abnormality occurs when the ureteral bud crosses to the opposite side where it induces nephron formation in the contralateral metanephric blastema. Clinical symptoms: rare. These patients generally present in adulthood with abdominal pain, pyuria, or urinary tract infection. There is a slightly higher incidence of urinary tract calculi, probably related to stasis.

varies depending on the secondary symptoms and complications. In the absence of associated complications and symptoms, the condition may be incidentally discovered on images obtained for reasons other than the evaluation of crossed fused kidneys. Many cases of crossed fused renal ectopia remain undiagnosed, although the exact number is unknown. Crossed fused renal ectopia often is clinically silent unless it is detected during imaging for the evaluation of urinary tract infection or abdominal symptoms (e.g. abdominal pain). A urinary tract infection may cause dysuria, fever, or nonspecific symptoms (e.g. failure to thrive), especially in the young child. An associated urinary tract calculus may present with hematuria or flank pain. Anatomical Basis

The ectopic kidney, located entirely or primarily on the opposite side of the abdomen, typically forms the lower portion of the renal fusion mass. Usually, the lower kidney is malrotated, and both pelves point toward the midline. The ureter of the upper renal component descends on the ipsilateral side into the bladder, while the ureter from the crossed ectopic kidney crosses the midline to enter the bladder on the contralateral side. Multicystic dysplasia of the crossed renal unit is reported. PREFERRED INVESTIGATIONS

IVU Figure 4.14A.

CLINICAL FEATURES

Age

Crossed fused renal ectopia is a congenital malformation that is present at birth. The patient’s age at diagnosis

FIGURE 4.14A: IVU: Thyroid kidney

Congenital Anomalies of Urorenal Tract Ultrasonography (USG)

It is the preferred radiologic modality for detecting the condition because it is noninvasive, involves no ionizing radiation, usually is readily available, and is less expensive than either CT or MRI. Features: Crossed fused renal ectopia is not definable on plain radiographs. Usually, crossed fused renal ectopia is apparent on intravenous urograms (IVUs), which demonstrate an atypical renal mass, 2 collecting systems, and 2 ureters. Ultrasonograms demonstrate an atypical or complex appearance of the renal parenchyma, with no definable contralateral kidney. The overall renal dimensions should exceed the normal range for the patient’s age. Usually, fusion occurs along the longitudinal aspect, with the kidneys side by side. The result is a dysmorphic appearance, with a sigmoid or S shape on the ultrasonogram. The fused lower pole unit is positioned medially and extends anterior to the spine (Figure 4.14B).

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Accuracy is high with MRI, primarily as a result of its excellent anatomic delineation and the absence of image degradation due to bowel gas or osseous structures, unlike with US. Nuclear Medicine Studies

It demonstrates a single focus of isotope excretion or localization by a kidney, with no contralateral isotope excretion or localization. MORTALITY/MORBIDITY

No mortality or morbidity is observed unless crossed fused renal ectopia is associated with renal failure that results from obstruction or chronic pyelonephritis. Patients with ectopic kidneys have an increased risk for complications such as hydronephrosis, infection, and calculus formation. SUMMARY

Crossed ectopy is defined as a kidney that is located on the opposite side of the midline from its ureter. The crossed kidney usually lies below the normally situated kidney. In 90% of cases, at least partial fusion between the kidneys is present (called crossed fused ectopy). In the remainder, two discrete kidneys are present on the same side (crossed unfused ectopy). Other variations include solitary crossed ectopy and bilateral crossed ectopy. HORSESHOE KIDNEY INTRODUCTION

FIGURE 4.14B: Ultrasonography: crossfused ectopia right kidney fused to lower pole of left kidney

A multicystic mass of variable size that is contiguous with the lower pole of the upper renal unit is present in patients with multicystic dysplasia. Limitations: On ultrasonograms, overlying abdominal gas may obscure a portion of the fused kidneys, making precise diagnosis difficult. This diagnosis should be considered when 2 separate kidneys cannot be identified. MRI

MRI findings include fused renal masses with two collecting systems.

Horseshoe kidney is probably the most common fusion anomaly. The term “horseshoe kidney” refers to the appearance of the fused kidney, which results from fusion at one pole. In more than 90% of cases, fusion occurs along the lower pole. Technically, the term horseshoe kidney is reserved for cases in which most of each kidney lies on one side of the spine. It includes: • Symmetric horseshoe kidney (midline fusion) or • Asymmetric horseshoe kidney (L-shaped kidney) when the fused part, or the isthmus, lies slightly lateral to the midline (lateral fusion). Horseshoe kidney is generally differentiated from crossed fused ectopia in which both fused kidneys lie on

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one side of the spine and the ureter of the crossed kidney crosses the midline to enter the bladder. PATHOPHYSIOLOGY

The development of the normal kidney depends on the union of ureteric buds from the mesonephric ducts with the nephrogenic cords in the embryo. It is believed to occur around the fourth gestational week. This union normally occurs at the level of the first or second sacral vertebral segment. Subsequent straightening of the hind end of the embryo, along with differential growth of the developing pelvic structures, leads to the ascent of both kidneys to their normal dorsolumbar regions between the fourth and ninth weeks of gestation. The abnormal fusion probably occurs at the 5 to 12 mm embryonic stage when the kidneys are in the true pelvis and the renal capsule has not yet matured. One embryologic explanation regarding midline fusion is that, at that stage, abnormal variation in growth, ventral flexion of the hind end of the embryo, or other variations in the growth of pelvic structures may bring the metanephric blastemas (developing kidneys) abnormally close together for a longer period; this proximity can lead to fusion. The explanation for lateral fusion is that, during early embryonic life, lateral flexion of the lumbosacral spine may push one of the developing kidneys toward the midline. This positioning can lead to asymmetric fusion. In later embryonic life, the ascent of the fused kidney is limited at the level of the inferior mesenteric artery, when the isthmus of the horseshoe kidney gets trapped under it. Consequently, the horseshoe kidney always lies at a position that is lower than normal. However, whether the cause is abnormal fusion, abnormal migration of the posterior nephrogenic areas, or another teratogenic factor is not yet clear.

Horseshoe Kidney with Associated Anomalies

About one-third of cases of horseshoe kidney are associated with other congenital anomalies, which include anomalies of the urogenital, gastrointestinal, neurologic, and skeletal systems, as well as some chromosomal abnormalities. These anomalies include multisystem abnormalities such as urogenital anomalies (e.g. ureteropelvic obstruction, vesicoureteric reflux, ureteral duplication, hypospadiasis, undescended testis, ectopic ureter, retrocaval ureter, bicornuate and/or septate uterus). GI abnormalities include anorectal malformations such as imperforate anus, malrotation, and Meckel diverticulum. CNS anomalies such as neural tube defects may be seen. Skeletal anomalies include rib defects, clubfoot, or congenital hip dislocation. Cardiovascular abnormalities, such as a ventricular septal defect (VSD), may occur in some patients. Horseshoe kidney has also been found in association with some chromosomal abnormalities such as Turner’s syndrome and trisomy 18. The clinical course largely depends on the nature of the anomalies, because horseshoe kidney itself is relatively asymptomatic. Isolated Horseshoe Kidney

CLINICAL FEATURES

In the pediatric clinical setting, about 90% of patients are asymptomatic, and the most common presentation is UTI. When symptoms are present, they are usually related to hydronephrosis, infection, stone formation, or hematuria. The most common symptom is vague abdominal pain, which may radiate to the back. Occasionally, nausea and vomiting may be reported. Also, the so-called Rovsing sign (nausea, vomiting, and abdominal pain with hyperextension of the spine) may be positive in some patients. A small percentage of patients may have a palpable lump in the abdomen. Horseshoe kidney has been reported to be associated with increased risk for renal neoplasms such as Wilms’ tumors, renal carcinoids, and transitional cell carcinoma.

Clinically, horseshoe kidney can be divided into two groups: one with associated anomalies and the isolated horseshoe kidney without any associated anomaly.

Sex: Renal fusion anomalies occur predominantly in males. The male-to-female ratio is approximately 2:1 for horseshoe kidney and 6:1 for crossed fused ectopia.

INCIDENCE

In general population, the incidence of horseshoe kidney is about 1 case in 400 persons worldwide, and it is the most common renal fusion anomaly.

Congenital Anomalies of Urorenal Tract Age: Clinically, this congenital anomaly is diagnosed in individuals of all ages, from fetuses to the elderly. However, because of its association with other congenital anomalies, horseshoe kidney is more commonly diagnosed in children. ANATOMICAL BASIS

In horseshoe kidney, fusion occurs at the lower poles in about 95% cases. This region of fusion, called the isthmus, is usually composed of renal parenchymal tissue. However, in many cases, it may consist of fibrous tissue. The isthmus may be wide or narrow, depending on the degree of fusion. The isthmus usually lies anterior to the aorta and inferior vena cava (IVC) and posterior to the inferior mesenteric artery. However, rarely, the isthmus may pass between the aorta and IVC or even posterior to these vessels. The ureters usually pass anterior to the isthmus, and they may have a high insertion point in the renal pelvis. The renal pelves are usually malrotated and lie anteriorly or laterally. In the midline fusion variety, the kidneys are symmetric, with lower poles converging toward the midline. In the lateral fusion variety, one kidney is more vertical, while the other kidney is more horizontal; the isthmus lies slightly toward one side. In rare cases, the upper poles may fuse, reversing the appearance of horseshoe. Also rarely, both the poles may fuse; the result is a ringlike mass termed disc kidney, doughnut kidney, or pancake kidney. Blood supply of the horseshoe kidney may vary. In about 30% cases, it consists of one renal artery to each kidney. Other variants include supply from 2 or 3 renal arteries to one or both kidneys. The blood supply of the isthmus also varies. It may come from the renal artery, or it may directly arise from the aorta above or below the isthmus. Occasionally, it arises from the common iliac, external iliac, or inferior mesenteric arteries.

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3. Recurrent stone formation related to PUJ obstruction or infection may occur. 4. An increased risk of trauma to the isthmus exists because of its position anterior to the spine. 5. Horseshoe kidney may pose problems for the surgeons during abdominal surgery for other abdominal problems. 6. Some evidence suggests an increased incidence of certain renal tumors in horseshoe kidney. 7. Horseshoe kidney may occur as an isolated anomaly or in association with other congenital anomalies. The morbidity and mortality rates largely depend on whether it is associated with other anomalies. PREFERRED INVESTIGATIONS

Plain Radiographs

Plain KUB films may show low-lying renal outlines with an altered renal axis. Usually, the kidneys follow the axis of the psoas muscles, with the lower poles lying at a more lateral position than the upper poles. In horseshoe kidney, this axis is reversed, and the lower poles lie closer to the spine (Figure 4.15). IVU

For the purpose of diagnosis, IVU is usually the firstline investigation, followed by CT or scintigraphy in cases with doubtful findings.

COMPLICATIONS OF HORSESHOE KIDNEY

1. Pelviureteric junction (PUJ) obstruction is a common complication, possibly because of the high insertion of the ureter. 2. Recurrent infections occur because of urine stasis and associated vesicoureteric reflux.

FIGURE 4.15: Plain KUB film showing the altered axes of renal shadows with lower poles lying closer to spine→horseshoe kidney

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Findings: IVU usually reveals the classical findings associated with horseshoe kidney. Findings on the initial tomogram may be deceptive because of the exclusion of the anteriorly lying isthmus. Renal axis abnormalities are confirmed, as seen on the plain radiographs. In midline fusion, the kidneys are symmetric, with the lower pole calyces lying closer to or actually overlying the spine. The lower calyces are usually medially rotated, and they may actually lie medial to the ureters. Some degree of malrotation of the kidneys is usually present. A renal pelvis is often extrarenal and large. The degree of malrotation has been associated with the degree of fusion. If the isthmus is narrow, the kidneys are usually less malrotated, with pelvis lying anteromedially in its near normal position. In cases of a wide isthmus, the renal pelves lie anteriorly or laterally. Associated UPJ obstruction may be present because of the higher ureteric insertion point that leads to delayed pelvic emptying. Ureters may have the so-called flowervase appearance in which the upper ureters diverge laterally over the isthmus and then converge inferiorly. The lateral fusion variety with an L-shaped kidney can also be readily appreciated on IVUs. In this variety, one kidney has a relatively vertical position while the other is relatively horizontal. Limitations: 1. Most of the time, IVU cannot be used to differentiate between a fibrous isthmus and a parenchymal isthmus. Also, in many cases, the diagnosis of a horseshoe kidney is difficult on the basis of only IVU findings. In these cases, CT or scintigraphy may be helpful. 2. On IVUs, a malrotated or ectopic kidneys may sometimes be confused with a horseshoe kidney. 3. Gibbous deformity of the spine may alter the renal axis, which may then resemble horseshoe kidney (Figure 4.16).

FIGURE 4.16: IVU: Altered axes of both kidney, lower poles lying closer to spine and calyces seen end-on→Horseshoe kidney

in which the continuity of the poles with the isthmus cannot be clearly demonstrated. Findings: Ultrasonography can be useful for diagnosing this anomaly. The most important feature in establishing the diagnosis on the basis of sonographic findings is the isthmus and its continuity with the lower poles. Other features, such as malrotation and an altered renal axis, may be difficult to assess at ultrasonography. In cases in which the isthmus is composed of only a thin fibrous band, this midline soft tissue may not be seen. Findings such as a curved configuration of the lower poles, elongation of the lower poles, and poorly defined lower poles, suggest the presence of this anomaly. Other associated findings, such as stones, hydronephrosis, and cortical scarring, are reliably depicted on sonograms. Ultrasonography has also been useful in the diagnosis of this anomaly in utero.

Ultrasonography

CECT

Utility of USG depends on the visualization of the isthmus and the proof of its continuity with both the lower poles. In many patients, especially patients with a large body habitus, overlying bowel gas makes the acquisition of adequate scans difficult, for technical reasons. In cases

Contrast-enhanced CT has a high degree of accuracy in defining the structural abnormalities such as the degree and site of fusion, degree of malrotation, associated renal parenchymal changes (e.g. scarring, cystic disease), and collecting system abnormalities (e.g.

Congenital Anomalies of Urorenal Tract duplex system, hydronephrosis). It can also be used to differentiate a fibrous isthmus from a parenchymal isthmus and show its relation to the surrounding structures. Although routine CT may show the variant arterial supply, this is better defined with CT angiography with 3D reconstruction and volume rendering. The use of 3D multisection helical CT has also been advocated in cases of neoplasm associated with horseshoe kidney, because it further clarifies the structural details. Limitations: Figure 4.17. MRI

Although MRI accurately reveals the anatomy, it is not generally used for diagnosis because of its high cost. MR angiography provides additional information about the vascular anatomy. A voiding cystourethrogram is usually required to evaluate associated vesicoureteric reflux. Findings: MRI has an advantage in depicting the structural details because of its ability to permit multiplanar imaging, but it is more costly than other examinations. However, an added advantage may be obtained by using MR angiography to delineate the vascular anatomy. MRI is probably the best modality to use in evaluating the extent of renal tumors associated with horseshoe kidney. With MRI diagnosis, as well as defining other associated structural findings is better. However, associated small stones may be missed on MRIs.

FIGURE 4.17: CECT–Axial section: Enhancing/functioning parenchyma isthmus seen joining the two kidneys

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RNI

A diuretic renal scintigram is helpful in differentiating obstructed and nonobstructed dilated collecting systems. Findings: Scintigraphy demonstrates the fusion best if the isthmus consists of functioning parenchymal tissue, because this imaging modality depends not only on the structure but also on the function of the tissue. 99mTc– labeled dimercaptosuccinic acid (DMSA) can be used to define the fused segments, as well as the altered axis of both kidneys. This condition is incidentally diagnosed on bone scans, 99m Tc-labeled RBC studies, or other nuclear medicine studies obtained for reasons other than the evaluation of horseshoe kidney. The use of mercaptoacetyltriglycine (MAG-3) with diuresis is helpful in differentiating nonobstructed and obstructed parts of the collecting systems. Horseshoe kidney can be confidently diagnosed with scintigraphy, which reveals the functioning parenchymal isthmus (Figure 4.18).

FIGURE 4.18: Renal scintigraphy: altered axis of both kidneys with functioning isthmus seen joining lower poles of kidneys

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Angiography

It is usually reserved for presurgical planning to fully evaluate the arterial supply pattern. CTA: CT angiography with 3-dimensional (3D) reconstruction may also reveal the vascular anatomy and collecting system for presurgical planning. Angiography is not normally performed to diagnose this condition, but it is performed to evaluate the vascular anatomy and its variations in a presurgical setting. Angiograms may show 1, 2, or 3 renal arteries on either side and a large variation in the blood supply of the isthmus. However, in cases of associated renal tumors, angiography is used to evaluate tumor vascularity. Angiography is occasionally performed to check renal artery stenosis in hypertensive patients who have this anomaly. INTERVENTION

Image-guided percutaneous nephrostomy can be performed to relieve hydronephrosis associated with horseshoe kidney. Percutaneous stone removal may also be achieved with image guidance AUTOSOMAL RECESSIVE POLYCYSTIC KIDNEY DISEASE (ARPKD) INTRODUCTION

It is the most common heritable cystic renal disease occurring in infancy and childhood. It is distinct from autosomal dominant polycystic kidney disease (ADPKD), which tends to occur in an older population. The clinical spectrum shows a wide variability, ranging from perinatal death to a milder progressive form, which may not be diagnosed until adolescence. PATHOPHYSIOLOGY

ARPKD follows an autosomal recessive inheritance pattern, with siblings of either sex having a 25% chance of developing disease while the parents are unaffected. The disease has variable expression, such that siblings may manifest different degrees of disease. Despite the clinical variability of ARPKD, it appears that a single unidentified gene is responsible for all forms of the disease. Linkage studies have localized an area on chromosome

6 (PKHD1) as the genetic locus. The frequency of the heterozygous state is estimated to be one in 70. The PKHD1 gene is expressed at high levels in the fetal and adult kidney and at lower levels in the liver, which corresponds to the principle sites of disease. ARPKD is characterized by pathologic changes in the kidney and/or liver. In the kidney, epithelial hyperplasia occurs along the collecting duct of the nephron. The hyperplastic cells undergo a functional change from being resorptive to becoming secretory. The fluid secreted from these abnormal cells is rich in epithelial growth factors, which further stimulate epithelial proliferation. The combination of epithelial hyperplasia and fluid secretion results in significant ductal ectasia. Approximately 10-90% of the ducts may be affected, resulting in a wide variability of renal dysfunction. Depending on the number of ducts involved, the kidneys may be massively enlarged. Examination of the kidney reveals multiple small subcapsular cystic spaces that correspond histologically with radially oriented, ectatic collecting ducts. Liver disease is present in every patient with ARPKD, with the manifestations varying according to the patient’s age at presentation. The chief pathologic hallmarks of liver disease are periportal fibrosis and biliary duct ectasia. Significant liver involvement is referred to as congenital hepatic fibrosis. Although the mechanism is not clearly defined, the most common clinical manifestation of congenital hepatic fibrosis is portal hypertension. CLASSIFICATION OF ARPKD

Blyth and Ockenden initially classified ARPKD into four groups: 1. Perinatal 2. Neonatal 3. Infantile 4. Juvenile The four categories are based on the individual’s age and the onset of clinical manifestations; however, the disease is expressed as a part of a spectrum of findings rather than fitting into clearly defined subcategories. 1. Category 1 is perinatal ARPKD. Patients with the perinatal form are born with a markedly enlarged abdomen due to nephromegaly, which may interfere with delivery. Approximately 90% of the collecting

Congenital Anomalies of Urorenal Tract ducts are dilated with minimal liver involvement. Severe renal impairment in utero leads to oligohydramnios and subsequent pulmonary hypoplasia. Other clinical findings may include sequelae of oligohydramnios, such as Potter facies and clubfoot. Most of these infants do not survive beyond the first week of life. Unfortunately, approximately 75% of all cases of ARPKD is this severe. 2. Category 2 is neonatal ARPKD. Patients with the neonatal form have palpable kidneys at birth. Approximately 60% of the kidney is affected and there is mild liver disease. Pulmonary involvement is less of a factor in this form because renal impairment is often less severe in utero. Progressive renal failure is the dominant feature of this form, resulting in death within a few months. 3. Category 3 is infantile ARPKD. The infantile form of the disease tends to present after a few months of life. Approximately 25% of renal collecting ducts are dilated, with moderate hepatic periportal fibrosis. Clinical presentation includes large kidneys and hepatosplenomegaly. Patient often develops chronic renal failure and/or portal and systemic hypertension. The disease often progresses to end-stage renal failure by adolescence, which is the predominant cause of mortality. 4. Category 4 is juvenile ARPKD. The hallmark of the juvenile form is pronounced hepatic involvement. Renal insufficiency is generally absent or mild, with less than 10% of the kidneys affected. The disease has a wide range of age presentations, from 6 months to 5 years. The presentation is characterized by variable renal enlargement and hepatosplenomegaly. Significant liver involvement results in portal hypertension. Morbidity and mortality are often secondary to the sequelae of portal hypertension, including variceal bleeding and thrombocytopenia or anemia secondary to hypersplenism. Mortality for this type is lowest among the 4 categories, with approximately 80% of patients surviving beyond the age of 15 years.

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INCIDENCE

ARPKD has an incidence of 1 in 6,000 to 1 in 55,000 live births. Notably in Finland, the incidence is reported to be higher (1 in 1000). CLINICAL FEATURES

Race: No information has shown a racial predominance. Sex: Both sexes are affected equally. Age: ARPKD may initially occur anytime between perinatal period to five years of age depending on classification. Two constant features of the disease are kidney and liver involvement of variable severity. Generally, renal and hepatic disease manifest opposite degrees of severity. Patients that develop severe kidney disease early in life tend to succumb to renal failure before significant hepatic disease can develop. On the other hand, patients with a milder form of kidney disease tend to develop severe hepatic complications later on in life. The main characteristic of kidney involvement is dilatation of the collecting system resulting in multiple cysts, which manifests as progressive renal failure. Disease in the liver is typically diffuse, presenting as portal and interlobular fibrosis, dilatation and hyperplasia of bile ducts, or a combination of both. Liver disease ultimately results in portal hypertension. ANATOMICAL BASIS

ARPKD results in bilaterally generally symmetrically enlarged kidneys that maintain their reniform shape. Beneath the capsule are scattered opalescent cysts from dilated collecting ducts, usually 1–2 mm in diameter, but sometimes larger. On sections, the renal parenchyma resembles a sponge with ectatic, nonobstructed, radially oriented collecting tubules that have areas of hyperplastic cuboidal or low columnar lining epithelium. Interstitial fibrosis develops but the glomeruli remain normal. ARPKD results in dilated bile ducts with protrusions from the walls and bridging tissue between the duct walls. There are often increased numbers of ducts. There is congenital hepatic fibrosis with increased connective tissue in the enlarged portal tracts.

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Generally, there is a reciprocal relationship between the degree of renal and hepatic involvement in individual patients. Those with more severe renal involvement have less severe hepatic disease. PREFERRED INVESTIGATIONS

IVU It helps to differentiate ARPKD from ADPKD, Glomerulocystic disease and renal dysplasia by demonstrating bilateral and symmetrical enlargement of the kidneys and ‘streaky/ chaotic/ Swiss-cheese’ nephrogram as the contrast clears in the ectatic collecting ducts. Ultrasonography

It is the primary modality for the evaluation of ARPKD, especially during the perinatal and neonatal periods, which characteristically shows bilateral renomegaly with uniformly increased reflectivity. CT and MRI

In older children, CT and MRI are often used to evaluate liver disease. MORTALITY/MORBIDITY

ARPKD accounts for 1.5% of children in renal replacement therapy prior to the age of 15 and 0.6% of patients treated because of end-stage real failure before the age of 20 years. ADULT POLYCYSTIC KIDNEY DISEASE (ADPKD) INTRODUCTION

It is transmitted as an autosomal dominant trait and affects approximately 1 in 1000 people. Cysts arise from the nephrons and the collecting tubules. Islands of normal parenchymal renal tissue are interspaced between the cysts. Microdissection reveals that the cysts communicate directly with the nephrons and collecting tubules. Patients present with hypertension and progressive renal failure after their third decade of life. Uncommonly, autosomal dominant polycystic kidney disease (ADPKD) appears in children, and it is rarely seen in neonates. Of patients with ADPKD, 25–50% have associated hepatic cysts, 9% have associated pancreatic cysts, and 5% have associated splenic cysts; pulmonary cysts occur uncommonly. These extrarenal manifestations are not found in neonates and children.

PATHOPHYSIOLOGY

ADPKD is an inherited condition comprising at least 3 phenotypically indistinguishable but genetically distinct entities caused by mutations in 3 genes: PKD1, PKD2, and PKD3. The gene is located on chromosome arm 16p and chromosome 4 in 90% of patients and is related to spontaneous mutation in 10%. ADPKD is transmitted as an autosomal dominant trait, with almost 100% penetrance if patients live long enough. Because of the variable expressivity and spontaneous mutation, a family history is not found in nearly one half of patients. Histologically, ADPKD is characterized by an abnormal rate of tubule divisions, with hypoplasia of portions of tubules left behind as the ureteral bud advances. Cystic dilatation occurs in the Bowman’s capsule, loop of Henle, and proximal convoluted tubule interspersed with normal renal tissue. Thus, in distinction to simple renal cysts in which the contents are biochemically similar to plasma, the biochemical features of the fluid content of cysts in ADPKD is closer to those of urine, particularly when samples are taken from distal nephrogenic cysts. Cysts in ADPKD are lined by flattened or cuboidal epithelium. Stromal changes are nonspecific and are those of renal failure; dystrophic calcification is common. With minimal disease, the kidneys are normal in size and are smooth, and the cysts are discovered only on cut pathologic specimens. As the size of cysts increases, the kidneys enlarge, often asymmetrically, and the kidneys may become bosselated and lose their reniform shape. The age of patients at onset of cyst formation varies; 54% appear by the first decade of life, 72% occur by the second decade, and 86% occur by the third decade. By the age of 80 years, evidence of cyst formation exists in all persons who have the gene. True unilateral disease is rare because most genetic diseases involving paired organs are bilateral. Segmental ADPKD also occurs rarely, although some doubt the existence of segmental disease and suggest that it should not be considered a forme fruste of ADPKD. Segmental disease is not inherited and not associated with renal failure. Rarely, ADPKD may be detected in utero, usually in the third trimester, although the earliest diagnosis recorded was at 14 weeks gestation.

Congenital Anomalies of Urorenal Tract With small cysts, ADPKD can be confused with autosomal recessive polycystic kidney disease (ARPKD) because the kidneys may be enlarged and echogenic. Sometimes, the cortical cysts are large enough to be demonstrated on ultrasonographic images, which can confirm the diagnosis when cysts are demonstrated in the fetus of a parent with the disease. With progression of the disease, impaired renal function ensues. Hypertension precedes renal failure. Extrarenal manifestations include liver cysts in 25–50% of patients, pancreatic cysts in 9%, and splenic cysts in 5% of patients. Other cysts reported include cysts of the thyroid, parathyroid, lung, brain, pituitary gland, pineal gland, ovary, uterus, testis, seminal vesicles, epididymis, bladder, and the peritoneum. Aneurysms of cerebral arteries (berry aneurysms) have been reported in 3–50% of patients. A variety of cardiac and aortic abnormalities have been associated with ADPKD, including aortic root dilatation, aortic regurgitation, bicuspid aortic valves, coarctation of the aorta, mitral regurgitation, and abdominal aortic aneurysm. Cysts vary in size from those barely visible to those that are several centimeters in diameter. Cysts usually contain clear straw-colored fluid, but hemorrhage into 1 or more cysts is common, which may change the gross, biochemical, and histologic character of the fluid. Cysts may become infected, and aspiration of the fluid may reveal purulent contents. Incidence of renal cell carcinoma is only slightly increased in patients with ADPKD; a greater increased incidence is associated with cystic disease of dialysis. Approximately 50 cases of renal cell carcinoma have been reported in association with polycystic kidneys; some of the cases were associated with von Hippel-Lindau disease and tuberous sclerosis. No correlation exists between the severity of renal disease and the number of liver cysts. Liver function usually remains normal, but with longer survival of patients with ADPKD, liver function abnormalities may occur, particularly in patients with portal hypertension. An association between ADPKD and congenital hepatic fibrosis has been described. INCIDENCE

One in 1000 people carry the ADPKD trait. ADPKD is the most common genetically linked renal disorder.

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CLINICAL FEATURES

Race: No race predilection exists. Sex: No sex preponderance exists. Age: Patients of any age can be affected, but the mean age at diagnosis is 43 years. In rare cases, renal cysts are incidentally discovered in people aged 70–90 years. Although the disease probably begins in utero in most patients, symptoms are unusual until the fourth or fifth decade. With increasing use of cross-sectional imaging, ADPKD is discovered incidentally in asymptomatic patients in their 80s. However, the most common presentation is a palpable mass, hypertension, abdominal pain, and hematuria. Hypertension often predates renal failure. Renal failure ultimately affects most patients by the time they are aged 60 years. Patients may present with fever, dysuria, and leukocytosis due to urinary tract infections. Renal and/or ureteric colic from calculi is a known complication. Hemorrhage, which may be intracystic or retroperitoneal, may present with hematuria, abdominal pain and, rarely, massive hemorrhagic shock or anemia. Polycythemia is a rare but known association secondary to increased erythropoietin production. Rarely, intracystic hemorrhage within a liver cyst may cause acute abdominal pain, mimicking an acute cholecystitis. Urinalysis may reveal proteinuria and hematuria. PREFERRED INVESTIGATION

Plain radiographs offer limited information. Plain radiographic findings are normal in the early stages of ADPKD, but with enlargement of the kidneys, soft-tissue masses displace the normal intra-abdominal organs. IVU when multiple cysts are readily visible on USG the IVU will show compression and displacement of calyces by the intrarenal cysts. There is difficulty in identifying the renal outline. Puddling of contrast medium on IVU is differentiating feature of ADPKD from that of ARPKD, especially in infants. Ultrasonography is the modality of choice in the workup of patients with ADPKD, and it is an ideal modality for screening the family of patients. In earlier studies in young children, intravenous urography and

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nephrotomography were shown to be slightly more sensitive than ultrasonography. CT scanning is as sensitive as ultrasound in the detection of cystic disease, although problems may arise with smaller cysts. CT appears to be more specific than sonography in differentiating an obstructed renal pelvis from a parapelvic cyst. CT scans also appear superior to ultrasonographic images in helping assess retroperitoneal rupture of a cyst and perinephric extension of blood or pus from an infected cyst. MRI is especially useful in patients who are allergic to iodinated contrast media and in patients with compromised renal function who are at risk for iodinated contrast-induced renal failure. MRI also has advantages in patients in whom hemorrhagic cysts are considered. MRI is probably superior to other modalities in characterizing complicated cysts (Figure 4.19). RNI: A 99mTc DMSA scan will give info regarding the differential function and will show photon-deficient areas occupied by the cysts with uptake in the intervening normal renal parenchyma. The kidneys have lost their normal reniform appearances and the appearances can be quite misleading for the unwary. Angiography: Its role in the diagnosis of ADPKD is limited. Although angiography has a high degree of accuracy in the diagnosis of ADPKD, its specificity is low.

FIGURE 4.19: Coronal T2WMR: Bilateral polycystic kidneys–ADPKD

Radionuclide studies have a complementary role in the assessment of renal function in ADPKD. These studies do not have the added hazard of an exposure to iodinated contrast material. Limitations of above Modalities in General

On plain radiographs, nephromegaly may occur because of causes other than ADPKD. Similarly, curvilinear calcification is not specific for ADPKD and may be found in other types of cysts and in tumors and granulomas. Cysts similar to those of ADPKD can occur in nongeneticrelated simple renal cysts and in von Hippel-Lindau disease. These findings apply to intravenous urography, ultrasonography, CT scanning, MRI, and angiography. Cysts associated with ADPKD cannot always be differentiated from multiple simple cysts and cysts associated with von Hippel-Lindau disease or tuberous sclerosis. MORTALITY/MORBIDITY

Renal failure affects most patients with ADPKD by the time they are aged 60 years. Hypertension predates renal failure. Complications from hypertension secondary to ADPKD are similar to essential hypertension. Patients who are normotensive at presentation have a better prognosis in terms of survival. Infections, hemorrhage, cyst rupture, and renal calculus disease are recognized complications of ADPKD. Results of experimental studies have suggested that cystic kidneys become infected more easily than noncystic kidneys. The urinary tract carries a particular risk of serious infections in ADPKD, which adds considerably to morbidity and mortality. Rarely, massive intracystic or retroperitoneal hemorrhage can occur; these require nephrectomy. Before the availability of renal dialysis and renal transplantation, most patients died within 10 years after the onset of symptoms. Liver and other extrarenal cysts seldom cause symptoms; however, with longer survival of patients with ADPKD, liver impairment may cause increased morbidity and mortality rates. Rare complications of hepatic cystic disease include cyst hemorrhage, infection, portal hypertension, biliary obstruction from cystic mass effect, and cholangiocarcinoma. The variety of cardiac and aortic problems associated with ADPKD may add to morbidity and mortality.

Congenital Anomalies of Urorenal Tract Approximately 10% of patients with ADPKD die from a ruptured intracranial berry aneurysm. MULTICYSTIC DYSPLASTIC KIDNEY (MCDK) DEFINITION

A non-functional kidney, replaced by multiple cysts and dysplastic tissue, can vary in size from .10-15 cm to only 1–2 cm. It is the second most common abdominal mass in a neonate (Figure 4.20). It probably due to atresia of ureter. Equal incidence in males and female. Gross pathologic-surgical features include Walls of cysts vary in thickness fibrotic, renal stroma, may be quite large and bizarre. By classic imaging appearance: 2 forms are generally recognized: 1. Pelvoinfundibular MCDK more common type—results from atresia of ureter or renal pelvis, cysts are remnants of dilated calyces 2. Hydronephrotic type of MCDK occurs less frequently —results from atretic segment of ureter, cysts are the entire pelvocalyceal system.

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• Tend to involute with time, cysts shrink and residual tissue does not have a reniform shape, typically not surgically removed. • A few reports of Wilms’ tumor occurring in MCDK may change management. • Up to 40% of patients with MCDK have contralateral abnormality-PUJ obstruction and vesicoureteral reflux are most common. • Can be segmental in duplicated kidneys. INCIDENCE

0.03% in autopsy series. IMAGING FINDINGS

Sonography to document cystic nature and exclude enlarging mass over time (potential for Wilms’ tumor) Nuclear scintigraphy to document non-function and confirm normal drainage of contralateral kidney. Nuclear Scintigraphy

Best imaging clue: Nuclear scintigraphy documents lack of renal function. If some excretion is present, consider poorly functioning hydronephrosis. Initial blood flow images show perfusion of the MCDK, but sequential images document lack of any excretory function. Note that 99mTc DMSA may localize to the renal cortex in MCDK due to the presence of tubular cells, but this is different than true excretion of radiopharmaceutical. a. Longitudinal sonogram of MCDK showing cysts of varying sizes and echogenic intervening fibrous stroma. b. Posterior images from 99mTc MAG3 scan showing normal drainage of left kidney and absent function on the right in a toddler with right-sided MCDK. MAG3, DTPA, Glucoheptonate are typically agents of choice. CT/MR Findings

FIGURE 4.20: Multicystic dysplastic kidney (For color version see Plate 3)

Typically an incidental finding on CT or MRI scans, cystic kidney with some enhancement possible in solid components, but no true excretion of contrast, cortex replaced by cysts.

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Ultrasound

PATHOPHYSIOLOGY

Multiple anechoic cysts of varying size, largest cyst is not generally centrally located, echogenic fibrous tissue in intervening septa.

The pathogenesis of MSK is unknown. Most authors believe that MSK is a developmental defect affecting the formation of the collecting tubules. Some authors believe that MSK is a progressive degeneration of the collecting tubules that occurs later in life. According to Osathanondh and Potter, the primary abnormality is hyperplasia of part of the medullary collecting tubules. The size of the kidney may be normal or slightly enlarged. On pathologic sections, multiple cysts representing dilated terminal collecting tubules are seen, measuring from 1–7 mm. The cysts usually communicate proximally with collecting tubules and distally with papillary ducts or calyx. Intercommunicating and noncommunicating cysts are seen occasionally. Calculi may be seen within the cysts.

INTRAVENOUS UROGRAPHY (IVP)

It will also confirm non-function, but seldom used in pediatrics. RETROGRADE URETEROGRAM (RUG)

It will show blind ending ureter, different from rapid change in caliber of ureter and communication with calyces seen in UPJ obstruction or other causes of hydronephrosis. DIFFERENTIAL DIAGNOSIS

1. Hydronephrosis: Calyces should communicate with each other in hydronephrosis, look for connections on ultrasound. 2. Congenital mesoblastic nephroma: Solid tumor of infancy. 3. Wilms’ tumor: Can be difficult to separate by USG, absent excretory function is key.

INCIDENCE

The frequency of MSK in the general population has been estimated to be 1 case per 5,000–10,000 population, and MSK is seen in approximately 0.5% of patients examined by using intravenous urography (IVU) for various reasons.

PROGNOSIS

CLINICAL FEATURES

Excellent when uncomplicated.

Sex: The sex predilection varies. Sometimes, the frequency is reported to be higher in males than in females, and sometimes, it is higher in females.

MEDULLARY SPONGE KIDNEY (MSK) INTRODUCTION

It is a developmental abnormality occurring in the medullary pyramids of the kidney. MSK is characterized by cystic dilatation of the collecting tubules in 1 or more renal pyramids in 1 or both kidneys. Lenarduzzi first described MSK in 1939. The etiology is unknown. Most patients remain asymptomatic, and MSK is detected incidentally on urograms unless it is complicated by infection, stone formation, or hematuria. Most cases are sporadic, but a few hereditary cases have been reported. MSK also has been documented in siblings and in several generations of families. The disease occurs in persons of all ages and is more common in males than in females.

Age: MSK usually is diagnosed in persons aged 10–30 years, although MSK has been reported in children as young as 2 years. Most patients with MSK remain asymptomatic throughout life, and the condition is discovered incidentally when IVU is performed for reasons other than the assessment of MSK. Patients with MSK are usually asymptomatic, although acidification or impaired concentration of urine has been documented. Complications such as infection, hematuria, and stone formation may be the presenting complaint in approximately 10% of patients. The frequency of calculus disease is increased and manifested by hematuria, renal colic, flank pain, fever, and dysuria.

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ASSOCIATED SYNDROMES

MSK has been associated with hemihypertrophy, EhlersDanlos syndrome, adult polycystic disease, congenital hypertrophic pyloric stenosis, Caroli disease, parathyroid adenoma, anodontia, Beckwith-Wiedemann syndrome, distal renal tubular acidosis, horseshoe kidney, Marfan’s syndrome, renal artery stenosis, pyeloureteritis cystica, and ureteral duplication. When associated with MSK, Beckwith-Wiedemann syndrome has a high rate of tumors, including Wilms’ tumor and hepatoblastoma. MSK has been reported to cause growth failure in children due to incomplete renal tubular acidosis type 1, and it accounts for hypertension in pregnancy in 1% of patients. PREFERRED EXAMINATION FIGURE 4.21: Plain KUB X-ray: Nephrocalcinosis

Plain Radiograph

It may demonstrate nephrocalcinosis. Although MSK cannot be diagnosed by using plain radiographic findings alone, the presence of linear and rounded medullary calcifications may suggest the diagnosis. The specific diagnosis of MSK cannot always be made with plain radiographic findings alone because MSK is one cause of nephrocalcinosis, which has a wide differential diagnosis. Findings: Plain radiograph findings may be normal or may demonstrate nephrocalcinosis. Nephrocalcinosis is characteristic of MSK, with several discrete pyramidal medullary calcifications occurring in clusters. When passed into the collecting systems, calculi may be seen in the renal pelvis, ureter, or bladder. Renal size is usually normal, but the kidneys can be enlarged if the condition is associated with polycystic kidney disease (Figure 4.21). IVU

The principal method for diagnosing MSK is IVU, in which discrete linear papillary densities, characteristic of MSK, are seen. IVU appearances depend on the type of tubular changes present. Changes form a spectrum that ranges from mild dilatation of the renal collecting tubules (often called renal tubular ectasia), which shows discrete linear opacities in 1 or more papillae through increasing severity of tubular dilatation and cystic changes, to gross

deformities with multiple cyst and cystlike cavities of various sizes with beaded or striated cavities extending through the pyramid from tip to base. In patients with full-blown MSK, calyces tend to be broad, shallow, distorted, and widely cupped. If calculi are present, they tend to be arranged in groups around a calyx, similar to a cluster of grapes or a bunch of flowers. Renal function decreases with subsequent poor depiction of the kidney. In view of the high incidence of nephrolithiasis in MSK, many patients have ureteral calculi. In these patients, the excretory urogram may show obstruction, calyceal distortion or destruction, and evidence of urinary tract infection. USG

Ultrasonographic (USG) and CT findings are more sensitive than plain radiographic findings in showing medullary calcifications, but they are less specific than IVU findings. The sonographic appearances of MSK are also nonspecific because hyperechoic medulla with or without shadowing has been documented in a large variety of conditions. Findings: USG findings demonstrate echogenic medullary pyramids in patients with MSK, irrespective of the presence of medullary nephrocalcinosis. The echogenic

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medulla may cast acoustic shadowing. The increased echogenicity is seen in particular at the periphery of each pyramid between the interlobar cortices. US findings can demonstrate complications related to calculus disease. CT

Findings: CT can be helpful in confirming the presence of nephrocalcinosis, when it is suggested on USG images, and CT scans can demonstrate tubular ectasia. In MSK, unenhanced CT scan findings may be normal or demonstrate medullary nephrocalcinosis. Enhanced scans may demonstrate contrast accumulation within the papillae. CT scans readily depict obstructive changes and help identify complications such as interstitial infection and abscess formation. Ill-defined areas of low attenuation representing interstitial infection can readily be distinguished from normally enhancing renal parenchyma. CT scans also can help in differentiating interstitial infection from abscess formation because abscesses appear as sharply defined low-attenuation areas with thick walls. CT scans can also help in assessing the perinephric extension of abscesses, and they can guide percutaneous drainage. Although CT has a limited role in evaluating patients with MSK, it plays a significant role in evaluating complications such as infection or abscess formation, and CT can be used to guide percutaneous drainage of these collections (Figure 4.22).

FIGURE 4.22: CECT: MSK with medullary calcification is marked by contrast

RNI

The role of radionuclide scans in MSK is limited to the assessment of renal function and to the identification of a focus of renal infection. INTERVENTION

Radiologic intervention is seldom required; however, percutaneous nephrostomy may occasionally be useful in treating a ureteric obstruction due to a calculus. Although urinary tract infection occurs in approximately one-third of symptomatic patients with MSK, renal abscess is a rare complication of the disorder. The diagnosis of renal abscess should be suspected in patients with MSK and acute pyelonephritis which do not respond to appropriate antibiotic therapy. CT scans may reveal large abscesses that require percutaneous or open surgical drainage or small abscesses that require prolonged highdose antibiotic therapy.

MRI

MORTALITY/MORBIDITY

MRI is insensitive in detecting calcification. The role of radioisotope uptake imaging is to assess renal function and to show the site of renal parenchymal scarring. CT appearances of MSK are nonspecific. MRI has a complementary role and is a useful alternative in patients who are allergic to iodinated contrast media.

Morbidity associated with MSK appears to be higher in women than in men. In the vast majority of patients, MSK is associated with a normal life expectancy. A few cases do progress, with deterioration of renal function and eventual renal failure.

MRI is poor in depicting calcification. The role of MRI in MSK is yet to be defined, but MRI may provide an alternative to IVU in patients who are allergic to radiographic iodinated contrast medium.

CALYCEAL DIVERTICULUM INTRODUCTION

Calyceal diverticulum, also known as pylogenic cysts, is typically a symptomatic and incidentally found on IVUs.

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They are found in both males and females of all ages. Calyceal diverticulums are composed of uroepithelium lined pouches that extend from the collecting system into the renal parenchyma. TYPES

They can be of three types: 1. Type I originates from the minor calyx, 2. Type II originates from the calyceal infundibulum and 3. Type III from the renal pelvis. These diverticuli may lead to urinary stasis, which may predispose the patient to stone formation or urinary tract infections. During an intravenous urogram, the calyceal diverticulum will appear opaque later in the pylographic phase. It typically remains radiopaque after the remainder of the kidney has drained due to the slow exchange of urine caused by a narrow communicating neck. The diverticulum should have a round, smoothwalled appearance. It should not be confused with a hydro calyx that develops from an infundibular stricture and has a squared off appearance. A calyceal diverticulum is a lesion that results from an out pouching of a portion of the collecting system that protrudes into the corticomedullary region. They can arise in any part of the collecting system from a fornix to the renal pelvis. Size varies anywhere from a few millimeters to several centimeters in diameter. They are uroepithelial-lined cavities that communicate via a narrow channel to a nearby calyx. They may be congenital, or acquired lesions (Figure 4.23). It is not uncommon to see calcified stones characteristically layering in the dependent portion of the diverticulum. The stones that form within the diverticulum may pass and cause symptomatic renal colic but they are typically confined to the diverticulum due to its narrow neck connection to the distal collecting system. They are regions of urinary stasis and the dependent sediment that eventually develops in a calyceal diverticulum is referred to as “milk of calcium”. Larger stones may form that are confined to the diverticulum and may be a source of chronic pain. On CT, the diagnosis is made with delayed imaging showing the diverticulum fill with contrast. Alternatively if stones are present, the patient can be rescanned in the opposite position. If the stones settle dependently, and are confined to the lesion, the diagnosis can be made in the absence of delayed imaging.

FIGURE 4.23: Retrocard ureter

TREATMENT

Management of symptomatic stone disease associated with calyceal diverticula has changed from an open surgical approach to include ESWL, percutaneous, laparoscopic or ureteroscopic techniques. The choice of therapy depends largely on the anatomic location of the diverticulum. COMPLETE URINARY COLLECTING SYSTEM DUPLICATION INTRODUCTION

It can be complicated by upper pole moiety obstruction and lower pole moiety vesicoureteral reflux. PATHOPHYSIOLOGY

Partial duplication is caused by branching of the ureteral bud prior to its connection with the metanephric blastema (“Y” ureter). The two ureters may join between the kidney and the bladder or one will end in a blind pouch. When two separate buds arise from the mesonephric duct, complete duplication occurs as each ureteric bud separately joins the metanephric blastema. This forms both upper and lower pole “moieties”.

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The Weigert-Meyer rule specifies the upper pole moeity ureter enters the bladder inferior and medial to the insertion of the lower pole moiety ureter. While uncomplicated duplex kidney is considered a normal variant, there are potential complications as in this case: a. Ectopic ureterocele of ureter draining upper pole may result in upper pole hydroureteronephrosis. b. Vesicoureteral reflux into lower pole due to abnormal development of lower pole ureter-bladder wall valve mechanism. Less commonly, the ectopic upper pole ureter may insert distal to the urethral sphincter causing continuous urinary dribbling/incontinence or an ectopic ureter may reflux. VARIETIES

Duplex kidney refers to two ureters draining one kidney. Most common (1 in 160) anomaly of the upper collecting system. Spectrum from bifid renal pelvis to complete duplication. Incomplete form with bifurcation of the ureter high (bifid renal pelvis), anywhere along the ureter (bifid mid-ureter) or near the bladder (low bifid ureter). Incomplete duplication more common than complete duplication. Weigert-Meyer rule applies if the duplication is complete: Ureteral orifice of the upper pole moiety inserts ectopically into the bladder medial and inferior to its normal location and to the ureter draining the lower renal segment. With complete duplication, the ureter draining the lower pole has a more perpendicular course through the bladder wall making it more prone to reflux. The ectopic ureter from the upper pole is prone to obstruction, reflux or both. If large, a ureterocele may block the contralateral ureteral orifice and/or the urethral orfice at the bladder neck. Ureterocele treatment is surgical. Ectopic ureterocele is a cyst like protrusion into the bladder lumen of the dilated submucosal distal portion of an ectopic ureter. Associated with duplication, usually with the upper pole moiety. Upper pole of the duplex kidney is dilated and connects with a dilated, tortuous ureter. There may be dilatation of the lower moiety due to VUR or extrinsic PUJ obstruction of the lower pole ureter by the crossing dilated upper pole ureter. At the level of the bladder, the hydroureter terminates in a round, thin-walled anechoic intravesical ureterocele.

Duplications are familial. Incomplete duplication results in no increased incidence of disease. Complete duplication results in higher incidence of UTI, VUR, parenchymal scarring and obstruction. If no reflux or obstruction, considered a normal variant. CLINICAL FEATURES

Frequently discovered during evaluation of a urinary tract infection in a child or prenatally as hydronephrosis. Results in variable to normal function with malfunction due to both dysplasia of upper pole cortex due to obstruction and/or lower pole reflux nephropathy. ROLE OF RADIOLOGY AND IMAGING

On sonography, a duplex collecting system is seen as two central echogenic renal sinuses with intervening bridging hypoechoic renal parenchyma. On CT, the two ureters can be followed on sequential contrast-enhanced images as they exit the renal sinus and extend to join each other or the bladder. With obstructed systems, the hydronephrotic segment of the kidney and the nonenhancing dilated ureter can be followed to its point of termination. MRI is useful in that the ureteral insertion can be display in multiple planes. Sonography, especially in children, is ususally sufficient for diagnosis. DIFFERENTIAL DIAGNOSIS

Renal ectopia, congenital ureteropelvic junction obstruction, megaureter. TREATMENT

Endoscopic ureterocele incision (upper pole moeity’s ureteral herniation into bladder) - relieves hydonephrosis AND re-implantation of lower pole moiety ureter into a more oblique course through bladder wall eliminating continued reflux into lower pole. DUPLICATED COLLECTING SYSTEMS INTRODUCTION

Duplicated collecting systems can be defined as renal units containing two pyelocalyceal systems associated with a single ureter or with double ureters. The two ureters empty separately into the bladder or fuse to form a single ureteral orifice.

Congenital Anomalies of Urorenal Tract Duplicated collecting systems can be unilateral or bilateral and occur in 15% of the population. Duplicated systems can be associated with a variety of congenital genitourinary tract abnormalities. Most patients are asymptomatic and genitourinary tract abnormalities are detected incidentally on imaging studies performed for other reasons. Symptomatic patients usually have complete ureteric duplication in which the ureters are prone to developing obstruction, reflux, and infection. Ureteropelvic obstruction is more common when a duplex kidney exists and can be inherited in an autosomal dominant pattern. PATHOPHYSIOLOGY

During embryogenesis, if a single ureteral bud bifurcates before bifurcation of the ampulla, a duplex kidney results with bifid pelvis or bifid ureter (Figure 4.24). If two ureteral buds arise from the Wolffian duct, a duplex kidney results with complete ureteral duplication. The ureteral bud associated with the future lower pole separates first from the Wolffian duct and the orifice progresses superiorly and laterally as a result of growth of the urogenital sinus. The common excretory duct, with the remaining ureter still attached, is taken up in to the urogenital sinus. The orifice of the ureter draining the upper pole opens medial and inferior to the orifice draining the lower pole. A duplex kidney may be drained by a single ureter or by two ureters that unite to form a single ureter or drain separately. Usually, the lower pole system is dominant; a large renal pelvis drains the lower pole through many calices. The upper pole pyelocalyceal system may have only a single calyx and a single infundibulum and drain directly into the ureter. Bifid ureters draining a duplex kidney join to form a single ureter, which can be extravesical (common; Y- shaped) or intravesical (V-shaped) and usually empties into the bladder.

FIGURE 4.24: Development of complete ureteral duplication

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Rarely, a single proximal ureter divides distally to form an inverted Y appearance. Usually, 2 ureteral orifices are observed on the same side; rarely, one of the ureters can be ectopic. Infrequently, the middle third of the ureter may be duplicated, with a single proximal third and a single distal third. Double ureters remain completely separated and in approximately 85% of patients, the upper pole ureter drains below and medial to the lower pole ureter (Weigert-Meyer rule). Certain potential abnormalities result from or are related to duplicated systems. The following are wellknown examples: • Upper pole hydronephrosis from stenosis of the upper pole ureteral orifice • Ectopic insertion of the upper pole ureter • Ectopic ureterocele of the upper pole ureter • Reflux involving the lower pole from maldevelopment of the valve mechanism. INCIDENCE

The incidence of duplex kidney appears to be 12-15% in the general population. CLINICAL FEATURES

Race: No racial predilection has been recorded. Sex: No sex predilection is found among patients with bifid collecting systems and partial ureteric duplication. The presence of double ureters appears to be 10 times more common in females. Duplex kidney with uterus didelphys has been reported in identical twins. Age: A duplicated collecting system is a developmental anomaly and patient age at presentation varies depending on the type of abnormality. Patients with duplex kidney are usually asymptomatic and duplex kidney is detected incidentally on imaging studies performed for other reasons, unless complications arise. Presentation in patients with duplicated collecting systems varies depending on the type of anomaly. Patients with duplex kidney are usually asymptomatic. Ureteropelvic junction obstruction is more common when duplex kidney exists. Giant hydronephrosis in a duplex kidney can manifest as a huge abdominal and retroperitoneal mass and, rarely, can cause hypertension.

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The incidence of vesicoureteric reflux, urinary tract infection, and parenchymal scarring is increased in patients with duplicated collecting systems; patients can present with pyrexia and dysuria. Prolapsed ureterocele associated with a duplicated ureter can cause urethral obstruction in males and females. Patients with ectopic insertion of the ureter with completely duplicated ureters can present with urinary incontinence, particularly in females. Males are always “dry” since the insertion is proximal to the sphincter. Because of the widespread use of antenatal ultrasound, duplicated collecting systems are diagnosed in utero. An ectopic ureter observed in a patient with complete ureteral duplication can present in the early stage, especially in female patients, since the ectopic ureter may insert below the sphincter or outside of the urinary tract (e.g. vagina). Duplicated ureter complicated by transitional cell carcinoma occurs in the elderly population. ANATOMICAL BASIS

When a single ureteral bud bifurcates before the ampulla bifurcates, a duplex kidney with a bifid renal pelvis or bifid ureter results. If two ureteral buds arise from the Wolffian duct, a duplex kidney with complete ureteral duplication ensues. TERMS RELEVANT TO DUPLEX COLLECTING SYSTEMS

1. Duplex kidney: The duplex kidney has a single renal parenchyma drained by two pyelocalyceal systems. 2. Upper or lower pole: The poles represent one component of a duplex kidney. 3. Duplex system: The kidney has two pyelocalyceal systems and is associated with single or bifid ureters (partial duplication) or two ureters (double ureters) that drain separately into the urinary bladder (complete duplication). 4. Bifid system: Two pyelocalyceal systems join at the ureteropelvic junction (bifid pelvis) or the 2 ureters join before draining into the urinary bladder (bifid ureters). 5. Double ureters: Two ureters open separately into the renal pelvis superiorly and drain separately into the bladder or genital tract.

6. Upper and lower pole ureters: The upper pole ureter drains the upper pole of a duplex kidney while the lower pole ureter drains the lower pole of a duplex kidney. PREFERRED INVESTIGATIONS

Plain Radiography

Plain radiography makes no major contribution but a renal mass may be apparent because the duplex kidney is almost always longer than the nonduplex kidney. Hydronephrotic upper or lower pole moiety in a duplicated collecting system can also be observed as a renal mass. Features: The duplex kidney is almost always longer than the nonduplex kidney. In a duplicated collecting system, hydronephrotic upper or lower pole moiety can be observed as a renal mass. Limitations: Plain radiographs can demonstrate a renal mass, which is a nonspecific finding. IVU/ Excretory Urography

IVU findings are almost always diagnostic in most patients. Difficulty may arise when function is poor or absent in one of the moieties. Features: A duplex kidney is usually longer than the nonduplex kidney. Parenchymal thickness of one of the poles of the duplex kidney is less than the thickness of the other pole. The calyces are asymmetric. An ectopic upper pole ureteric insertion can cause a nonopacified segment. This mass effect results in the “drooping lily” sign with the depression of the lower pole pelvicaliceal system (Figure 4.25). If the lower pole of the duplex kidney is poorly functioning or nonfunctioning, the lower pole collecting system may not opacify and no discernible parenchyma surrounds it (nubbin sign). This may resemble a nonduplicated kidney with a lower polar mass or renal infarct. Reduction in the number of calyces, depiction of a portion of the collecting system, and the presence of a straight inferior border help differentiate a duplicate collecting system from a renal mass. Anomalies of the ureter, such as partial or complete ureteral duplication, may be demonstrated.

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Ultrasound findings provide excellent anatomic information but do not necessarily differentiate a bifid renal pelvis from a bifid ureter or two complete ureters. A large Bertin column can mimic a duplex collecting system on CT. It is valuable in evaluating an intravesical ureterocele, either orthotopic or ectopic. Features: The duplex kidney appears as two central echo complexes with intervening renal parenchyma. Hydronephrosis of one pole is suggestive of a duplex kidney. Although hydronephrosis can occur in either pole, it is more common in the upper pole. Occasionally, two distinct collecting systems and ureters can be observed on ultrasound images. CT with Contrast

CT with contrast is superior to ultrasound and excretory urography in diagnosing the nubbin. FIGURE 4.25: Complete duplication of right PC system hydronephrosis of lower pole calyces

Limitations: On excretory urography, an obstructed nonfunctioning upper or lower pole may mimic a renal mass. MCU/VCUG

Ectopic ureter of a nonfunctioning moiety can be demonstrated best using voiding cystourethrogram if vesicoureteral reflux exists. Features: The intravesical ectopic ureter of a nonvisualized moiety is demonstrated better using voiding cystourethrogram. Antegrade Pyelography

Antegrade pyelography is useful in patients with hydronephrosis to demonstrate the presence of a second ureter and to determine the level of ureteric termination. Features: Antegrade pyelography: Antegrade pyelography is useful in patients with hydronephrosis for demonstrating the presence of a second ureter and to determine the level of termination. Ultrasound

Ultrasound is a noninvasive and extremely useful examination, particularly in children. The sonographic appearance of a duplex kidney is specific but not sensitive.

Features: The intervening renal parenchyma in a duplex kidney lacks a collecting system and major vessels and is termed a faceless kidney. CT can help determine whether an obstruction exists and can help assess the renal parenchyma. CT can help determine whether insertion of the duplicated ureter is intravesical or extravesical. CT can demonstrate the collecting system in the nubbin or mass effect of tissue at the pole. CT scanning is superior to ultrasound and IVU in diagnosing the lower pole nubbin. CT is helpful when function is poor or absent. Magnetic Resonance (MR) Urography

Magnetic resonance (MR) urography may be used as a primary diagnostic method in assessing a duplicated ectopic ureter and the complications associated with duplex kidneys. Spatial resolution is a limiting factor. Features: MR urography can provide information similar to that of excretory urography when renal function is poor or absent. An ectopic ureter extending from a poorly functioning moiety of a duplex kidney invisible on other imaging may be observed with MR urography. MR urography may be used as a primary diagnostic method in assessing a duplicated ectopic ureter and complications associated with duplex kidneys. Limitations: Availability of MRI is limited, the procedure is expensive, and it requires sedation of patients with

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claustrophobia. However, MR urography is an extremely useful technique in patients who have the probability of an adverse reaction to radiopaque contrast media.

ectopia, a hemitrigone is found in the bladder. With bilateral single ectopia (very rare), there is no trigone; the bladder fails to completely develop.

Scintigraphy

INCIDENCE

Scintigraphy is useful in the assessment of relative renal function and detection of renal scars.

Females to males 6:1 ratio.

Features: Duplex kidneys appear as two separate collecting systems on the same side of the body. Scintigraphy may demonstrate reflux up the ureter in a nonfunctioning duplex kidney with ureteral duplication.

The ureteral bud fails to separate from the mesonephric duct. Its orifice opens in a urogenital sinus or Wolffian duct structures, such as the bladder neck, urethra, seminal vesicles, vas deferens, or ejaculatory duct in males, and bladder neck, vestibule, or urethra in females. Ureteral ectopy into the uterus, vagina or cervix may also be seen.

Limitations: Scintigraphy can reveal differential functioning. However, if functioning is markedly depressed, imaging is limited. Arteriography

Arteriography is an invasive procedure and is no longer used to diagnose duplex collecting systems but may occasionally be useful in planning nephron-sparing surgery. Findings: Invariably, two separate arteries arise, mostly independently from the aorta. Hydronephrosis of a moiety appears as a filling defect displacing arterial branches. Arteriography is an invasive procedure and is no longer used to diagnose a duplex collecting system. MORTALITY/MORBIDITY

Most cases of duplicated collecting system are detected incidentally; however, the incidence of ureteropelvic obstruction is increased with duplex kidney, hydronephrosis, and pyelonephritis in patients with complete ureteral duplication.

EMBRYOLOGY

CLINICAL FEATURES

In males, urinary infection and obstruction but not incontinence may be experienced, since the the ureter opens above the urogential diaphragm. By contrast, urinary incontinence may be seen in females. In many cases, the diagnosis may not be made until adulthood, especially if incontinence is absent. IMAGING

Urography will demonstrate upper moiety obstruction due to a stenotic ectopic ureteral orifice in cases associated with duplication. Cystoscopy and retrograde pyelography may be used to confirm the diagnosis if the ectopic orifice terminates within the urinary tract. Otherwise, ultrasound or CT may be useful. If a single ureter is present, a nonfunctioning dysplastic kidney will be seen on the side associated with the ureteral ectopia. URETEROCELE INTRODUCTION

ECTOPIC URETER INTRODUCTION

A ureter that does not terminate at the trigone of the bladder, which is its normal location. The term is used to describe a ureter that opens outside the bladder. ASSOCIATED ANOMALIES

Eighty percent of ectopic ureters are associated with complete ureteral duplication. With unilateral single

A ureterocele is a submucosal cystic dilation of the terminal segment of the ureter. CLASSIFICATIONS

A ureterocele may be classified most easily as: 1. Intravesical, defined by its presence entirely within the bladder 2. Extravesical, defined by the permanent presence of some portion of the ureterocele at the bladder neck or urethra.

Congenital Anomalies of Urorenal Tract Other classification systems for ureteroceles are based on the location of insertion of the ureter into the bladder: 1. Simple (orthotopic) 2. Ectopic 3. Cecoureterocele 4. Pseudoureterocele. According to their morphology, ureteroceles may be: 1. Stenotic (obstructive ureteral orifice within the bladder) 2. Sphincteric (ureteral orifice at the bladder neck), or 3. Sphincteric stenotic (obstructive ureteral orifice at the bladder neck) 4. In addition, they can also be cecoureteroceles (extension of the ureterocele past the bladder neck into the urethra and may cause bladder outlet obstructions). Ureteroceles are most commonly found in association with complete ureteral duplication (80%), but they can also be seen at the terminus of a single system. The association of a fluid-filled structure within the bladder leading to an ectopic dilated ureter and a hydronephrotic upper pole of a kidney is the sine qua non of a ureterocele associated with a duplicated system. The function of the upper pole segment is variable depending on the relative degree of obstruction caused by the ureterocele. A ureterocele associated with the upper pole moiety is located medially and inferiorly to the lower pole ureter inserting in a more superolateral location (WeigertMeyer rule). Aphorism: UU-LR, i.e. upper moiety is associated with ureterocele and obstruction and the lower moiety with reflux, in which case the draining moiety is dysplastic. Intravesical single-system ureteroceles are typically associated with good renal function (>80% with excretory function), whereas extravesical single-system ureteroceles are seen with poor renal function ( cystine or uric acid. Usually associated with recurrent urinary tract infections from bacterial pathogens that produce alkaline urine (thus, F>M cases). Staghorn can be disrupted if infection complicates obstruction related to the stone. Renal enlargement from pyonephrosis or xanthogranulomatous pyelonephritis may produce a fragmented staghorn.

3.

4.

5. 6.

7.

8.

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therefore, metabolic evaluation is indicated. Combined obstruction and infection frequently cause renal destruction and, potentially, renal failure if both kidneys are affected. Uric acid stones account for 5–10% of urinary stones. These small smooth stones usually appear radiolucent on conventional radiographs but opaque on CT scans. Predisposing factors include acidic concentrated urine, excess urinary uric acid, smallbowel disease or resection, gout, and cell lysis (e.g., resulting from treatment of leukemia or from starvation). Treatment and prevention for these stones is alkalinization and dilution of the urine. Cystine stones account for only approximately 1% of urinary stones. These ground-glass stones, which result from cystinuria (a rare autosomal recessive metabolic disorder), are homogeneous; less opaque; and less fragile than other stones, especially if they are smooth. Xanthine stones are relatively radiolucent stones. Several other less common forms of urolithiasis may produce stones that appear relatively lucent, even on CT scans. Inspissation of indinavir, an antiretroviral protease inhibitor used to treat HIV infection, may cause stones that appear lucent on CT scans. Matrix stones formed from inspissated mucoproteins in patients with a chronic Proteus infection may demonstrate soft tissue attenuation on CT scans. Stones can also be caused by metabolic byproducts and drugs (e.g. sulfa drugs, salicylates, triamterene ephedrine). Orotic acid stones are rare to occur.

INCIDENCE

Renal calculi occur in 5–12% of the population, and they are bilateral in 10–15% of patients. The prevalence of urinary lithiasis is as high as 2–3% in the general population. A slightly lower prevalence of urinary stones is found in less developed countries, possibly because of diets lower in protein. CLINICAL FEATURES

• Acute ureteral obstruction by stone causes severe colicky (intermittent) flank pain that can radiate throughout the groin, testicles, back, and periumbilical region.

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• Some patients with renal calculi may have no symptoms at all • Hematuria • Occasionally, recurrent infection may result in pyelonephritis or abscess. Stones can result in renal scarring, damage, and renal failure. • They are also more prevalent in highly developed countries, possibly as a result of a higher protein diet. • Sex: Males are at a greater risk than females, with a male-to-female ratio of 3:1 (except for struvite stones and in black populations). • Age: Stones the peak age for development is in persons aged 40–60 years. DIFFERENTIAL DIAGNOSIS

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28.

Appendicitis (Figure 6.1) Cholecystitis, acute Cholelithiasis Colon, diverticulitis Crohn disease Duodenum, ulcers Epididymitis Gastric ulcer Gout Meckel diverticulum Midgut volvulus Nephrocalcinosis Obstructive uropathy, acute Ovarian torsion Ovarian vein thrombosis Pancreatitis, acute Pancreatitis, chronic Papillary necrosis Pelvic inflammatory disease/Tubo-ovarian abscess Renal cell carcinoma Renal vein thrombosis Retroperitoneal fibrosis Testicular torsion Transitional cell carcinoma Tuberculosis, Genitourinary tract Ureterocele Ureteropelvic junction obstruction, congenital Vesicoureteral reflux

FIGURE 6.1: KUB film: Appendicolith

29. Wilms tumor 30. Xanthogranulomatous pyelonephritis. ROLE OF RADIOLOGY AND IMAGING

The goals of imaging are to determine the presence of stones within the urinary tract, evaluate for complications, estimate the likelihood of stone passage, confirm stone passage, assess the stone burden, and evaluate disease activity. When acute flank pain suggests the passage of a urinary stone, many methods of examination can be used. Often, conventional radiography is initially used to screen for stones, bowel abnormalities, or free intra-abdominal air. Radiographs can also be used to monitor the passage of visible stones. IVU (excretory urography) provides important physiologic information regarding the degree of obstruction. Ultrasonography (USG) is useful in young or pregnant patients and in patients allergic to iodinated contrast material. USG is also helpful in problem solving. All of these methods have become less useful with the advent of more sensitive and specific nonenhanced CT scanning. When CT is available, it is now considered the examination of choice for the detection and

Calculus Diseases of Kidney localization of urinary stones. Almost all studies conducted to date show that IVU provides no additional clinically important information after nonenhanced CT is performed. As a result of the higher radiation dose of CT, conventional or digital radiography should be used to monitor the passage of stones if radiographic followup studies are indicated and if the stone is visible on conventional radiographs. Conventional Radiography

Conventional radiography is often performed as a preliminary examination in patients with abdominal pain possibly resulting from urinary calculi. These images should be obtained before contrast material is administered to prevent obscuring calcifications within the collecting system or calyceal diverticula. Conventional radiographs should include the entire urinary tract, and, often, 2 images are required. Stones are often found at key points of narrowing such as the UPJ, the ureterovesical junction (UVJ), and the point at which the ureter crossing the iliac vessels. An addition site is on the right side where the ureter passes through the root of the mesentery. Calcium stones as small as 1–2 mm can be seen. Cystine stones as small as 3–4 mm may be depicted, but uric acid stones are usually not seen unless they have become calcified. An erect or posterior oblique radiograph obtained on the side of the calcification may help in distinguishing urinary stones from extraurinary calcifications. This view can also depict calcifications that are projected over the sacrum or transverse processes on the frontal view. (Figure 6.2). Preinjection renal tomography may depict additional stones, and it can be used to confirm the relationship of stones to the kidneys. Because stones are more visible with a lower peak kilovoltage (kVp), maintaining a maximum of 60–80 kVp is best, if possible. Larger patients may require a higher peak kilovoltage for acceptable exposure and scatter. In this situation, compression of the abdomen and collimation is critical. Mild bowel preparation may be helpful for increasing the sensitivity of conventional radiography for small stones

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in patients undergoing screening or follow-up observation for stones. Typically, phleboliths are round or oval, and they may demonstrate a central lucency. However, they are often difficult to distinguish from ureteral calculi. Phleboliths in the pelvis are usually located lower than and lateral to the ureter, but they overlap with the ureter. Because gonadal veins parallel the upper ureters, contrast enhancement may be needed to opacify the ureter and demonstrate the extraurinary location of phleboliths in the gonadal veins. Although 90% of urinary calculi are opaque on abdominal radiographs, the sensitivity for the prospective identification of individual stones is only 50–60%, and the specificity is only approximately 70%. Approximately 10% of stones are radiolucent on conventional radiographs. Limitations Because of the higher radiation dose with CT, conventional or digital radiography should be used to monitor the passage of stones if radiographic follow-up is believed to be indicated and if the stone is visible on conventional radiographs. Pregnant or pediatric patients

FIGURE 6.2: KUB film: Multiple small ‘gravel’ calculi in right kidney, right lower ureter and in the right ureterocele

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may be imaged with US first to avoid radiation exposure. The rare false-negative finding is usually due to reader error or a protease-inhibitor CT-lucent stone. Falsepositive results are usually due to phleboliths adjacent to the ureter. In some cases, intravenous contrast material may be needed to opacify the ureter. Intravenous Urography

IVU is useful for confirming the exact location of a stone within the urinary tract. IVU depicts anatomic abnormalities such as dilated calyces, calyceal diverticula, duplication, UPJ obstruction, retrocaval ureter, and others that may predispose patients to stone formation or alter therapy. Because contrast agents can obscure stones in the collecting system, scouting the entire urinary tract prior to their administration is critical. When an acute urinary stone is the primary consideration, compression may not be used to increase sensitivity for detection of low-grade obstruction. A caveat is that the contralateral kidney may have an abnormality that requires ureteric compression for adequate examination. In rare cases, the use of compression has been associated with forniceal rupture. When a stone causes acute obstruction, an obstructive nephrogram may be present. This may be prolonged and hyperopaque, with increasing opacity over time. The nephrogram of acute obstruction is usually homogeneous, but may also be striated or occasionally not visible on radiographs. Other signs include delayed excretion, dilatation to the point of obstruction, or blunting of the calyceal fornices. Immediately after the passage of a stone, residual mild obstruction or edema can be detected at the UVJ. Delayed images may be needed to opacify to the point of the obstruction, but using gravity to position the more opaque and more distal contrast material–laden-urine is also possible by placing the patient in a prone or erect position. Extravasation of urine at the fornices may result in pyelosinus or pyelolymphatic extravasation, which is often first indicated by blurring of the calyceal fornices. Greater extravasation may outline the collecting system, and the contrast may dissect into the perinephric space; however, if the urine is not infected, this is usually clinically insignificant.

FIGURE 6.3: IVU: Large right lower ureteric calculus with nonfunctioning right kidney with focal caliectasis at upper pole of left kidney

Limitations IVU is the traditional examination for the assessment of urinary stone disease, and it does provide physiologic information related to the degree of obstruction. The radiation dose is generally smaller than that of CT, but it is of the same order of magnitude. Intravenous contrast is required, with resultant risks of an allergic reaction or nephrotoxicity. IVU is less sensitive than CT, especially for small or nonobstructing stones (Figures 6.3 to 6.5). Ultrasonography

On sonograms, stones are demonstrated as bright echogenic foci with posterior acoustic shadowing. Stones are visualized fairly well with USG in the kidneys and the distal ureter at or near the UVJ, especially if dilatation is present. USG is good for the visualization of complications such as hydronephrosis (or other signs of obstruction); however, some patients with acute obstruction have little or no dilation. In particular, USG is helpful in evaluating those with renal insufficiency or contraindications for the use of contrast media; however, USG is often skipped in favor of nonenhanced CT.

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or after forniceal rupture. Absence of the ureteral jet, as visualized with color Doppler on the symptomatic side, is presumptive evidence for a high-grade obstruction in a well-hydrated patient. USG is very insensitive for stones, especially stones smaller than 2 mm, stones at the UPJ, or stones in the mid ureter. Fowler et al suggest that USG has a sensitivity as low as 24%, compared with nonenhanced CT. Furthermore, estimations of stone size may not be accurate. Compared with nonenhanced CT, USG is more dependent on the operator’s ability and more time consuming.

FIGURE 6.4: Lateral view (overlapping of PCS on spine)

Limitations: USG has limited sensitivity for smaller stones, and does not depict the ureters well. It should be used mainly in patients who are young, those who are pregnant, or those undergoing multiple examinations (eg, patients with spine injury). CT

With a sensitivity of 94–97% and a specificity of 96– 100%, helical CT is the most sensitive radiologic examination for the detection, localization, and characterization of urinary calcifications; therefore, helical CT is considerably more effective than IVU. Helical CT scans frequently depict non-obstructing stones that are missed on IVU (Figure 6.6). CT is faster and no contrast agent is needed in most patients.

FIGURE 6.5: IVU: Filling defect of calculus seen in left lower ureter with mild left hydronephrosis

In addition, USG is good for characterizing lucent filling defects that are visualized as stones on IVU. However, USG does not provide direct physiologic information regarding the degree of obstruction. Doppler imaging may demonstrate a high resistive index in acute obstruction, but this may not occur immediately

FIGURE 6.6: Non-contrast spiral CT scan section showing small nonobstruction bilateral renal calculi

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FIGURE 6.7: Non-contrast CT: Left staghorn calculus

CT easily differentiates between non-opaque stones and blood clots or tumors (compared with IVU, which may depict only a filling defect) (Figure 6.7). In addition, helical CT is better than USG or IVU in detecting other causes of abdominal pain. In fact, in most studies, IVU added little or no information. Rarely, pure matrix stones may demonstrate softtissue opacity on CT scans, and indinavir stones appear lucent. However, all other stones appear opaque on CT scans.

To discern between phleboliths and urinary stones, 50 ml of low-osmolar contrast agent should be administered. After 3–5 minutes, a 5 mm helical scan is obtained through the area of concern. Fewer contrastenhanced studies are needed with increasing experience. Soft tissue around the rim of a calculus can differentiate it from a phlebolith. A phlebolith may have a comet tail of soft tissue extending from it; this finding differentiates it from a calculus. On CT scans, phleboliths do not have radiolucent centers, as often seen on plain radiographs (Figures 6.8 and 6.9). When contrast-enhanced scans are required to evaluate pain not related to stones, routine abdominal and/or pelvic CT should be performed. In this situation, 100-150 ml of a low-osmolar oral and rectal contrast agent is used, and a 5 mm helical CT scan is obtained with

CT Protocol for Calculus Disease

Because stones in the collecting system may be obscured by contrast material, nonenhanced CT is usually performed. Helical CT is important to avoid missing stones because of section misregistration. A 5 mm helical technique with a pitch of 1.5:1 or less is preferred, although some radiologists choose to use a pitch of as much as 2:1. The kidneys and, if possible, the entire abdomen should be scanned during a single breath hold to prevent section misregistration. Because patients with stones are often young and because stone disease may recur, minimizing the radiation dose is critical. A fairly high level of noise as a result of the inherently high contrast levels is tolerable in most patients. Reported radiation doses for CT are 2.8–4.5 mSv compared with 1.3–1.5 mSv for a 3-image IVU. However, the uterine dose is approximately 0.006 Gy for 4 image IVU compared with 0.0046 Gy for nonenhanced CT.

FIGURE 6.8: Non-contrast CT: Calculus in right lower ureter

FIGURE 6.9: Non-contrast CT: Tiny right UVJ calculus pouting in bladder

Calculus Diseases of Kidney a pitch of 1.5:1. Patient selection determines the number of examinations needed. Stones at the UVJ may be difficult to distinguish from stones that have already passed into the bladder. If the distinction changes therapy, a repeat scan through the UVJ in the prone position may be helpful. Stones that have already passed into the bladder will drop into a dependent location. CT findings 1. Stones in the ureter 2. Enlarged kidneys 3. Hydronephrosis (83% sensitive, 94% specific) 4. Perinephric fat stranding ± fluid (82% sensitive, 93% specific) 5. Ureteral dilatation (90% sensitive, 93% specific) 6. Soft-tissue rim sign (good positive predictive value with a positive odds ratio of 31:1) 7. White pyramid sign absent. The amount of perinephric fluid is correlated with the degree of obstruction seen on IVU, and as with the obstruction, the amount of fluid is correlated with the likelihood of stone passage. Normal hyperattenuating renal pyramids sometimes are seen. These indicate that significant obstruction is not present. However, this finding has been seen with proven ureteral calculi and is often absent in patients without stones. For this reason, the usefulness of IVU is limited. If contrast material is administered, a delayed or hyperattenuating nephrogram may also be visible on CT scans if the ureter has an obstruction. Conventional radiography may be helpful in visualizing larger stones, once they are identified on CT scans, to provide a baseline to follow passage of the stone. If kidney, ureter, and bladder radiographs fail to depict the stone, CT may be needed to follow its passage. Approximately 40–55% of stones are not visible on abdominal radiographs. Almost no stones with attenuation values of less than 200 HU are visible, and repeat CT scans are usually required if passage of the stone is to be followed. Cystine and urate stones have an attenuation of 100-500 HU; calcium stones usually demonstrate attenuation higher than 700 HU. Considerable overlap exists in the CT attenuation values of calcium stones. Individual CT signs are associated with varying degrees of confidence, as noted in CT findings above.

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Limitations Nonenhanced CT results are usually diagnostic, but if contrast material is needed, actions can be taken to decrease the risk of an adverse reaction in patients. The patient can be premedicated with steroids and histamine blockers. Use of low-osmolar contrast agent also helps. Use of iodinated contrast agents should be avoided in patients who have had previous life-threatening reactions. Nonenhanced CT is usually sufficient with the aid of USG and MRI as problem-solving tools. Nuclear scintigraphy may also be helpful in confirming obstruction. Usually, in patients with renal insufficiency, nonenhanced CT is sufficient. Very poor renal function results in a failure to opacify the collecting system. As in pregnant patients, USG, MRI, and scintigraphy can be useful as problem-solving tools MRI

Stones are not directly visible on MRIs because they produce no signal. However, they may be indirectly visualized as a filling defect in the ureter or collecting system on heavily T2-weighted images or on gadoliniumenhanced T1-weighted images. MRI can be useful as a problem-solving tool if the use of iodinated contrast material or radiation is contraindicated (e.g. during pregnancy). RNI

Nuclear medicine studies may demonstrate the retention of activity in the cortex or collecting system when the obstruction is ongoing. Nuclear medicine tests are useful in determining differential renal function for treatment planning and for assessing how much renal function might return after the obstruction is relieved. For example, a kidney with very little function might be removed if very little function persists after a trial of drainage. Occasionally, confirming the obstruction with nuclear medicine studies is useful if the administration of iodinated contrast material is contraindicated. INTERVENTION

Retrograde or antegrade pyeloureterography may be indicated if the collecting system cannot be opacified otherwise. This becomes much less useful as a diagnostic

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examination when CT is available. Retrograde stent placement is indicated if obstruction is present with proximal infection (pyonephrosis). Stent placement is performed to prevent sepsis and irreversible renal damage. If retrograde stent placement is unsuccessful, nephrostomy or antegrade stent placement serves as a reliable backup.

whereas stones larger than 8 mm pass in only approximately 20% of patients. Occasionally, recurrent infection may result in pyelonephritis or abscess. Stones can cause renal scarring, damage, or even renal failure if they are bilateral. In 10% of patients, stones recur within 1 year. This percentage increases to 50% within 10 years.

SPECIAL CONSIDERATIONS

RADIOLUCENT UROLITHIASIS

In the diagnosis and treatment of kidney stones, special concerns exist in patients who are pregnant, in those who have contraindications to the use of contrast media, and in those with renal insufficiency. Pregnancy does not predispose patients to stone formation; however, stone formation is a complication in as many as 0.05% of pregnancies, and the diagnosis may be difficult to establish with imaging because of the displacement and obscuration of organs by the enlarged uterus and fetus. Consider using USG first in a pregnant patient, especially in the first trimester. IVU can be used, but the views should be limited to scout and 10 to 30 minute images if possible. CT can also be useful, and the radiation dose may be justified (especially if the clinical picture is confusing), because any fetal damage is unlikely at the typical radiation doses. Minimize the dose by increasing the pitch and decreasing the milliamperage. MRI may be a useful tool for problem solving.

The prevalence of urolithiasis is approximately 2 to 3 percent in the general population, and the estimated lifetime risk of developing a kidney stone is about 12%. The classic presentation of renal colic is excruciating unilateral flank or lower abdominal pain of sudden onset that is not related to any precipitating event and is not relieved by postural changes or nonnarcotic medications. With the exception of nausea and vomiting secondary to stimulation of the celiac plexus, gastrointestinal symptoms are usually absent. Approximately 75% of urinary calculi are composed of calcium oxalate, calcium phosphate, or a mixture of the two. Phosphate-containing stones account for about 15% of urinary calculi, with struvite (magnesium ammonium phosphate) being the most common. Uric acid stones account for approximately 5 to 10% of urinary calculi. The radiodensity of ureteral calculi also clearly affects their visibility on plain radiographs. In general, calcium phosphate stones have the greatest density, followed by calcium oxalate and magnesium ammonium phosphate. Cystine calculi are only mildly radiodense. Uric acid stones and matrix stones are usually entirely radiolucent. It has been estimated that most (85–90%) of all renal stones are radiopaque. There are several modalities used to make the diagnosis of urolithiasis. With its increasing availability and technical superiority, helical CT has been shown to be more accurate than KUB radiography, IVU, and US for the diagnosis of ureteral calculi. It has been proposed that because of its safety, speed, cost-effectiveness, accuracy, and ability to assess other potential causes of flank pain, nonenhanced helical CT should replace IVU, in most instances, as the most effective study used for the diagnosis of ureteral calculus disease. Furthermore, essentially all stones, including uric acid stones, appear dense on CT.

MORTALITY/MORBIDITY

Passage of a renal stone is the most common cause of acute ureteral obstruction. When this occurs, pressure in the collecting system and renal blood flow acutely increase, followed by decreased blood flow after 1–2 hours. Hematuria usually occurs. This can be intermittent or persistent and microscopic or gross. However, as many as 10% of patients with acute stones may not have hematuria. Acute ureteral obstruction by stone causes severe, colicky (intermittent) flank pain that can radiate throughout the groin, testicles, back, or periumbilical region. Some patients with renal calculi may have no symptoms at all. Stones smaller than 4 mm pass spontaneously in approximately 80% of patients. Stones that are 4–6 mm pass in approximately 50% of patients,

Calculus Diseases of Kidney The primary use of CT in suspected renal stone disease is to differentiate stones from other causes of filling defects. Uric acid, xanthine, and cystine stones that are radiolucent on plain film are appropriately identified as high density on CT, with densities of 100 to 600 Hounsfield units (H). Uroepithelial tumors usually range from 8 to 30 H unenhanced, whereas blood clots are typically 50 to 65 H with or without contrast. In other cases of obstruction, CT demonstrates the dilated collecting structures, delayed excretion of contrast agent, as well as calculi, tumor, or extrinsic masses. In addition to its sensitivity, a helical CT of the entire urinary tract can be performed in 30 seconds, allowing a diagnosis to made much faster than urography, sonography, or radiography. CT for flank pain identifies an alternative diagnosis up to 50% of the time, and typically exposes the patient to less than half the radiation of an intravenous urogram with nephrotomography. A circumferential rim of ureteral tissue (tissue rim sign) is seen around 90% of stones less than 4 mm in diameter, helping distinguish stones from phleboliths. Secondary signs such as unilateral hydronephrosis, unilateral hydroureter, unilateral perinephric stranding, and unilateral nephromegaly may also be seen. In fact, hydroureter with ipsilateral stranding around the kidney or ureter has a positive predictive value of 98% for the presence of ureteral stone, and the absence of these two findings has a negative predictive value of 93%. Stones >4 mm in the upper ureter are less likely to pass spontaneously, and are often associated with intractable nausea, vomiting, and fever. In the case of giant hydronephrosis, defined as the presence of more that one liter in the collecting system, nephrectomy is often performed due to severe renal failure. Giant hydronephrosis is seen more on the left than the right, and more commonly in males than females. Typical etiologies include PUJ obstruction, congenital abnormalities, or stones. The first diagnosis is often erroneous, with entities such as ovarian cysts or hepatic cysts considered initially. NEPHROCALCINOSIS INTRODUCTION

This was a termed coined by Albright in 1934 to describe the deposition of calcium salts in the renal parenchyma

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in hyperparathyroidism. The term has now acquired more of a radiologic concept and is used to describe diffuse, fine, renal parenchymal calcification that is radiologically demonstrable. This appearance is different from that of calcification within the lumen of the collecting system, ureter, and bladder, which represents nephrolithiasis. Many causes of nephrocalcinosis have been added since the original description. These include the several causes of hypercalcemia and hypercalciuria. Nephrocalcinosis can be subdivided into the cortical type, which is classically the result of acute tubular necrosis (ATN), and the medullary type, which may be an extension of cortical nephrocalcinosis or seen in isolation with several metabolic disorders. In nephrology, the term nephrocalcinosis is applied only to the medullary type. Nephrocalcinosis can be demonstrated on plain radiographs, sonograms, or CT scans. CT is the most accurate and sensitive technique and therefore the modality of choice. It can be unilateral or bilateral. PATHOPHYSIOLOGY

Disorders of Calcium Metabolism

Disorders of calcium metabolism, such as hypercalcemia and hypercalciuria, may induce the formation of calcium renal stones and deposition of calcium salts in the renal parenchyma (nephrocalcinosis). The extensive deposition of calcium may lead to chronic tubulointerstitial disease and renal insufficiency. The first signs of damage induced by hypercalcemia are seen at the intracellular level, in the tubular epithelial cells. This results in mitochondrial distortion, and eventually, calcium deposits can be demonstrated within the mitochondria, the cytoplasm, and the basement membrane. Calcified cellular debris results in occlusion of the tubules, leading to obstructive atrophy of the nephron, nonspecific inflammation, and interstitial fibrosis. Impaired urine drainage through calcified tubules may result in areas of cortical atrophy leading to scared cortices. Functional abnormality of urine concentration is the earliest detectable renal change. This effect is related to decreased chloride transport in the ascending thick segment of the nephron. Other defects of tubular function, such as tubular acidosis and salt-losing nephritis, may also occur.

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The continuing and unchecked deposition of calcium eventually leads to chronic renal insufficiency. Nephrocalcinosis may be complicated by renal stone formation, which adds another element to the causation of renal insufficiency secondary to an obstructive uropathy. The histologic findings include calcium phosphate or calcium oxalate crystal deposits that mainly appear in the renal interstitium, but deposits may also be seen within the renal tubules. Special stains, such as von Kossa and Pizzolato stains, can be used to specifically depict these deposits.

7. 8. 9. 10.

11.

CAUSES OF CORTICAL NEPHROCALCINOSIS

1. Acute cortical necrosis: This can follow placenta abruptio, placenta previa, septic abortion, transfusion reactions, burns, snake bite, severe dehydration, shock, severe heart failure, and abdominal aortic surgery. In children, the condition may follow dehydration, fever, sepsis, and hemolytic uremic syndrome. 2. Chronic glomerulonephritis 3. Alport syndrome 4. Prolonged hypercalcemia and/or hypercalciuria 5. Poisoning and toxicity (e.g. Ethylene glycol (antifreeze) poisoning) 6. A severe form of primary hyperoxaluria 7. Methoxyflurane anesthesia toxicity 8. Rejected renal transplants can give rise to cortical necrosis. 9. Sickle cell disease is a rare cause of cortical nephrocalcinosis. Sickle cell disease is related to infection. 10. Vitamin B6 (pyridoxine) deficiency can be associated with xanthurenic aciduria related to deficiency of phosphate dependent enzyme kynureninase. Vitamin B6 (pyridoxine) deficiency is another cause of secondary hyperoxaluria. It is a rare cause of cortical nephrocalcinosis.

12. 13. 14.

15.

CAUSES OF MEDULLARY NEPHROCALCINOSIS

1. 2. 3. 4. 5. 6.

Hyperparathyroidism Medullary sponge kidney Tuberculosis of the kidneys Renal tubular acidosis Renal papillary necrosis Immobilization

16.

Milk-alkali syndrome Hypervitaminosis D Sarcoidosis Nephrocalcinosis has been described in 16% of preterm infants. On univariate analysis, gestation age, male sex, duration of ventilation, oxygen dependency, duration and frequency of gentamicin treatment, toxic gentamicin/vancomycin levels, low fluid intake, and postnatal dexamethasone were significantly associated with nephrocalcinosis. Nephrocalcinosis has been described in premature infants treated with high doses of furosemide for prolonged periods because of congestive heart failure secondary to patent ductus arteriosus or pulmonary disease. Both nephrocalcinosis and nephrolithiasis may occur. These complications occur 11–50 days after the commencement of furosemide therapy. The addition of chlorothiazide to furosemide prevents further calculi formation, and it may also lead to the dissolution of existing stones. Therefore, preterm infants who are taking furosemide should be regularly screened with renal ultrasonography. Long-term furosemide abuse can also cause medullary nephrocalcinosis in adults. Hyperoxaluria Miscellaneous causes A variety of conditions can cause bone destruction associated with hypercalcemia and hypercalciuria. These include bony metastases, multiple myeloma, Paget disease, Cushing disease, and both hyperthyroidism and hypothyroidism (though the incidence associated with hypothyroidism is low). Chronic paraneoplastic hypercalcemia may also cause nephrocalcinosis. Sickle cell anemia is a rare cause of nephrocalcinosis. A variety of radiographic renal abnormalities have been associated with sickle cell disease, including renal enlargement, thickening of the renal cortex, focal hypertrophy, papillary necrosis, and changes associated with infection. Ochronosis (alkaptonuria) is an autosomal recessive disorder involving deficiency of the enzyme homogentisic acid oxidase. It is a rare cause of nephrocalcinosis; renal stone formation is more common.

Calculus Diseases of Kidney INCIDENCE

Regarding cases of nephrocalcinosis and nephrolithiasis in children, 64% are associated with an underlying structural renal lesion or urinary tract infection, 10% are associated with hypercalcemia or hypercalcuria, 6% are associated with cystinuria, and 20% are idiopathic. Oxalosis and miscellaneous conditions may be involved. In adults, 40% of cases of medullary nephrocalcinosis are attributed to hyperparathyroidism, and 20% are attributed to RTA. The remaining 40% are divided among the other multiple causes. Conversely, 5% of patients with hyperparathyroidism have nephrocalcinosis. The medullary type accounts for 95% of all nephrocalcinosis, whereas 5% represent cortical nephrocalcinosis. In 70% of patients with RTA type I, both nephrocalcinosis and nephrolithiasis eventually develop. CLINICAL FEATURES

Sex: Both sexes are equally affected. Age: All age groups can be affected, but the disease is more common in childhood than at other times. The clinical presentation is determined by the underlying etiology of nephrocalcinosis. Most cases are asymptomatic, and nephrocalcinosis is identified as a radiologic abnormality. Renal tubular disorders may be first diagnosed on biochemical examination of the urine, which often reveals glycosuria, aminoaciduria, and phosphaturia. Polyuria and polydipsia may be the presenting features, with loss of the concentrating ability of the renal tubules. Anatomy: The basic unit of renal function is the nephron (Figure 6.1). The nephron consists of the glomerulus; the proximal convoluted tubule, the loop of Henle; and the distal convoluted tubule, which finally drains into the collecting ducts. Anatomically, the glomerulus and proximal convoluted tubules are placed in the renal cortex, while the descending loop of Henle enters the medullary tissue. The ascending loop goes back to the cortex, where it drains into the distal convoluted tubule. Finally, the distal convoluted tubule drains into the collecting ducts, which again enters the renal medulla and drains into the calyx.

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Each normal kidney contains about 1,250,000 nephrons. The gross anatomic renal functioning unit is the lobule consisting of the medullary pyramid with its base oriented toward the renal cortex, the apex oriented toward the calyx. Its sides are covered by renal cortical columns. At the glomerulus, all the constituents of plasma are filtered, except the cellular elements, and the plasma proteins and are transported via of tubules to the renal sinus. In healthy adults, 180 L of filtrate is formed per day. About 80% of the filtrate is reabsorbed in the proximal convoluted tubule, and 20% is absorbed in the distal tubular structures, dependent on antidiuretic hormone (ADH). Disorders of calcium metabolism, such as hypercalcemia and hypercalciuria, may cause extensive deposition of calcium within the renal tubules, and chronic tubulointerstitial disease and renal insufficiency may result. Calcified cellular debris results in occlusion of the tubules, leading to obstructive atrophy of the nephron, nonspecific inflammation, and interstitial fibrosis. Impaired urine drainage through calcified tubules may result in areas of cortical atrophy, leading to scared cortices. Functional abnormality of urine concentration is the earliest detectable renal change (osmolality). This is related to decreased chloride transport in the ascending thick segment of the nephron. Other defects of tubular function, such as tubular acidosis and salt-losing nephritis, may also occur. PREFERRED INVESTIGATIONS

Most cases of nephrocalcinosis are asymptomatic and usually identified on plain abdominal radiographs. Planar radiography provides a useful adjunct to plain radiography. Findings: Plain radiographic detection is not possible until the attenuation of renal parenchyma exceeds 100 HU. The calcification resolution also depends on the size of the stones (those 25,000–35,000 RBCs per highpowered field). Gross hematuria is highly suggestive and certainly warrants full investigation. Gross hematuria is present in 95% of patients, and the remaining patients have microscopic hematuria. A problem can arise when bladder trauma is presumed to be the cause of hematuria because this finding is not specific and can stem from more ominous sources such as renal fracture. Collect urine from the first few hundred milliliters of the initial sample to prevent errors in interpretation. Furthermore, always rule out urethral trauma before placing a Foley catheter, especially when

Urorenal Trauma gross hematuria is present. Suggestive findings include blood at the meatus, a high-riding prostate, the patient’s inability to void, perineal hematoma or scrotal swelling, and pelvic fracture. Bladder injury is strongly associated with pelvic fracture. Of bladder ruptures associated with pelvic fracture, 80% are extraperitoneal. Pelvic fracture is associated with bladder injury in 80% of patients, but the reverse is not true: Only 10% of pelvic fractures are associated with major bladder trauma. When a pubic rami fracture is present or if pubic symphysis diastasis is present, maintain a higher index of suspicion. A great deal of effort has been made to determine which pelvic fractures are associated with bladder injury. Patients with disruption of the pubic symphysis, pubic rami, and vertically unstable pelvic fractures have high degrees of concomitant bladder trauma, whereas those with isolated acetabulum, femur, and ileac crest fractures have a low incidence of bladder injury or rupture. ANATOMICAL BASIS

The bladder is located within the bony pelvis and in adults is considered to be a mostly extraperitoneal organ. There, the bladder, prostate, and proximal urethra are protected by one of the most secure bony enclosures in the body. It has a tetrahedral form when empty and has four primary surfaces. A superior, posterior, and two inferolateral surfaces define the shape. The superior portion is triangular and lined completely by the visceral peritoneum. This portion extends into the abdomen when distended and has little support from other structures. It is considered to be a dome when distended and contacts the uterus in the female and the sigmoid colon in addition to loops of bowel in the male. The posterior surface or fundus of the bladder is anterior to the rectum but remains mostly retroperitoneal. A male bladder has the seminal vesicles coursing between the posterior bladder wall and the rectum. The posterior base of the bladder is supported by the rectum and secured by the rectovesicular ligaments. In females, the posterior and superior surface is loosely fixed to the upper vaginal wall and uterus. The pelvic floor musculature and overlying loose areolar tissue support the inferolateral margins of the bladder.

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The pubovesicular, medial, and paired lateral umbilical ligaments strengthen the association with the anterior body wall. The space of Retzius exists anterior to the bladder. This area is loose connective tissue that allows easy mobilization of the bladder from other surrounding structures. There is little preventing motion of the bladder, in that the only rigidly fixed point is the bladder neck. This is the primary adaptation allowing distention during filling. PREFERRED INVESTIGATIONS

Radiologic examination is of paramount importance and should be performed to identify and classify the injury and to plan surgical repair, but it should not hinder patient treatment and stabilization. Several radiologic evaluations are appropriate, ranging from CT cystography to basic retrograde cystography. All have been moderately well studied and require different equipment, locations, protocols, and operator expertise. Always consider the stability of the patient’s condition with regard to airway patency and circulation during transfer and radiologic evaluation of the patient. The amount and type of radiologic evaluation required depends on the patient’s condition and on the size of the area that may be affected. Many patients in stable condition require extensive screening, thus diagnostic procedures should ideally provide views of large area with quick and common preparation. For many patients in unstable condition or those with penetrating abdominal injuries who are immediately treated in the operating theater (at the discretion of the surgeon) intraoperative radiologic evaluation is needed. Retrograde Cystography

Retrograde cystography performed after urethrography, was considered the criterion standard for evaluation of bladder trauma. However, in recent years, support has grown for using CT cystography in proper diagnosis. Initial studies were not indicative of the reliability of CT when retrograde contrast enhancement was not used. However, contemporary studies have overwhelmingly demonstrated that the technique is both sensitive and accurate, provided that adequate bladder distention with at least 300-400 mL of contrast material is achieved before

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the study is performed. In diagnosing bladder rupture, CT cystography, performed with 400 mL of contrast material administered in a retrograde fashion, is as accurate as plain radiography with retrograde cystography. Ultrasonography

Ultrasonography is not sensitive or specific enough to be useful for evaluation of bladder rupture. However, blood clots and at times site of tear in bladder wall can be depicted (Figure 9.8). Retrograde cystograms have long been used for detecting bladder rupture. They are nearly 100% sensitive for detecting rupture, provided adequate distention is accomplished and postvoiding images are obtained. However, they are time consuming, the examinations are costly when one considers value relative to the benefit, and they require extra radiography that does not occur in addition to necessary trauma evaluation. Furthermore, they are not useful in thoroughly evaluating other structures present in the abdomen and pelvis. CT Retrograde Cystograms

CT retrograde cystograms are completed in the radiology suite when routine spiral scans of the head, neck, chest, and abdomen and pelvis are performed. The same retrograde introduction of contrast agent is generally performed as with retrograde cystography. However, multiple images, including postvoiding and oblique views, are not necessary as in plain radiography. Thus, this

FIGURE 9.8: Large clot in bladder with tear in its posterior wall

procedure is less time consuming and, some would argue, less costly. At 1 hospital cited in the literature, the cost of CT cystography was $500 or more, a marginal increase over a plain radiographic examination. Costs should be specifically evaluated at each institution. A final step is the washout study. After the full-bladder findings are recorded (on radiographs or CT scans), the bladder is drained. If no residual contrast enhancement is present, the examination is completed, and the results are negative. If residual contrast enhancement is present in the bladder area, fluid (e.g. sterile water) is used to lavage the bladder. If no residual contrast enhancement is noted after drainage, the examination is completed, and the results are negative. If contrast enhancement remains, a bladder wall injury is present. CT Cystography

CT cystography may be used somewhat less often in patients not undergoing CT for another reason. In a study of 157 patients with hematuria, an absence of free fluid on abdominopelvic CT was a strong negative predictor of bladder rupture. In these patients, not performing cystography may be reasonable. Further study is warranted regarding this matter. Perhaps one of the greatest advantages of retrograde CT cystography with prior abdominopelvic CT is the ability to detect renal parenchymal injury. In these patients, intravenous urography is not necessary, as it commonly is with traditional retrograde cystography. A few studies have focused on delayed evaluation of the bladder. For example, the use of contrast material for chest and abdominal CT (for which a large amount is routinely required) has been studied. In these examinations, the contrast agent was allowed to distend the bladder in an anterograde fashion. However, this distension occurs at the expense of valuable time, because the Foley catheter should be clamped for at least 20–30 minutes to have any opportunity to achieve accurate results. Furthermore, if preexisting renal insufficiency or renal pedicle injury is present, this method may be inadequate. The author does not recommend this diagnostic strategy for the reasons mentioned. Because results of

Urorenal Trauma recent studies have also cast doubt on the consistent accuracy of this method in the evaluation of blunt trauma, its use is discouraged.

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CT evaluation. This is true especially when microhematuria is present and a possibility of renal trauma exists. MORTALITY/MORBIDITY

Limitations of Techniques

Cystography generally has served to greatly decrease trauma morbidity and mortality by helping in successfully screening for bladder rupture. Little doubt exists concerning the accuracy of plain-film cystography, as long as a bladder hematoma does not occlude a rift in the bladder wall and prevent dye from flowing out into the surrounding spaces. The primary concern is that the examination often does not occur in parallel with other radiologic examinations of patients with trauma who require CT scanning. A caveat should be noted: A normal cystogram finding does not exclude bladder rupture. At surgery, intraperitoneal or extraperitoneal extravasation may be found. The consideration in this scenario is the spasm of the detrusor muscle, which is possibly secondary to the irritation effect of the contrast medium that causes a leak to become sealed. With general anesthesia, the detrusor relaxes; this is associated with the eventual intraoperative leak. CT cystography is faster than plain radiographic studies; it has no labor-intensive requirements for completion; and it can be used to diagnose large hematomas of the bladder, which potentially could overlie an occult breech in the bladder wall. Furthermore, classification of bladder injury patterns requires CT scanning because cystography addresses perforations but not more-subtle findings. Consider the cost in each prospective hospital, because the monetary costs, which favor classic cystography, may not reflect actual benefits. For instance, because X-ray technologists currently are in short supply, increasing their use adds to the expense. Furthermore, time is valuable in the trauma setting, especially because patients in seemingly stable conditions can deteriorate quickly, and a more-rapid evaluation can facilitate their transfer to the trauma intensive care unit or operating theater. In general, the author believes that evaluation with CT cystography is the study of choice when patients already require transfer to the radiology suite for

Morbidity and mortality is most commonly infectious in nature. Therefore, complications are usually associated with bladder rupture. Bladder disruption occurs in 5-10% of patients with pelvic fractures, and the type of perforation, with respect to classification, is important to prognosis. Broadly classified, approximately 50-85% of ruptures are extraperitoneal (many of which have associated pelvic fractures), 15-45% are intraperitoneal, and only 1-10% of disruptions are both. In the event of intraperitoneal rupture, morbidity and mortality are greatly influenced by preexisting urinary tract infection. Thus, sepsis can ensue within 24 hours in certain circumstances. Treated properly with operative repair and urologic consultation, nearly all patients with intraperitoneal bladder ruptures have few or no long-term complications. URETHRAL TRAUMA INTRODUCTION

Trauma to the urethra can be attributed to guns, knives, surgical or urologic instruments, blunt trauma, straddle injuries, or penile fracture. Most male posterior urethral injuries, however, are the result of blunt pelvic trauma most often associated with a vehicular accident or a fall from a height. Most cases of anterior urethral trauma result from straddle injuries. The male posterior urethra is entirely encased within the rigid pelvis, a protective structure that must be disrupted before the posterior urethra can be damaged by blunt external trauma. The potential for urethral trauma is thus influenced by the extent of the pelvic injury, and this potential has been classified as no risk, low risk, and high risk). Examples of no risk injuries include isolated fractures of the acetabulum, ilium, or sacrum; low-risk injuries include single ischiopubic ramus or ipsilateral rami fractures; and high-risk injuries include straddle fractures or Malgaigne fractures. Overall, disruption of both the anterior and posterior sides of the pelvic ring introduces greater risk of urethral trauma.

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Damage of the posterior urethra is thought to occur as its support mechanism becomes disrupted. As soft tissue becomes compressed, the puboprostatic ligament ruptures, disconnecting the prostate from the anterior pubic arch. This mobilizes the prostate and bladder. In many cases, a hematoma develops inferior to the prostate from sheared periprostatic vessels. The prostate is then driven cephalad by the growing hematoma. The posterior urethra, however, is firmly attached to the pubic arch by the perineal membrane. The resultant shearing force stretches or ruptures the urethra in varying locations as described by radiographic findings). Anterior urethral injuries are seen in a small minority of patients because of the mobility of the anterior urethra compared with the posterior urethra. Most cases are the result of straddle incidents, in which the patient falls on the crossbar of a bike or the top of a fence. Force from the structure on the perineum compresses the corpora spongiosum and bulbous urethra against the pubic symphysis, disrupting the urethra. In some mild cases, the resulting injury will go untreated; however, a stricture develops over time. The patient presents at this time with an inability to void. In some cases, the patient is unaware of the relationship to the past straddle injury. If the Buck fascia remains intact, the injury will be limited to the space between the fascia and the tunica albuginea. If, however, the Buck fascia is also disrupted, a hematoma may spread within the confines of the Colles fascia. Thus, blood or contrast material extravasation may extend to the scrotum, perineum, or anterior abdominal wall. Contrast would not extend into the thigh because of the insertion of the Colles fascia into the fascia lata of the thigh. Penile fracture results only when the penis is erect, and the injury results in disruption of the corpora and tunica albuginea. Among women, the most common types of urethral injuries described are longitudinal tears and avulsiondistraction injuries, with the later attributed to more severe lateral compressive pelvic trauma.

INCIDENCE

Most posterior urethral trauma cases in males result from pelvic injury. Among male pelvic traumas, the reported frequency of urethral injury varies widely from 1-25% with an average of approximately 10%. Urethral injury in women with pelvic trauma is considered a less common event; however, some studies have reported incidences as high as 4-6%. Anterior urethral trauma is thought to occur less frequently due to its higher mobility, but the frequency of occurrence has not been established. ANATOMICAL BASIS

Historically, the male urethra has been divided into anterior and posterior parts, which are demarcated at the urogenital diaphragm. The proximal posterior urethra begins at the interface with the bladder, the internal urethral orifice, and the prostatic urethra. The prostatic urethra is entirely contained within the prostate and is continuous with the membranous urethra at the prostatic apex inferiorly. A principal support structure, the puboprostatic ligament, firmly attaches the prostate to the anterior pubic arch. This anatomy is important for locking the posterior urethra and prostate into their relative positions within the extraperitoneal pelvis. The membranous urethra is located within the anterior tip of the urogenital diaphragm and becomes the proximal portion of the anterior urethra after passing through the perineal membrane. The principal mechanism of continence, the external urethral sphincter, is located within the urogenital diaphragm around the membranous urethra. The Cowper glands are also located within the urogenital diaphragm adjacent to the urethra. The bulbous urethra, a swelling in the proximal anterior section, travels within the proximal corpus spongiosum and is continuous with the penile urethra. The ducts to the Cowper glands drain into the bulbous urethra. The penile or pendulous urethra extends the length of the penis where it ends as the fossa navicularis and urethral meatus. CLINICAL DETAILS

Sex: Urethral traumas are more frequent in the male population than in the female population among women,

Urorenal Trauma the most common types of urethral injuries described are longitudinal tears and avulsion-distraction injuries, with the later attributed to more severe lateral compressive pelvic trauma. Age: An age-linked risk of urethral injury associated with pelvic fracture has been shown for children younger than 15 years. The suggested cause for this pattern is the difference in pelvic fracture severity seen between children and adults. For pelvic fractures in children, approximately 56% of cases are at high risk for urethral injury. Among adults, only 24% are at high risk for urethral injury. A diagnosis of urethral trauma should be investigated in the presence of pelvic fracture, straddle injury, penetrating trauma in the vicinity of the urethra, or penile fracture. While there are no findings specific for urethral trauma, there are many that suggest its presence. Findings can include blood at the urethral meatus, gross hematuria, an inability to spontaneously void, and a high riding prostate on rectal examination. For many patients with urethral injury, extravasation of blood contained within different fascial planes is also present. ROLE OF RADIOLOGY AND IMAGING

Retrograde Urethrography

The possibility of urethral trauma should be properly investigated by retrograde urethrography. This should always be done prior to the insertion of a urethral catheter. If, however, a urethral catheter is properly in place prior to evaluation for urethral trauma, it should not be removed in order to perform urethrography. In such a case, a pericatheter urethrogram may be obtained. After a diagnosis of urethral trauma has been made, management and repair can be planned with the possible aid of other imaging modalities, such as MRI and ultrasonography. MRI has some utility in planning surgical approach for posterior urethral disruptions, and ultrasonography has been used at times to aid in the repair of urethral trauma. Limitations: While RUG provides clinically valuable information on the presence, location, and severity of

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urethral extravasation, it provides limited information about the details of surrounding soft tissue damage. Furthermore, imaging of the proximal urethra can occasionally be inadequate. This is usually caused by subpar contrast-agent filling of the proximal urethra or by gross extravasation of contrast blocking visualization of the proximal urethra. Technique: The standard imaging method used to diagnose urethral trauma is RUG. While various techniques have been described to implement RUG, the most common utilizes a Foley catheter. With this method, the patient is ideally positioned for imaging in an approximate 45° oblique angle with the penis stretched so that the meatus points cephalad. This produces a C configuration from the bladder level to meatus tip. If the penile shaft points caudad, the femur may obscure the opacified urethra. For some patients with multiple injuries, this position is unobtainable. In this case, the patient should be supine with the penis stretched perpendicular to the leg. When the image is obtained in this anteroposterior projection, however, the urethra can appear foreshortened, allowing for possible errors in interpretation of extravasation. The Foley catheter is then placed inside the urethra with the balloon inflated in the fossa navicularis. Approximately 20-30 mL of 30% contrast material is injected into the urethra, with the exposure being made during the active injection of the last few mL of contrast. Obtaining the image during the injection allows for maximum filling of the deeper bulbar, membranous, and prostatic urethral sections. In the most ideal conditions, the entire procedure should be performed under fluoroscopic control; however, in the emergent environment this is often impossible. Classification of Retrograde Urethrography Findings

The most accepted and unified classification of RUG findings for urethral injuries is the Goldman classification, with its foundation in the earlier system developed by Colapinto and McCallum (Table 9.2). The Goldman classification of urethral trauma is defined entirely on the anatomical findings of the injury and not on its mechanism.

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Uroradiology: Text and Atlas Table 9.2: Classification of urethral injuries

Grade I Grade II

Grade III

Grade IV

Colapinto and McCallum

Goldman and Sandler

Posterior urethra stretched, But intact Posterior urethral tear above Intact urogenital diaphragm (UGD) Posterior urethral tear with Extravasation through torn UGD

Posterior urethra stretched but intact Partial or complete Posterior urethral tear above intact urogenital diaphragm Partial or complete tear of combined anterior and posterior Urethra with torn UGD Bladder neck injury with Extension to the urethra Injury to bladder base with Extravasation simulating type IV (pseudo grade IV) Isolated anterior urethral injury

—

Grade IVa

__

Grade V

__

This system defines five major types of urethral injuries as seen in RUG. Type I urethral injury results when the puboprostatic ligament is ruptured, and the prostate is allowed to move superiorly. The urethra remains intact however, and is only severely stretched by the movement of the prostate. No extravasation of contrast material is seen with radiography, and continuity is maintained with the bladder. True cases of Type I urethral injury are uncommon. Type II urethral trauma is the classically described posterior urethral injury in which the urethra is torn superior to the urogenital diaphragm. In such an injury, contrast-agent extravasation is seen within the extraperitoneal pelvis, but contrast material is not present within the perineum. Here, the urogenital diaphragm is intact, preventing the spread of contrast material inferiorly. This type exists in approximately 15% of urethral trauma cases resulting from pelvic crush injuries. Type III urethral injury: The most common type of urethral trauma has proven to be type III urethral injury. Type III urethral injury, like type II, shows disruption above the urogenital diaphragm. Unlike type II, though, this injury extends through the urogenital diaphragm and includes the proximal bulbous urethra. In this injury, extravasation can be found within the extraperitoneal pelvis and within the perineum. The amount of contrast material found above or below the urogenital diaphragm

depends upon the exact location of the injury and the degree of disruption to the perineal membrane. Type II or III urethral injury can be further classified as a partial or complete urethral tear (Goldman, 1997). With RUG, partial tears are diagnosed when extravasation of contrast material occurs with the presence of contrast material in the bladder. Complete tears are diagnosed when extravasation is present and no contrast agent is present in the bladder or in the proximal torn end of the urethra. The relative frequency of partial tears versus complete tears is highly variable in the literature, and no reason for this variance has been agreed upon. Type IV urethral trauma is a tear to the bladder neck that extends into the proximal urethra. Contrast-agent extravasation is seen in the extraperitoneal pelvis around the proximal urethra. Such injuries can damage the internal urethral sphincter, resulting in incontinence. Proper diagnosis is therefore essential to ensure adequate patient care. A related injury, as described in the Goldman classification, is type IVA. This is not a urethral injury; however, it can easily be mistaken for a proximal urethral tear. In this case, the base of the bladder is disrupted, with periurethral extravasation of contrast agent. The resulting radiographs can easily mimic those of a true type IV urethral trauma. Distinguishing the two conditions is important because type IV injury is typically treated surgically and type IVA injury is not. Dynamic RUG under fluoroscopic control facilitates the differentiation.

Urorenal Trauma Type V urethral trauma describes all cases that are isolated to the anterior urethra. Such an injury occurs distal to the urogenital diaphragm and is more associated with perineal crush or straddle injuries. The resulting urethral injury is usually a partial tear of the bulbous urethra, though complete tears can also occur. In this case, contrast-agent extravasation occurs inferior to the urogenital diaphragm. If the Buck fascia remains intact, the extravasation is limited to its confines, ie, the penile shaft. If the Buck fascia is disrupted, the contrast material contained within the limits of the Colles fascia. In this case, contrast agent might be found in the lower abdomen and in the scrotum. Ultrasonography

Like MRI and CT, ultrasonography alone has not yet proven adequate and is not typically used for the primary diagnosis of urethral trauma. However, a few reports suggest that ultrasonography can be used for defining the extent of urethral damage in certain cases and for preparing for surgical repair. High-frequency probes used in sonourethrography provide a high spatial resolution; therefore, details of urethral anatomy can be studied after the injection of a saline solution. This saline solution technique uses a Foley catheter in a similar manner as described for RUG to promote distension of the urethra. The presence of saline in the urethra produces high contrast relative to the urethral mucosa. Thus, this technique allows accurate visualization of the urethral wall as well as the urethral lumen. Only a limited number of reports exist in the literature regarding the usage of sonourethrography. Such cases include the use sonography for the diagnosis of urethral trauma associated with penile fracture and in evaluating anterior urethral trauma prior to delayed urethroplasty. Sonourethrography has been shown to accurately depict trauma to soft tissues surrounding the urethra, such as the tunica albuginea. Other investigators have shown that sonourethrography can more accurately measure stricture length than RUG. This information could prove useful for planning surgical repair for specific cases.

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historically described few applications of CT in diagnosing urethral injuries. A distance of 2 cm between the prostatic apex and urogenital diaphragm was specific for type I urethral injuries. The CT findings specific for type II and type III urethral trauma were contrast-agent extravasation above the urogenital diaphragm and extravasation below the urogenital diaphragm, respectively. CT findings associated with but not specific for urethral trauma were distortion or obscuration of the urogenital fat plane, hematoma of the ischiocavernosus muscle, distortion or obscuration of the prostatic contour, distortion or obscuration of the bulbocavernosus muscle, and hematoma of the obturator internus muscle. Because many patients with generalized trauma undergo CT before a specific evaluation for urethral trauma, CT might serve as an initial screening examination for such injuries. Presently, no test supersedes RUG for the confirmation of urethral trauma. CT might help exclude unnecessary RUG. Because few studies have been conducted to evaluate the accuracy of CT in identifying urethral trauma, further investigation is necessary for a well-defined degree of confidence (Figures 9.9 and 9.10). All specific findings are found only in patients with urethral trauma. Among associated findings, distortion and obscuration of the urogenital fat plane was found in 88% of those with urethral trauma and in 3% without urethral trauma. Hematoma of the ischiocavernosus muscle was found in 88% with urethral trauma and in 17% without urethral trauma. Distortion or obscuration of the prostatic contour was present in 59% with urethral

CT

Despite the prevalent use of CT as the initial screening modality for general acute trauma, the literature has

FIGURE 9.9: Posterior urethral rupture with contrast extravasation

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Uroradiology: Text and Atlas MRI has proven clinical utility in its ability to define damage to soft-tissue neighboring the urethral trauma. Alone, however, MRI should not be used to investigate urethral extravasation or to define urethral trauma as partial or complete. INTERVENTION

FIGURE 9.10: Extraperitoneal bladder rupture

trauma and in 7% without urethral trauma. Distortion or obscuration of the bulbocavernosus muscle was present in 47% with urethral trauma and in 10% s without urethral trauma. Hematoma of the obturator internus muscle was found in 53% of patients with urethral trauma and in 13% without urethral trauma. MRI

Traditionally, MRI has not been used as an initial diagnostic tool for urethral traumatic injuries; nevertheless, some researchers have demonstrated the advantage of using MRI as a preparatory tool when planning surgical repair of urethral disruption. One of the most common methods of treatment for urethral injury is delayed reconstruction after 3–4 months of suprapubic cystotomy. After the initial delay, the surgical reconstruction is usually done with a transperineal or combined transperineal and transpubic approach with pubectomy. The approach chosen is dependent on the length of the urethral disruption, the degree of prostatic dislocation, and the amount of scar tissue present. MRI has shown positive results in evaluating the anterior-posterior, superior-inferior, and lateral displacement of the prostate; the degree of scar tissue around a urethral defect; and the precise length of a posterior urethral defect. In one study, the results of MRI preoperative evaluations changed the surgical repair approach in 26% of the patients studied. Because of its superiority in defining local disruption to adjacent tissues, MRI can be an important tool in combination with RUG in evaluating urethral trauma for management.

Interventional radiology has played only a small role in the treatment of urethral injuries. In a few situations, delayed realignment of the urethra following suprapubic diversion has been accomplished under radiological guidance. Fluoroscopic guidance for percutaneous suprapubic cystotomy has also been suggested for clinical use when the bladder is distorted by a retroperitoneal hematoma or when the bladder has been displaced superiorly. Treatment techniques for urethral tears include suprapubic cystotomy with delayed repair, immediate realignment, and immediate suturing. For suprapubic cystotomy with delayed repair, the incidence of stricture is 97%, the incidence of incontinence is 4%, and the incidence of impotence is 19%. With immediate realignment, the incidence of stricture is 53%, the incidence of incontinence is 5%, and incidence of impotence is 36%. For immediate suturing, the incidence of stricture is 49%, the incidence of incontinence is 21%, and the incidence of impotence is 56%. MORTALITY/MORBIDITY

The three most common morbidities associated with urethral trauma are stricture, incontinence, and impotence. The incidence of these morbidities is dependent on the severity of the injury and the method of management and repair. SUMMARY

Urethral trauma primarily affects males, because of the short length of the female urethra. The male urethra is divided into posterior (membranous and prostatic) and anterior (bulbous and pendulous) portions, at the urogential diaphragm. Urethral injuries are associated with high rates of stricture, impotence and incontinence. Anterior urethral injuries usually result from a low velocity, compressive injury of the perineum –e.g. a straddle injury.

Urorenal Trauma Again, blood at the urethral meatus, perineal hematoma, hematuria and difficulty in voiding are often present. RUG demonstrates contrast extravasation below the urogenital diaphragm. Primary repair of urethral injuries is associated with severe stricture formation, incontinence, and impotence. Initial treatment may consist of endoscopic realignment. Catheter drainage for several weeks is then undertaken allow healing. Subsequent treatment of short segments of scarring is frequently necessary. In the evaluation of urethral strictures, the RUG is again the initial examination. Voiding cytourethography is complementary, as it allows better distension of proximal urethral segments. Both techniques can underestimate bulbar strictures because of the oblique angle of this portion of the urethra to the beam. Sonography of the urethra is helpful in these cases to provide a more accurate measurement of the length of the bulbar stricture, which has a major impact on operative planning. Ultrasound is also useful in the assessment of penile

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scarring, or spongiofibrosis. Scanning is performed during retrograde injection of saline. Nodularity of the urethral margins, acoustic shadowing, and narrowing of the urethra all are indicative of spongiofibrosis. Posterior urethral injuries are associated with high velocity blunt force injury, pelvic fractures, and multiorgan trauma. The spleen, liver, bowel and bladder are often also injured. A spectrum of injuries occurs, from stretching and elongation of the urethra, to laceration, to transection. Exam findings include a high riding, boggy prostate, blood at the urethral meatus, and perineal hematoma. Hematuria and difficulty in voiding are also often present. Retrograde urethrogram (RUG) is the initial study of choice, and demonstrates abnormal urethral contour. Extravasation of contrast occurs in cases of laceration or transection. If the urogenital diaphragm is intact, contrast will collect in the pelvic extraperitoneal space. If the UGD has ruptured, contrast will be present in the perineum.

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RENAL NEOPLASMS (PEDIATRIC AND ADULT) CLASSIFICATION OF RENAL NEOPLASMS (TABLE 10.1)

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.

Wilms’ tumor Nephroblastomatosis Mesoblastic nephroma Ossifying renal tumor of infancy Multilocular cystic partially differentiated nephroblastoma Clear cell sarcoma Rhabdoid tumor of kidney RCC (Gravitz tumor/Hypernephroma) Multilocular cystic nephroma Renal medullary carcinoma Oncocytoma Angiomyolipoma Metanephric adenoma Lymphoma (Hodgkin and Non-Hodgkin lymphoma) Metastasis.

WILMS’ TUMOR/ NEPHROBLASTOMA

Table 10.1: Most common age at presentation for solid renal malignancies Renal neoplasm Wilms’ tumor Unilateral form Bilateral form Nephroblastomatosis Renal cell carcinoma Mesoblastic nephroma Multilocular cystic renal tumor Cystic nephroma Cystic partially differentiated nephroblastoma Clear cell sarcoma Rhabdoid tumor Angiomyolipoma Renal medullary carcinoma Ossifying renal tumor of infancy Metanephric adenoma Lymphoma Hodgkin Non-Hodgkin

Age range

Peak age

1–11 yr 2 mo–2 yr Any age 6 mo–60 yr 0–1 yr

3½ yr 15 mo 6–18 mo 10–20 yr* 1–3 mo

Adult female

Adult female

3 mo–4 yr 1–4 yr 6 mo–9 yr 6–41 yr 10–39 yr 6 d–14 mo 15 mo–83 yr

1–2 yr 2 yr 6–12 mo 10 yrt 20 yr 1–3 mo None

>10 yr Any age child

Late teens < 10 yr

* von Hippel-Lindau syndrome t Tuberous sclerosis, neurofibromatosis, von Hippel-Lindau syndrome

is the most common solid abdominal mass and by far the most common renal pediatric malignancy.

INTRODUCTION

It is a malignant, embryonic neoplasm containing epithelial, blastemal, and stromal elements. It has almost the same overall incidence as neuroblastoma, accounts for approximately 8% of all childhood malignant tumors,

INCIDENCE

Incidence is around three years of age; approximately 80% of all cases are detected between 1 and 5 years of age. An asymptomatic mass is the most common

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clinical presentation. Uncommonly, it may present as abdominal pain, anorexia, hematuria and hypertension.

tumors (multiple separate primary tumors separated in time) have a survival rate of only 40%.

GENETICS

STAGING OF WILMS’ TUMOR

Although most Wilms’ tumors are sporadic, 1% demonstrate autosomal dominance with variable penetrance. A child with a sibling or parent with bilateral Wilms’ tumor has a 30% risk for development of the tumor.

Staging of Wilms’ depends on the involvement as determined by imaging, surgery, and pathology. Anatomic staging of Wilms’ tumor is as follows: • Stage I, tumor limited to the kidney and completely resected; • Stage II, tumor extending beyond the kidney but completely resected; • Stage III, residual tumor confined to the abdomen without distant metastasis; • Stage IV, hematogeneous metastases to lung, liver, bone, brain; • Stage V, bilateral renal involvement appearing initially or during the course of treatment.

ASSOCIATIONS

Wilms’ tumor is associated with (Acronym: WHAGR) • Hemihypertrophy (overgrowth disorders) • Aniridia (Sporadic) • Genital and renal malformations. In congenital hemihypertrophy and BeckwithWiedemann syndrome (macroglossia, hepatomegaly, gigantism, omphalocele, Wilms’ tumor), the mean age of diagnosis of Wilms’ tumor is similar to that of the general Wilms’ population. However, Wilms’ tumor occurs at an earlier age when associated with aniridia and Drash syndrome (pseudohermaphroditism, renal failure). Weakly associated with Wilms’ tumor are Soto syndrome (cerebral gigantism), neurofibromatosis and Klippel-Trenaunay-Weber syndrome. PATHOPHYSIOLOGY

Wilms’ tumor is usually bulky and replaces most of the involved kidney. The renal capsule is usually intact; rarely, the tumor breaks through this capsule and extends into the extrarenal spaces. Wilms’ tumor may invade the renal vein and inferior vena cava. Venous extension of Wilms’ tumor follows the “rule of 10’s”: 10% extend into the renal vein; 10% of that group extends into the IVC; 10% of the latter further extend into the right atrium. Distal metastases most commonly involve the lungs; the liver is next most common.

ROLE OF RADIOLOGY AND IMAGING

Imaging of Wilms’ tumor should define the size and location of the primary tumor, any local spread, and any distant metastases. Imaging is also used for surveillance of individuals at risk for primary or recurrent Wilms’ tumor. Plain Radiography

Usually shows a soft-tissue mass that displaces bowel. The dystrophic calcification which occurs in 5% of Wilm’s tumors is curvilinear or amorphous is distinguished from the stippled or flaky calcifications that occur in 55% of neuroblastomas (Figure 10.1).

MORTALITY AND MORBIDITY

The most important prognostic factor in Wilms’ tumor is histology. Approximately 10% of all Wilms’ tumors have unfavorable histology with anaplasia. Wilms’ tumor is bilateral in approximately 5% of cases. Synchronous tumors (bilateral tumors at initial presentation) have a 87% survival while metachronous

FIGURE 10.1: Two well circumscribed nodules in right upper zone: Metastases from Wilms’ tumor with, haziness of mass on right side of abdomen without calcifications

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IVU

See Figure 10.2.

structures, identifies nodal involvement, and evaluates for liver metastases, and images the contralateral kidney. The tumor mass is usually rounded, low attenuation and heterogeneously enhancing. The vessels are displaced, not encased as in neuroblastoma. Abdominal CT also evaluates the renal vessels, IVC, lymph nodes, liver and contralateral kidney. Chest CT is also performed, as pulmonary metastases are present in up to 20% of patients at the time of diagnosis. CT is also excellent for surveillance after resection (Figures 10.4 to 10.6).

FIGURE 10.2: Displaced, stretched and distorted calyces due to mass involving right kidney at mid and lower pole

Ultrasound

It is usually the first imaging modality for a child with a palpable abdominal mass. Wilms’ tumor is seen as a large, sharply marginated, echogenic mass. Hypoechoic areas may represent hemorrhage, necrosis or dilated calyces. Venous extension is diagnosed when intravascular echogenic focus is identified (Figure 10.3).

FIGURE 10.4: CECT-Axial section: well-defined, rounded low attenuation mass in the right side of abdomen showing heterogenous but bright enhancement

FIGURE 10.3: Large, sharply marginated, isotohyperechoic mass involving mid and lower pole of right kidney

Computed Tomography

CT confirms the presence of an intrarenal mass, determines the extent of the Wilms’ tumor, visualized vascular

FIGURE 10.5: Coronal reconstruction image of same patient, showing lung metastases and the Wilms’ tumor, together

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FIGURE 10.6: Coronal reconstruction of thorax showing lung metastasis

Magnetic Resonance Imaging

MRI is becoming the preferred imaging modality because the multiplanar imaging capability and excellent contrast between vessels and adjacent soft tissues. In general, Wilms’ tumors are T1 dark and T2 bright. Differences between Wilms’ tumor and neuroblastoma are important (Table 10.2) Table 10.2: Differentiating features of Wilms’ tumor and Neuroblastoma Finding

Wilms’ tumor

Neuroblastoma

1. Location and epicenter 2. Shape 3. Hemorrhage and necrosis 4. Calcifications 5. Vasculature

Intrarenal Round or oval Common

Extrarenal Irregular Rare

Rare Invades

Common Encases and displaces Common Rare Common

6. Crosses midline 7. Distorts calyces 8. Retroperitoneal lymph

Uncommon Most Uncommon nodes or contiguous extension

NEPHROBLASTOMATOSIS INTRODUCTION

It is a complex abnormality of nephrogenesis. Normal developmental anatomy of the kidney occurs when the ureteric bud contacts aggregates of primitive nephroblasts (metanephric blastema) in the paraspinal region of the developing embryo. Renal development occurs as a result

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of the interaction of the advancing and bifurcating ureteric bud which branch and form the collecting system of the kidney and the metanephric blastema which give rise to form epithelial and stromal elements of the kidney. Metanephric blastema lies peripherally in the subcapsular and interlobular spaces. Nephrons and associated supporting structures arise from the metanephric blastema. Nephrogenesis is complete in the normal fetus at 34–36 weeks of gestation. Nephroblastomatosis is defined as the persistence of metanephric blastema, also known as nephrogenic rests, into infancy and childhood. Beckwith classified nephrogenic rests as: 1. Dormant (nascent), 2. Sclerosing (obsolescent) or 3. Hyperplastic/neoplastic. Thus, nephrogenic rests may regress, sclerose or become hyperplastic/mitotically active or give rise to larger and frankly neoplastic rests such as Wilms’ tumor. ROLE OF RADIOLOGY AND IMAGING

Nephroblastomatosis can be differentiated from Wilms’ tumor by its gross and microscopic appearance and imaging characteristics. Nephroblastomatosis is usually diffuse, involves the entire subcapsular portion, has no renal capsule, has a lobulated margin separating it from underlying uninvolved kidney and has a uniform pinkflesh appearance and firm consistency. On the other hand, Wilms’ tumors are usually a bulky, spherical mass, occupies one portion of the kidney with areas of necrosis, hemorrhage and macroscopic cysts. On ultrasound, nephroblastomatosis may show enlarged kidneys and hypoechoic foci in a diffuse or mutifocal pattern or normal appearing enlarged kidneys. On CT, nephroblastomatosis may appear as a multifocal or diffuse subcapsular layer of abnormal hypodense tissue. Nephrogenic rests may not demonstrate enhancement with IV contrast material. Normal enhancing renal tissue is typically seen in the central portion of the kidney (Figure 10.7). TREATMENT

Treatment options for patients with nephroblastomatosis include follow-up with ultrasound or CT every 2–6 months. Chemotherapy in nephroblastomatosis is controversial.

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FIGURE 10.7: Right sided nephroblastomatosis

Beckwith recommends use of chemotherapy in stage 1 WT and histologically proven nephroblastomatosis to decrease the size of the lesion. Although potential for malignant transformation is low, the mass effect of growing nephrogenic rests may mechanically injure the kidney. These benefits may be outweighed against the potential long-term side effects and unproven efficacy of chemotherapy. MULTILOCULAR CYSTIC NEPHROMA

General features • Best imaging clue – CECT: Multilocular cystic mass herniating into renal hilum • Plain film – Soft tissue mass (particularly if large and displaces adjacent structures) – Curvilinear/amorphous calcification CT Findings. NECT – Large/well-defined/encapsulated/multiloculated cystic mass – CT HU equal to water/higher than water (gelatinous fluid) – Solid component (CT depict very small cysts as solid component) – Curvilinear/amorphous calcification • CECT (Figures 10.8A and B) – Septa: Moderate enhancement (regular and thick) – Capsule: Enhancement – Cystic component: No enhancement (Figures 10.8A and B) (A) Cystic mass wit – Distortion of colli MR Findings • T1 WI: Multiloculated I.

Mass consisting of multiple noncommunicating cysts herniates into the renal pelvis. Key Facts

• Synonym(s): Multilocular cystic renal tumor/benign cystic nephroma • Definition: Multiple noncommunicating cysts within a well-defined capsule. Other key facts • Rare nonhereditary benign renal neoplasm • Usually solitary but rarely multiple • Location: Typically unilateral (usually lower pole) • Usually symptomatic in adults/asymptomatic palpable mass in children 0 tumor may grow slowly over years or rapidly within months • Males: Approximately 90% of tumors occur in first 2 years of life • Females: Equally divided between < 5 years and between 40 and 60 years.

FIGURE 10.8A: Schematic representation of multicolor cystic nephroma (For color version see Plate 3)

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Ultrasound Findings • Large/well-defined multiloculated cystic mass • Innumerable anechoic cysts+hyperechoic septa • Thick hyperechoic fibrous capsule • Hyperechoic areas within cystic tumor mimicking a solid component (due to numerous tiny cysts causing acoustic interfaces) Angiography Findings • Hypovascular mass (rarely avascular/hypervascular) Imaging Recommendations • NE+CECT; MR+CEMR; US. Differential Diagnosis

FIGURE 10.8B: Axial CECT section of abdomen: Large, well defined, encapsulated, multiloculated low-attenuation cystic mass in left side of abdomen with moderate enhancement of septae

• T2WI: Multiloculated / CET1WI: Enhanced excertory urography film. • Depending on size and I. – Obstructed collect 0 : Tumor herniates/p tumor of collecting Differential Diagnosis

1. Multilocular Cystic Renal Cell 2. Cystic Wilms’ Tumor 3. Multicystic Dysplasia 4. Renal neoplasm (A) Cystic mass with thick septa and wall. (B) Mass herniates into renal hilum. • Distortion of collecting system/herniation of mass into renal hilum MR. Findings

• TlWI: Multiloculated hypointense mass (fluid intensity) • T2WI: Multiloculated hyperintense mass • CET1WI: Enhancement of thick septa. Excretory Urography Findings • Depending on size and location of mass – Obstructed collecting system/pyelocaliectasis – Tumor herniates/protrudes into renal pelvis (mimicking a primary tumor of collecting system) • Tomogram of nephrographic phase: May show septations.

• Multilocular cystic renal cell carcinoma (RCc) • Usually has mural nodularity/solid component • May be indistinguishable from multilocular cystic nephroma. Cystic Wilms’ Tumor • Grows entirely by expansion of large cystic spaces within stroma • Septa: Numerous and thick. Multicystic Dysplasia • Usually involves entire kidney • Segmental multicystic dysplasia: Associated with ureteral duplication. Pathology

General • Embryology–Anatomy – Tumor arises from metanephric blastema • Etiology–Pathogenesis – Unknown – Theories of pathogenesis: Dysplasia/hamartoma/ neoplasia • Epidemiology – Rare tumor Gross Pathologic–Surgical Features • “Honeycombed” cystic areas of varied sizes/thick fibrous capsule. Non-communicating locules separated by thick fibrous septa • Mostly intraparenchymal tumors. Microscopic Features • Locules: Lined by flattened/cuboidal epithelium • Septa contains fibrous tissue + tubular elements

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• Cystic poorly differentiated nephroblastoma – Septa contain blastemal cells I other embryonal elements • Cystic nephroma: Septa have no undifferentiated elements.

• Excessive weight • Chronic dialysis use • Several genetic syndromes (familial RCC, hereditary papillary RCC, von Hippel-Lindau syndrome, and tuberous sclerosis).

Clinical Issues

PATHOPHYSIOLOGY

Presentation • Adults: Abdominal pain/I palpable mass/hematuria/ urinary tract (UT) infection • Children: Nonpainful palpable abdominal mass I hematuria UT infection . Age: Biphasic age + sex distribution • Predominantly boys in childhood and women in adulthood • Size: Few cm to > 30 cm (average size 10 cm) • Lab: U/A may show RBC/WBC • Complications: Local recurrence/obstructive uropathy/ rarely malignancy.

RENAL CELL CARCINOMA (RCC)

RCCs arise from the tubular epithelium and are usually based in the renal cortex. Several pathologic subtypes have been described, including the clear cell, papillary, granular cell, chromophobe cell, sarcomatoid, and collecting duct subtypes. These tumors vary from being nearly completely cystic to being completely solid. The imaging features reflect this heterogeneity. Bilateral RCCs are common in von Hippel-Lindau syndrome, tuberous sclerosis, and chronic dialysis; however, bilateral RCCs occur in only approximately 2% of sporadic cases of RCC. RCCs are multicentric in as many as 25% of patients. Spread by means of direct local invasion of adjacent structures, such as the adrenal glands, liver, spleen, colon or pancreas, can occur. Local regional lymph node metastases are also common. RCCs have a propensity to extend into the renal vein and, subsequently, into the inferior vena cava. The lungs are the most common sites of distant metastases. Liver, bone, adrenal gland, and kidney metastases may also occur. Typically, skeletal metastases are purely lytic and expansile.

INTRODUCTION

STAGING

It is the most common primary renal malignant neoplasm in the adult. It accounts for approximately 85% of renal tumors and 2% of all adult malignancies. RCC is more common in men than in women (ratio, 2:1), and it most often occurs in patients aged 50–70 years. One-fourth to one-third of patients have metastatic disease at the time of presentation. In only approximately 2% of sporadic cases are bilateral tumors seen at presentation, especially in von Hippel-Lindau syndrome.

RCCs can be staged by using the American Joint Committee on Cancer TNM classification, as follows: • Stage 1: RCCs are 7 cm or smaller and confined to the kidney. • Stage 2: RCCs are larger than 7 cm but still organ confined. • Stage 3: tumors extend into the renal vein or vena cava, involve the ipsilateral adrenal gland and/or perinephric fat, or have spread to one local lymph node. • Stage 4: tumors extend beyond the Gerota fascia, to more than one local node or have distant metastases. Recent literature has questioned whether the cutoff in size for stage 1 and 2 tumors should be 5 cm instead of 7 cm.

Treatment

• Surgical: Nephrectomy (complete/partial) Prognosis • Good: After nephrectomy • Few cases: Local recurrence.

RISK FACTORS

• Increased age • Male sex, smoking • Cadmium, benzene, trichloroethylene and asbestos exposure

Urorenal Neoplasms Staging of RCC (Robson vcrsus TNM staging) (Figures 10.9 to 10.13B).

Robson I

II IIIA IIIB IIIC IVA IVB

Disease extent Tumor confined to kidney Small < 2.5 cm Large > 2.5 cm Tumor spread to perinephric fat Tumor spread to renal vein or inferior vena cava Tumor spread to local lymph nodes Tumor spread to local vessels and nodes Tumor spread to adjacent organs, outside Gerota’s fascia Distant metastasis.

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ANATOMICAL BASIS

The kidney is a retroperitoneal structure surrounded by a fibrous capsule and enclosed in the perirenal space with the adrenal gland and fat. In the general population, 70–80% of individuals have single renal arteries to each kidney, and the remainders have multiple arteries. Multiple renal veins are rarer, occurring in approximately 10% of patients. The vascular anatomy becomes important whenever minimally invasive surgery or

INCIDENCE

Approximately 2% of adult malignancies.

A

B FIGURE 10.9: Schematic: Stage 1 RCC-limited to capsule (For color version see Plate 4)

FIGURES 10.10A AND B: Stage 2 RCC-Perinephric spread been (For color version for figure 10.10A see Plate 4)

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A A

B

B FIGURES 10.11A AND B: RCC with thrombus in renal vein (For color version for figure 10,11A see Plate 5)

FIGURES 10.12A AND B: RCC with thrombus up to IVC (For color version for figure 10.12A see Plate 5)

nephron-sparing surgery is considered because control of potentially bleeding vessels is paramount.

pain, or (less frequently than in the past) a flank mass. Currently, nearly half of RCCs are discovered incidentally during imaging for indications other than the assessment of RCC. In one series, 0.3% of all CT scans demonstrated incidental RCC. Incidental detection has also increased on ultrasound. Occasionally, patients present with systemic symptoms such as fever, nausea, anorexia, and weight loss. Rarely, patients have symptoms related to humoral factors such as parathormone, prolactin, erythropoietin, or renin.

CLINICAL DETAILS

Sex: RCC is more common in men than in women, with a male-to-female ratio of approximately 2:1. Age: The incidence peaks in patients aged 50–70 years, but the age distribution is broad. RCC rarely occurs in young children. Clinically, patients present with hematuria, flank

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FIGURE 10.13A: Left RCC with RV thrombosis

FIGURE 10.14: Plain radiography in case of RCC

FIGURE 10.13B: RCC with right renal vein thrombosis

PREFERRED INVESTIGATIONS

Plain Radiography

Plain radiographic findings are often unrevealing in patients with RCC unless the mass contains detectable calcification or is large enough to distort the normal renal contour. Plain radiography has no role in the primary search for RCC or in the follow-up observation of patients with RCC because of its limited sensitivity and specificity (Figure 10.14). Intravenous Urography

IVU is also limited in depicting RCCs. Large lesions, which can distort the renal contour or the collecting system, may be detected. If RCC is suggested, further imaging with CT or MRI is necessary to confirm a solid mass and to

stage the disease. If the lesion appears to be a cyst, USG is the next best test in the patient’s work-up. Findings of RCC are nonspecific and include mass effect on the collecting system, distortion of the renal contour, enlargement of a portion of the kidney, and calcifications. If good nephrotomograms are obtained at peak renal enhancement, most RCCs are less attenuating than surrounding renal parenchyma. Renal vein invasion may be inferred if contrast material excretion by the affected kidney is poor or absent. Alternatively, this finding may result from extensive involvement of the kidney or ureteral obstruction caused by mass effect. USG

The primary limitations of USG include problems related to incomplete staging (bones, lungs, regional nodes) and to the detection of small non-contour deforming masses. In addition, large patients are not good candidates for USG. For the work-up in RCC, USG is used primarily to differentiate solid masses from simple cysts and to visualize the internal architecture of lesions more effectively than can be accomplished by using CT or MRI.

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Findings: On sonograms, RCC can be isoechoic, hypoechoic, or hyperechoic relative to the remainder of the renal parenchyma. Smaller lesions with less necrosis are more likely to be hyperechoic and may be confused with AMLs. Isoechoic tumors are detected only by distortion of the renal contour, focal enlargement of a portion of the kidney, or distortion of the central sinus fat. A prominent column of Bertin or fetal lobulation may mimic a solid renal mass and can be resolved with dedicated CT or MR. CECT

Although a variety of modalities can be used in the workup of patients with suspected RCC, the preferred method of imaging these patients is dedicated renal CT. In most cases, this single examination can be used to detect and stage RCC and to provide information for surgical planning without additional imaging. Protocol: The dedicated renal CT examination consists of thin-section (2.5–5 mm) helical imaging of the kidneys before the intravenous administration of contrast agent, followed by imaging after 60-70 seconds and after 3–5 minutes. The imaging parameters (kV, mA, field of view, section thickness) should be kept constant for all phases of imaging to enable comparison of the attenuation measurements. The addition of an arterial phase CT (either with bolus tracking or after a 20–25 second delay) with thin slices (1–2 mm) may be helpful to evaluate arterial anatomy, especially if partial resection is contemplated or renal parenchymal or vascular anomalies are suspected. Findings: On nonenhanced CT scans, RCCs may appear as isoattenuation, hypoattenuation, or hyperattenuation relative to the remainder of the kidney. Calcifications may be present and are usually amorphous and internal, although rim-like calcifications can also be present. On contrast-enhanced CT scans, RCC is usually solid, and evidence of necrosis is often present. Sometimes RCC is a predominantly cystic mass, with thick septa and wall nodularity. RCC may also appear as a completely solid and highly enhancing mass (Figures 10.15 to 10.18).

FIGURE 10.15: Well circumscribed left RCC with central necrosis

FIGURE 10.16: IVC thrombus upto right atrium

FIGURE 10.17: Right RCC with extension into IVC and RRV

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than 8–10 mm in which pseudoenhancement may be a problem. In these cases, USG may be of some use in characterizing the lesions as cysts. In addition, spread to regional lymph nodes in the absence of lymph node enlargement can be missed. If contrast material cannot be intravenously administered, CT is a poor choice and MRI should be performed instead. MRI

FIGURE 10.18: Right RCC with multiple dilated vascular channels supplying it–hypervascular mass

FIGURE 10.19: Right RCC on T2 MRI

Staging of RCC, which can be performed by using CT or MRI, includes the assessment of ipsilateral or contralateral adrenal involvement, direct extension into adjacent organs, enlargement of retroperitoneal lymph nodes, invasion of the ipsilateral renal vein (with or without extension into the inferior vena cava), and distant metastatic disease (liver, bone, lungs). Retrocrural, subcarinal, or mediastinal lymph nodes can also be enlarged. Limitations: The primary limitation of CT is in the characterization of hypoattenuation in masses of smaller

Findings: MRI findings are similar to those of CT, with masses ranging from predominantly cystic with septa or nodularity to solid with enhancement. The numeric criteria for enhancement are not defined for MRI as they are for CT, but MRI signal intensity changes can be measured. On nonenhanced T1 eighted images, RCCs usually appear isointense or hypointense relative to the remainder of the kidney. With chemical shift imaging, some clear cell carcinomas show focal or diffuse loss of signal intensity. On T2 weighted images, RCCs are usually hyperintense. Most often, they are heterogeneous. The presence of necrosis or hemorrhage may alter these signal intensity characteristics. MRI may be especially helpful in imaging the superior or inferior poles of the kidneys, in direct coronal or sagittal imaging, and in determining invasion of venous structures (Figure 10.19). MRI is limited by patient cooperation because MRI is more sensitive to motion artifact than CT. In addition, MRI is more expensive and less readily available than CT. Furthermore, patients with pacemakers, those with certain types of medical implants, and those with severe claustrophobia are excluded from undergoing MRI. MRI has no advantage compared with contrastenhanced CT for the diagnosis of RCC, but MRI is superior to nonenhanced CT. RNI

Findings: In a patient with a suspected renal mass, nuclear medicine studies help in differentiating the mass from a pseudomass (e.g. column of Bertin, dromedary hump, fetal lobulation). Scintigraphy with technetium dimethylsuccinic acid demonstrates normal uptake in the region

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of a pseudomass, whereas a real mass causes a focal photopenic defect. Bone scanning with technetium methylene diphosphonate is indicated to confirm bony metastatic disease in a patient with RCC and symptoms referable to the skeleton.

Complication rates are low. Radiofrequency ablation can also be considered in patients with local recurrence. In patients considered for ablation, preprocedure biopsy may be important because, in one series, nearly 10 (nearly 40%) of 27 patients referred for ablation had a benign diagnosis.

Angiography

DIFFERENTIAL DIAGNOSIS

Noninvasive cross-sectional imaging (CT, MRI, US) has replaced angiography in the work-up of patients with known or suspected RCC. Advances in CT angiography and magnetic resonance angiography have diminished the need for preoperative conventional angiographic mapping of the renal vasculature prior to nephron-sparing or minimally invasive surgery. Angiography is still occasionally used if the origin of a tumor (e.g., renal vs adrenal) is not certain. In these patients, selective injection of the renal and adrenal arteries, as well as additional vessels, may be necessary.

Oncocytomas cannot be reliably differentiated from RCC without pathologic analysis. Macroscopic areas of fat in the tumor mass are reported in RCC, but they are extremely rare. Almost all renal tumors with measurable areas of fat are angiomyolipomas (AMLs), but some AMLs do not contain visible fat and may be mistaken for RCCs. In one series, homogeneous and prolonged enhancement were valuable predictors for differentiation of AML with minimal fat from RCC. High attenuation on nonenhanced CT scans and the degree of enhancement were helpful but less valuable.

INTERVENTION

Because RCCs are usually resistant to chemotherapy and radiation therapy, surgical resection offers the best likelihood of cure. Unresectable RCCs have a 5-year survival rate of less than 20%. When a solitary mass is noted in a patient with suspected RCC, image-guided biopsy is generally unnecessary. In one series, fine-needle aspiration of solitary proven RCC had a yield of 40% definitely malignant, 36% questionably malignant, and 24% negative tumors. In a patient with a prior malignancy, lymphoma, or multiple masses, fine-needle aspiration or core biopsy guided with CT or US may prove helpful in treatment planning. In one series, 31 of 54 biopsies performed for a new renal mass in a patient with a known malignancy proved to be RCC. Image-guided radiofrequency or cryogenic ablation has been used to treat patients with RCC, especially patients with a high surgical risk, aversion to surgery, or bilateral lesions. Recent studies have reported shortterm success rates of up to 97% with 1 or 2 ablation sessions, with size (