MEGACALYCOSIS Urology Presentation

MEGACALYCOSIS Urology Presentation
By Moussa A. Chalah

Outline Anatomy & Embryology
Megacalycosis: Definition & Clinical findings Pathophysiology Diagnosis & Differential diagnoses Management Take-Home Message

Embryology The embryonic kidneys are, in order of their appearance, the pronephros, the mesonephros, and the metanephros Embryologically, all three kidneys develop from the intermediate mesoderm At this time there is a progressive craniocaudal development of the bilateral longitudinal mesodermal masses, called nephrogenic cords, each bulging from the posterior wall of the coelomic cavity, producing the urogenital ridge The first two kidneys regress in utero, and the third becomes the permanent kidney Campbell-Walsh, CHAPTER 111, Normal Development of the Genitourinary Tract

Embryology Development of pronephros and mesonephros. A, Pronephros develops in each of five to seven cervical segments, but this primitive renal structure degenerates quickly during the fourth week. The (meso)nephric ducts first appear on day 24. B and C, Mesonephric vesicles and tubules form in a craniocaudal direction throughout the thoracic and lumbar regions. The cranial pairs degenerate as caudal pairs develop, and the definitive mesonephros contains about 20 pairs confined to the first three lumbar segments.) Modified from Larsen WJ. Human embryology. New York: Churchill Livingstone; 1997.

Embryology The pronephros, cervical region (late 3rd –early 5th week): Transient non functional kidney, similar to that in fish. Development of the pronephric tubules starts at the cranial end of the nephrogenic cord and progresses caudally. As each tubule matures it immediately begins to degenerate along with the segment of the nephric duct to which the tubules are attached The nephric ducts can be seen as a pair of solid longitudinal tissue condensations at about the 24th day, developing parallel to the nephrogenic cords in the dorsolateral aspect of the embryo The blind distal ends of the nephric ducts grow toward the primitive cloaca and soon fuse with it at about the 28th day, to form a lumen at the caudal end. The process of canalization then progresses cranially in a reverse direction Figure 111–3. Development of pronephros and mesonephros. A, Pronephros develops in each of five to seven cervical segments, but this primitive renal structure degenerates quickly during the fourth week. The (meso)nephric ducts first appear on day 24. B and C, Mesonephric vesicles and tubules form in a craniocaudal direction throughout the thoracic and lumbar regions. The cranial pairs degenerate as caudal pairs develop, and the definitive mesonephros contains about 20 pairs confined to the first three lumbar segments. Campbell-Walsh, CHAPTER 111, Normal Development of the Genitourinary Tract

Embryology The mesonephros (thoracolumbar region, 4th week- 4th month): Also transient, but serves as an excretory organ while the definitive kidney, the metanephros, begins its development Mesonephric vesicles begin to form along the medial side of the nephrogenic cords in a craniocaudal manner and results in the formation of pairs of mesonephric tubules, from which only 30 pairs are seen at any one time because the cranially located tubules start to degenerate starting at about the 5th week Degeneration with some contribution to reproductive systems: Efferent ductules of the testes, epididymis, vas deferens V/S Nonfunctional mesosalpingeal structures (epoöphoron, paroöphoron) Campbell-Walsh, CHAPTER 111, Normal Development of the Genitourinary Tract

Embryology The metanephros, definitive kidney (sacral region): Ureteric buds, sprout from the distal portion of the nephric duct and come in contact with the condensing blastema of metanephric mesenchyme at about the 28th day The tip of the dividing ureteric bud, the ampulla, interacts with the metanephric mesenchyme to induce formation of future nephrons: mesenchymal-epithelial interaction Figure 111–4. Metanephric mesenchyme condenses from the intermediate mesoderm during the early part of the fifth week and comes into contact with the ureteric bud, an outgrowth of the nephric duct, while the cranial mesonephros continues to degenerate. Figure 111–5. The ureteric bud divides to form enlarged tips, called ampullae, around which the metanephric mesenchyme condenses and begins nephron differentiation. The remaining mesenchymal cells remain stromal and continue to interact with tubular mesenchymal cells and dividing ureteric bud epithelial cells. Modified from Larsen WJ. Human embryology. New York: Churchill Livingstone; 1997 From Potter EL. Normal and abnormal development of the kidney. Chicago: Year Book Medical Publishers; 1972

Embryology Many candidate genes have been identified to play a critical role in this process : The RET-GDNF-GFRα1 pathway Nephric duct FoxC1/C2 Figure 111–13. A, Stimulation of ectopic ureteric buds by GDNF. To determine whether GDNF is sufficient to promote outgrowth of nephric duct epithelial cells, heparin acrylamide beads preadsorbed with recombinant GDNF (asterisks) were placed between two nephric duct organ cultures. The native metanephros (m) is seen anteriorly. GDNF alone induces multiple ectopic ureteric buds in the posterior nephric ducts (arrowheads). B, However, the effect of GDNF is suppressed when Bmp4 is also added to the beads (asterisks). Cultures were stained with anti-cytokeratin (green) and anti-Pax2 (red) antibodies. (From Dressler GR. Tubulogenesis in the developing mammalian kidney. Trends Cell Biol 2002;12:390–5.) GDNF) RET receptor GPI-linked protein GFRα1 BMP4 Metanephric mesenchyme

Embryology The tip of the dividing ureteric bud induces the metanephric mesenchyme to condense, which then differentiates into a renal vesicle This vesicle coils into an S-shaped tubule and ultimately forms a Bowman capsule as well as the proximal convoluted tubules, distal convoluted tubules & loops of Henle Development of the renal collecting ducts and nephrons. The tip of the dividing ureteric bud induces the metanephric mesenchyme (in pink) to condense, which then differentiates into a renal vesicle. This vesicle coils into an S-shaped tubule and ultimately forms a Bowman capsule as well as the proximal convoluted tubules, distal convoluted tubules, and loops of Henle. The ureteric bud (in purple) contributes to the formation of collecting ducts. Modified from Larsen WJ. Human embryology. New York: Churchill Livingstone; 1997.

Embryology Campbell-Walsh, CHAPTER 111, Normal Development of the Genitourinary Tract

Embryology The Ret gene plays an integral role in kidney development. As is covered in any basic embryology class, the cross-talk between the ureteric bud (destined to become the collecting system of the kidney) and the metanephrogenic mesenchyme (destined to become the renal parencyma and tubules) is a prime example of how reciprocal signals from two distinct tissue types can influence the development of the other. In the case of the kidney, GDNF (glial-derived neurotrophic factor) secreted by the mesenchyme interacts with the Ret receptor, a membrane tyrosine kinase, on the ureteric bud. This interaction is critical for branching morphogenesis, the process by which the kidney serially reiterates in order to create an organ with a million nephrons, as demonstrated by the fact that mice deficient in the Ret gene have a congenital absence of the kidney. Ret is important other human diseases as well. It is a proto-oncogene, as gain-of-function mutations lead to various forms of multiple endocrine neoplasia (MEN). Loss-of-function mutations in contrast can lead to either Hirschprung's disease (a congenital absence of the enteric nerves) or renal hypoplasia. University of Michigan Medical School, Renal Fellow Network ,

Anatomy Calices: The tips of the minor calices (8-12 in number) are intended by the projecting pyramids. These calices unite to form 2 or 3 major calices which join to form the renal pelvis. Renal pelvis: May be entirely intrarenal or partly (intrarenal and extrarenal) Ureter: About 30 cm long, varying in direct relation to the height of the individual. It follows a rather smooth S curve Areas of relative narrowing: UPJ Where the ureter crosses over the iliac vessels Where it courses through the bladder wall.

Introduction “Only one current urologic text includes a section on congenital megacalycosis” Smith Textbook? Campbell-Walsh text included a paragraph John F. Redman & Andrew D. Neeb: “ Congenital Megacalycosis: A Forgotten Diganosis” Forgotten Diagnosis?”. Urology 65: 384–385, 2005

Definition Dilatation of the renal calyces without evidence of distention of the pelvis or ureter First described by Dr Anthony Puigvert in 1963 Subsequently reported in the English literature by Gittes and Talner in 1972 Puigvert A: “Le Megacalice”. J. Urol. Nephrol. 70: 321(1964). Garcia CJ, Taylor KJ, Weiss RM. “Congenital megacalyces. Ultrasound appearance”. J Ultrasound Med 1987;6:

Epidemiology The condition is thought to be sporadic, but familial cases has been described Egyptian family with history of consanguinity & prominent history of renal stones Parents had normal US findings without evidence of craniofacial abnormalities All the children (2 boys, 1 girl) were morphologically normal had radiological evidence of bilateral megacalycosis Lam AH: “Familial megacalycosis with autosomal recessive inheritance. Report of 3 affected siblings”. Pediatr Radiol 1988; 19:28-30.

Epidemiology Excretory urogram Lam AH: “Familial megacalycosis with autosomal recessive inheritance. Report of 3 affected siblings”. Pediatr Radiol 1988; 19:28-30.

Epidemiology Primarily reported in Caucasians, with a strong male predominance (6:1) Also reported in: African American woman Egyptian children Adult Chinese woman Lam AH: “Familial megacalycosis with autosomal recessive inheritance. Report of 3 affected siblings”. Pediatr Radiol 1988; 19:28-30. Hamrick LC, Burns JR: “Congenital megacalices in a black woman”. J Urol 1985;134:

Epidemiology Mostly unilateral, with some reported cases being bilateral Bilateral disease has been seen almost exclusively in males, whereas segmental unilateral involvement occurs only in females (Cacciaguerra et al, 1996), suggesting an X-linked partially recessive gene with reduced penetrance in females (Gittes, 1984). Except for one report of two affected brothers, the entity has not been thought to be familial (Briner and Thiel, 1988). PHC Lau, AF McKenzie: “Megacalycosis Revisited”. HK Coll Radiol 2002;5:

Pathophysiology One theory: Abnormal development of the renal medulla, which leads to hypoplastic renal pyramids and blunted, dilated calyces By Puigvert’s’ definition, the papillary tissue of the renal medulla is delicate and rather than project into the lumen of the calyx surrounds the distended hypotonic calyx Impaired development of the renal pyramid as linked with proliferation and distention of the calyces

Pathophysiology Another theory: Transient delay in the recanalization of the upper ureter after the branches of the UB hook up with the metanephric blastema This produces transient obstruction when the glomeruli start producing urine The fetal calyces may dilate and retain their obstructed appearance, despite the lack of evidence of obstruction in postnatal The increased number of calyces may be an aborted response by the branching UB to the obstruction

Pathophysiology

Pathophysiology Calyces are numerous (polycalycosis) & appear polygonal and faceted (caliectesis) rather than rounded The medullary pyramids have a semilunar configuration, instead of the normal triangular or cone shape, and the tip of each papilla is flat The collecting tubules are not dilated but are definitely shorter than normal, and they are oriented transversely rather than vertically from the corticomedullary junction

Pathophysiology The renal pelvis is not distended, and there is no evidence of hypertrophy of the smooth muscle or the walls The pelvis drains properly into the ureter which is of normal diameter The kidney is usually of normal appearance, and size or slightly distended

Pathophysiology Angiography: Proper layout of the blood vessels with a moderately arched course of the arteries around the distended calyces Histopathology: Renal cortex of normal thickness, and a sparse medulla V/S hydronephrosis (scarring due to hight intra renal pressure)

Clinical Picture The condition is usually asymptomatic and is detected by its complications such as formation of calculi or UTIs resulting in pain, hematuria, and fever Puigvert A: Le Megacalice, J. Urol. Nephrol. 70: 321(1964).

Associated Findings Pereira Arias JG, Guturbay Arrieta I, Escobal Tamayo V, Ibarluzea Gonzalez JG, Jorge Catalina A, Bernuy Malfaz C (1995) Megacalycosis and lithiasis. Arch Esp Urol 48:310–314

Associated Findings Megaureter
Mandell GA, Snyder HM 3rd, Heyman S, Keller M, Kaplan JM, Norman ME (1987): “Association of congenital megacalycosis and ipsilateral segmental megaureter.” Pediatr Radiol 17:28–33

Associated Findings 20% of obstructive uropathy in pediatrics
More common in boys, more on the L side Bilateral in 25%, the contralateral kidney is absent/dysplastic in 10–15% of cases Runs in families, no genetic predisposition Structural V/S Functional Obstructive, Refluxive, Both, None (Smith et al.) Primary V/S secondary Clinically significant V/S insignificant, treat V/S observe Hodges et al. “Megaureter” The Scientific World JOURNAL (2010) 10, 603–612

Associated Findings CM as an associating feature of a rare syndrome “Schinzel-Giedion Syndrome” characterized by: Midfacial retraction Genitourinary and renal malformations Multiple skeletal abnormalities Severe psychomotor impairment Seizures Frontal view: coarse face with tall forehead, widely patent metopic suture, hypertelorism, shallow orbits, infraorbital folds and anteverted nares. Ear lobes are prominent. Lateral views: midface hypoplasia and lowest, posteriorly rotated ear with prominent lobules Minn D, Christmann D, De Saint-Martin A, Alembik Y, Eliot M, Mack G, Fischbach M, Flament J, Dollfus H (2002): “Further clinical and sensorial delineation of Schinzel-Giedion syndrome: report of two cases”. Am J Med Genet 109:211–217

Associated Findings 16 year-old-guy presented for R flank pain & multiple episodes of previous hematuria (1, 2, 4 & 10 years). IVP was done and showed pattern that might be explained as chronic pyelonephritis. Urine analysis and culture were however negative. Surgery was done and showed a vascular polyp, finger-like, 2-6mm in size at the UPJ. 3 years later after the repair, megacalycosis remained in the absence of any documented radiological new obstruction. IVP showed typical megacalycosis of the right kidney w/o pelvis enlargment. Retradrade pyelopragphy was done to R/O filling defect which was though to be radiolucent tumor or stone, and showed Glikman J, Kaneti J, Lismer L, Blank C: “Vascular polyps of ureter associated with megacalycosis and nephrolithiasis”. Urology 1987;30:

Diagnosis Laboratory findings show usually normal renal funtion V/S obstructive uropathies Perera Soler R, Ruiz Gonzalez AP, Molini Menchon N, Garcia Nieto VM (2004): “Unilateral multicystic dysplastic kidney and contralateral megacalycosis. An unusual association”. An Pediatr (Barc) 60:473–476

Diagnosis Radiological findings: a normal-sized kidney or nephromegaly
Normal renal parenchyma or thinned but not scarred parenchyma Malformed, dilated polygonal calyces are noted which appear faceted Smooth renal contour with a uniformly hypoplastic medulla The renal pelvis, UPJ and ureter appear normal

Diagnosis IVP shows typical dilatation of the calyces without enlargement of pelvis and supports the diagnosis of CM, it gives the best functional picture and anatomic structure of the kidney, which are not provided by the others & plays the most important role in diagnosis US usually shows the same findings Voiding cystourethrograms: Absence of reflux Diuretic renal scintigraphy: Normal excretion and wash out with diuretic, with normal rate of urine formation but a delay in demonstration of the collecting system due to the large number of calyces Renal angiography demonstrates a normal arterial system Radiographic findings and renal function tests have remained stable in CM cases that were followed up for several years B. S. PARLAKTA et al. “Megacalycosis: A Rare Renal Developmental Anomaly” Turk J Med Sci 34 (2004) T.BÜTAK

Diagnosis Megacalycosis. A, Sagittal ultrasonogram shows dilated calyces and normal-appearing pyramids. B, Enlarged view of A demonstrates distinct megacalyx (m) and normal pyramid (arrow).

Diagnosis IVP No obstruction Gross dilatation of the renal calyces without blunting was evident The renal pelves were normal in size. Renal calculi were seen in the lower pole calyces on both sides Absence of infundibular strictures and enlarged renal size were noted These features were not consistent with tuberculous infection The chinese women PHC Lau, AF McKenzie: “Megacalycosis Revisited”. HK Coll Radiol 2002;5:

Diagnosis IVP Dilated calyces in both kidneys UPJs are normal with normal non distended pelvis and normal dependent ureters Axial rotation of the kidneys is also noted B. S. PARLAKTA et al. “Megacalycosis: A Rare Renal Developmental Anomaly” Turk J Med Sci 34 (2004) T.BÜTAK

Diagnosis IVP (A) normal right renal collecting structures
(B) left renal collecting structures with classical findings of congenital megacalycosis, including ectatic polygonal calyces with a normal renal pelvis John F. Redman & Andrew D. Neeb: “ Congenital Megacalycosis: A Forgotten Diagnosis?”. Urology 65: 384–385, 2005

Diagnosis IV Contrast enhanced CT scan:
Gross dilatation of all renal calyces with parenchymal thinning and normal renal pelves (Fig. 2a) & renal calculi in both lower pole calyces (Fig. 2b) The chinese woman PHC Lau, AF McKenzie: “Megacalycosis Revisited”. HK Coll Radiol 2002;5:

Differential Diagnosis
The condition originates in and usually affects only one kidney and is not the result of: Obstructive uropathy Intermittent hydronephrosis Vesicoureteral reflux Papillary necrosis Chronic infection Gittes RF, and Talner LB: Congenital megacalices versus obstructive hydronephrosis, J. Urol. 108: 833 (1972).

Hydronephrosis, causes distension of the renal pelvis and calyces secondary to obstruction in the renal collecting system Histopathologic examination in megacalycosis reveals a rather sparse medulla in contrast to hydronephrotic kidney, in which there is degeneration of medulla due to elevation of intrarenal pressure The presence of more than 18 calyces is the most important radiological feature for differentiating megacalycosis from hydronephrosis Chronic pyelonephritis, which is usually associated with focal parenchymal scarring

Hydrocalyx A single calyx is distended because of obstruction of the infundibulum that can occur in the context of many pathologies (obstruction of by vessels or stenosis due to trauma, infection, etc…) Genito-urinary TB is the most common manifestation of extrapulmonary TB Classic CT findings: calcifications, deformation of calyces, obstructive hydronephrosis or hydrocalyx & papillary necrosis Maximum-intensity projection showing segmental dilatation of the upper urinary tract owing to fibrosclerosing tuberculosis, with a tuberculous stricture at the superior infundibulum with regional hydrocalycosis (arrow Emilio Quaia: “Imaging Findings in Renal Tuberculosis on Computed Tomography Urography” European Urological Review 2010

Papillary necrosis: Central necrosis and sloughing of the papilla create a cavity, which is occasionally large, that fills with contrast material and communicates with the calyceal concavity and makes a blunted calyx : golf ball– on-tee sign Eccentric necrosis, which originates at the margin of the papilla, will cause irregular cavitation at the margin of the papilla and make the angle of the calyx appear elongated: “lobster claw” deformity Chronically: nephrocalcinosis Causes: NSAID NSAIDS, Sickle cell, analgesics, Infections, and diabetes Different patterns of excavation that can be seen with papillary necrosis: normal (A), central excavation with ball-on-tee appearance (B),forniceal excavation (C), lobster claw appearance (D), signet ring appearance(E), and sloughed papilla with clubbed calix (F).

Papillary necrosis: NSAIDS, Sickle cell, analgesics, Infections, and diabetes

Pyelocalyceal diverticulum Uroepitheliumlined outpouchings of the collecting system into the renal parenchyma, typically connected to the calyceal fornix and project into the renal cortex (including a column of interlobar cortex) and not into the medulla Calyceal diverticula may be congenital or may be acquired from a ruptured cyst or infection Best diagnostic modality is US 41-year-old female with hypertension. (a) Transverse ultrasound image of the right kidney. A bilobed cyst-like lesion with hyperechogenic mobile material in the lateral part and posterior acoustic shadow. (b) Pre-contrast supine CT shows a bilobed hypodense mass with mobile gravity-dependent calcified material in the lateral portion. (c) Pre-contrast prone CT: change in position of the calcified material in the lateral part of the bilobate cyst

Pyelocalyceal diverticulum Type I Type I: Arising from a minor calyx Type II: Arising from the infindibulum Type III: Arising from the pelvis

Management This nonobstructive dilatation of the calyces causes UTIs and calculus formation because of stagnant urine If differential diagnosis is made from obstructive conditions inappropriate surgery is avoided and presenting clinical conditions respond well to conservative therapy Surgery is not necessary for the treatment of a primary anomalous kidney with CM but the presence of a stone and infection mandates appropriate therapy Treatment alternatives: F/U, ESWL, surgery for urinary calculus, and in order to control supervening UTI appropriate antibiotic therapy is administered & more adequate hydration F/U period should be in a continuous and close follow-up program because of the high risk of infection and stone formation, and annual check-up with routine blood chemistry, urinalysis and IVP are recommended Only in serious cases of severe, life-threatening infection or a large, irremovable stone should one contemplate excision of the affected kidney, provided the second kidney is healthy B. S. PARLAKTA et al. “Megacalycosis: A Rare Renal Developmental Anomaly” Turk J Med Sci 34 (2004) T.BÜTAK

Take Home Message Megacalycosis is a rare congenital abnormality in which all the renal calyces are enlarged, +/- increased in number, w/o any evidence of obstruction Usually occurs unilaterally, as an isolated anomaly, more frequent on the left , with male preponderance The renal papillae are hypoplastic & instead of protruding into the calyceal cavity, they surround the hypotonic calyces DDx should be established with obstrucitve uropathies, congenital hydronephrosis, hydrocalycosis resulting from infundibular stenosis, etc… Association with congenital primary megaureter, multicystic dysplastic kidneys &Schinzel–Giedion syndrome Patients have normal renal function and show normal interval growth of the affected kidney

Take Home Message Containment of the urine in the distended calyces results in infection and the formation of calculi in the urinary tract The goal of therapy should be to preserve the kidney affected by megacalycosis and to treat only its complications, avoiding unnecessary surgery in the region of the renal pelvis thereby insuring a wellfunctioning kidney despite the inherent anatomic defect in it The diagnosis is suggested by laboratory & radiological findings: US diuretic renography confirms the absence of obstruction Voiding cystourethrogram to R/O vesicoureteral reflux MRI & IVP can clarify the diagnosis In cases of UTIs suitable hydration and appropriate antibiotic treatment should reduce to a minimum the likelihood of calculus formation Surgery in severe cases Occupied Palestinian territories Kimche D, Lask D (1982) Megacalycosis. Urology 19:478–481

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