100+ Free Cert Nephrology(SA) Paed Practice Questions

Explanation: The 'keyhole sign' on antenatal ultrasound represents a dilated posterior urethra proximal to the obstruction alongside a thick-walled, distended urinary bladder, which is pathognomonic for posterior urethral valves (PUV) in a male fetus.

Explanation: Unilateral multicystic dysplastic kidney (MCDK) in an asymptomatic neonate with a normal solitary functioning contralateral kidney is managed conservatively with serial renal ultrasonography, blood pressure monitoring, and urinalysis, as the majority undergo spontaneous regression over childhood.

Explanation: Ureteropelvic junction (UPJ) obstruction is the single most common cause of congenital upper urinary tract obstruction and primary antenatal hydronephrosis, accounting for approximately 40-50% of cases.

Explanation: Grade IV VUR is characterized by moderate dilation and tortuosity of the ureter and renal pelvis with complete blunting of the calyceal fornices while preserving some calyceal impressions. Grade III shows mild dilation without blunting, and Grade V shows severe gross dilation and tortuosity with loss of papillary impressions.

Explanation: Prune Belly Syndrome (Eagle-Barrett syndrome) is characterized by the classic clinical triad of: (1) partial or complete absence/hypoplasia of abdominal wall muscles, (2) bilateral cryptorchidism, and (3) urinary tract anomalies (dilated megaureters, megacystis, renal dysplasia).

Explanation: The Weigert-Meyer law dictates that in a complete duplex system, the upper pole ureter drains ectopic, inferomedial to the lower pole orifice, and is prone to obstruction/ureterocele formation. The lower pole ureter inserts more superiorly and laterally with a short intravesical tunnel, making it prone to vesicoureteral reflux (VUR).

Explanation: In a horseshoe kidney, fusion of the lower poles occurs in the pelvis. As the fused kidney ascends during development, its central parenchymal or fibrous isthmus is trapped anterior to the abdominal aorta by the root of the inferior mesenteric artery (IMA) at the level of L3.

Explanation: All patients with ARPKD have varying degrees of congenital hepatic fibrosis characterized by ductal plate malformation, periportal fibrosis, and dilated intrahepatic bile ducts, which can lead to portal hypertension and hypersplenism.

Explanation: The initial decompression of posterior urethral valves in a neonate is performed by transurethral insertion of a small (5 or 6 Fr) feeding tube or specialized non-balloon urethral catheter. Suprapubic catheters are avoided initially due to risks of bladder wall tears or bleeding.

Explanation: On a 99mTc-MAG3 diuresis renogram, a tracer clearance half-life (T1/2) greater than 20 minutes following furosemide administration indicates significant mechanical urinary obstruction. A T1/2 < 10 minutes indicates non-obstructed drainage, while 10-20 minutes is equivocal.