Multiple-Choice Questions on Renal and Collecting System Anomalies
Based on the evidence provided and general urology knowledge, here are five four-option multiple-choice questions covering key anomalies of the kidneys and collecting system:
Question 1: Multicystic Dysplastic Kidney (MCDK)
A 2-month-old infant is diagnosed prenatally with a unilateral multicystic dysplastic kidney confirmed on postnatal ultrasound. The contralateral kidney appears normal on ultrasound. What is the most appropriate initial management?
A) Immediate nephrectomy to prevent malignant transformation
B) Conservative management with limited radiographic follow-up
C) Routine voiding cystourethrogram (VCUG) for all cases
D) Nuclear medicine renal scan every 6 months
Correct Answer: B
Rationale: MCDK follows a benign course and should be managed conservatively with very limited radiographic evaluation 1. VCUG or nuclear medicine scans should only be directed by abnormalities on renal ultrasound or development of urinary tract infections, not performed routinely 1. The incidence ranges from 1 in 1000 to 4300 live births, making it one of the most common cystic diseases in children 1. The key clinical focus is detecting contralateral kidney anomalies rather than aggressive intervention on the MCDK itself.
Question 2: Duplex Collecting System with Ureterocele
A 6-month-old girl presents with recurrent febrile UTIs. Imaging reveals a complete duplex collecting system with an obstructing ureterocele affecting the upper moiety, which shows severely reduced function (15%) on DMSA scan. The lower moiety has normal function. What is the most appropriate surgical approach?
A) Endoscopic ureterocele incision alone
B) Upper moiety heminephroureterectomy
C) Common-sheath ureteral reimplantation of both ureters
D) Observation with continuous antibiotic prophylaxis
Correct Answer: B
Rationale: When the upper moiety is dysplastic or severely non-functional (<20% differential function), heminephroureterectomy is the definitive treatment 2. In the reported series, laparoscopic upper moiety heminephroureterectomy proved safe and feasible in properly selected cases 2. The upper moiety in duplex systems typically drains through an ectopic ureter that may be obstructed by a ureterocele, leading to hydronephrosis and recurrent infections 3, 2. When function is preserved, reconstructive options like ureteroureterostomy or reimplantation are preferred, but with <20% function, removal is indicated.
Question 3: Horseshoe Kidney with Associated Anomalies
A prenatal ultrasound at 20 weeks gestation identifies a horseshoe kidney with bilateral hydronephrosis. Postnatal evaluation at 1 month shows persistent bilateral hydroureteronephrosis. What additional anomaly should be specifically evaluated for in this patient?
A) Vesicoureteral reflux (VUR)
B) Multicystic dysplastic kidney
C) Renal agenesis
D) Simple renal cysts
Correct Answer: A
Rationale: Horseshoe kidneys are associated with ureteropelvic junction (UPJ) obstruction and vesicoureteral reflux due to abnormal ureteral insertion and drainage 4. The case report demonstrates a horseshoe kidney with duplicated collecting system, UPJ obstruction, and renal pelvic fusion requiring both pyeloplasty and vesicoureteral neostomy 4. In the setting of bilateral high-grade hydronephrosis, VCUG is recommended to detect VUR, as the likelihood is much higher 5. The abnormal position and fusion of horseshoe kidneys predispose to collecting system anomalies and drainage problems.
Question 4: Posterior Urethral Valves (PUV) - Pop-off Mechanism
A male neonate is diagnosed with posterior urethral valves. Imaging reveals severe bilateral hydroureteronephrosis, but the right kidney shows high-grade (grade V) vesicoureteral reflux with dysplastic changes, while the left kidney appears better preserved. What is the significance of the unilateral high-grade VUR in this clinical scenario?
A) It indicates need for immediate bilateral ureteral reimplantation
B) It represents a "pop-off valve" that may protect the contralateral kidney
C) It always predicts progression to end-stage renal disease
D) It requires immediate nephrectomy of the affected kidney
Correct Answer: B
Rationale: Unilateral high-grade VUR with ipsilateral renal dysplasia acts as a "pressure pop-off valve" that potentially protects the contralateral kidney and may lead to more favorable prognosis 6. This is observed in at least 50% of PUV patients 6. Other pop-off mechanisms include large bladder diverticulum, urinary extravasation, and patent urachus 6. However, the renoprotective effects remain equivocal, as long-term outcomes have been inconsistent across studies—some demonstrating protective effects while others show no significant benefit 6. The discrepancies may relate to differences in defining what constitutes a true pop-off mechanism 6.
Question 5: Vesicoureteral Reflux (VUR) Management in Toilet-Trained Children
A 4-year-old girl presents with recurrent febrile UTIs. VCUG confirms bilateral grade III vesicoureteral reflux. During evaluation, the parents report daytime urinary frequency, urgency, and occasional enuresis. Uroflowmetry shows a staccato pattern. What is the most appropriate initial management?
A) Immediate bilateral ureteral reimplantation
B) Endoscopic injection therapy for the reflux
C) Treatment of bladder and bowel dysfunction (BBD) before addressing VUR
D) Continuous antibiotic prophylaxis alone without BBD evaluation
Correct Answer: C
Rationale: All children presenting with UTIs should be carefully evaluated for bladder and bowel dysfunction (BBD) and managed accordingly before any treatment of VUR 5. Detection of lower urinary tract dysfunction (LUTD) is essential, and if found, initial treatment should always be for LUTD 5. Among toilet-trained children, those with both LUTD and VUR are at higher risk of developing recurrent febrile UTIs than children with isolated VUR 5. The presence of both BBD and VUR doubles the risk of UTI recurrence 5. VUR with LUTD resolves faster after LUTD correction 5. Effective management of BBD may be as impactful as continuous antibiotic prophylaxis 5. The staccato voiding pattern indicates dysfunctional voiding requiring behavioral therapy and possible anticholinergics before surgical intervention.
Common Pitfalls to Avoid:
- Do not routinely perform VCUG for all MCDK cases—reserve for contralateral abnormalities or UTI development 1
- Do not overlook BBD evaluation in toilet-trained children with VUR—this is a critical step that directly impacts outcomes 5
- Do not assume all pop-off mechanisms in PUV are equally protective—evidence remains equivocal 6
- Do not perform heminephroureterectomy when upper moiety function is preserved—consider reconstructive options first 2