Mesonephric duct anomalies in unilateral multicystic dysplastic kidney: A two-center retrospective study

Unilateral multicystic dysplastic kidney (UMCDK) is a congenital anomaly detectable already in utero. The affected kidney is non-functioning. While the ureter is typically absent, UMCDK may rarely associate with mesonephric duct (MND) remnants such as ureterocele or ureteral stump.

To determine the frequency, clinical implications, and management of ipsilateral MND anomalies in children with UMCDK under comprehensive prenatal and postnatal surveillance.

Retrospective analysis of 349 children (0-19 years) with UMCDK, followed by pediatric nephrologists and/or urologists in two tertiary centers between 2005 and 2024, was performed. MND anomalies were classified as: - Type Ia: Orthotopic ureterocele; - Type Ib: Orthotopic ureterocele plus ureteral remnant (stump); - Type II: Ectopic ureteral remnant (stump); - Type III: Complex anomalies involving seminal vesicles/epididymis.

Based on medical record and imaging result evaluation, twenty-five patients (7.2 %) with MND anomalies (21 males, 4 females) were identified. Of those, four males (16 %) developed clinical complications (lower urinary tract dysfunction, urinary tract infection (UTI), recurring epididymitis) at different age (3, 8, 12 and 16 years). These symptomatic cases involved Type Ib and Type III anomalies. Median age at diagnosis of MND anomalies was 2 months and median follow-up duration was 10.7 years. All patients had normal glomerular filtration rate (GFR) at the beginning of the observation period, however, two children developed stage 2 chronic kidney disease (CKD 2) until the end of the follow-up. UMCDK resolved spontaneously in 15 patients. MND anomalies regressed below the USG detection threshold only in 3 conservatively managed children (type Ia or Ib). Five patients with MND anomalies required surgical management: 3 children endoscopic incision of ureterocele and 2 children exstirpation of ureterocele with ureteral stump.

MND anomalies in UMCDK are uncommon and mostly follow a benign course. Nevertheless, endoscopic or surgical intervention may be required due to late-onset complications, predominantly lower urinary tract dysfunction. Lifelong monitoring is suggested.