Clinical significance and management of antenatally detected hydronephrosis due to ureteropelvic junction obstruction: a retrospective single-center study

BACKGROUND: Antenatal hydronephrosis (ANH) is a common prenatal finding with a heterogeneous postnatal course. This study aims to describe an institutional experience and protocol adherence regarding the clinical course, intervention timing, and surgical outcomes of severe ANH secondary to ureteropelvic junction obstruction (UPJO) and its rare coexistence with ureterovesical junction obstruction (UVJO). METHODS: We retrospectively reviewed the records of infants referred to our tertiary center with severe prenatal urinary tract dilation (UTD A2-3 / high risk). Out of 400 initially screened patients, 80 infants who completed a standardized 1-year postnatal follow-up protocol were included, representing a highly selected completer cohort. Postnatal evaluation included serial ultrasounds (USG) and mercatoacetyltriglycine 3 (MAG-3) renography. Surgical intervention (dismembered pyeloplasty) was indicated based on standardized empirical consensus criteria: anterior-posterior renal pelvic diameter (APRPD) ≥ 19 mm, parenchymal thickness ≤ 5 mm, or split differential renal function (DRF) ≤ 40% with obstructive clearance patterns. Postoperative complications were graded using the Clavien-Dindo classification. RESULTS: The final analysis included 80 infants. Isolated UPJO was diagnosed in 12 patients (15.0%), transient/physiological hydronephrosis in 35 (43.75%), vesicoureteral reflux (VUR) in 29 (36.25%), and coexisting UPJO and UVJO in 4 patients (5.0%). Pyeloplasty was performed in all 12 isolated UPJO patients and 4 coexisting UPJO+UVJO patients (total n = 16 surgical cases) at a median age of 3 months. Postnatal USG at 12 months demonstrated a significant reduction in pelvic dilatation and marked parenchymal thickening. No deterioration in renal function was observed during follow-up, and no postoperative complications were recorded in this cohort. CONCLUSION: Adherence to a strict, conservative management protocol with standardized surgical thresholds was associated with favorable outcomes in high-risk ANH patients. Given the single-center descriptive nature and substantial loss-to-follow-up within this completer cohort, these findings represent descriptive institutional experiences rather than statistically validated threshold models.