Supranormal renal function in pediatric ureteropelvic junction obstruction: a multiparameter analysis to guide clinical management.

Background: The clinical significance and optimal management of supranormal differential renal function (DRF ≥ 55%) in pediatric ureteropelvic junction obstruction (UPJO) remain debated. This study investigated supranormal DRF clinical characteristics and evaluated surgical versus conservative management outcomes to guide decision-making.

Methods: We retrospectively reviewed 76 children with unilateral UPJO who underwent standardized DMSA and DTPA scans at a single center (2020-2022). Patients were stratified into: normal DRF (40-55%) with pyeloplasty (n = 38), supranormal DRF with pyeloplasty (n = 12), and supranormal DRF with observation (n = 26). Primary outcomes included changes in DRF, renal parenchymal parameters, and hydronephrosis severity.

Results: Supranormal DRF occurred in 11.1% of cases, predominantly in younger children (median 20 vs 42 months, p = 0.01). Surgically managed supranormal cases demonstrated more severe hydronephrosis (75% grade 4, median APD 3.6 cm) compared to conservatively managed cases (27% grade 4, median APD 2.9 cm, p < 0.001). Post-pyeloplasty, supranormal kidneys showed consistent normalization of both DRF (58.2% to 51.6%, p < 0.001) and anatomical parameters. However, 77% of conservatively managed cases with less severe hydronephrosis maintained stable supranormal function without deterioration over median 14-month follow-up. Only 8% required delayed surgery for clinical progression.

Conclusion: Supranormal DRF warrants careful evaluation, particularly when accompanied by severe hydronephrosis (grade 4 or APD ≥ 3.0 cm). While early pyeloplasty effectively normalizes renal parameters in severe cases, observation may be appropriate for selected patients with less severe hydronephrosis. Treatment decisions should prioritize anatomical severity over DRF values alone.