Nature and fate of supranormal differential renal function: lessons from long-term follow-up after pyeloplasty.

To understand the nature and long-term fate of supranormal differential renal function (snDRF), analysis of a post-pyeloplasty database was performed. Preoperative diethylenetriaminepentaacetic acid (DTPA) diuretic renal scans (DRS) identified 33 children with snDRF (>55%). Postoperatively, all showed improved hydronephrosis in ultrasound imaging or normalized drainage pattern in DRS during more than 5 years of follow-up. The fate of snDRF was described, and the nature of snDRF was speculated by associating it with clinical and ultrasound-related variables. Median age at operation was 22 months. Preoperative hydronephrosis was grade III in 27 patients (82%) and grade IV in 6 (18%). Hydronephrosis was normalized or improved, showing relief of obstruction. Overall fate of snDRF revealed significant reduction of DRF in 23 patients (70%), of whom 18 (81%) showed normalization during 5 years of follow-up. Stationary change of snDRF was seen in one-third of patients. Comparison of clinical and ultrasound-related variables revealed lower age, lower renal parenchyma thickness (RPT) increase, and higher preoperative DRF in the normalized group compared with the other group. The normalized group also showed a higher number in Society of Fetal Urology grade 4 hydronephrosis and lower RPT, although they reached borderline statistical significance. Long-term follow-up revealed that 70% of snDRF significantly decreased and normalized in most patients. The normalized group was younger and showed more hydronephrotic changes. Hydronephrotic change is suggested as a possible cause of snDRF.