An initial differential renal function between 35% and 40% has greater probability of leading to normal after pyeloplasty in patients with unilateral pelvic-ureteric junction obstruction.

Purpose: We compared the outcomes in patients who were <1 year old and had hydronephrosis with SFU grade 3-4 PUJ obstruction to observe the potential recovery of renal morphology and DRF after successful pyeloplasty.

Methods: All children younger than 1 year old with SFU grade 3-4 PUJ obstruction from January 2013 to June 2015 were retrospectively analyzed. A total of 92 children were grouped according to their DRF value at pyeloplasty as follows: DRF from 30 to ≤35% (group I) and DRF from 35 to ≤40% (group II). We evaluated changes in anteroposterior diameter and differential renal function using ultrasound and diuretic renography. Outcomes were compared using Student t test.

Results: Group I comprised 45 patients, and group II included 47 patients. No significant difference was observed in the initial APD, final APD and the improvement of APD after pyeloplasty between two groups. Significant differences were observed between the initial and final DRF values in both groups. The difference in DRF improvement after pyeloplasty between groups I and II was significant. The DRF improved to a normal stage significantly more frequently in group II (21/47; 44.7%) than in group I (13/45; 28.9%).

Conclusion: The improvement in DRF after pyeloplasty was significant for patients with an initial DRF from 30 to ≤35%. However, patients with an initial DRF from 35 to ≤40% had a greater probability of achieving normal renal function. Patients with severely impaired initial renal function had a marginal probability of achieving a normal value.