Clinical impact of differential renal function to indicate and assess pyeloplasty and the significance of coexisting vesicoureteral reflux.

Abstract

In patients with ureteropelvic junction obstruction (JPJO) who are conservatively treated, 5% to 10% of them show a deterioration of renal function without recovery after delayed pyeloplasty. Should surgery be indicated based on observed deterioration of differential renal function (DRF)? Can we expect improvement of the DRF after pyeloplasty? What other influencing parameters may affect DRF? In this study, the authors examined 85 ureterorenal junctions that had undergone the Anderson-Hynes technique for surgical correction of UPJO. Based on the values obtained from the preoperative DRF (Tc-99m mercaptoacetyltriglycine), the cases were separated into three categories: group I had poor DRF (less than 11% of total renal function [TRF]), group II had moderate DRF (11% to 33% of TRF), and group III had adequate DRF (more than 33% of TRF). Twelve months after surgery, renal function was reassessed. The results were correlated with age at surgery, symptoms, coexisting vesicoureteral reflux, and drainage. Seven ureterorenal junctions (8%) comprised group I, 15 (18%) comprised group II, and 63 (74%) comprised group III. After UPJO repair, 13% showed marked improvement in DRF, 86% remained stable, and 1% exhibited diminished function. In 50% of the renal cases with preoperative DRF less than 33%, postoperative improvement was seen. In follow-up renal scans, 30 cases (35%) revealed nonobstructive drainage, whereas the remaining 53 junctions (62%) showed moderate delayed drainage. Both the moderate delayed group (57%) and the nonobstructive group (50%) showed similar DRF improvement. Sixty-six percent of the patients with impaired DRF improved after pyeloplasty performed within the first 3 months of life, compared with 42.8% of patients in whom surgery was performed after 5 years of age. Vesicoureteral reflux was evident in 27.2% of the patients with preoperative impaired DRF compared with 11% with normal DRF. Forty-five percent of the patients with impaired DRF and no improvement after surgery had coexisting vesicoureteral reflux, compared with 9% of those with postoperative improvement. Sustained renal impairment after pyeloplasty is likely as a result of preexisting renal dysplasia with vesicoureteral reflux. Moderate delayed drainage after surgery does not affect DRF. Surgery for UPJO should be indicated independent of a DRF follow-up (except very low DRF) or the age at the time of diagnosis.