Predictive value of renal histological changes for postoperative renal function improvement in children with congenital ureteropelvic junction stenosis

Background: The aim of this study was to evaluate the relationship between renal function, as measured by diuretic radionuclide renography, and the outcome of pyeloplasty. A study was designed to evaluate renal parenchymal biopsy specimens derived from children undergoing corrective surgery for ureteropelvic junction (UPJ) stenosis, and compare these to preoperative and postoperative renal function status. Methods: Thirty-five children with congenital unilateral UPJ stenosis were evaluated. In addition to all conventional diagnostic procedures for UPJ stenosis, differential renal functional (DRF) activity was assessed in each of these children by obtaining (99m) Tc diethylenetriaminepentaacetic acid renogram curves. All children underwent dismembered pyeloplasty, and follow-up renogram evaluation was conducted 6 and 12 months after surgical repair. Biopsy specimens from renal cortical regions obtained during the surgical correction of UPJ stenosis were evaluated, and changes in renal histology were graded from I to V according to their severity. Spearman's correlation test was used to compare the histological evaluation results and the basal, 6- and 12-month follow-up DRF findings. A Wilcoxon paired test was used to evaluate statistical differences between values. Results: The findings showed a positive correlation between the severity of histological changes and DRF activity. All kidneys (22) with a DRF activity value of < 40% preoperatively demonstrated at least grade III changes when biopsy specimens were examined. Of children with a DRF activity value > 40% (13), only three showed severe histological changes. Histological grades were correlated between basal (r = -0.4; P = 0.019), 6-month (r = 0.54; P = 0.002) and 12-month (r = 0.54; P = 0.02) findings. In the Wilcoxon paired test, there was a statistically significant difference between basal and 6-month values (P < 0.05), and also between basal and 12-month values (P < 0.01). There was no statistically significant difference between 6- and 12-month values (P > 0.20). Conclusion: Comparative evaluation of postoperative renal function with DRF activity and renal parenchymal histological alterations revealed a close correlation in terms of renal function improvement potential following reconstructive surgery in children with UPJ stenosis.