Best ultrasound parameter for prediction of adverse renal function outcome after pyeloplasty

OBJECTIVE: To evaluate the clinical value of preoperative ultrasound parameters for post-pyeloplasty outcomes in pediatric patients with ureteropelvic junction obstruction. METHODS: The medical records of 187 pediatric and adolescent patients who underwent pyeloplasty as a result of ureteropelvic junction obstruction between 2010 and 2016 were retrospectively reviewed. The severity of hydronephrosis was measured by the Society for Fetal Urology grade, anteroposterior pelvic diameter, urinary tract dilation, hydronephrosis index, and the hydronephrosis area to renal parenchyma ratio at 3, 6 and 12 months. Adverse renal function outcome was defined as ≥10% decrease in postoperative differential renal function compared with preoperative values. RESULTS: Of the 187 patients, preoperative hydronephrosis was categorized as Society for Fetal Urology grade 3 in 26 patients (13.9%) and grade 4 in 161 patients (86.1%). No surgical failures, defined as requirement of repeat surgery or deterioration of hydronephrosis grade, were noted. The mean changes in Society for Fetal Urology grade, anteroposterior pelvic diameter, urinary tract dilation and hydronephrosis area to renal parenchyma ratio showed similar trends of recovery during the follow-up period. In total, 19 patients (10.2%) showed >10% decrease in differential renal function during follow up (mean 42 months). Multivariate logistic regression analysis showed that the hydronephrosis area-to-renal parenchyma ratio was the only significant prognostic factor for adverse renal function outcome (hazard ratio 1.806, 95% confidence interval 1.210-2.859, P = 0.005). Receiver operating characteristic analysis showed that the hydronephrosis area-to-renal parenchyma ratio was the most significant predictive value (area under the curve 0.711, 95% confidence interval 0.618-0.804, P = 0.006). CONCLUSIONS: Pediatric patients with high hydronephrosis area-to-renal parenchyma ratio values before surgery are more likely to show renal function decline after pyeloplasty.