Change in bladder capacity and prognostic predictors of post-transplant vesicoureteral reflux in pediatric kidney transplant recipients: a single-center retrospective cohort study

Background Kidney transplantation (KT) is the preferred treatment for pediatric end-stage kidney disease. However, vesicoureteral reflux (VUR) is a common occurrence post-KT. This single-center retrospective cohort study investigated bladder capacity changes, and identified post-transplant VUR predictors, in pediatric KT recipients. Methods Pediatric patients with or without pre-transplant anuria (< 0.5 mL/kg/h) who underwent KT, from January 2009 to December 2023, were analyzed. Expected bladder capacity (EBC) was calculated based on age. Maximum bladder capacity (MBC) and post-transplant VUR presence were evaluated using voiding cystourethrography. Logistic regression was used to identify independent risk factors for post-transplant VUR. Receiver operating characteristic curve analysis was used to determine the predicted probability of post-transplant VUR. Results Among 93 patients (males: 60%; median age: 6.1 [2.3–17.7] years), 25 (26.9%) had pre-transplant anuria. Bladder capacity (from 37.5 to 120 mL; p < 0.001) and MBC/EBC ratio (from 19.7 to 62.3%; p < 0.001) increased post-KT in only patients with anuria. Multivariate analyses revealed that pre-transplant MBC/EBC ratio predicted post-transplant VUR (odds ratio: 0.980, 95% confidence interval: 0.965–0.996; p = 0.006; sensitivity: 76.5%, specificity: 72.4%, area under the curve: 0.745 [cut-off: 57.8%]). Conclusions Pre-transplant MBC/EBC ratio is a useful bladder capacity indicator and predicts post-transplant VUR in pediatric KT recipients.