Increasing bladder capacity and vesicoureteral reflux in pediatric kidney transplant patients

Objectives To investigate the frequency of vesicoureteral reflux, and the relationship of pretransplant decreased bladder capacity and post‐transplant vesicoureteral reflux in children undergoing kidney transplantation. Methods A voiding cystourethrography was carried out in 172 pediatric kidney transplantation recipients before, and 4 months after, transplantation to evaluate bladder capacity and vesicoureteral reflux. The correlation of post‐transplant vesicoureteral reflux with pretransplant bladder capacity, vesicoureteral reflux in the native kidney and the method of ureteral reimplantation (intravesical/extravesical) was analyzed. Atrophic bladder was defined as having ≤50% functional bladder capacity (age in years + 2) × 25 (mL) or ≤150 mL in patients aged >10 years. Results Bladder capacity increased remarkably after transplantation in both post‐transplant vesicoureteral reflux− group (from 180 to 253 mL) and vesicoureteral reflux+ group (from 82 to 171 mL). Voiding cystourethrography showed vesicoureteral reflux in 12 cases of kidney transplantation (7%; grade 1: 2, grade 2: 3, grade 3: 7). Pretransplant atrophic bladder was an independent risk factor of post‐transplant vesicoureteral reflux (P = 0.004, hazard ratio 9.5). There was no difference in renal function between the vesicoureteral reflux− group and vesicoureteral reflux+ group at 4 months to 5 years post‐transplantation. Conclusions Pretransplant atrophic bladder is a risk factor of post‐transplant vesicoureteral reflux in pediatric patients. However, bladder capacity can remarkably increase after transplantation, and kidney function in the post‐transplant vesicoureteral reflux+ group is stable.