BACKGROUND: Urinary bladder capacity is reduced in patients undergoing long-term dialysis, which may increase the risk of vesicoureteral reflux (VUR) to a transplanted kidney. This study investigated the correlations between dialysis duration, pretransplant and posttransplant bladder capacity, and prevalence of VUR to the graft. METHODS: Voiding cystography was performed in 101 adult renal transplant recipients without neurogenic disorders immediately before and 1 year after transplantation to evaluate bladder capacity and VUR. Nonstented extravesical antireflux ureteroneocystostomy was performed in all patients. RESULTS: The median dialysis duration and pretransplant bladder capacity were 32 months (range 1-426 months) and 120 mL (range 15-450 mL), and 21 patients (20.8%) underwent dialysis for more than 120 months, and 30 patients (29.7%) had a pretransplant bladder capacity of less than 80 mL. Dialysis duration was correlated with pretransplant bladder capacity (R=0.466, P<0.001). Bladder capacity expanded more than 6-fold from pretransplantation to posttransplantation, and all recipients had a bladder capacity greater than 150 mL at 1 year posttransplantation. Thirty patients had VUR to the graft. Dialysis duration longer than 60 months (P=0.021) and pretransplant bladder capacity of less than 130 mL (P=0.024) were associated with VUR. VUR was associated with lower graft function. CONCLUSIONS: Although bladder capacity decreased because of long-term dialysis, it exceeded 150 mL at 1 year posttransplantation. A small bladder can be used in renal transplantation, but it may increase the risk of VUR.