Assessment of increase in renal pelvic size on post-void sonography as a predictor of vesicoureteral reflux

Background. During the course of our routine renal ultrasound examinations, we noticed that some children who developed dilatation of a renal pelvis following voiding had reflux found on voiding cystourethrography (VCUG). Purpose. To determine if increase in renal pelvic size on post-void ultrasound is an accurate predictor of vesicoureteral reflux. Materials and methods. Fifty-seven children (113 kidneys) underwent renal ultrasound and VCUG on the same day. Anteroposterior dimensions of the renal pelves were prospectively measured on ultrasound prior to and following patient voiding and correlated with the results of the VCUG. Results. The diameter of the renal pelvis increased in 12 and decreased in 38 kidneys on post-void ultrasound. Vesicoureteral reflux occurred in 19 kidneys and among these kidneys, renal pelvic diameter increased in 2, decreased in 7, and was unchanged in 10 following voiding. There was no significant correlation between post-void change in renal pelvic diameter and the presence of vesicoureteral reflux. Conclusion. Increase in renal pelvic size on post-void ultrasound is not a reliable indicator of vesicoureteral reflux.