Unsuspected ureterocele and ureteral duplication.

Four patients presenting with high grade unilateral vesicoureteral reflux were discovered at surgery to have an unsuspected duplex system with a ureterocele associated with the upper pole of the refluxing kidney. No preoperative radiographic study was diagnostic for duplication or ureterocele but when studies were reviewed retrospectively subtle evidence suggesting this possibility could be identified in a few cases. This rare situation should be considered whenever massive unilateral vesicoureteral reflux is encountered.