A ureterocele is a congenital dilatation of the intramucosal portion of the ureter. A ureterocele may be simple or ectopic. Ectopic ureterocele is almost always associated with a duplicated collecting system, and is more common than the simple type. Ureterocele may be associated with either reflux or obstruction. A ureterocele may prolapse into the bladder neck and cause bladder outlet obstruction. The prognosis is related to the degree of associated reflux or obstruction.