A case is reported of a large left ureterocele in a duplicated system at the expense of the upper renal pelvis. This ureterocele caused acute pyelonephritis and dilatation of both left systems. It was treated by a classic endoscopic incision of its roof but 18 months later, infecting vesico-renal, grade 2, reflux was developed. This secondary reflux was treated successfully by submeatal polytetrafluoroethylene's (Teflon) paste injection. This new combination of endoscopic techniques proved to be available in this case.