Urolithiasis in horseshoe kidney with duplex collecting system.

Horseshoe kidney is a congenital renal fusion abnormality that can be complicated by stones; in rare cases, it has also been associated with a duplex collecting system. We present images of a horseshoe kidney with a right partial duplex collecting system that was not detected on the preoperative computed tomography scan. The use of a prone-split leg position for percutaneous nephrolithotomy facilitated the performance of flexible ureterorenoscopy of the lower pole moiety and percutaneous nephrolithotomy of the upper pole moiety in 1 setting with complete stone clearance.