A 21-year-old athletic woman had been suffering from flank pain during fluid intake after sports for some time. Urological work-up revealed hydronephrosis with a "fishhook" shape and medial displacement of the ureter. This ureteral narrowing was studied ureterorenoscopically, bioptically and endoscopic-radiologically without the correct diagnosis of a retrocaval ureter being made. Therapeutically, a DJ stent was inserted several times, a balloon dilatation was performed under anaesthesia three times and finally a permanent DJ catheter was inserted. Due to the patient's dissatisfaction, an endoscopic endopyelotomy using Acucise was offered.