[A case of idiopathic retroperitoneal fibrosis accompanied by asynchronous bilateral urinoma].

The patient was a 68-year-old female with the complaint of left flank pain. On examination, hydronephrosis of the left kidney and the urinoma of left retroperitoneal space were disclosed by abdominal computed tomographic (CT) scan. The urinoma disappeared spontaneously, but 4 months later right hydronephrosis and the urinoma of ipsilateral retroperitoneum emerged. Enhanced CT scan revealed aneurysm of bilateral common iliac arteries and perianeurysmal fibrotic mass. After steroid therapy under the diagnosis of idiopathic retroperitoneal fibrosis (IRPF), the fibrotic mass reduced in size and the urinoma disappeared. We should be aware that urinomas, which are thought to be caused by sudden obstruction of the upper urinary tract, could be brought about by IRPF.