[Magnetic resonance imaging for retroperitoneal fibrosis: report of two cases].

The first case was a 63-year-old man with edema in the lower extremities, and the second case was a 78-year-old man complaining of general fatigue and loss of appetite. Both cases had bilateral hydronephrosis and renal failure due to ureteric obstruction. Both patients with histologically proven idiopathic retroperitoneal fibrosis were studied by magnetic resonance imaging (MRI). MRI was performed using a superconducting magnet operating at 0.5 tesla and spin echo images were obtained. The retroperitoneal fibrous plaque appeared at an intermediate intensity on T1 weighted image and at a high intensity on T2 weighted image. They underwent intraperitoneal ureteral transposition and postoperative administration of prednisolone. Although their renal functions and hydronephrosis improved after the treatments, the fibrous plaque was still observed on MRI. It was considered that MRI was an excellent method of choice in the diagnosis and follow-up of retroperitoneal fibrosis.