[A case of infected renal cyst suspected of originating from retrograde infection].

A 63-year-old man who had undergone Miles' operation for rectal cancer in another hospital was referred due to a high fever and renal failure. Abdominal computed tomographic (CT) scan revealed metastatic liver tumor, paraaortic lymph node swelling, bilateral hydronephrosis and a left simple renal cyst located at the lower pole. Bilateral ureteral stenting was undertaken for relieving ureteral obstruction. Serum creatinine and high fever improved immediately. However, at 11 days after the ureteral stenting the high fever recurred. CT scan and ultrasonography revealed persistent left hydronephrosis and a change of left simple renal cyst into infected cyst. After an exchange of left ureteral stent and percutaneous pus drainage from the left infected renal cyst, high fever declined immediately. A review of the literature suggests that this is the 100th case report of infected renal cyst in Japan. We discuss the clinical features, etiology, imaging study and treatment of infected renal cyst.