[A case of infected renal cyst: the usefulness of magnetic resonance imaging for preoperative diagnosis].

A 22-year-old woman was admitted to our hospital with complaints of fever and left flank and back pain. Laboratory examinations showed leukocytosis and high C-reactive protein level. On the upper pole of the left kidney, two renal cysts were disclosed by ultrasonography and computerized tomography. A simple renal cyst and an infected renal cyst could be distinguished by magnetic resonance images (MRI), because the infected renal cyst was less intense than the simple renal cyst on T2 weighted MRI. Percutaneous puncture and drainage of the cyst were performed under the guidance of ultrasonography. Bacterial culture of the infected cyst fluid was positive for E. coli. Two months after treatment, computerized tomography showed no evidence of recurrence of the infected renal cyst.