Evolving concepts in the diagnosis of xanthogranulomatous pyelonephritis.

Xanthogranulomatous pyelonephritis (XGP) is a rare inflammatory process of the kidney that results in focal or diffuse renal enlargement and nonexcretion. In the past, XGP often has been misdiagnosed as renal carcinoma. Newer investigative modalities and an increased awareness of XGP should make preoperative diagnosis possible. Thirty-two cases of XGP are presented, with emphasis on recent advances in radiographic approach to diagnosis.