Preoperative diagnosis of xanthogranulomatous pyelonephritis.

Preoperative diagnosis of xanthogranulomatous pyelonephritis may be correctly made in a significant proportion of affected patients thus preventing unnecessary radical surgery especially in the poor-risk patient. The diagnosis should be suggested in the patient with a history of chronic urinary tract infection and certain radiologic features. These include unilateral renal enlargement (either localized or diffuse), nonfunction on excretory urography, presence of renal and/or ureteral calculi, angiographic demonstration of avascular mass or masses with stretched, attenuated intrarenal vessels, prominent capsular and periureteric vessels, and an irregular impaired nephrogram with prominent avascular areas.