Sonographic features of xanthogranulomatous pyelonephritis

Purpose. The purpose of this study was to describe the various sonographic features of xanthogranulomatous pyelonephritis (XGP). Methods. We retrospectively reviewed the CT, sonographic, and medical recor ds of patients diagnosed with XGP from January 1981 to December 1998. Twent y-seven patients for whom XGP was histopathologically confirmed were includ ed in the study. There were 12 men and 15 women, with an age range of 21-86 years (mean, 57 years). All patients had undergone sonography of the kidne ys. The renal size, shape, and outline were recorded. The presence of perin ephric fluid accumulation, of obstructive uropathy, or of internal echoes i n the dilated collecting system and the echotexture of the renal parenchyma were documented. Results. We categorized the XGP into 4 groups on the basis of the sonograph ic features: (1) diffuse hydronephrotic, 12 patients (44%); (2) diffuse par enchymal, 9 patients (33%); (3) diffuse contracted, 4 patients (15%); and ( 4) segmental or focal, 2 patients (7%). A localized perinephric fluid colle ction was present in 4 patients (15%). The preoperative sonographic diagnos es were pyonephrosis (n = 14, 52%), renal pelvic tumor with possible associ ated infection (n = 5, 19%), renal parenchymal mass (n = 2, 7%), hydronephr osis (n = 2, 7%), and chronic pyelonephritis with renal atrophy (n = 4, 15% ), XGP was considered a possible diagnosis in only 11 patients (41%). Conclusions. XGP has no specific sonographic features but is suggested by p arenchymal thinning and hydronephrosis, sonographic signs of chronic obstru ctive uropathy caused by stones; echoes in the dilated collecting system; a nd a perinephric fluid collection. CT, needle biopsy, or both are recommend ed to further evaluate and confirm sonographically suspected XGP. (C) 2001 John Wiley & Sons, Inc.