title: Sonographic features of xanthogranulomatous pyelonephritis.
abstract: OBJECTIVE
  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 records of patients diagnosed with XGP from January 1981 to December 1998. Twenty-seven patients for whom XGP was histopathologically confirmed were included 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 kidneys. The renal size, shape, and outline were recorded. The presence of perinephric fluid accumulation, of obstructive uropathy, or of internal echoes in 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 sonographic features: (1) diffuse hydronephrotic, 12 patients (44%); (2) diffuse parenchymal, 9 patients (33%); (3) diffuse contracted, 4 patients (15%); and (4) segmental or focal, 2 patients (7%). A localized perinephric fluid collection was present in 4 patients (15%). The preoperative sonographic diagnoses were pyonephrosis (n = 14, 52%), renal pelvic tumor with possible associated infection (n = 5, 19%), renal parenchymal mass (n = 2, 7%), hydronephrosis (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 parenchymal thinning and hydronephrosis, sonographic signs of chronic obstructive uropathy caused by stones; echoes in the dilated collecting system; and a perinephric fluid collection. CT, needle biopsy, or both are recommended to further evaluate and confirm sonographically suspected XGP.
authors.affiliation: Department of Radiology, Veterans General Hospital-Taipei and National Yang-Ming University School of Medicine, 201 Shih-Pai Road, Section 2, Taipei 11217, Taiwan.
authors.forename: C M
authors.initials: CM
authors.lastname: Tiu
authors.forename: Y H
authors.initials: YH
authors.lastname: Chou
authors.forename: H J
authors.initials: HJ
authors.lastname: Chiou
authors.forename: C B
authors.initials: CB
authors.lastname: Lo
authors.forename: J Y
authors.initials: JY
authors.lastname: Yang
authors.forename: K K
authors.initials: KK
authors.lastname: Chen
authors.forename: M H
authors.initials: MH
authors.lastname: Hsu
authors.forename: J H
authors.initials: JH
authors.lastname: Wang
authors.forename: Y G
authors.initials: YG
authors.lastname: Su
authors.forename: C Y
authors.initials: CY
authors.lastname: Chang
authors.forename: C
authors.initials: C
authors.lastname: Yu
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D006869:Hydronephrosis / Q000000981:diagnostic imaging / Q000473:pathology; D007668:Kidney / Q000000981:diagnostic imaging / Q000473:pathology; D007669:Kidney Calculi / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D011705:Pyelonephritis, Xanthogranulomatous / Q000000981:diagnostic imaging* / Q000473:pathology; D012189:Retrospective Studies; D014463:Ultrasonography