Wednesday, September 7, 2011

Xanthogranulomatous Pyelonephritis: Bullets

  • Chronic destructive granulomatous process.
  • Results from an incomplete immune response to a subacute bacterial infection.
  • The renal parenchyma is destroyed and replaced by low-attenuation xanthomatous masses (-10 to 30 HU, depending on the lipid content).
  • Calcifications can be seen within these xanthomatous masses (pink arrows).
  • Can be focal (10% of cases) or diffuse (90%).
  • Focal form can mimic neoplasm.
  • Risk factors include diabetes mellitus (10% of patients), female gender (2:1 female:male ratio), and low socioeconomic status.
  • Most patients have no specific risk factor.
  • Radiography: Large staghorn calculus (nonspecific), enlarged kidney, obscuration of the psoas margin (late finding).
  • Intravenous urography: Pronounced decrease in renal function with little or no excretion on delayed imaging (nonspecific).
  • Ultrasound: Enlarged kidney with a large shadowing echogenic structure in the renal pelvis (staghorn calculus). Loss of normal renal architecture.
  • CT: Combination of the following findings is strongly suggestive of diffuse disease: Nonfunctioning enlarged kidney + staghorn calculus in a contracted renal pelvis + expanded calices (usually filled with a low-attenuation inflammatory exudate) + inflammatory changes in the perinephric fat.
  • Focal disease can mimic neoplasm, and should be considered malignant until proven otherwise. Urine culture can be helpful.
The CT images show an enlarged left kidney with multiple low-attenuation parenchymal lesions. One of these in the upper pole has fine calcifications that can be seen on the radiograph (pink arrow). The renal pelvis and the calyces are dilated.


  • Al-Ghazo MA, Ghalayini IF, Matalka II, Al-Kaisi NS, Khader YS. Xanthogranulomatous pyelonephritis: Analysis of 18 cases. Asian J Surg. 2006 Oct;29(4):257-61.
  • Craig WD, Wagner BJ, Travis MD. Pyelonephritis: radiologic-pathologic review. Radiographics. 2008 Jan-Feb;28(1):255-77.
  • Fan CM, Whitman GJ, Chew FS. Xanthogranulomatous pyelonephritis. AJR Am J Roentgenol. 1995 Oct;165(4):1008.

No comments:

Post a Comment

Note: Only a member of this blog may post a comment.