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Xanthogranulomatous Pyelonephritis
 XGPN


General considerations

  • Rare, chronic inflammatory disease almost always associated with long-term obstruction
    • Most often associated with Proteus or E. Coli infection
  • Produces either diffuse (80-90%), or sometimes focal (10-20%), destruction of the kidney
  • Almost always unilateral; may affect either kidney with equal frequency
  • Four times more common in women than men, usually 45-65 years of age
  • Pathognomonic microscopic feature is lipid-laden, foamy macrophage (xanthoma cells)
  • Has tumor-like behavior and can spread to involve and/or destroy adjacent organs

Clinical findings

  • Anorexia
  • Fever, chills
  • Weight loss
  • Dull and aching flank pain
  • Palpable flank mass
  • Obesity and diabetes are comorbidities

Imaging Findings

  • On ultrasound
    • Enlarged kidney which maintains reniform shape
    • Loss of corticomedullary differentiation
    • Multiple hypoechoic abscesses, granulomas or dilated calyces
    • Loss of renal cortical tissue
    • Calculi do not usually shadow
  • CT is modality of choice
    • Heterogeneous, non-enhancing mass
    • Hydronephrotic kidney
    • Destruction of the normal renal parenchyma
    • Stones, of staghorn size, occur in 80% of cases
      • May also demonstrate small calcifications
    • Extrarenal extension

Differential Diagnosis

  • May not be able to be distinguished from renal cell carcinoma radiographically and clinically
  • Chronic pyelonephritis

Treatment

  • Surgical removal
    • Nephrectomy or sometimes partial nephrectomy

Complications

  • XGPN is notorious for fistulization
    • Pyelocutaneous and ureterocutaneous fistulae have been well-described

Prognosis

  • Good
  • Death is rare

Xanthogranulomatous Pyelonephritis. Pre- and post-contrast enhanced CT axial CT scans through the kidneys show a staghorn calculus in an enlarged right kidney (image on left, white arrow) which enhances slightly (image on right) revealing low attenuation deposits (red arrow). There is inflammatory stranding surrounding the right kidney.
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Xanthogranulomatous Pyelonephritis. eMedicine. Khan, A; MacDonald, S; Boylan,  Costello, and B; Mahmood, K.