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Xanthogranulomatous pyelonephritis

Alain Meyrier, MD
Section Editor
Stephen B Calderwood, MD
Deputy Editor
Allyson Bloom, MD


Xanthogranulomatous pyelonephritis (XPN) is an unusual variant of chronic pyelonephritis. Most cases occur in the setting of obstruction due to infected renal stones [1-6]. Affected patients usually have massive destruction of the kidney due to granulomatous tissue containing lipid-laden macrophages; the appearance may be confused with renal malignancy.

Studies performed in the 1970s found XPN in 8.2 percent of kidneys surgically removed or biopsied for chronic pyelonephritis and in as many as 25 percent in patients with pyonephrosis [1,7].


The clinical picture of XPN is somewhat different in adults and children.

Adults — XPN most often occurs in middle-aged women with a history of recurrent urinary tract infections [2]. The typical presenting symptoms include flank pain, fever, malaise, anorexia and weight loss. A unilateral renal mass can usually be palpated on physical examination. Blood tests reveal nonspecific abnormalities including anemia, an increased erythrocyte sedimentation rate, and liver function abnormalities reflecting mild biliary retention.

Examination of the urine confirms the presence of urinary tract infection. The urinalysis reveals pyuria and bacteriuria. Urine culture typically demonstrates Enterobacteriaceae. The most common organisms associated with XPN are E. coli, Proteus mirabilis, Pseudomonas, Enterococcus faecalis and Klebsiella [6]. The urine cultures are sterile in 25 percent of cases [4].

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Literature review current through: Oct 2017. | This topic last updated: Apr 19, 2017.
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