Xanthogranulomatous pyelonephritis.

Xanthogranulomatous pyelonephritis is an uncommon chronic destructive granulomatous process of renal parenchyma in association with long-term urinary tract obstruction and infection. It affects females more often than males, with a wide range of age, from newborn to elderly. Almost all patients are symptomatic and the most common symptoms are flank or abdominal pain, lower urinary tract symptoms, fever, palpable mass, gross hematuria, and weight loss. The common laboratory findings are leukocytosis and anemia. Urine cultures most often reveal Escherichia coli and Proteus mirabilis . Computed tomography is the mainstay of diagnostic imaging for xanthogranulomatous pyelonephritis. Imaging studies may demonstrate diffuse or focal form. Histologically, xanthogranulomatous pyelonephritis presents a granulomatous inflammatory infiltrate composed of neutrophils, lymphocytes, plasma cells, xanthomatous histiocytes, and multinucleated giant cells. The differential diagnosis includes clear cell renal cell carcinoma, papillary renal cell carcinoma, sarcomatoid renal cell carcinoma, leiomyosarcoma, malakoplakia, and megalocytic interstitial nephritis. Both antibiotics and surgery can be treatment options depending on the patient's disease status.