Xanthogranulomatous pyelonephritis refers to an unusual form of localized chronic bacterial renal infection. Characterized by inflammation and granuloma formation with lipid-laden macrophages, it is typically found in obstructed kidneys containing stones. The kidney, which may be nonfunctional, contains a localized abscessed area that may be mistaken for a tumor on intravenous urography. CT and magnetic resonance imaging may help clarify the diagnosis. The pathogenesis of xanthogranulomatous pyelonephritis is unknown.
Treatment consists of antibiotic therapy and surgical resection of the abscessed area.
The first well-described cases of AIN were not secondary to adverse drug reactions but were found at autopsy of patients who had died of scarlet fever or diphtheria. This adverse renal reaction has been associated with bacterial, viral, and parasitic infections, including streptococcal infections, diphtheria, leptospirosis, leishmaniasis, toxoplasmosis, infectious mononucleosis, Epstein-Barr virus infection, measles, brucellosis, syphilis, mycoplasmal pneumonia, infections with HIV, Kawasaki disease, and Legionnaires' disease. Some infectious agents, such as those responsible for leptospirosis, mycobacterial infections, cytomegalovirus infection, Rocky Mountain spotted fever, and Hantaan virus infection, may directly infect the kidney and cause interstitial inflammation during the course of systemic infection. The acute inflammatory infiltrate can be composed of lymphocytes, plasma cells, monocytes, and polymorphonuclear cells, but eosinophils are not commonly found. The acute renal dysfunction is manifested by an acute decrease in the GFR or isolated tubular defects.