Diagnosis: Renal Papillary Necrosis
• Necrosis of the renal papilla (papillary necrosis) is a condition that occurs mainly in one of four clinical settings: obstructive pyelonephritis, diabetic nephropathy, sickle cell anemia, and analgesic abuse.
• The pathogenesis of papillary necrosis in diabetic nephropathy probably involves a combination of ischemia (owing to frequently severe small vessel disease) and infection.
• In sickle cell anemia, papillary necrosis is caused by repeated sickling of erythrocytes in the vasa recta renis with resulting medullary ischemia.
• Analgesic abuse (consumption of large quantities of analgesics over years) frequently leads to chronic interstitial nephritis and papillary necrosis. Papillary damage is thought to result from combined direct toxic effects of phenacetin metabolites on tubular cells with aspirin-induced or nonsteroidal antiinflammatory drug–induced inhibition of prostaglandin synthesis. The latter predisposes to ischemia by reduction in medullary synthesis of vasodilatory prostaglandins.
