Snapshot A 50-year-old man with a history of diabetes mellitus presents to the emergency room for gross amounts of blood in his urine. He denies any pain with urination and has never had hematuria before. He has no family history of cancer and does not smoke. Physical exam is unremarkable. His urinalysis reveals hematuria, proteinuria, and necrotic tissue. Introduction Clinical definition necrosis and sloughing of renal papillae Epidemiology demographics middle-aged adults uncommon in children, except in those with sickle cell disease or trait risk factors sickle cell disease or trait acute severe pyelonephritis analgesics such as NSAIDs one of the most common and preventable risk factors phenacetin diabetes mellitus tubulointerstitial nephritis kidney stones causing obstruction indinavir (anti-retroviral drug) Pathogenesis due to ischemia in sickle cell trait or disease sickling is promoted in the renal medulla due to low oxygen tension, low pH, and high osmolality (pulling water out of red blood cell and increasing concentration of hemoglobin S) increased blood viscosity leads to infarcts and causes papillary infarcts in analgesic use NSAIDs inhibit prostaglandin synthesis (remember that prostaglandins vasodilate) this predisposes patients to renal hypoperfusion and ischemia, especially in those with pre-existing renal disease or any other risk factors for renal papillary necrosis Prognosis prognostic variable negative concomitant diabetes older age Presentation Symptoms primary symptoms fever and chills sudden onset flank or abdominal pain may be asymptomatic hematuria pyelonephritis Physical exam tenderness to palpation in the flank or abdomen Imaging Radiographs indications if obstruction, such as kidney stones, is suspected not diagnostic recommend views kidneys, ureters, and bladder (KUB) findings hydronephrosis from obstruction may visualize kidney stones CT indications typically performed if patients present with hematuria, even if renal papillary necrosis is suspected, as hematuria can indicate malignancy in the bladder views CT of abdomen and pelvis findings hydronephrosis kidney stones ring shadows in medullae loss of papillae Intravenous urography (IVU) indications if CT scan is inconclusive and suspicious for renal papillary necrosis remains high if there is no suspicion of obstruction but suspicion of renal papillary necrosis remains high findings ring shadow from desquamated papillae - “ring sign” Studies Labs serum creatinine if there is a sudden rise in creatinine, consider renal papillary necrosis in patient with diabetes or chronic urinary obstruction Urinalysis hematuria pyuria proteinuria Differential Nephrolithiasis kidney stone seen on imaging without evidence of renal papillary necrosis Tubulointerstitial nephritis often presents with rash, arthralgias, and eosinophilia in the urine Treatment Medical supportive care with fluid resuscitation indications for all patients Complications Chronic pyelonephritis Sepsis