Snapshot A 60-year-old woman presents to the emergency room with fever, chills, sudden flank pain, and gross hematuria. She has a history of recurrent urinary tract infections. Urinalysis reveals pyuria, hematuria, proteinuria, and dead tissue. An intravenous urography is obtained, revealing a ring sign. She is immediately given hydration and appropriate antibiotics. Introduction Clinical definition necrosis and sloughing of renal papillae Epidemiology Incidence 30-40% in those with sickle cell disease or trait 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) congenital urinary tract obstructions such as posterior urethral valves shock Etiology Pathogenesis in sickle cell disease or trait increased blood viscocity in the renal medulla causes renal papillary infarcts the renal medulla has a low oxygen tension resulting in red blood cell sickling in analgesic use NSAIDs inhibits prostaglandin synthesis prostaglandins promote vasodilation Presentation History may be chronic and asymptomatic or acute gross blood in urine may have history of recent infection or autoimmune flare pyelonephritis Symptoms primary symptoms fever and chills sudden onset flank or abdominal pain may be asymptomatic 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 patient presents with hematuria, even if renal papillary necrosis is suspected, as hematuria can indicate malignancy in the bladder if renal obstruction is suspected most accurate test views CT of abdomen and pelvis findings hydronephrosis kidney stones ring shadows in medullae loss of papillae Intravenous urography 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 shrinkage of renal papillae ring shadow from desquamated papillae - “ring sign” filling defect in renal pelvis contrast-containing tiny cavities in papillae 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 best initial test and results may show hematuria pyuria proteinuria sloughed papillae 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 Conservative avoid analgesics or any other nephrotoxic medications Medical supportive care with fluid resuscitation indications for all patients antibiotics indications if pyelonephritis is suspected Complications Chronic pyelonephritis Sepsis Prognosis Prognostic variable negative concomitant diabetes older age