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 login to view 2 more bullets 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 login to view 2 more bullets in analgesic use login to view 2 more bullets 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 login to view 2 more bullets may be asymptomatic Physical exam tenderness to palpation in the flank or abdomen Imaging Radiographs indications login to view 2 more bullets recommend views login to view 1 more bullet findings login to view 2 more bullets CT indications login to view 3 more bullets views login to view 1 more bullet findings login to view 4 more bullets Intravenous urography indications login to view 2 more bullets findings login to view 4 more bullets Studies Labs serum creatinine login to view 1 more bullet Urinalysis best initial test and results may show login to view 4 more bullets 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 login to view 2 more bullets antibiotics login to view 2 more bullets Complications Chronic pyelonephritis Sepsis Prognosis Prognostic variable negative login to view 2 more bullets