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Renal Papillary Necrosis

General Considerations

  • Necrosis of the renal medullary pyramids and papillae with many causes, all of which mediate the development of ischemia
  • Infection is frequent finding, contributing to the clinical presentation of with fever and chills in about 2/3 of patients and positive urine cultures in 70%
    • But papillary necrosis can also develop without infection being present
  • Inflammatory reaction in the interstitium of the kidney compresses and compromises the medullary vasculature and predisposes the patient to ischemia and papillary necrosis
  • Other diseases can also impair this circulation, among them
    • Diabetes mellitus
    • Urinary obstruction
    • Analgesic nephropathy
      • Phenacetin, with its toxic metabolite, p-phenetidin
      • Also occurs with NSAIDS (non-steroidal anti-inflammatory drugs)
      • But usually with another predisposing factor present
  • Any condition associated with ischemia predisposes a person to papillary necrosis, such as
    • Shock
    • Dehydration
    • Hypovolemia
    • Sickle cell disease
    • Tuberculosis
    • Trauma
    • Cirrhosis = alcoholism
    • Coagulopathy
    • Renal vein thrombosis
    • Hemophilia
    • Christmas disease
    • Acute tubular necrosis
  • Most patients who develop papillary necrosis have two or more contributing factors
  • Usually bilateral
    • Can affect a single papilla or entire kidney may be involved
  • Mean age of onset is 53 years
    • More than 90% of cases occur in individuals older than 40
    • Uncommon in patients younger than 40 and in the pediatric population
  • More often in women than in men
  • Types
  • Clinical findings
    • Fever and chills
    • Flank and/or abdominal pain
    • Hematuria
    • Acute ureteral obstruction from sloughed papillae manifests as flank pain and colic from hydronephrosis or pyonephrosis
      • Hematuria is almost always present
      • Clinical picture in such cases may also include fever, chills and sepsis.
  • Imaging findings
    • The kidneys are usually normal in size until they contract in the late stages of the disease
    • Linear streak of contrast may appear inside of calyces representing void left by sloughed papilla (lobster claw sign)
    • Widening of the fornices from shrinking of the papillae
    • Larger collection of contrast may fill cavities inside of calyces representing a calyx without a papilla
    • Ring shadows can develop in the medulla outlining detached papilla within contrast material-filled cavity
      • Often in a triangular shape, referred to as the ring sign
    • Sloughed papillae can produce filling defects in internal collecting system or ureters
    • The ring shadow or sloughed papilla can rarely calcify
  • Complications
    • Infection
    • Obstruction

Renal Papillary Necrosis. Image from a CT Urogram shows numerous irregular collections of contrast arising from the calyces, some streak-like densities and overall distortion of the normal medullary-calyceal anatomy (yellow circles).
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eMedicine. JM Donohoe, JH Mydlo, AN Khan, M Chandramohan, and S Macdonald