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
• Focal = involves only the tip of the papilla
• Diffuse = involves the whole papilla and parts of the medulla
• Pathologically divided into medullary form and papillary form dictated by degree of ischemia
• 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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Renal Papillary Necrosis. Image of left kidney 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.

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eMedicine. JM Donohoe, JH Mydlo, AN Khan, M Chandramohan, and S Macdonald