·         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%

o       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

o       Diabetes mellitus

o       Urinary obstruction

o       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

o       Shock

o       Dehydration

o       Hypovolemia

o       Sickle cell disease

o       Tuberculosis

o       Trauma

o       Cirrhosis = alcoholism

o       Coagulopathy

o       Renal vein thrombosis

o       Hemophilia

o       Christmas disease

o       Acute tubular necrosis

·         Most patients who develop papillary necrosis have two or more contributing factors

·         Usually bilateral

o       Can affect a single papilla or entire kidney may be involved

·         Mean age of onset is 53 years

o       More than 90% of cases occur in individuals older than 40

o       Uncommon in patients younger than 40 and in the pediatric population

·         More often in women than in men

·         Types

o       Focal = involves only the tip of the papilla

o       Diffuse = involves the whole papilla and parts of the medulla

o       Pathologically divided into medullary form and papillary form dictated by degree of ischemia

·         Clinical findings

o       Fever and chills

o       Flank and/or abdominal pain

o       Hematuria

o       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

o       The kidneys are usually normal in size until they contract in the late stages of the disease

o       Linear streak of contrast may appear inside of calyces representing void left by sloughed papilla (lobster claw sign)

o       Widening of the fornices from shrinking of the papillae

o       Larger collection of contrast may fill cavities inside of calyces representing a calyx without a papilla

o       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

o       Sloughed papillae can produce filling defects in internal collecting system or ureters

o       The ring shadow or sloughed papilla can rarely calcify

·         Complications

o       Infection

o       Obstruction

 

Coronal image of the 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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