Renal papillary necrosis

Renal papillary necrosis refers to ischemic necrosis of the renal papillae. Necrosis also occurs in the medullary pyramids.

Clinical features

Patients can present with both acute episodes or chronic renal papillary necrosis. Calyceal or ureteral obstruction by sloughed papillae manifest with flank pain, haematuria and varying degrees or renal impairment.  Anuria or oliguria may be present in the fulminant stage, if renal failure develops. Urinary stasis leads to pyelonephritis with fever, chills or rigours.  

Pathology 

Papillary necrosis is characterised by necrosis and sloughing of papillary tissue, which may result in a substantial loss of renal function.

For a list of causes, check the article on renal papillary necrosis (mnemonic).

Radiographic features

Fluoroscopy/CT IVP

Renal papillary necrosis is visible when excreted contrast material, e.g. at IVP, fills a necrotic cavity located centrally or peripherally in the papillae. Contrast enhanced CT during the excretory phase can depict necrosis as clearly as does IV urography and thus allow accurate diagnosis of the condition ². 

CT urography typically demonstrates multiple small collections of contrast material in the papillary regions peripheral to the calyces. The entire papilla may become necrotic. The papillary defects may eventually become peripherally calcified. Sloughed papillae appear as filling defects in the collecting system and ureters and may obstruct them and cause renal colic ³.

Classical features may appear as ⁴:

• ball on tee
• forniceal excavation
• lobster claw
• signet ring
• sloughed papilla with clubbed calyx​