Renal papillary necrosis
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Renal papillary necrosis refers to ischemic necrosis of the renal papillae. Necrosis also occurs in the medullary pyramids.
Patients can present with both acute episodes or chronic renal papillary necrosis. Calyceal or ureteral obstruction by sloughed papillae manifests with flank pain, hematuria and varying degrees of 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 rigors.
Papillary necrosis is characterized by necrosis and sloughing of papillary tissue, which may result in a substantial loss of renal function. The renal medulla and papilla are susceptible to ischemic necrosis due to their blood supply and hypertonic environment.
For a list of causes, check the article on renal papillary necrosis (mnemonic).
Fluoroscopy / CT
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:
- 1. Spencer B. Gay, Richard J. Woodcock. Radiology Recall. (2008) ISBN: 9780781765596 - Google Books
- 2. Jung D, Kim S, Jung S, Hwang S, Kim S. Renal Papillary Necrosis: Review and Comparison of Findings at Multi-Detector Row CT and Intravenous Urography. Radiographics. 2006;26(6):1827-36. doi:10.1148/rg.266065039 - Pubmed
- 3. Kawashima A, Vrtiska T, LeRoy A, Hartman R, McCollough C, King B. CT Urography. Radiographics. 2004;24 Suppl 1(suppl_1):S35-54; discussion S55-8. doi:10.1148/rg.24si045513 - Pubmed
- 4. Dyer R, Chen M, Zagoria R. Classic Signs in Uroradiology. Radiographics. 2004;24 Suppl 1(suppl_1):S247-80. doi:10.1148/rg.24si045509 - Pubmed