[1670] Renal Medullary Angiitis

Allen Hendricks, Alexis Harris, Patrick Walker, Christopher Larsen. Nephropath, Little Rock, AR

Background: Renal medullary angiitis is a lesion seen in small vessels involving the vasa recta of the renal medulla. It consists of interstitial hemorrhage with associated karyorrhexis and polymorphic inflammatory infiltrate surrounding the peritubular capillaries in the medulla. A PubMed review revealed a total of 15 cases of medullary small vessel vasculitis in three publications, all of which were in the setting of ANCA-associated disease. The scarcity of cases in the literature detailing this lesion is likely due to a lack of medullary tissue in many biopsies, and due to the fact that it is often mistaken for acute interstitial nephritis.
Design: We searched our renal biopsy cases from January 2008 through August 2011 and identified 38 cases of medullary angiitis. All cases were examined by light microscopy, immunofluorescence, and electron microscopy. The clinical history submitted at the time of renal biopsy was reviewed and pertinent information including patient's age, gender, indication for biopsy, serum creatinine, and any positive serologic tests, including ANCA, was collected.
Results: Acute renal failure was the indication for biopsy in 29/38 (76%) cases, while rapidly progressive renal failure was second at 16%. In total, 23 (60.5%) cases of medullary angiitis were determined to be ANCA-associated while 15 (39.5%) were determined to be secondary to other etiologies. The most common non-ANCA etiology of medullary angiitis was IgA nephropathy (18.4%) followed by antibiotic treatment in the setting of infection (15.8%). There was also one patient with cryoglobulinemia and one patient with salicylate toxicity. Twenty-seven showed focal involvement of the medulla and 11 had diffuse involvement. ANCA-associated cases showed diffuse involvement in 7/23 while non-ANCA cases showed diffuse involvement in 4/15. There was no involvement of renal cortex in any of the 38 cases.
Conclusions: To our knowledge, this is the largest study to date detailing the morphological and clinical spectrum of renal medullary angiitis. This is an important lesion to recognize because in the majority of cases its presence suggests systemic vasculitis, which should prompt ANCA serologies. If ANCA serologies are negative and there is no evidence of IgA nephropathy, then a drug-induced etiology should be considered. When interstitial hemorrhage and/or inflammation are present in the medulla on renal biopsy, close inspection should be undertaken to exclude the presence of medullary angiitis. This lesion can be seen outside the setting of ANCA-associated disease, and in our series was also present in IgA nephropathy, drug toxicity, and cryoglobulinemia.
Category: Kidney (does not include tumors)

Monday, March 19, 2012 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 253, Monday Morning

 

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