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Microscopic Colitis: Not Always “Microscopic”
By Joel Joseph, MD, Troy Pleasant, MD and Klaus Mönkemüller, MD, PhD, FASGE, FJGES
Virginia Tech Carilion School of Medicine, Virginia, USA
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80-year-old patient with ongoing watery diarrhea for several weeks. Colonoscopy images shown here. Note that there is significant patchy edema, hypervascularity, punctate erythema, thickened folds and patchy superficial erythema.

Classically, microscopic colitis (collagenous and lymphocytic) is thought to have normal colon mucosa, but several studies now have shown that many patients have abnormal colon mucosal findings, such as the ones depicted in our case (1-3). The best review on the topic was written by A. Kolaouzidis and A. Saeed (1). The authors performed a systematic electronic and manual search of PubMed and EMBASE for publications on distinct endoscopic findings in microscopic colitis, resulted in 42 relevant reports for inclusion in this review (1). The authors found four broad categories of distinct endoscopic findings in collagenous colitis: (1) pseudomembranes; (2) mucosal vascular pattern alteration which includes an indistinct appearance of the blood vessels and a variable degree of pruning of the mucosal vasculature, or a crowded, dilated and tortuous capillary network; (3) mucosal abnormalities such as red spots and some mucosal nodularity or textural alteration, evident with or without chromoendoscopy and (4) a continuum of mucosal breaks/defects, i.e., mucosal lacerations/tears, including the so-called “cat scratch colon” pattern, or fractures usually along the long axis of the colonic wall to the fine linear cicatricial lines or thick scar-like ridges of the mucosal surface (effects of the mucosal healing process of mucosal defects) (1).
Interestingly, they only found one publication describing a characteristic endoscopic pattern in lymphocytic colitis. Thus, our case adds to the growing literature on “macroscopic” endoscopic changes in “microscopic colitis”.
References:
1. Koulaouzidis A, Saeed AA. Distinct colonoscopy findings of microscopic colitis: not so microscopic after all? World J Gastroenterol. 2011 Oct 7;17(37):4157-65. doi: 10.3748/wjg.v17.i37.4157. PMID: 22072846; PMCID: PMC3209563.
2. Wickbom A, Lindqvist M, Bohr J, Ung KA, Bergman J, Eriksson S, Tysk C. Colonic mucosal tears in collagenous colitis. Scand J Gastroenterol. 2006 Jun;41(6):726-9. doi: 10.1080/00365520500453473. PMID: 16716973.
3. Park HS, Han DS, Ro YO, Eun CS, Yoo KS. Does lymphocytic colitis always present with normal endoscopic findings? Gut Liver. 2015 Mar;9(2):197-201. doi: 10.5009/gnl13373. PMID: 25167800; PMCID: PMC4351026.
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