A case of collagenous colitis associated with novel oral anticoagulants use.

An 84-year-old man was referred to our hospital because of watery diarrhea. Due to cerebral infarction, he had started treatment with a novel oral anticoagulants (NOAC) 1 month prior to admission. The patient underwent blood tests, enhanced computed tomography, and colonoscopy, which indicated infectious or medicinal colitis. The diarrhea persisted and he developed hypokalemia, so a second colonoscopy was performed, which showed edematous mucosa. Colonic mucosal biopsies showed a thick collagen band in the subepithelial region, and collagenous colitis was diagnosed. The watery diarrhea subsequently resolved 1 week after changing the NOAC to warfarin. Reports on collagenous colitis caused by NOAC are very rare, and we consider this case valuable.