A subtype of MICROSCOPIC COLITIS, characterized by chronic watery DIARRHEA of unknown origin, a normal COLONOSCOPY but abnormal histopathology on BIOPSY. Microscopic examination of biopsy samples taken from the COLON show larger-than-normal band of subepithelial COLLAGEN.

Synonyms: Colitis, Collagenous, Collagenous Colitis