Monarch Disease Ontology id MONDO_0000703 (collagenous colitis) can be described as follows. A type of microscopic colitis of unknown etiology. It is characterized by the presence of collagen deposits in the lamina propria of the colonic mucosa. Patients present with chronic watery diarrhea. Colonoscopy reveals normal-appearing mucosa. The diagnosis is made with the microscopic examination of the colonic biopsy samples.