Efficacy and Safety of Oral Rifaximin in Patients With Active Microscopic Colitis

Inclusion Criteria: * Collagenous colitis (CC) or lymphocytic colitis (LC) diagnosed on colon biopsies reviewed by 2 separate pathologists * CC will be defined histologically to be the following: thickness of the collagenous subepithelial table \>10 micrometer using an ocular micrometer, inflammation in the lamina propria consisting of mainly lymphocytes and plasma cells, lack of crypt architectural distortion, and regenerative-appearing changes in the surface and/or crypt epithelium * LC will be defined histologically to be the following: intraepithelial lymphocytes \>20 per 100 epithelial cells in the subjective area of highest lymphocyte density, inflammation in the lamina propria consisting of mainly lymphocytes and plasma cells, and regenerative-appearing changes in the surface and/or crypt epithelium * Subjects in active flare, defined as \>3 watery/loose stools per day on \>4 / 7 days over \>4 weeks in the past 3 months. Exclusion Criteria: \-