[A case of collagenous colitis with watery diarrhea due to lansoprazole use in an elderly woman].

We report a case of a 75-year-old woman with urgent watery diarrhea, occurring 5 to 8 times per day, which began after starting lansoprazole (30 mg/day) for erosive gastritis. Her chronic watery diarrhea persisted for over 2 years with mild weight loss. Colonoscopy was performed and biopsies showed collagenous colitis in her transverse colon. We therefore replaced lansoprazole with famotidine (20 mg/day). Within 3 days after the discontinuation of lansoprazole, her watery diarrhea resolved and she recovered, and reported normal feces. Increasing age and female gender are major risk factors for collagenous colitis. The differential diagnosis of collagenous colitis should include: 1) an appropriate clinical history, excluding other etiologies, 2) normal or near-normal endoscopic and/or radiographic findings, and 3) colonoscopic biopsy histopathologic findings consistent with collagenous colitis. The histopathologic findings of colonoscopic biopsy are important for diagnosis. However, because of the colonoscopic burden in elderly patients, we first recommend the discontinuation of medications suspected to cause collagenous colitis.