After a monthslong bout of diarrhea, blood work, and a colonoscopy, I’ve been diagnosed with microscopic colitis. Can you explain what microscopic colitis is, what causes it, and how to avoid flares? ANSWER: Microscopic colitis is a chronic inflammatory disease of the colon. Some medicines are associated with the risk of microscopic colitis, so they should be stopped if possible. — Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible.