Colitis: Colitis is an inflammation of the colon. There are many cause of colitis, infectious colitis (bacterial or viral), ischemic colitis, inflammatory bowel disease (Crohn's disease, ulcerative colitis), microscopic colitis (lymphocytic and collagenous), and chemical colitis. Symptoms of colitis are generally diarrhea (may be bloody) and abdominal pain and/or cramping. Treatment of colitis depends upon the cause.