Colitis

Colitis is inflammation of the inner lining of the colon (large intestine), a structural change that's visible on imaging or during a colonoscopy.

Colitis vs. IBS: A Critical Distinction

This distinction matters and is worth stating clearly: colitis involves actual, visible inflammation and tissue changes in the colon, while IBS is a functional disorder — the colon looks structurally normal, but doesn't function normally. They can share symptoms like abdominal pain and altered bowel habits, but colitis is diagnosed through direct visualization (colonoscopy) or tissue biopsy, not by excluding other causes the way IBS often is.

Common Causes

Infectious colitis results from a bacterial, viral, or parasitic infection — including Clostridioides difficile (C. diff) colitis, which commonly develops after a course of antibiotics disrupts the colon's normal bacteria. Ischemic colitis results from reduced blood flow to part of the colon. Inflammatory bowel disease — including ulcerative colitis and Crohn's disease — is caused by the immune system mistakenly attacking the digestive tract's lining, causing chronic, recurring inflammation; ulcerative colitis affects only the colon's lining, while Crohn's disease (Crohn's colitis when it involves the colon) can affect the full thickness of the bowel wall anywhere along the digestive tract.

Symptoms

Diarrhea (sometimes with blood or mucus), abdominal pain and cramping, an urgent need to have a bowel movement, and, depending on the cause, fever or fatigue.

Treatment

Treatment depends entirely on the specific cause: infectious colitis may resolve on its own or need targeted treatment for the specific organism; ischemic colitis requires addressing the blood flow issue; ulcerative colitis is managed long-term with medications that control the immune response and inflammation.