Ulcerative colitis (UC)

Ulcerative colitis is a form of inflammatory bowel disease affecting the colon and rectum. It is understood to arise from an interaction between genetics, environmental factors, gut microbiota, and an immune system that mounts a sustained inflammatory response against the colon's lining, producing continuous inflammation that begins at the rectum and extends upward in an unbroken stretch. Unlike Crohn's disease, it usually stays confined to the colon and affects the surface lining rather than the full thickness of the bowel wall.

Research describes global incidence estimated at roughly 1 to 20 cases per 100,000 people yearly, with rates rising in newly industrialized regions. Ulcerative colitis tends to follow a bimodal age pattern, with one diagnosis peak in the second and third decades of life and a second later between ages 50 and 80.

Common signs

Loose stools often mixed with blood or mucus, urgency, a feeling of incomplete emptying, abdominal cramping, fatigue, and at times fever or weight loss. Symptoms tend to flare and then settle, and some people also have joint, skin, or eye involvement.

This is a plain-language summary for orientation, not a diagnosis. Mechanisms are described as current understanding, not settled fact. Work with your own clinician for your care.