Ulcerative Colitis

Ulcerative colitis (UC) is a chronic, immune-mediated inflammation of the colonic mucosa. In a genetically susceptible person, the immune system responds abnormally to intestinal microbiota and sustains inflammation in the bowel lining. The injury is mucosal and usually continuous, beginning in the rectum and extending proximally to a variable distance. A raw, inflamed mucosal surface bleeds easily and loses its ability to handle stool normally. The resulting pattern is frequent, urgent, often small-volume stools with visible blood, mucus, cramping, and sometimes tenesmus—the feeling of needing to pass stool even when little remains. This distribution helps distinguish UC from Crohn disease. Crohn disease can affect any part of the gastrointestinal tract and is typically patchy and transmural; UC is limited to the colon and primarily affects its mucosal surface. A patient with UC can still develop infectious colitis, so a new flare-like presentation should not automatically be attributed to UC alone. Repeated bloody stools can produce iron-loss anemia. Diarrheal losses can reduce circulating volume and disturb electrolytes. Severe inflammation can also impair bowel motility; increasing abdominal distension in a patient who...