[MSH Definition]: Inflammation of the COLON that is predominantly confined to the MUCOSA. Its major symptoms include DIARRHEA, rectal BLEEDING, the passage of MUCUS, and ABDOMINAL PAIN.

[NCIt Definition]: An inflammatory bowel disease involving the mucosal surface of the large intestine and rectum. It may present with an acute or slow onset and follows an intermittent or continuous course. Signs and symptoms include abdominal pain, diarrhea, fever, weight loss, and intestinal hemorrhage.

[HPO Definition]: A chronic inflammatory bowel disease that includes characteristic ulcers, or open sores, in the colon. The main symptom of active disease is usually constant diarrhea mixed with blood, of gradual onset and intermittent periods of exacerbated symptoms contrasting with periods that are relatively symptom-free. In contrast to Crohn's disease this special form of colitis begins in the distal parts of the rectum, spreads continually upwards and affects only mucose and submucose tissue of the colon. [HPO:sdoelken]

[RADLEX Definition]: Inflammation of the colon that is predominantly confined to the mucosa. Its major symptoms include diarrhea, rectal bleeding, the passage of mucus, and abdominal pain. [MeSH]

[CSP Definition]: chronic, recurrent ulceration of the colon mucosa and submucosa.