Inflammation of the colon, the first part of the large intestine. The subject suffers from diarrhoea – usually passing blood and mucus – abdominal pain or discomfort, and fever. Colitis can be caused by various micro-organisms: for example, CAMPYLOBACTER, CLOSTRIDIUM and SHIGELLA bacteria, viruses or amoeba. Anxiety and antibiotic drugs may also cause colitis, the latter by directly irritating the lining of the gut.

Colitis is classified as an INFLAMMATORY BOWEL DISEASE (IBD) of which ULCERATIVE COLITIS and CROHN'S DISEASE are the two main varieties. (See IRRITABLE BOWEL SYNDROME (IBS)).