Ischaemic colitis.

THE CONCEPT of ischaemia as a cause of colitis is a relatively new one (Marston et al., 1966). It seems to be an uncommon type of colitis and is certainly much less frequent than ulcerative colitis and segmental colitis due to Crohn's disease. However, it is possible that in large general hospitals, dealing particularly with geriatric patients, ischaemic colitis may be recognized more frequently in the future. It is a disease that characteristically presents in patients past the age of 50 with a sudden onset of bleeding per rectum and abdominal pain. Ischaemic colitis also occurs in patients after reconstructive operations on the aorta, in diabetics and in association with certain systemic diseases which have a vascular component, such as scleroderma and rheumatoid arthritis. Ischaemic colitis is usually a segmental inflammation, that is, one in which there is normal bowel on either side of a diseased area. These segments are usually short but may be quite long. They particularly affect the splenic flexure of the colon. The pathology of ischaemic colitis can be described in three phases. Firstly, the acute phase; this is variously called acute ischaemic colitis or infarction of the colon. So-called necrotizing colitis is probably a form of acute ischaemic disease. Secondly, transient ischaemia of the colon. Lastly, ischaemic stricture. Before describing these three phases I would like to emphasize that ischaemia may affect the small intestine in just the same form as it affects the colon. Indeed, lesions may be present in both parts of the intestine in the same patient. In the small bowel ischaemic strictures must be distinguished from Crohn's disease. So-called solitary ulcers of the small intestine which seem to have the ingestion of potassium chloride tablets as an initiating factor also have an ischaemic component in their pathogenesis. Acute ischaemic colitis presents as infarction of the bowel but often the pathological appearances are modified by secondary infection with mucosal ulceration, gangrene and perforation.