Dalziel first described Crohn’s disease in Scotland in isolated cases in 1913. However, in 1932, Crohn and colleagues named the disease Regional Ileitis. This was later changed to Regional Enteritis when, after further work, it was discovered the disease affected other areas of the gut.

It is a chronic inflammatory disease, which can affect the whole of the alimentary tract (digestive tube) from mouth to anus. The inflammation extends through all layers of the gut wall (transmural) and is characteristically patchy in distribution (skip lesions) with areas of normal tissue between.

The most commonly affected sites are the terminal ileum (the lower part of the small intestine), and the large intestine. It frequently affects the anus.

The disease has several characteristics:

1. The course of the disease is chronic with periods of remission, when patients are symptom-free, and relapses, when symptoms flare up.

2. It has a wide range of symptoms.

3. Complications outside the intestine are common.

4. There is a strong tendency for it to recur after surgery.