Inflammatory Bowel Disease (IBD) is an auto-immune disease, where there is a dysfunction in the immune system leading to attacks on healthy bowel tissue for prolonged periods of time. This results in bowel damage of varying degrees depending on the severity of the condition. It is not known why this happens, only that there seem to be links with genetics and environmental triggers. (NB. Irritable bowel syndrome IBS is not an IBD.)

There are two main types of IBD, Crohn's disease and Ulcerative Colitis.

Crohn's disease (CD) - Affected areas occur in patches in the colon and ileum. The inflammation tends to go deep into the gut wall, causing scarring and thickening of the affected area, and gives the inner surface of the affected GIT the characteristic cobblestone appearance. There is ulceration and bleeding. Prolonged damage can lead to complications such as strictures (sections of narrowed GIT), adhesions, fistulae (abnormal connection between two loops of gut). Formation of abscesses is common.

Ulcerative Colitis (UC) affects the colon only, and is not patchy the way CD is. Inflammation tends to stay on the mucosa layer.

Diagram showing CD vs UC. In CD the entire thickness of the GIT wall is affected and over time this leads to thickening of the wall due to hypertrophy and scarring, and the formation of the cobblestone appearance and fissuring.

In UC the inflammation stays in the mucosa, causing surface ulceration.

Diagram showing how the affected areas in CD occur in patches through out the colon and up into the ileum.

In UC the inflammation is not patchy, it is one continuous area of inflammation which may or may not enlarge. In UC only the colon is affected.

Fistulae

Suggested further reading:

CD vs UC

Complications of IBD