Page last reviewed: 13/07/2011
Inflammatory bowel disease (IBD) is not a single disease. The term IBD is used mainly to describe two diseases:
Both Crohn's disease and ulcerative colitis are chronic (long-term) diseases that involve inflammation of the gastrointestinal tract (gut). However, there are important differences between the two - see box, below left.
It is sometimes difficult to tell the difference between the two main types of IBD. If this is the case, it known as indeterminate colitis.
There are other, rarer types of IBD called collagenous colitis and lymphocytic colitis. Together these are often called microscopic colitis.
IBD is not the same as irritable bowel syndrome (IBS).
What happens in IBD?
Over time, inflammation damages the lining of the gut, and this causes ulcers to form, which may bleed or produce mucus.
In Crohn's disease, the inflammation can make the gut narrower, which creates an obstruction (this is called stricturing disease). Holes may also develop in the bowel wall and cause it to leak (this is called fistulating disease).
What are the symptoms?
The main symptoms of Crohn's disease and ulcerative colitis are similar. They include:
- abdominal (tummy) pain - this is more common in Crohn's disease than ulcerative colitis
- a change in bowel habits: urgent and/or bloody diarrhoea or (rarely) constipation
- weight loss
- extreme tiredness
Not everyone has all of these symptoms, and two individuals with the same condition can have very different symptoms. Some people may experience additional symptoms, including nausea and fever.
The symptoms of IBD can come and go over long periods. People may experience periods of severe symptoms (flare-ups), and go through periods when they have few or no symptoms at all (remission).
Who is affected?
IBD is usually diagnosed in people in their late teens or early twenties, but it can appear at any age.
What’s the difference between Crohn’s disease and ulcerative colitis?
The main difference is in the area of the gut that is affected, and the type of ulcers that occur:
- in Crohn’s disease, anywhere in the gut from the mouth to the anus can be affected, and the ulcers can impact all the layers of the gut walls
- in ulcerative colitis, just the colon (large intestine) is affected, and the ulcers only affect the inner lining of the gut
Each condition is treated differently.