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.
Ulcerative colitis only affects the colon (large intestine), while Crohn’s disease can affect the entire digestive system, from the mouth to the anus.
It is sometimes difficult to tell the difference between the two main types of IBD. If this is the case, it is 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), which is a common yet poorly understood condition that causes symptoms such as constipation or diarrhoea, or sometimes both, and abdominal pain.
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 in 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).
Read more about the symptoms of Crohn’s disease and ulcerative colitis.
The causes of Crohn’s disease and ulcerative colitis are unclear, though it appears that some sort of environmental factor in susceptible individuals causes the immune system (the body’s defence against infection) to malfunction. The immune system then starts attacking healthy tissue inside the digestive system, leading to inflammation.
Read more about the causes of Crohn’s disease and ulcerative colitis.
Both Crohn’s disease and ulcerative colitis are treated with medications such as corticosteroids, which help reduce inflammation, and immunosuppressants, which block the harmful activities of the immune system.
Surgery may be required in cases that fail to respond to medication. Surgery usually involves removing an inflamed section of the digestive system.
Read more about the treatment of Crohn’s disease and ulcerative colitis.
Who is affected?
IBD is usually diagnosed in people in their late teens or early 20s, but it can appear at any age.
IBD is more common in white people than in black people or those of Asian origin. The condition is most prevalent among Jewish people of European origin.
IBD affects slightly more women than men.
How common is it?
In the UK, IBD affects about one person in every 350. About 100,000 people have ulcerative colitis, and 52,000 people have Crohn’s disease in England for example.
The outlook for most people with ulcerative colitis is usually quite good. Symptoms are often mild to moderate and can usually be controlled using medication.
However, an estimated one in five people with ulcerative colitis have severe symptoms that often respond less well to medication. In these cases, it may be necessary to surgically remove the colon.
The outlook for Crohn’s disease is highly variable. People can have long periods of remission that last for weeks or months where they have no, or very mild, symptoms, followed by periods where their symptoms flare up and are particularly troublesome.
There is currently no cure for Crohn’s disease. However, medication is available that can be used to treat the symptoms and prevent them from returning.
About four out of five people with Crohn’s disease will require surgery to relieve their symptoms, repair damage to their digestive system and treat complications of the condition.