What is Crohn's disease?
Crohn's disease (CD) is a long-term condition in which parts of the gut become inflamed. It can affect any part of the digestive tract from the mouth to the anus, but it most often involves the end of the small intestine (the terminal ileum) and the colon. The inflammation can pass through the full thickness of the bowel wall and often occurs in patches, with healthy bowel in between.
CD and ulcerative colitis (UC) are the two main forms of inflammatory bowel disease (IBD). About half a million people in the UK live with one or the other. CD usually starts between the ages of 15 and 40, although it can begin at any age, including in childhood.
CD is not infectious and it is not a form of cancer. It tends to flare up from time to time, with periods of good health in between, and with the right treatment most people lead full and active lives.
Symptoms
The symptoms depend on which part of the gut is inflamed and how severe the inflammation is. The most common are:
- Diarrhoea, sometimes with blood or mucus
- Abdominal pain, often in the lower right side and after meals
- Tiredness
- Poor appetite and weight loss
- Mouth ulcers
Some people also have problems outside the gut, such as painful joints, sore red eyes or tender lumps on the skin. In children, slow growth may be the first sign. More detail is given in The Symptoms of Crohn's Disease and Complications of Crohn's Disease.
What causes it?
The cause is not fully understood. It is believed that CD results from an abnormal immune reaction against the bacteria that normally live in the bowel, in people whose genes make them more likely to react in this way. Smoking roughly doubles the risk of CD and makes it harder to control. Diet also plays a part, which is why changing the diet can be an effective treatment. See What is the cause of IBD? and Smoking and Crohn's Disease.
How is it diagnosed?
Your GP will usually start with blood tests and a stool test called faecal calprotectin, which shows whether the bowel is inflamed. If CD is suspected you will be referred to a specialist for a colonoscopy, in which a flexible camera is passed into the bowel and small samples (biopsies) are taken. Scans such as MRI or ultrasound are used to look at the small intestine. The tests are described in Investigations into Crohn's Disease.
Treatment
There is no permanent cure for CD, but treatment can bring the disease under control and keep it there. The main approaches are:
- Diet. A liquid diet taken in place of food for a few weeks, followed by careful reintroduction of foods, settles CD in most people and avoids the side effects of drugs. It is the preferred first treatment for children. See Elemental and Polymeric Diets and The LOFFLEX Diet.
- Medicines. Steroids are used to settle a flare-up, while immunosuppressants such as azathioprine, and biological drugs such as infliximab and adalimumab, keep the disease quiet over the longer term. See Drug Treatment.
- Surgery. Many people with CD need an operation at some stage, usually to remove a narrowed or badly damaged section of bowel. See Surgery in Crohn's Disease.
Many patients ask whether they should choose drugs or diet. The answer depends on the person and the stage of the disease, and it is discussed in Should I go for drugs or diet?
Crohn's disease or ulcerative colitis?
UC affects only the large bowel and the inflammation is continuous, starting at the rectum. CD can affect any part of the gut and occurs in patches. Bleeding is more common in UC, while pain and weight loss are more common in CD. Diet works well as a treatment for CD but not for UC. The two are compared in Differences between Crohn's Disease and Ulcerative Colitis, and UC has its own section.
Living with Crohn's disease
CD affects work, travel, relationships and family life, and it helps to plan ahead. Our Living with IBD section covers everyday situations such as work, holidays, pregnancy, exercise and coping with stress.
This website gives general information only. Always talk to your GP, IBD nurse or consultant before changing your treatment or diet.