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Inflammatory bowel disease

When doctors talk of inflammatory bowel disease they usually mean people who either have Crohn's disease or ulcerative colitis. Both these conditions can cause inflammation of the colon and rectum (large bowel or large intestine) with similar symptoms, such as bloody diarrhoea, etc.

Although these conditions are similar and treatments are similar, there are differences. For example:

  • The inflammation of ulcerative colitis tends to be just in the inner lining of the gut (gastrointestinal tract), whereas the inflammation of Crohn's disease can spread through the whole wall of the gut.

  • Ulcerative colitis only affects the colon and rectum, whereas Crohn's disease can affect any part of the gut.

However, about 1 in 20 people with inflammatory bowel disease (IBD) affecting just the colon cannot be classified as having either Crohn's disease or ulcerative colitis because they have some features of both conditions. This is sometimes called indeterminate colitis.

Find out more about the gut (gastrointestinal tract) and how it works in our leaflet The digestive system.

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How common is inflammatory bowel disease?

  • Ulcerative colitis is the most common type of inflammatory disease of the bowel. It affects about 1 in 400 people in the UK. Crohn's disease affects about 1 in 700 people in the UK.

  • IBD can first present at any age but the most common age is between 15-30 years. There is a second smaller peak age for symptoms to start between 50-70 years.

  • Crohn's disease is more likely in those with a strong family history (first-degree relative affected, ie parent, brother or sister) and in people who smoke.

  • Infections (especially upper respiratory and bowel infections) ot taking non-steroidal anti-inflammatory drugs (NSAIDs) can also aggravate symptoms.

Causes of inflammatory bowel disease

The exact cause isn't known but it seems that there is a combination of genetic and environmental factors. It seems that the the body's immune system is triggered by factors such as bacteria or viruses to cause inflammation in the gut (bowel) wall.

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Symptoms of inflammatory bowel disease

The symptoms are very variable depending on severity and which part of the gut (bowel) is affected. The symptoms also tend to go through periods when they are more severe (relapses) and periods when they are much less severe (remissions). The symptoms may include:

  • Tummy (abdominal) pain and cramps.

  • Diarrhoea (may be bloody).

  • Urgent need to open your bowels.

  • High temperature (fever).

  • Weight loss.

  • Loss of appetite.

However, the symptoms are very variable, especially for people with Crohn's disease, which can affect any part of the gut (bowel).

How is inflammatory disease diagnosed?

If your symptoms suggest the possibility of inflammatory disease then you will need certain tests, which will include:

  • Blood tests, including a full blood count to check for anaemia and a blood test to check for any indication of inflammation. The main tests for inflammation are called erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP).

  • Stool tests to check whether there is any infection in your gut (bowel).

  • Scans, such as CT scan or MRI scan.

  • Sigmoidoscopy or colonoscopy to look at the lining of your large bowel (colon) and to take biopsies.

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What are the treatments for inflammatory bowel disease?


Changes to your diet may help to reduce your symptoms. The dietary advice will depend on your symptoms and it's essential to make sure you get enough energy and nutrients from your diet. Therefore it's very important to discuss any dietary advice with your doctor or with a dietician. This dietary advice may include reducing the amount of fibre in your diet and eating small regular meals.

A low-residue diet may also be used for IBD. This is a very restricted diet with less fibre. This diet can help to reduce symptoms such as diarrhoea and pain but needs supervision by a dietician. You will need to take vitamin supplements because a low residue diet doesn't contain all the nutrients you need.

Managing stress

Stress can make your symptoms worse so it's very important to learn how to manage stress. The ways we manage stress vary from person to person but meditation and regular exercise will help. See also the separate leaflet called Stress Management. It may also help to join a local support group so you can share how you feel with others and learn some tips to help you deal with your symptoms.


You will often need to take one or more medicines to help control the inflammation in your gut (bowel). Medicines may be used to control the symptoms when they are bad and also to help keep you well and reduce the risk of a flare-up once the symptoms are under control. The medicines used to treat IBD include:

  • Aminosalicylates - for example, mesalazine, balsalazide sodium and olsalazine sodium.

  • Medicines affecting the immune response - for example, azathioprine, mercaptopurine or methotrexate.

  • Biologic therapy - for example, infliximab, adalimumab, and golimumab. These medicines are called monoclonal antibodies. They are usually reserved for people with severe disease which has not responded to other treatments such as steroids and medicines which damp down the immune response.They should be used under specialist supervision.

  • Corticosteroids may be used when symptoms are severe (relapses) but should not be used to maintain remission.

  • Other medications to treat pain and change of bowel habit (diarrhoea or constipation) may also be needed.

See the separate leaflet called Aminosalicylates. These are one of the groups of medicines used to treat IBD. These medicines are still used in people who have acute flare-ups of Crohn's disease, but have become less widely used to maintain remission once the acute flare up has been achieved.

You can find out more about treatments, including the latest guidelines, from our separate leaflets called Crohn's Disease and Ulcerative Colitis.


Ulcerative colitis only affects the colon and rectum so an operation to remove the large bowel (total colectomy) will cure the condition. However, not everyone with ulcerative colitis needs to have their bowel removed.

Although surgery may be needed for Crohn's disease, it will not cure Crohn's disease and may cause more problems.

If the whole of the colon and rectum is removed (proctocolectomy) then the small bowel (ileum) may be connected directly with your back passage (ileoanal anastomosis) or connected to an opening at the front of your tummy wall (ileostomy). Read more in the separate leaflet called Stoma Dietary Care.

Are there any complications of inflammatory bowel disease?

Bowel complications may be serious and include:

  • Stoma formation (ileostomy or colostomy) - this may be needed after an operation to remove part of the bowel.

  • Persistent blood loss causing anaemia.

  • Rupture of the bowel wall (perforation).

  • Narrowing of the bowel causing obstruction (stricture), more common with Crohn's disease.

  • Ulceration and abnormal passages (fistulae) around the back passage (anus).

  • Severe dilatation of the large bowel (colon). This is called toxic megacolon and is more common with ulcerative colitis than Crohn's disease.

  • Greatly reduced absorption of food from the bowel (malnutrition).

  • Increased risk of bowel cancer (especially ulcerative colitis).

IBD can also cause problems affecting other parts of the body - for example, arthritis, skin conditions, eye inflammation, liver problems and bone loss.

What is the outlook?

  • The outlook (prognosis) for people with IBD is very variable. More severe symptoms are associated with a worse outlook.

  • More than one half of people with Crohn's disease need surgery within 10 years of diagnosis. However, about 1 in 3 people with Crohn's disease will have less severe symptoms.

  • Ulcerative colitis is a lifelong condition, with unpredictable relapses and remissions. However an operation to remove the large bowel (colectomy) will cure ulcerative colitis.

Further reading and references

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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