Crohn's disease

Crohn's disease is a condition that causes inflammation of the gastrointestinal tract (gut). The gut consists of the oesophagus (gullet), stomach, and small and large intestine.

Crohn's disease can affect any part of the gut. However, it most commonly occurs at the lower end of the small intestine, known as the ileum. Typical symptoms include pain, ulcers and diarrhoea. Daily medication can be taken to relieve the symptoms but surgery to remove part of the gut may sometimes be required.

Approximately one in 1,500 people have Crohn's disease, and the condition affects slightly more women than men. It can develop at any age, but usually starts between the ages of 15 and 40.

The outlook for people with Crohn's disease varies depending on which part of the gut is affected, and the severity and frequency of the symptoms.

The majority of people experience moderate symptoms from to time to time and most (80%) will require surgery at some point. Rare complications, such as a perforated gut, can be life-threatening.

The exact cause of Crohn’s disease is unknown. It is thought that there may be a genetic link because there is some evidence that it runs in families. One in ten people with the condition have a close relative who also has it.

A bacterium or virus (germ) may be a factor in the cause of Crohn’s disease. Some scientists think that in people who are genetically prone to the condition, a germ may trigger the immune system to cause inflammation in parts of the gut.

Crohn’s disease is more common in smokers and in women who use the combined oral contraceptive pill.

As well as weight loss and ill-health, there are a few physical signs that may indicate that you have Crohn’s disease. Sometimes, a mass can be felt in the abdomen when loops of inflamed bowels are stuck together. There may also be fatty stools.

A number of tests can be carried out to diagnose Crohn’s disease, and which ones are used will depend on the part of your gut that is affected. Tests that can be used include:

  • stool tests,
  • blood tests to check for anaemia and other deficiencies,
  • biopsy where a small sample of the lining of the gut is taken for analysis under a microscope,
  • sigmoidoscopy – investigation of the lower bowel using a sigmoidoscope (a short, flexible telescope), and
  • colonoscopy – investigation of the colon using a colonoscope (a long, flexible telescope).

If you have symptoms in the upper part of your gut, an endoscopy may be conducted. This involves an endoscope (a thin, flexible telescope) being passed down your oesophagus (gullet) and into your stomach, in order to allow the doctor to look inside.

For diagnosing Crohn’s disease, a barium X-ray of the large intestine (barium enema) or small intestine (barium meal) may be used. Barium is usually given in liquid form and will appear white on X-rays, highlighting which parts of the gut are affected. Further tests and scans may be required if a diagnosis of Chrohn’s disease is in doubt, or if there are complications.

The symptoms of Crohn's disease occur when the wall of the affected part of the gut becomes inflamed. The inflammation often causes one or more of the following symptoms:

  • pain – different people experience different severities of pain. The site of the pain will depend on which part of the gut is affected. The condition commonly occurs at the lower end of the small intestine (ileum), and so the pain will often be on the lower right side of the abdomen,
  • ulcers – a raw area of the gut wall that may bleed. If it does, you may notice blood in your stools (faeces). Mouth ulcers are also common.
  • diarrhoea – can vary from mild to severe, and may contain mucus, pus or blood. You may feel a frequent need to go to the toilet, but a lack of anything to pass (tenesmus) is common,
  • feeling generally unwell – fever and extreme tiredness,
  • loss of appetite and weight,
  • anaemia – can occur if you lose a lot of blood, and
  • anal fissures and rectal bleeding – the skin of the anus may become cracked (anal fissures), bleed and be painful.

The symptoms vary depending on the part of your gut affected. For example, if you have pain in your abdomen, with no other symptoms, it may be due to a small patch of Crohn's disease in your small intestine. However, if the condition causes severe diarrhoea and other symptoms, the large intestine will be affected.

Additional symptoms

Some people with Crohn's disease experience additional symptoms. These can include:

  • inflammation of the joints (arthritis),
  • inflammation of the eye (uveitis),
  • inflammation of the liver, and
  • skin rashes.

The reason why these other symptoms occur is not fully understood. However, it is thought that they may be triggered by the immune system as a reaction to the inflammation of the gut. 

Medicines or steroids, to reduce inflammation in your gut, are commonly used to treat Crohn's disease when it first develops. They are usually taken in oral tablet form or as an enema (a tablet inserted into your anus), if the rectum or lower part of the colon are affected.


If the symptoms of Crohn's disease are severe, a course of steroids (corticosteroids) may be recommended for a few weeks. In most cases (70%), the symptoms improve within four weeks of starting steroids. Once the symptoms improve, the dose is gradually reduced, and then stopped. As steroids can cause side effects, they are not usually used as a long-term treatment.

5-aminosalicylate medicines

5-aminosalicylate medicines can be used as an alternative to steroids, to treat mild to moderate symptoms of Crohn's disease. They include sulfasalazine, mesalazine, salazine, and balsalazide. However, they do not always work and you may need to switch to steroids if your symptoms are severe.

Antibiotics and immunosuppressants

Some people with Crohn's disease do not respond well to steroids or 5-aminosalicylate medicines. In such cases, a specialist may advise that you use antibiotics to combat infection, immunosuppressive medicines, such as methotrexate, antibody therapy (infliximab), or a combination of these treatments.


If you have particularly bad symptoms, which cannot be controlled using medicines, you may be given a strict diet to follow. In most cases, after sticking to the diet for a few weeks, the symptoms improve and a normal diet can be gradually resumed. The reasons why this works are not fully understood, but it is thought that some foods, such as dairy products, may trigger the symptoms of Crohn's disease and that resting the gut may help.


If other treatments do not work, surgery may be required to remove the affected part of your gut. The affected part is removed and the two ends are sewn together. Surgery may also be required to treat complications such as obstructions, abscesses or damage to your gut.

Other measures

Anti-diarrhoeal medicines can be taken to firm up your stools, and painkillers may be needed at times when your symptoms are particularly bad. If your symptoms are really severe, you may need to go to hospital to receive fluid intravenously (by a drip).

You may be prescribed iron tablets if you develop anaemia. Also, if your gut is not absorbing food properly, you may need to take vitamin supplements.  If you smoke, giving up will often decrease the frequency of your symptoms

The future

The development of new medications for Crohn's disease is ongoing, and it is likely that there will be a number of new treatment options available for the condition over the next decade.