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Crohn's disease

7-minute read

What is Crohn’s disease?

Crohn’s disease is an inflammatory bowel disease that causes painful swelling and redness (inflammation) inside the digestive tract. This can lead to symptoms such as abdominal pain and diarrhoea.

Inflammation is a normal way in which the immune system defends the body when fighting off invaders, such as bacteria or viruses. Usually, the inflammation is switched off once the invaders are destroyed. In Crohn’s disease, a problem with the immune system causes the inflammation to continue, damaging the walls of the digestive tract.

What are the symptoms of Crohn’s disease?

Common symptoms include diarrhoea, abdominal pain and cramping, fatigue, reduced appetite and weight loss. Symptoms tend to vary between individuals and come and go over time, as the inflammation flares up then eases again.

Other symptoms may include:

Who gets Crohn’s disease and what causes it?

Crohn’s disease can develop at any age, but usually first appears in people aged 15 to 30.

Experts are not sure why Crohn’s disease occurs in some people. But they don't believe it is caused by diet or stress alone.

A combination of genetic, environmental and infectious factors may cause a fault in the immune system, leading to inflammation of the bowel.


Studies have shown that you are slightly more likely to develop Crohn's disease if you have a close relative (mother, father, sister or brother) with the disease.

Researchers have identified several genes that are more common in people with Crohn's disease or colitis, but they have not been able to show that any of these genes actually cause these conditions.


Crohn's disease is more common in people living in Australia, Western Europe and America than in developing countries in Asia and Africa. Researchers have suggested that a modern, Western lifestyle may play some role in causing Crohn's disease in susceptible people.


Some scientists think that a previous bacterial infection can trigger an abnormal immune response in some people, leading to Crohn's disease developing. This is still under investigation.

How is Crohn’s disease diagnosed?

Crohn’s disease shares many symptoms with other common conditions, such as ulcerative colitis, irritable bowel syndrome, gastroenteritis and coeliac disease. Your doctor will probably examine you and take a detailed history of your symptoms to help rule these out.

There is no single test that can be used to diagnose Crohn's disease, so a combination of tests is usually required:

  • Blood tests can rule out other medical conditions, and certain 'markers' in the blood can indicate that inflammation is present.
  • A stool sample may find other possible causes of diarrhoea and inflammation, such as an infection.
  • A colonoscopy (or sigmoidoscopy) may be performed, where a thin, flexible tube containing a tiny camera looks inside the bowel for ulcers, inflammation and bleeding.
  • A biopsy (small sample of tissue) may be taken from inside the bowel so a pathologist can examine it under a microscope to look for signs of disease.

Other types of imaging (such as an x-ray) are sometimes used to help in the diagnosis and to help rule out other diseases.

How is Crohn’s disease treated?

Although there is no cure for Crohn’s disease, treatment can help to minimise the impact of the condition on your life. Your doctor or specialist may also recommend a specific diet that suits your situation.


Crohn’s disease involves periods of ‘relapse’ when the inflammation in the bowel flares up, and periods of ‘remission’ when the inflammation calms down. The aim of treatment is to treat relapses when they occur and give the bowel a chance to heal. Medications are also used to help maintain remission, improve general wellbeing and prevent complications from developing.

Medications commonly used to control inflammation in Crohn’s disease include:

You may also be advised to take medicines that control diarrhoea, relieve pain and supplement your diet (for example, to boost your iron levels, vitamin D and calcium).


Surgery for Crohn's disease can remove or widen sections of the bowel that are badly affected by disease. The healthy ends of the bowel are usually re-joined to each other.

Sometimes, a stoma (an artificial opening in the stomach that diverts faeces or urine into a bag) is required if the disease is very severe. It’s normal to feel uneasy about the idea of living with a stoma, but it often greatly improves a person’s quality of life.

Living with Crohn’s disease

With careful management, most people with Crohn’s are able to enjoy life, including work, travel, recreation, sex and having children.

To keep healthy, consider:

  • keeping a food diary to check if there are any foods that make your symptoms worse during a flare-up
  • asking your doctor about supplements if you think you may be malnourished
  • quitting cigarettes, if you have Crohn's disease and smoke. There is evidence that smoking can make Crohn's disease more severe and harder to control
  • exercising regularly to lift your mood and help relieve stress
  • learning relaxation techniques to help manage stress

What are the complications of Crohn’s disease?

A small number of people with Crohn’s can develop inflammation in other parts of the body, such as the liver, skin, joints and eyes.

Regular monitoring by a gastroenterologist, as well as colonoscopies, may help prevent complications from developing. Medications, including steroids and drugs designed to prevent inflammation — and occasionally surgery — may be needed.

Osteoporosis (thinning of the bones) can develop as a side effect of long-term corticosteroid use.

Crohn's disease can cause bowel obstruction. When this happens, symptoms include increasing abdominal pain and cramping, vomiting and bloating. This is a medical emergency that requires a trip to hospital.

If you suspect that you are having a life-threating medical emergency, call triple zero (000) immediately and ask for an ambulance.

Crohn's disease can also cause complications anywhere in the gut, from the mouth to the anus. Complications around the anus can include abscesses (boils), flaps of thickened skin, and fissures.

Fistulas occur in up to 1 in 3 people with Crohn’s disease. These are tunnels, or ‘tracks’, that connect the intestines to other parts of the gastrointestinal tract, other organs or to the outer skin surface. They usually develop in areas of severe scarring and ulceration. A large fistula may require surgery to flush out any contents and promote healing.

What is the difference between Crohn’s disease and ulcerative colitis?

Ulcerative colitis is also an inflammatory bowel disease (IBD). However, the 2 diseases affect the digestive tract in different ways:

  • Crohn’s disease can affect any part of the digestive tract, from the mouth to the anus (back passage) but usually affects the last section of the small bowel (the ileum) and/or the colon. Inflammation can extend into the entire thickness of the bowel wall.
  • Ulcerative colitis only affects the large bowel (colon and/or rectum), and inflammation is only in the surface layers of the bowel lining. It also causes ulcers (tiny sores) to form in the lining of the bowel.

Resources and support

Speak to your doctor or gastroenterologist. To find a health professional near you, use the healthdirect service finder.

For information and support, visit Crohn's & Colitis Australia or call the IBD helpline on 1800 138 029.

For more information about living with a stoma, visit the Australian Council of Stoma Associations.

To find an accredited practising dietitian, who may be able to help manage your Crohn’s disease with diet, visit the Dietitians Association of Australia.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: October 2020

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