Crohn's disease | Mate whēkau pauku

Also known as ileitis, inflammatory bowel disease, regional enteritis & granulomatous colitis

Crohn's disease (mate whēkau pauku) is a condition which causes swelling, thickening and inflammation of the digestive system. It is one of a group of diseases called inflammatory bowel disease.

On this page, you can find the following information:

Key points

  1. Crohn’s disease can affect any area of the digestive system from the mouth to the bottom (anus), but most commonly affects the lower part of the small intestine and colon. 
  2. It affects 1 in every 500 to 700 people, and can occur at any age, but is most often diagnosed in young adults (usually begins between 20 to 40 years of age). 
  3. The cause of Crohn's disease is still not well understood.
  4. The most common signs and symptoms are abdominal pain and diarrhoea.
  5. Treatments include medicines, nutrition supplements, and sometimes surgery.
  6. While the disease is life-long, some people have long periods of remission, when they are free of symptoms.

(Crohn's & Colitis UK, 2018)

What are the causes of Crohn's disease?

The exact cause of Crohn's disease is unknown. The following have been suggested:

Genetic factors (family history)

One in 4 people with Crohn's disease have a relative with Crohn's disease or ulcerative colitis. Recent research into how Crohn's disease runs in families has identified a human gene, called NOD2, which seems to play an important role in the interaction of the body's immune system with gut bacteria.

Immune system

Some scientists believe the cause of Crohn’s disease might be a defect in the body’s immune system. When your immune system tries to fight off infection caused by bacteria or viruses, an unusual immune response causes the immune system to attack the cells in the digestive tract.


It is unknown exactly how smoking is involved with Crohn’s disease, but tobacco smoking doubles the chance of both initial and recurrent Crohn’s disease.


There are no specific foods which cause Crohn's disease; however, there is emerging evidence that foods high in emulsifiers could lead to "leaky gut", which could trigger Crohn's. Westernisation of diet and improved sanitation has also been associated with an increase in inflammatory bowel disease (especially in Asian populations). 

What are the symptoms of Crohn's disease?

The symptoms of Crohn's disease depend on the location (where in the gut) and the spread (extent) of the swelling and inflammation in the gut. The symptoms can range from mild to severe.

The most common signs and symptoms are:

  • abdominal pain and diarrhoea (most common)
  • blood and mucus in your poo (faeces)
  • unintended weight loss.

Other general signs and symptoms include:

  • loss of appetite
  • extreme tiredness
  • fever
  • vomiting and/or constipation
  • the area in and around the anus is affected by ulcers, abscesses or fistulas (small holes in the wall of the bowel or rectum).

Symptoms can vary and depend on which part or parts of the gut are affected, for example:

  • If the disease is just in the small intestine, you may not have diarrhoea.
  • A persistent pain in the abdomen without any other symptoms may be due to a small patch of Crohn's disease in the small intestine.
  • A severe flare-up can make you generally very ill.
  • If large parts of the gut are affected, you may not absorb food well and you may become deficient in vitamins and other nutrients.

Symptoms in children

Children may not have major gut symptoms but instead have:

  • unexplained joint or bone pain
  • fever
  • low iron (anaemia)
  • slow or stunted growth.

How is Crohn's disease diagnosed?

Crohn's disease is diagnosed through a medical history, a physical examination, imaging tests to look at the intestines, and laboratory tests.

  • Your doctor will take a careful history to identify any patterns, recent travel, family history of bowel disorders and medication use.
  • This is followed by examination and investigations such as blood tests (to look for inflammatory markers, anaemia, nutrient deficiencies) and stool (poo) samples (to look for infection, parasites and more).
  • After this, referral to a specialist is often needed for further assessment and additional tests such as colonoscopy and sometimes a CT scan or MRI scan.

What are the treatment options for Crohn's disease?

The main aim of treatment for Crohn's disease is to stop inflammation in the gut, to prevent flare-ups and to keep you in remission. The kind of treatment depends on the type of symptoms and how bad they are.

  • Some people with mild symptoms may not need treatment as there is a chance that the symptoms will settle on their own.
  • Mild symptoms such as diarrhoea (watery poos) may respond to an antidiarrheal medicine, for example loperamide. This medicine slows or stops the painful cramps and spasms, and diarrhoea.


Medications are used to control the inflammation in your gut and to reduce your body’s immune response. Often medications are prescribed in a ‘stepped’ approach, depending on your response – beginning with fairly safe medications with few risks or side effects for moderate symptoms, and progressing to stronger medications with additional risks and side effects, for severe symptoms.The main groups of medicines to treat inflammation in Crohn’s disease are:

  • Aminosalicylates
    • These are often the treatment option for mild-to-moderate symptoms.
    • Examples include mesalazine, which may be given by mouth (as tablets or capsules), or by enema or suppository through the rectum (back passage), for mild flare-ups confined to the lower large intestine.
  • Steroids
    • These are used to treat sudden flare-ups and is not usually continued once the flare-ups have settled.
    • Examples include budesonide, prednisone and methylprednisone which are given as tablets or capsules, to be taken by mouth, or hydrocortisone which is given as an enema.
  • Immunosuppressants
    • These are prescribed when symptoms usually do not respond to mesalazine.  
    • An example is azathioprine . 
  • Biologics (TNF inhibitors)
    • TNF inhibitors are used in severe Crohn’s disease, in patients who do not respond to other medications, or in people who have a fistula.
    • Examples include infliximab and adalimumab. 

Read more about medications used in Crohn's disease.

Special diets

Some patients with bowel blockages or small holes in the bowel have improved when given a very strict liquid diet that contains basic proteins and other nutrients. This is called an elemental diet and is mainly used in children.

  • A flare-up can settle within four weeks in some people who have this diet.
  • After this, a normal diet is gradually restarted.
  • It is not clear why this treatment works. It may have some effect of 'resting' the gut. This may be an alternative for some people when medication has not worked so well, or has caused bad side-effects. However, it is a controversial treatment.


For certain high-risk patients, surgery may be considered. Surgery does not cure Crohn's disease but it is likely to provide relief from symptoms.

  • Surgery is sometimes necessary when the bowel keeps becoming blocked or when there are abscesses (swollen, infected areas) or small holes in the bowel wall.
  • Removal of the part of the bowel that is badly affected may relieve symptoms for a period of time but it does not cure the disease.
  • After surgery, symptoms return, usually where the bowel has been joined, in 60 to 95% of cases. Further operation is required in nearly 50% of cases.
  • Surgery is not performed unless there are specific complications or treatment with medication doesn’t provide relief. When operations have been performed; however, most patients consider their quality of life has been improved.
  • After surgery, you may be required to take long-term immunosuppressant drugs.

Read more about treatment and surgery options.

How can I care for myself with Crohn's disease?

In managing Crohn's disease, it is very important to maintain a healthy lifestyle, even when the disease goes into remission (becomes symptom-free) for long periods of time. For example, you can:

  • Exercise regularly and eat a healthy diet. 
  • Avoid problem foods such as spicy foods, high-fat foods.
  • Eat small meals.
  • If you smoke, quit smoking – this can help prevent symptoms from coming back. 

How will Crohn's disease affect me in the long term?

The outlook, or prognosis, for Crohn’s disease is different for different people and depends on which part or parts of the gut are affected and how often and how severe the flare-ups are.

Crohn's disease can range from being mild, or it can be very severe. Some people may experience only one episode and others (about 13–20% of people) may have ongoing episodes called chronic Crohn’s disease.

  • Although recurrences tend to be normal, disease-free periods can last for years or decades in some patients.
  • Although Crohn's disease cannot be cured even with surgery, treatments are now available that can help most patients.
  • People with long-standing Crohn's disease of the small intestine carry an increased risk of small bowel cancer, and those with Crohn's colitis (Crohn's disease that is only found in the colon) have a long-term risk of colon cancer.

Learn more 

Crohn's disease Gastro-info, NZ
What you need to know NIH, US, 2013
Nutrition and diet Crohn's and colitis, NZ, 2015
Treating crohn's disease NHS Choices, UK, 2013
Short bowel syndrome and crohn’s disease CCFA, US, 2018
Inflammatory bowel disease – a focus on crohn’s disease and ulcerative colitis Best Practice Journal, NZ, 2020


  1. Food preservatives linked to obesity and gut disease Nature, 2015
  2. Intestinal permeability in inflammatory bowel disease – pathogenesis, clinical evaluation and therapy of leaky gut Michielan A, D’Incà R. Mediators of Inflammation. 2014

Reviewed by

Derek is a consultant gastroenterologist at Counties Manukau Health and has also been in private practice since 2011. He has a broad interest in general gastroenterology and hepatology and has a subspecialty interest in pancreatic and hepatobiliary disease. He speaks Mandarin and Cantonese and is passionate about doing his bit for the Chinese community. He has been actively involved with the Auckland Chinese Medical Association for the past seven years as well as being on several committees with an interest in Asian Health.
Credits: Health Navigator Editorial Team. Reviewed By: Dr Derek JY Luo, MBChB (Otago) FRACP, Consultant Gastroenterologist Last reviewed: 23 Sep 2016