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.
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.
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
- 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
- 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:
- 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.
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.
Treatment and surgery options Gastro-info (NZ)
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 to 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.
Crohn's disease Gastro-info (NZ)
What you need to know NIH (US), July 2013
Nutrition and diet Crohn's and colitis (NZ), April 2015
Treating crohn's disease NHS Choices (UK), May 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
- Food preservatives linked to obesity and gut disease Nature, Feb 2015
- Intestinal permeability in inflammatory bowel disease – pathogenesis, clinical evaluation and therapy of leaky gut Michielan A, D’Incà R. Mediators of Inflammation. 2014