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What is Crohn’s disease?

Crohn’s disease is a type of inflammatory bowel disease affecting the length of the digestive system.

Inflammation happens when the immune system causes the gut to become red, swollen and sometimes painful.

For people living with Crohn’s, they may experience abdominal pain and diarrhoea, weight loss, and diseases of the area in and around the anus (perianal disease).

A lifelong condition, Crohn’s disease starts between the ages 15 and 30 years, with a smaller peak around age 50 [1].

Australia has one of the highest rates of inflammatory bowel disease (IBD) globally [4], with Crohn’s affecting about 3 in 1,000 people [5].

Generalised symptoms can include tiredness, fever, or weight loss [2]

Abdominal pain and diarrhoea are common, sometimes with passage of blood [2]

Up to 50% of people with Crohn’s require surgery within 20 years of diagnosis, due to complications such as [2]:

  • Stricture (narrowing) of the bowel causing obstruction (symptoms of obstruction include nausea, vomiting, abdominal bloating and pain, and constipation)
  • Abscess (collection of pus)
  • Fistula (a narrow tunnel growing between organs)

Perianal disease occurs in up to 42%of people with Crohn’s within 20 years of diagnosis. Fistulas are the most common disease, but also strictures, ulcers, haemorrhoids (piles), fissures (tears), skin tags and rarely cancer can occur [6].

Other organs can also be affected, such as the skin, eyes, and joints [1].

Crohn’s disease appears to be caused by a complex interplay between genetics, environment, gut bacteria, and the immune system [4,7].

Relatives of people with Crohn’s have a higher risk than average of developing the disease [1].

Smoking may double the risk of developing Crohn’s and its complications [8].

Whether diet has a role in inflammation is unclear [1,9].

Crohn’s disease is diagnosed after a thorough history, physical examination, and appropriate tests, as shown in Table 1.


Commonly used tests

Stool tests
  • Infection
  • Blood
  • Calprotectin levels (helps to show disease activity)
Blood tests
  • Full blood count and inflammatory markers (to look for anaemia, inflammation, infection), kidney and liver health, vitamin and mineral levels, coeliac test (gluten allergy)
  • A fibreoptic video camera is used to view the bowel wall, and allows the taking of biopsies (tissue samples)
Capsule endoscopy
  • A tiny wireless camera that is swallowed. Most useful for looking at the small intestine
Imaging tests
  • Such as abdominal X-ray, barium studies, computed tomography (CT), ultrasound, or magnetic resonance imaging (MRI)

Treatment aims to manage flares and maintain remission, with surgery for drug-resistant disease or complications [10].

The Montreal classification system helps doctors to decide on best treatment. This system categorises the disease as to which parts of the gut are inflamed, presence of strictures, whether inflammation has spread to the outer gut wall, and whether perianal disease is present [6].

Generally, medications are the first line of treatment. Medications range from antibiotics, to anti-inflammatory aminosalicylates and corticosteroids, to those suppressing the immune system, including biologics [10]. However, medications can cause side effects.

Surgery is always required for fistulas that have formed between gut and vagina or gut and bladder, and perianal fistulas are treated by drainage and sometimes further surgery.

If someone’s gut disease is severe, such as penetrating the full thickness of the bowel wall or abscesses within the abdomen, or their Crohn’s is not responding to medical treatment then surgery may be considered.

Operations do not always involve bowel resection (removal) of diseased gut, but can include keyhole treatments, and repairs of strictures [6].

Smoking and mental health issues should also be addressed [2,8].

Evidence for dietary manipulation is not strong [1,2,9].

New treatment under development at the Bionics Institute

Bionics Institute researchers are developing an electrical medical device for people with IBD that aims to:

• Improve symptoms

• Prevent recurrence of the disease after surgery and need for a second operation

• Avoid the need for further medications

How does it work?

• A tiny electrode array is attached to the vagus nerve just under the diaphragm

• The vagus nerve connects the brain to the gut and controls natural anti-inflammatory processes in the body

• The vagus nerve is stimulated by the electrode array in response to gut inflammation caused by Crohn’s disease.

• The vagus nerve initiates a natural anti-inflammatory response to reduce the symptoms of Crohn’s disease

• The electrode array is powered by a small battery implanted at hip level.

• The battery only needs to be replaced every 10 years ensuring the device provides a set-and-forget treatment

• The treatment causes fewer side effects than medications

Read more

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Medical disclaimer

This article contains general information relating to a medical condition. Such information is provided for informational purposes only and does not replace medical advice given by your healthcare professional.


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6. Meima-van Praag EM, Buskens CJ, Hompes R, Bemelman WA. Surgical management of Crohn’s disease: a state of the art review. (CC BY 4.0). Int J Colorectal Dis [Internet]. 2021 Jun 1 [cited 2022 Feb 23];36:1133–45. Available from:

7. Loddo I, Romano C. Inflammatory bowel disease: Genetics, epigenetics, and pathogenesis. Front Immunol [Internet]. 2015 [cited 2022 Feb 3];6(NOV). Available from: /labs/pmc/articles/PMC4629465/

8. Berkowitz L, Schultz BM, Salazar GA, Pardo-Roa C, Sebastián VP, Álvarez-Lobos MM, et al. Impact of cigarette smoking on the gastrointestinal tract inflammation: Opposing effects in Crohn’s disease and ulcerative colitis. (CC BY). Front Immunol. 2018 Jan 30;9(JAN):1–10.

9. Bernstein CN, Eliakim A, Fedail S, Fried M, Gearry R, Goh KL, et al. Inflammatory Bowel Disease: Update August 2015. World Gastroenterology Organisation Global Guidelines. 2016. p. 1–36.

10. GESA. Management Overview of IBD [Internet]. 2021 [cited 2022 Feb 4]. p. 1–2. Available from: