Crohn's Disease
A type of inflammatory bowel disease that can cause inflammation anywhere in the digestive tract, most often the end of the small intestine. With modern treatment, most people manage their symptoms well.
What is Crohn's Disease?
Crohn's disease is a long-term condition where the immune system causes inflammation that can appear anywhere along the gut, from the mouth to the anus. It most commonly affects the last part of the small intestine (the terminal ileum) and the start of the colon.
A key feature is that the inflammation comes in patches, with healthy stretches of bowel in between, and it can reach through the full thickness of the bowel wall. Over time this can sometimes lead to narrowing (strictures) or small tunnels between loops of bowel (fistulas).
Crohn's vs Ulcerative Colitis: Crohn's can affect any part of the gut, in patches, and through the whole bowel wall. Ulcerative colitis affects only the colon and rectum, in a continuous pattern, and only the lining.
Key fact: Crohn's most commonly affects the end of the small intestine (the terminal ileum), but it can appear anywhere from mouth to anus.
Where Crohn's commonly occurs
Crohn's can affect any part of the digestive tract. Here's how it typically distributes at diagnosis:
Terminal ileum only
End of the small intestine
Colon only
Large intestine (colonic Crohn's)
Ileum & colon
Both small and large intestine
Symptoms
Symptoms can vary depending on which part of the gut is affected:
- Tummy pain and cramping, often in the lower right side
- Persistent or recurring diarrhoea
- Fatigue and feeling generally unwell
- Unintended weight loss
- Blood or mucus in the stool
- Mouth ulcers, and soreness around the anus
Causes & risk factors
As with other forms of IBD, Crohn's results from a combination of factors:
Genetics & family history
More common if a close relative has IBD
The immune system
An over-active immune response in the gut
The gut microbiome
The community of bacteria living in the bowel
Environmental factors
Including smoking, which is linked to higher risk and severity of Crohn's
Diagnosis
Your doctor may use several tests to diagnose Crohn's and understand which parts of the gut are affected:
Treatment & management
Treatment can bring on and maintain remission and help prevent complications.
Steroids or liquid nutrition therapy
To settle a flare (e.g. prednisolone or budesonide, or exclusive enteral nutrition)
Immunosuppressants & biologics
To maintain remission (e.g. azathioprine, infliximab, adalimumab or ustekinumab)
Surgery
To remove or repair badly affected sections; common in Crohn's, though inflammation can return
Living with Crohn's Disease
With modern treatment and regular specialist review, most people with Crohn's manage their symptoms well:
Good nutrition — eating well supports healing and energy levels
Know your warning signs — recognise when a flare may be starting
Mental wellbeing — looking after your emotional health is an important part of care
Regular specialist review — stay in touch with your IBD team
References & further reading
- NHS. Crohn's disease. nhs.uk
- NICE NG129. Crohn's disease: management. nice.org.uk
- Crohn's & Colitis UK. Crohn's disease. crohnsandcolitis.org.uk
This page is for general information and does not replace advice from your doctor or specialist team.
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