Content Supplied by NHS Choices

Crohn's disease

Crohn's disease is a long-term condition that causes inflammation of the lining of the digestive system.

Crohn's disease is a long-term condition that causes inflammation of the lining of the digestive system.

Inflammation can affect any part of the digestive system, from the mouth to the back passage, but most commonly occurs in the last section of the small intestine (ileum) or the large intestine (colon).

Common symptoms can include:

  • diarrhoea
  • abdominal pain
  • fatigue (extreme tiredness)
  • unintended weight loss
  • blood and mucus in your faeces (stools)

People with Crohn's disease sometimes go for long periods without symptoms or with very mild symptoms. This is known as remission. Remission can be followed by periods where symptoms flare up and become particularly troublesome.

Read more about the symptoms of Crohn's disease and diagnosing Crohn's disease.

Why it happens

The exact cause of Crohn's disease is unknown. However, research suggests a combination of factors may be responsible. These include:

  • genetics – genes you inherit from your parents may increase your risk of developing Crohn's disease
  • the immune system – the inflammation may be caused by a problem with the immune system (the body's defence against infection and illness) that causes it to attack healthy bacteria in the gut
  • previous infection – a previous infection may trigger an abnormal response from the immune system
  • smoking – smokers with Crohn's disease usually have more severe symptoms than non-smokers
  • environmental factors – Crohn's disease is most common in westernised countries such as the UK, and least common in poorer parts of the world such as Africa, which suggests the environment (particularly sanitation) has a part to play

Read more about the possible causes of Crohn's disease.

Treating Crohn's disease

There's currently no cure for Crohn's disease, so the aim of treatment is to stop the inflammatory process, relieve symptoms (induce and maintain remission) and avoid surgery wherever possible.

The first treatment offered to reduce symptoms is usually steroid medication (corticosteroids). If this doesn't help, medication to suppress the immune system (immunosuppressants) and medication to reduce inflammation may be used.

In some cases, surgery may be needed to remove the inflamed section of intestine.

Once your symptoms are under control (in remission), further medication may be needed to help maintain this.

Who is affected?

Crohn's disease is a relatively uncommon condition. There are currently at least 115,000 people living with the condition in the UK.

Crohn's disease can affect people of all ages, including children. However, most cases first develop between the ages of 16 and 30. 

A large number of cases also develop between the ages of 60 and 80.

It affects slightly more women than men, but in children more boys are affected than girls.

The condition is more common in white people than in black or Asian people. It's most prevalent among Jewish people of European descent.

Read more about treating Crohn's disease.


Over time, inflammation can damage sections of the digestive system, resulting in complications such as narrowing of the intestine (stricture), or a channel developing between the end of the bowel and the skin near the anus or vagina (fistula). These problems usually require surgical treatment.

Read more about the possible complications of Crohn's disease.

Content Supplied by NHS Choices

Crohn's disease

A number of different tests may be needed to diagnose Crohn's disease, as it has similar symptoms to several other conditions.

A number of different tests may be needed to diagnose Crohn's disease, as it has similar symptoms to several other conditions.

Initial assessment

During your initial assessment, your GP will usually ask you about the pattern of your symptoms and check whether there may be any contributing causes, such as:

  • diet
  • recent travel – for example, you may have developed travellers' diarrhoea while travelling abroad
  • whether you're taking any medication, including any over-the-counter medicines
  • whether you have a family history of Crohn's disease

Your GP may also carry out a series of standard tests to assess your general state of health. For example, they may:

  • check your pulse
  • check your blood pressure
  • measure your height and weight
  • measure your temperature
  • examine your abdomen (tummy)

Blood tests

Your GP may then arrange a series of blood tests. These can be used to assess:

  • the levels of inflammation in your body
  • whether you have an infection 
  • whether you're anaemic, which could suggest you're malnourished or losing blood from your bowel

Stool sample

You may be asked to provide a stool sample, which can be checked for blood and mucus. It can also be used to determine whether your symptoms are being caused by a parasitic infection such as roundworm, or other infections.

A faecal calprotectin test may be offered to adults who have recently developed symptoms such as abdominal pain, diarrhoea or constipation and are being considered for specialist treatment. This test helps clinicians to distinguish between irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD).

After you've provided a stool and blood sample, you'll probably be referred to a gastroenterologist (a specialist in conditions of the digestive system). They'll discuss the results with you and carry out the tests described below if they're necessary.


colonoscopy is a test used to examine the inside of your colon. It involves inserting a long, flexible tube called an endoscope into your colon through your back passage (rectum).

The endoscope has a light and a camera on the end. The camera can be used to send images to a television screen. These show the level and extent of inflammation inside your colon.

The endoscope can also be fitted with surgical tools that can be used to take a number of small tissue samples from different sections of your digestive system. This is known as a biopsy. The procedure may feel uncomfortable, but it's not painful.

These tissue samples will be examined under a microscope for the cell changes known to occur in cases of Crohn's disease.

Wireless capsule endoscopy

A wireless capsule endoscopy is a new type of test that involves swallowing a small capsule (about the size of a large vitamin tablet). The capsule works its way down to your small intestines, where it transmits images to a recording device worn on a belt or in a small shoulder bag.

A few days after the test, the capsule passes out of your body in the stool. The capsule is disposable, so you don't have to worry about retrieving it from your stools.

As this is a relatively new test, availability may be limited. In some cases, MRE or CTE scans may be used instead of capsule endoscopy.

MRE and CTE scans

Scans called magnetic resonance enterography/enteroclysis (MRE) or computerised tomography enterography/enteroclysis (CTE) may be used to examine the small intestine in people with suspected Crohn's disease.

Before having these scans, you'll either need to drink a harmless liquid called a contrast agent (enterography), or contrast agent may be placed through a tube in your nose that leads to your small intestine (enteroclysis). These contrast agents allow your small intestine to show up more clearly during the scans.

During an MRE scan, magnetic fields and radio waves are used to produce detailed images of your small intestines. During CTE scans, several X-rays are taken and assembled by computer to create a detailed image.

These tests are increasingly used instead of a small bowel enema or small bowel follow-through, because they allow more detailed examination of the small intestine. MRE scans also avoid any exposure to X-ray radiation.

Small bowel enema or small bowel follow-through

A small bowel enema (SBE) and small bowel follow-through (SBFT) are two similar tests that have traditionally been used to examine the whole of the inside of the small intestine, usually at the point where it meets the colon. They're sometimes used because only about the last 20cm of the small intestine is usually seen during colonoscopy.

During an SBE/SBFT, a local anaesthetic spray is used to numb the inside of your nose and throat. A tube is passed down your nose and into your throat before being threaded into your small intestine. This can feel unpleasant at first, but most people find they get used to the sensation after a few minutes.

A harmless liquid called barium is passed down the tube. The barium coats the lining of your small intestines, so they show up clearly on X-ray. A series of X-ray images will then be taken. The images can often highlight the areas of narrowing and inflammation caused by Crohn's disease.

After the test, you'll be advised to drink plenty of fluid to help wash the barium out of your body. You may notice that your stools look white for the first few days after having an SBE or SBFT. This is perfectly normal and nothing to worry about.

Content Supplied by NHS Choices

Crohn's disease

People with Crohn's disease are at risk of developing a number of complications.

People with Crohn's disease are at risk of developing a number of complications.  

The two most common problems associated with Crohn's disease are discussed in more detail below.

Intestinal stricture

The inflammation of the bowel (intestines) in Crohn's disease can cause scar tissue to form, leading to the affected areas becoming narrowed. This is known as stricture.

If this happens, there's a risk of digestive waste causing an obstruction. This means you won't be able to pass any stools or you'll only be able to pass watery stools.

Other symptoms of bowel obstruction include:

  • abdominal pain and cramping
  • being sick (vomiting)
  • bloating
  • an uncomfortable feeling of fullness in your abdomen

Left untreated, there's a risk the bowel could split (perforate). This creates a hole that the contents of the bowel can leak from. You should contact your GP as soon as possible if you suspect your bowel is obstructed. If this isn't possible, call NHS 111.

Intestinal stricture is usually treated with surgery to widen the affected section of intestine. In some cases this may be achieved without surgery, using a procedure called balloon dilation, which is performed during colonoscopy.

During balloon dilation, a colonoscope is passed up your back passage (rectum) and a balloon is inserted through the colonoscope. This is then inflated to open up the affected area.

Read diagnosing Crohn's disease for more information on colonoscopy.

If this doesn't work or is unsuitable, a surgical procedure known as a stricturoplasty may be needed to widen the affected area. During this operation, the surgeon widens the narrowed part of the intestine by opening it, reshaping it and sewing it back together.


If your digestive system becomes scarred as a result of excessive inflammation, ulcers can develop.

Over time, the ulcers develop into tunnels that run from one part of your digestive system to another or, in some cases, to the bladder, vagina, anus or skin. These passageways are known as fistulas.

Small fistulas don't usually cause symptoms. However, larger fistulas can become infected and cause symptoms, such as:

  • a constant, throbbing pain
  • a high temperature (fever) of 38C (100F) or above
  • blood or pus in your stools
  • leakage of stools or mucus into your underwear

If a fistula develops on your skin (usually on or near the anus) it may release a foul-smelling discharge.

Biological medication is usually used to treat fistulas. Surgery is usually required if these aren't effective.

Read more about treating a fistula.

Other complications

People with Crohn's disease are also at an increased risk of other complications, such as:

  • osteoporosis – weakening of the bones caused by the intestines not absorbing nutrients and the use of steroid medication to treat Crohn's disease
  • iron deficiency anaemia – a condition that can occur in people with Crohn's disease because of bleeding in the digestive tract; common symptoms include tiredness, shortness of breath and a pale complexion
  • vitamin B12 or folate deficiency anaemia – a condition caused by a lack of vitamin B12 or folate being absorbed by the body; common symptoms include tiredness and lack of energy
  • pyoderma gangrenosum – a rare skin reaction that causes painful skin ulcers

Children with Crohn's disease may also experience problems with their growth and development because their bodies aren't absorbing enough nutrients.

Colorectal cancer

Some people with Crohn's disease have a slightly increased risk of developing colorectal cancer in later life.

You should be offered regular check-ups to look for colon cancer if your healthcare team feels you may be at an increased risk.

This usually involves a colonoscopy and a biopsy. See diagnosing Crohn's disease for more information about these tests.

Share this page