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Crohn's disease

The symptoms of Crohn's vary depending on which part of the intestine is inflamed.

The symptoms of Crohn's vary depending on which part of the digestive system is inflamed.

Common symptoms include:

  • recurring diarrhoea
  • abdominal pain and cramping, which is usually worse after eating
  • extreme tiredness (fatigue)
  • unintended weight loss
  • blood and mucus in your faeces (stools)

You may find that you experience all or only one of the above. Some people experience severe symptoms, but others only have mild problems.

There may be long periods that last for weeks or months where you have very mild or no symptoms (known as remission), followed by periods where the symptoms are particularly troublesome (known as flare-ups or relapses).

Less common symptoms include:

  • a high temperature (fever) of 38°C (100°F) or above
  • feeling sick (nausea)
  • being sick (vomiting)
  • joint pain and swelling (arthritis)
  • inflammation and irritation of the eyes (uveitis)
  • areas of painful, red and swollen skin – most often the legs
  • mouth ulcers

Children with Crohn's disease may grow at a slower rate than expected because the inflammation can prevent the body absorbing nutrients from food.

When to seek medical advice

You should contact your GP if you have:

  • persistent diarrhoea
  • persistent abdominal pain
  • unexplained weight loss
  • blood in your faeces (stools)

You should also see your GP if you are concerned about your child's development.

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Crohn's disease

The exact cause of Crohn's disease is unknown. Most researchers think that it is caused by a combination of factors.

The exact cause of Crohn's disease is unknown. Most researchers think that it is caused by a combination of factors.

These are thought to be:

  • genetics
  • the immune system
  • smoking
  • previous infection
  • environmental factors

There is no evidence to suggest a particular diet can cause Crohn's disease, although changes to your diet can help control certain symptoms and may be recommended by your specialist or dietitian.

Read treating Crohn's disease for more information.


There is evidence to suggest that genetics plays a role in the development of Crohn's disease.

Researchers have identified more than 200 different genes that are more common in people with Crohn's disease than in the general population.

There is also evidence that Crohn's disease can run in families. About 3 in 20 people with the condition have a close relative (mother, father, sister or brother) who also has Crohn's disease. For example, if you have an identical twin with the condition, you have a 70% chance of also developing it.

The fact that Crohn's disease is more common in some ethnic groups than in others also suggests that genetics plays an important role.

The immune system

The immune system provides protection against harmful bacteria that could potentially find their way into the digestive system.

The digestive system is also home to many different types of so-called "friendly bacteria" that help digest food. The immune system usually recognises these bacteria and lets them do their job without attacking them.

However, in Crohn's disease it seems that something disrupts the immune system, which sends a special protein known as tumour necrosis factor-alpha (TNF-alpha) to kill all bacteria, regardless of whether they are friendly or not. This causes most of the inflammation associated with Crohn's disease.

Previous infection

In certain genetically susceptible individuals, a previous childhood infection may lead to an abnormal immune response, causing the symptoms of Crohn's disease.

One possible source of this infection is a bacterium called Mycobacterium avium subspecies paratuberculosis (MAP). MAP is commonly found in cows, sheep and goats.

Research has found that people with Crohn's disease are seven times more likely to have traces of MAP in their blood compared with the general population.

MAP has been known to survive the pasteurisation process (where milk is treated with heat to kill bacteria), so it is possible that people have become infected with MAP by drinking milk from contaminated animals.

However, the exact role that MAP may play in the development of Crohn's disease is uncertain and some researchers dispute this theory.


Aside from family history and ethnic background, smoking is the most important risk factor for Crohn's disease. Smokers are twice as likely to develop the condition compared with non-smokers.

Furthermore, people with Crohn's disease who smoke usually experience more severe symptoms compared with those who have the condition but do not smoke.

Read more about how to get help to stop smoking.

Environmental factors

There are two unusual aspects of Crohn's disease that have led many researchers to believe that environmental factors may play a part. These are explained below:

  • Crohn's disease is a "disease of the rich". The highest number of cases occurs in developed parts of the world, such as the UK and the US, and the lowest number occur in developing parts of the world, such as Africa and Asia.
  • Crohn's disease became much more widespread from the 1950s onwards.

This suggests that there is something associated with modern Western lifestyles that increases a person's risk of developing the condition.

One theory to explain this is known as the hygiene hypothesis. It suggests that as children grow up in increasingly germ-free environments, their immune system does not fully develop because of a lack of exposure to childhood infections. However, there is little in the way of hard scientific evidence to support this theory.

An alternative theory is the cold-chain hypothesis, which suggests that the increase in the number of cases of Crohn's disease might be linked to the increased use of refrigerators after the Second World War.

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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, it is likely that your GP will 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 are taking any medication, including any over-the-counter (OTC) 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 weight and height
  • 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 are anaemic (have low levels of red blood cells), which could suggest you are malnourished

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.

After you have provided a stool and blood sample, you will probably be referred to a gastroenterologist (a specialist in conditions of the digestive system). They will discuss the results with you and carry out the tests described below if they are 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 will 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 is 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 a stool. The capsule is disposable so you do not 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 will either need to drink a harmless liquid called 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 are 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 that 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 that 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 that are caused by Crohn's disease.

After the test, you will 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 it is nothing to worry about.

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Crohn's disease

People with Crohn's disease are at risk of developing a number of problems associated with the condition.

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 is a risk of digestive waste causing an obstruction. This means you will not be able to pass any stools or you will 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 is a risk that the bowel could split (rupture). 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 that your bowel is obstructed. If this is not 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 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 about 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 do not usually cause symptoms. However, larger fistulas can become infected and cause symptoms such as:

  • a constant, throbbing pain
  • a high temperature (fever) of 38°C (100°F) or above
  • blood or pus in your faeces (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 are not 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 are not absorbing enough nutrients.

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Crohn's disease

Read Joseph Barr's story of being diagnosed with Crohn's disease and find out how he manages the condition.

Joseph Barr talks about managing Crohn's disease with medication and how he can still play the sports he loves.

"I had diarrhoea, weight loss and I was unable to keep my food down. I threw up three or four times a day. Eventually, I ended up in hospital for two weeks, where doctors carried out tests, including stomach X-rays, a colonoscopy and a barium meal test.  

"For the barium meal test, I had to swallow a liquid and 20 minutes later my stomach was X-rayed. Under the X-ray, the liquid highlights everything that's going on in the stomach.

"A colonoscopy isn't the greatest experience. A camera is attached to a microscope and inserted into the back passage. It goes quite far up into the colon and everything is recorded on video, which I was able to watch on a screen beside me. 

"I was finally diagnosed with Crohn's disease, an inflammatory disease of the gut. It affects the small and large intestine and can lead to internal bleeding.  

"Initially I was given steroids. It made a big difference straight away and reduced the inflammation a lot. I now take anti-inflammatory drugs every day, and I'll have to take them for the rest of my life. There's no cure for Crohn's disease, so the treatment I've been given helps me manage my condition. My life is now back on track. 

"I still do a lot of the things that I used to do. I still go out with my friends, I can drink alcohol and I don't need to avoid any types of food. I'm still quite active. I can play football and cricket, and I go to the gym as often as I can."

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