About Crohn’s Disease – Symptoms, Investigations, Diagnosis, Treatment, Causes & Facts

Approximately 115,000 people in the UK are thought to have Crohn’s disease. The illness can occur at any age, but often begins in younger people aged 10-40. There are up to 18,000* new cases a year.

Crohn’s disease is a chronic inflammatory condition of the bowel.  Inflammation means the tissues involved become red, hot, swollen and painful and are unable to do their job well (which for the bowel means absorbing important nutrients from your food).  It is an incurable disease which usually begins in young adulthood and lasts throughout life with episodes of disease (relapse or flares) and other episodes when the disease is under control (remission).

In Crohn’s the inflammation can occur anywhere in the gut from the mouth down to the anus but the most commonly affected areas are the small bowel (ileum) where it joins the large bowel (colon) known as the ileo-caecal region, the rest of the colon and the anus and the skin surrounding it (known as the perineum or perianal area).

As well as different locations in the gut, Crohn’s also affects different people with a different severity of disease.  Some people have a relatively mild inflammation which bothers them from time to time but does not necessarily affect their life much.  Others require multiple operations and have problems throughout their lives.  The severity of an individual’s disease can also change during their lifetime and in fact reducing severity of symptoms and inducing remission are key goals in the treatment of inflammatory bowel diseases.

Another form of Inflammatory Bowel Disease (IBD) is Ulcerative Colitis (UC) which affects mostly the colon and does not usually involve the anus or anything other than the last few inches of the small bowel.  Irritable Bowel Syndrome (IBS) is totally different and does not involve any inflammation of the bowel but instead is thought to represent an ‘over-excitability’ of the bowel such that normal stimuli produce disproportionate symptoms such as pain, bloating or a change in bowel habit.  It is possible to have both IBS and Crohn’s Disease.


It is not known what causes Crohn’s Disease.  There is a genetic component and recent research has identified some genetic abnormalities which make some aspects of Crohn’s Disease more likely in some people.  There is also a higher chance of having Crohn’s Disease if you have a relative with either Crohn’s or UC but there is no direct inheritance – that means a parent with IBD will not necessarily have a child who is affected and one child having Crohn’s does not mean another child will too.

As well as genetic abnormalities, it is generally accepted that in people with Crohn’s the normal immune function of the body is disrupted.  This might mean that the reaction of a normal person to bacteria in their gut, which is to tolerate the bacteria and allow it to live on the surface of the bowel, is altered in someone with Crohn’s meaning that inflammation occurs in response to these normal bacteria causing damage to the bowel wall itself.

Crohn’s Disease is not an infection you can catch, nor a condition brought on by bad diet or something that an individual did but there are factors which make some people more likely to get

Crohn’s than others (like family members with IBD or their ethnicity) and also factors which mean people are more likely to suffer with severe Crohn’s (like developing the disease at a younger age or smoking).  It is well known that smoking is bad in Crohn’s Disease, increasing the need for surgery, frequency of flares and severity of disease – in fact stopping smoking is one of the single most valuable things a person with Crohn’s can do.


It can be difficult to diagnose Crohn’s Disease.  The symptoms can vary a great deal from a patient with bloody diarrhoea and pain in their tummy to someone else who may have weight loss, a loss of appetite and a feeling of being generally unwell.

The main symptoms depend on the location of the Crohn’s within the bowel but most commonly patients will get diarrhoea (sometimes with blood in), abdominal pain and weight loss.  They may also feel generally ill or tired and may have a fever and feel nauseous (sick) or vomit.

The first symptoms can also be those of an acute or severe attack.  For example a patient may come to hospital with pain in the bottom right hand corner of their tummy – a bit like someone with appendicitis, and may even undergo surgery to remove their appendix at which point the Crohn’s Disease is discovered.  They may come to hospital with severe pain in their tummy, vomiting and a temperature, perhaps with a lump in their tummy which their doctor can feel from the outside which is due to an abscess (infected collection inside the tummy) or very severe inflammation in the bowel.

On the other hand, the patient may come to their GP with a long history of feeling generally under the weather, tired and mildly unwell.  They might have anaemia (lack of red blood cells which makes you feel tired) or weight loss (because they’re not absorbing nutrients form their food properly.

There are some features that suggest that an inflammatory bowel disease (Crohn’s or Ulcerative Colitis) might be the diagnosis.  Things like having blood relatives with inflammatory bowel disease, having mouth ulcers or having problems around the anus (bottom) such as painful swellings, fissures

(little tears) or abscesses (boils, collections of pus) don’t mean a patient definitely has Crohn’s but do make it a more likely diagnosis


First, most doctors will perform blood tests looking for signs of inflammation, anaemia and poor nutrition.  They may also look for signs of other diseases so a wide range of blood tests is often performed at this stage.  Samples of a patient’s stool (poo) are often sent to look for evidence of infection which can cause similar symptoms, especially if there is diarrhoea.

The best tests and those most likely to make the diagnosis are those which allow doctors to look at the bowel and hopefully take biopsies (small samples of the bowel).  The various imaging tests like Xrays, scans and so on are generally less unpleasant for patients but do not allow biopsies to be taken.  They are sometimes good enough to make a diagnosis of Crohn’s Disease and are able to look in places that telescopes find it hard to reach like far up inside the small bowel.  A colonoscopy (telescope inside the large bowel passed up to reach the end of the small bowel, the terminal ileum) allows doctors to look at the lining of the bowel directly and see inflammation that is visible but also take biopsies which can not only see inflammation that is invisible to the naked eye, but also allow examination of the inflammation under the microscopy which helps doctors tell Crohn’s Disease apart from other causes of inflammation in the large bowel.


Before colonoscopy, patients have to drink ‘prep’ which is a strong laxative to empty the bowel completely so that the lining of the bowel can be examined.  It causes diarrhoea which empties the bowel in the 24 hours prior to the test.

The colonoscope is a long, thin black telescope with a fibre optic camera on the end.  It can be passed in through the anus and around the large bowel right up to the end of the small bowel (terminal ileum).  Pain killers and sedative drugs are often used to make the procedure more comfortable.  As well as looking at the bowel a doctor can take pictures, videos and also small biopsies – samples of the tissue taken with a little forceps (like a tiny mouth that takes a small bite of the tissue of the bowel) which can be collected and looked at under the microscope.

The biopsies are examined (this is called histology) to look for features typical of Crohn’s Disease.  Other diseases such as Ulcerative Colitis, some infections of the bowel and other rarer diseases can be identified by histology.


Surgery in Crohn’s Disease used to be mainly undertaken after complications (such as a narrowing or fistula) had occurred but increasingly it is believed that an early operation can sometimes help to prevent these complications and get better and longer lasting control of the disease from an earlier stage.  Surgery can often greatly improve the quality of life of a person with Crohn’s Disease

Fast Facts – Surgery:

Many Crohn’s sufferers, perhaps up to 80%, will undergo surgery of some kind during their lives.

Surgery does not cure Crohn’s Disease but it is designed to either treat a complication (like a fistula or stricture[narrowing]), or to prevent them.

After surgery, the problems the operation treated can return but some people experience long periods of remission after surgery.

Generally speaking surgery for Crohn’s Disease is either on the abdomen (to remove an inflamed section of intestine or to remove or widen bits of intestine with fistulas or strictures in), or around the back passage to treat fistulas or other problems in this area.

A stoma (colostomy or ileostomy bag) is sometimes necessary for safety and can provide a better period of relief from symptoms but it is not always needed and is often temporary when it is used.

Major surgery always has a long recovery time and this is particularly true in people who are underweight or already ill such as those suffering from active Crohn’s Disease before the operation.

Healing after surgery can be slow for Crohn’s sufferers.


Medication plays a large role in the management of Crohn’s Disease.  Most people diagnosed withCroh n’s will have to take different types of medication for their management of Crohn’s at some stage.

There are many different drugs used in Crohn’s Disease and new drugs appear on a regular basis.  As, the exact cause of Crohn’s Disease is not known, most of the drugs used tend to reduce inflammation (anti-inflammatories) or dampen the action of the immune system (immunosuppressants or immunomodulators).

The range of disease in Crohn’s is quite large.  Some people just get a bit of diarrhoea which is controlled using drugs like loperamide or codeine which simply thicken the stool (poo) and make you need to go less often.  More severe symptoms may require more powerful drugs.


When first diagnosed with Crohn’s Disease many patients ask if this was because of something they ate or as a consequence of their diet. Although research has tried to answer this question it has not yet been possible to prove that Crohn’s Disease results from diet. The western diet is often implicated as a cause of Crohn’s. It has been found that patients who immigrate to the west, especially those from the Indian sub-continent, and have changed  their diet accordingly, are now developing Crohn’s Disease. A possible reason for this is due  to different fats as the western diet contains fats which are more likely to result in  inflammation than other fats which are thought to be anti-inflammatory. This is a very difficult  issue and is far from fully understood and as the development of Crohn’s Disease is thought to have many different risk factors it will require much more research to answer these questions.

As any part of the gastrointestinal tract can be affected by Crohn’s Disease it is easy to understand how eating and drinking can become problematic. Therefore, it is really important that patients have access to advice from a dietician who has a good knowledge of Crohn’s Disease and its consequences. The dietician can then provide individualised advice depending on the site of the Crohn’s Disease and the symptoms experienced. Everyone with Crohn’s Disease is different. You may know someone with Crohn’s Disease who has been advised by a dietician to follow a particular diet but this advice may not be suitable for another patient.

Patients with Crohn’s can become malnourished very quickly for several reasons:

  • Reduced appetite causing a reduction in food intake
  • An increase in nutritional requirements resulting from Crohn’s
  • Side effects of the treatments such as nausea and vomiting  Malabsorption due to on-going inflammation

The dietary management of active Crohn’s focuses on three aspects of the disease:

  • Achieving remission
  • Reduction in symptoms
  • Maintaining or improving nutritional status

One approach to the treatment of active disease is the use of a liquid diet known as exclusive enteral nutrition. This is when patients do not eat or drink anything except specially formulated liquids which contain all of the essential nutrients required for health. These  liquids are known as oral nutritional supplements (e.g. Ensure Plus, Fortisip, Fresubin Energy drink, Modulen, Peptamen, Elemental 028). This treatment is usually required for up to 8 weeks to achieve remission. After 10 days patients should notice a difference in the symptoms but it can take up to 8 weeks to show that the lining of the gut has healed (known as mucosal healing).

One of  the most difficult aspects of following this diet is the lack of any other food allowed.

Some of the side effects from these diets can be quite  surprising although often harmless (your poo may turn green) and so it is vital that the patient is in regular contact with their dietician to discuss these issues.

Sometimes patients find it difficult to drink the volume of liquid diet recommended by the dietician and in this situation the diet can be given via a tube that is passed via the nose into the stomach known as a nasogastric tube. The advantage of this tube is that the nutrition can be infused slowly during the day and the night which can ensure that the full amount is being delivered. Some patients choose to pass their own nasogastric tube each night so that they can remove it during the day.

Once patients have completed the recommended period of time on the liquid diet, food will be reintroduced. After such a long time without any normal food it is tempting for patients to  eat everything and anything. However it is a good idea to introduce foods back into your diet  in a slow way so that your bowel can get used to dealing with solid food again. It is also  important to assess if any particular foods cause symptoms and if remission can be maintained.

*Figures published by NICE Guidelines (2013)