Crohn’s disease

Crohn’s disease

Crohn’s disease is a condition that causes inflammation of the wall of the gut. Any part of the gut can be affected. This can lead to various symptoms.

Who gets Crohn’s disease?

Crohn’s disease is diagnosed in about 1 in 10,000 people every year. It can develop at any age but most commonly starts between the ages of 15 and 30. It affects women slightly more often than men. An individual with a family member with Crohn’s disease, is more likely to develop the condition. It is also more common in people who have had their appendix removed, for the first five years after the operation.

Which part of the gut is affected in Crohn’s disease?

In Crohn’s disease, one or more patches of inflammation develop in parts of the gut. Any part of the gut can be affected. However, the most common site for the disease first to start is the last part of the small intestine (the ileum). The ileum is affected in about half of cases.

A patch of inflammation may be small, or spread quite a distance along part of the gut. Several patches of inflammation may develop along the gut, with normal sections of gut in between.

What causes Crohn’s disease?

The cause is not known. About 3 in 20 people with Crohn’s disease have a close relative who also has it. This means there may be some genetic factor. However, other factors such as a bacterium or virus (germ) may be involved. One theory is that a germ may trigger the immune system to cause inflammation in parts of the gut in people who are genetically prone to develop the disease.

Crohn’s disease has become more common in recent years, but the reason for this is not known. It is about twice as common in smokers than average. The oral contraceptive pill and non-steroidal anti-inflammatory tablets (usually used for joint inflammation) have also been implicated as possible factors in triggering the disease to start.

What are the symptoms during a flare-up of Crohn’s disease?

When the disease flares up, the inflammation may cause one or more of the following:

  • Diarrhoea is the most common first symptom. It can vary from mild to severe. The diarrhoea may be mixed with mucus, pus or blood. An urgency to get to the toilet is common. A feeling of wanting to go to the toilet but with nothing to pass is also common.
  • Pain occurs in about 7 in 10 cases. The site of the pain depends on which part of the gut is affected. When Crohn’s disease first develops it is sometimes mistaken for appendicitis. The severity of pain can vary from person to person. Also, a sudden change or worsening of pain may indicate a complication (see below).
  • Weight loss that is not intentional.
  • Ulcers. An ulcer is a raw area of the lining of the gut which may bleed. Blood may be seen in the stools (motions or faeces).
  • Generally feeling unwell, which may include loss of appetite, fever, and tiredness.
  • Anaemia may occur if a lot of blood is lost.
  • Mouth ulcers are common.
  • Anal fissures may occur. These are painful cracks in the skin of the anus. Skin tags (small fleshy wart-like lumps) may also appear around the anus.

Other symptoms

Other parts of the body are affected in some people in addition to the gut. These include: inflammation and pain of some joints (arthritis); skin rashes; inflammation of the eye (uveitis); liver inflammation.

How does Crohn’s disease progress?

Crohn’s disease is a chronic, relapsing condition. Chronic means that it is ongoing. Relapsing means that there are times when symptoms flare up (relapse), and times when there are few or no symptoms (remission). The severity of symptoms, and how frequently they occur, varies from person to person. The first episode (flare-up) of symptoms is often the worst.

What are the possible complications of Crohn’s disease?

Complications may occur, particularly if flare-ups are frequent or severe. These include the following which often need treatment with surgery:

  • Stricture. This is a narrowing of part of the gut. It is due to scar tissue that may form in the wall of an inflamed part of the gut. A stricture can cause difficulty in food passing through (a blockage). This leads to pain and vomiting.
  • Perforation. This is a small hole that forms in the wall of the gut. The contents of the gut can then leak out and cause infection or an abscess inside the abdomen. This can be serious and life-threatening.
  • Fistula. This is when the inflammation causes a channel to form between two parts of the body. For example, a fistula may form between a part of the small intestine and a part of the colon. Fistulas can also form between part of the gut and other organs such as the bladder or uterus (womb). The contents of the gut may then leak into these other organs. A perianal fistula sometimes develops. This is a fistula that goes from the anus or rectum and opens on to the skin near to the anus.
  • Cancer. People with Crohn’s disease have a small increased risk of developing cancer of the colon compared with the risk of the general population.
  • Osteoporosis (thinning of the bones). The increased risk of this is related to the poor absorption of food that occurs in some people with severe Crohn’s disease.


Depending on where the symptoms arise from, various tests may be done to confirm the diagnosis, and to determine how much of the gut is affected. For example, if the symptoms come from the colon or ileum, then a doctor may look inside the colon and ileum, using a special flexible telescope called a colonoscope. The colonoscope is passed through the anus, up into the colon, and a little further into the ileum.

The typical appearance of the inside lining of the colon or ileum suggests Crohn’s disease. Biopsies (small samples) of the lining of various parts of the colon and ileum are usually taken. These are looked at under a microscope. The typical pattern of the cells may confirm the diagnosis.

If the symptoms comeg from the upper part of the gut, then a doctor may suggest a gastroscopy (endoscopy). This is where a thin, flexible telescope is passed down the oesophagus into the stomach.

A special X-ray of the large intestine (barium enema) or small intestine (barium meal) may be advised. Barium coats the lining of the gut and shows up as white on X-ray films. Typical patterns on the films show which parts of the gut are affected. Other tests such as an MRI or CT scan may be preferred, depending on which part of your bowel is affected, whether there are any complications and whether these tests are available in your area.

Also, blood tests are helpful from time to time to assess the level of inflammation within the gut, to check for anaemia and other deficiencies, and to assess general well-being.

A stool sample may be taken for analysis to check for various germs that are sometimes present in people with Crohn’s disease.


There are two main aspects of treatment:

  • When a flare-up develops – a main aim is to clear symptoms.
  • When a flare-up has settled – a main aim is to prevent any further flare-ups of symptoms.

What are the treatment options for a flare-up of Crohn’s disease?

The treatment advised can depend on various factors. For example, the severity of the symptoms, the site or sites of the inflammation in the gut, whether associated problems have developed. Treatment decisions can become complex and a specialist will usually advise. Options that may be considered include the following:

No treatment

This is an option for some people who have mild symptoms. There is a chance that the symptoms will settle on their own. If symptoms get worse, then decisions about treatment can be reviewed.

A course of steroids (corticosteroids)

Steroid medicines work by reducing inflammation.  In about 7 in 10 cases, symptoms are much improved within four weeks of starting steroids. The dose is reduced gradually, and then stopped once symptoms ease.

Immunosuppressant medicines

Newer powerful medicines that suppress the immune system have become available in recent years. These have made a big impact on the treatment of Crohn’s disease in recent years.


Antibiotics may need to be added to other treatments if infective complications are suspected – for example, if you develop an infected fistula such as an infected perianal fistula.

Dietary treatments

A very strict liquid diet that contains basic proteins and other nutrients has been found to help in some cases. This is called an elemental diet and is mainly used in children. A flare-up can settle within four weeks in some people who have this diet. After this, a normal diet is gradually restarted.


An operation to remove a severely affected section of gut may be needed if other treatments do not work. The gut is cut above and below the affected part which is removed. The two ends are then joined up. Surgery is also usually needed to treat complications such as fistulas, strictures and abscesses.

General measures

  • Iron tablets may be prescribed if anaemia develops.
  • Vitamins and other nutrient supplements may be needed if food is poorly absorbed.
  • Nutritional support such as dripping nutrients directly into a vein (parenteral nutrition) may be needed in severe cases.
  • Painkillers may be needed for a while during flare-ups.
  • Hospital admission for intravenous fluids (drip) and intensive treatment may be needed if you have a severe flare-up.
  • Vaccinations may be offered to people with Crohn’s disease, to protect them from a variety of infections, especially if they are on treatment which stops their immune system from working properly.

Crohn’s disease and pregnancy

A pregnant woman may need extra folate supplements, and certain medicines which may be used for Crohn’s disease, such as methotrexate, must not be used during pregnancy.

What is the outlook (prognosis)?

The outlook is variable. It depends on which part or parts of the gut are affected and how often and how severe the flare-ups are. Without treatment:

  • About 3 in 20 people with Crohn’s disease have frequent and/or severe flare-ups.
  • A few people would have just one or two flare-ups in their lives, but for most of their lives have no symptoms.
  • Most people would fall somewhere in between, have flare-ups from time to time, but can have long spells without symptoms.

Sometimes a severe flare-up is life-threatening and a small number of people die as a result of a serious complication such as a perforated gut.

Crohn’s disease and cancer of the colon

If you have Crohn’s disease that affects at least half the surface of your large intestine (colon), you will be at a slightly increased risk of developing cancer.

People with this risk are usually advised to have their large intestine routinely checked after having had Crohn’s disease for about ten years. This involves a look into the large intestine by a flexible telescope (colonoscopy) every now and then and taking small samples of bowel (biopsies) for examination.

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