What is Crohn's disease

What is Crohn’s disease?

Crohn’s disease is an illness in which inflammation develops in parts of the gut leading to symptoms such as diarrhoea, abdominal pain and tiredness. The inflammation can be mild in many cases but can sometimes be severe requiring strong medication or an operation to remove an affected part of the intestine. Crohn’s disease is one of the two conditions known as inflammatory bowel diseases (or ‘IBD’), the other being ulcerative colitis. The symptoms and effects are similar to those of gastroenteritis (food poisoning) but differ in that they are not due to an infection and persist for a long time or until treated.

Who gets Crohn’s disease?

The disease affects mainly young adults but can affect teenagers or younger children and can sometimes start later in life. Men and women are affected equally. Crohn’s disease is not a common condition affecting about 1 in 1000 people (most people know one person affected by the condition). Crohn’s disease and ulcerative colitis can run in families – about one-fifth of people with the condition will have another family member affected.

What causes it?

It is thought that Crohn’s disease develops as a result of the immune system in the intestine reacting abnormally to bacteria at the surface of the gut. This abnormal immune reaction is likely to be inherited: a number of genes that may contribute to causing Crohn’s disease have now been identified, mostly involved in how we handle bacteria in the gut. It is still not known if one, a few or many types of bacteria are involved. Other factors affect the chances of getting Crohn’s disease, with smoking being the most important risk factor. Many patients ask whether there is a dietary cause but there is no firm evidence of this.

 
Where does Crohn’s disease affect?

Any part of the gut can be affected in Crohn’s disease. The most common area is the last part of the small intestine (terminal ileum) and the first part of the large intestine (or ‘colon’), near the appendix. In some people, only the colon is affected, in a pattern similar to ulcerative colitis. In others, multiple parts of the gut are affected. Rarely, the mouth, gullet or stomach may be involved. In some people, the inflammation in the gut also triggers inflammation outside the intestine leading to arthritis, eye inflammation or skin complaints.

 
What does it do to the intestine?

The mildest form of Crohn’s disease results in patches of inflammation in the lining of the intestine with groups of small ulcers, similar to mouth ulcers. In moderate or severe Crohn’s disease, these ulcers become much larger and deeper with a lot of surrounding redness. The inflammation can make the intestine become thickened, blocking the passage of digested food. In some cases, deep ulcers break through the wall of the intestine causing infection outside the bowel (an abscess) and this can then spread to the skin or a nearby part of the body. This is known as a fistula. These most frequently occur around the anus. As the inflammation heals, scar tissue may form which can in some cases also lead to a blockage in the intestine.