Do I need any tests?
There is no test that confirms the diagnosis of IBS. A doctor can usually diagnose IBS from the typical symptoms.
However, a blood sample is commonly taken to do some tests to help rule out other conditions such as ulcers, colitis, coeliac disease, gut infections, etc. The symptoms of these other diseases can sometimes be confused with IBS. Tests done on the sample of blood commonly include:
- Full blood count (FBC) - to rule out anaemia which is associated with various gut disorders.
- Erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) - which can show if there is inflammation in the body (which does not occur with IBS).
- Antibody testing for coeliac disease.
More complicated tests such as endoscopy (a look into the bowel with a special telescope) are not usually needed. However, they may be done if symptoms are not typical, or if you develop symptoms of IBS in later life (over the age of about 45) when other conditions need to be ruled out.
What causes irritable bowel syndrome?
The cause is not clear. It may have something to do with overactivity of parts of the gut. The gut is a long muscular tube that goes from the mouth to the anus. The small and large bowel (also called the small and large intestine) are parts of the gut inside the abdomen. Food is passed along by regular contractions (squeezes) of the muscles in the wall of the gut. Pain and other symptoms may develop if the contractions become abnormal or overactive. The area of overactivity in the gut may determine whether constipation or diarrhoea develops. The cause of overactivity in parts of the gut is not clear. One or more of the following may play a part:
Overactivity of the nerves or muscles of the gut. It is not known why this may occur. It may have something to do with overactivity of messages sent from the brain to the gut. Stress or emotional upset may play a role. About half of people with IBS can relate the start of symptoms to a stressful event in their life. Symptoms tend to become worse during times of stress or anxiety.
Intolerance to certain foods may play a part in some cases. However, this is thought to be only in a small number of cases.
Infection and bacteria in the gut. IBS is not caused by an ongoing gut infection. However, in about 1 in 6 cases, the onset of symptoms seems to follow a bout of gastroenteritis (a gut infection which can cause diarrhoea and vomiting). So, perhaps a virus or other germ may 'sensitise' or 'trigger' the gut in some way to cause persisting symptoms of IBS. Also, in some cases, symptoms get worse after taking a course of antibiotics. Antibiotics kill certain harmless bacteria in the gut which changes the balance of bacteria types in the gut.
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