What are functional gastrointestinal
(bowel) disorders?

These are conditions where the function rather than the structure of the gut is disordered. Consequently, when tests such as x-rays or endoscopies are done they don't show any abnormality. This does not mean that there is nothing wrong with the gut it just means that diseases such as cancer and ulcers etc have been eliminated. If you take an x-ray of the head in somebody with a migraine it will not show anything but that doesn't mean they haven't got a headache. Similarly, just because the tests are all normal in IBS it does not mean that it is imagined in any way.  

IBS is the commonest functional bowel disorder but there are others such as functional dyspepsia which is associated with upper rather than lower gastrointestinal symptoms. Another one is non cardiac chest pain which gives chest pain like angina but it is likely that the pain is coming from the gullet (oesophagus) rather than the heart. Biliary dyskinesia is a condition that mimics gall bladder problems and gives rise to pain just below the ribs on the right hand side of the tummy. Proctalgia fugax is the name given to a condition where the anus goes into spasm and this can be extremely painful and alarming when it occurs. There is often considerable overlap between the functional gastrointestinal disorders (FGD) so that, for instance, some patients with IBS may also suffer from chest pains or some other FGD symptom.