A disorder of the intestinal tract that aﬀects its motility and causes abdominal distension and irregular defaecation. Traditional, but now discarded, names have been spastic or irritable colon. The disease aﬀects around 20 per cent of the general population but in most it is no more than a minor nuisance. The causes are not fully understood, but it is generally believed that symptoms develop in response to psychological factors, changed gastrointestinal motility, or altered visceral sensation. About 50 per cent of patients meet criteria for a psychiatric diagnosis. Anxiety, depression, neurosis, panic attacks, acute disease are among possible triggering factors. Some patients have diarrhoea, others are constipated, and some alternate between the two. Many have increased sensitivity to distension of the intestine. Dietary factors such as intolerance to dairy products and wheat are apparent in certain patients.
Common features of IBS include:
altered bowel habit.
colicky lower abdominal pain, eased by defaecation.
mucous discharge from rectum.
feelings of incomplete defaecation.
Investigations usually produce normal results. Positive diagnosis in people under 40 is usually straightforward. In older patients, however, barium ENEMA, X-rays and COLONOSCOPY should be done to exclude colorectal cancer.
Reassurance is the initial and often eﬀective treatment. If this fails, treatment should be directed at the major symptoms. Several months of the antidepressant amitriptyline (see ANTIDEPRESSANT DRUGS) may beneﬁt patients with intractable symptoms, given at a dose lower than that used to treat depression. The majority of patients follow a relapsing/remitting course, with episodes provoked by stressful events in their daily lives. (See also INTESTINE, DISEASES OF.)