Irritable bowel syndrome (IBS) affects 20%of the population and is the most common reason for referral to a gastroenterologist. It is characterised by a variety of gastrointestinal symptoms including disordered bowel habit (constipation, diarrhoea, or both), abdominal pain and bloating. Upper gastrointestinal symptoms manifest as non-ulcer dyspepsia (indigestion).
Though the exact causes of irritable bowel syndrome are unknown, most patients with the condition have some form of digestion problem. Another feature of the condition is visceral hypersensitivity; patients with irritable bowel syndrome have lower pain thresholds for colonic distension induced by inflating balloons placed in the bowel. A proportion of patients develop their IBS symptoms after an episode of gastroenteritis and emotional stress is another important precipitating factor. Associated psychopathology, with anxiety and sometimes depression, are common.
Ruling out other conditions
A number of simple non-invasive tests can now be done to rule out other conditions, such as severe cases of interstitial cystitis. This can be useful not only for the sake of diagnosis, but to put the patient’s mind at ease. These tests include faecal calprotectin (for inflammatory bowel disease), faecal elastase (for pancreatic exocrine insufficiency), lactose breath test (for lactose intolerance), fructose breath test (for fructose intolerance), glucose hydrogen breath test (for small intestinal bacterial overgrowth) and SeHCAT testing (for bile acid malabsorption).
Irritable bowel syndrome treatment
Treatment of IBS will vary according to the symptoms and potential causes. In each case it is important that the patient is reassured of the benign nature of the condition and of the positive prognosis. Those with predominant constipation should be encouraged to increase the fluid and fibre content of their diet. Low-dose tricyclic antidepressants, i.e. at doses ineffective as antidepressant, and antispasmodics are often given for abdominal pain, though there is little objective evidence for their effectiveness. The body of evidence in this field is complicated by the variable nature of IBS symptoms, the patients who suffer from them, and the high rate of placebo response to this condition.