Irritable bowel syndrome (IBS) is the commonest bowel disorder. The typical features are of variable bowel habit, often alternating between constipation and diarrhoea and passing stool of variable consistency as well. There is often associated abdominal pain, which is usually poorly localised, and may be altered by having the bowels open. Many patients have troublesome bloating and distension of the abdomen which can be quite distressing. There is often a sense of urgency and having to rush to the toilet. Although mucus may be passed from the rectum (back passage) there is never frank bleeding due to an irritable bowel.