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OBJECTIVE--To determine the prevalence of symptoms compatible with a clinical diagnosis of irritable bowel syndrome in the general population. DESIGN--Validated postal questionnaire sent to 2280 subjects randomly selected in 10 year age bands from the lists of eight general practitioners. The Manning criteria were used to define irritable bowel syndrome. SETTING--Urban population in Southampton and mixed urban-rural population in Andover, Hampshire. RESULTS--A response of 71% yielded 1620 questionnaires for analysis, of which 412 (25%) reported more than six episodes of abdominal pain in the preceding year, with 350 (22%) reporting symptoms consistent with the diagnosis of irritable bowel syndrome. The male: female ratio was 1:1.38. More subjects with irritable bowel syndrome had constipation and diarrhoea and 35% with the syndrome reported rectal bleeding compared with an overall prevalence of 20%. Other symptoms and conditions including heartburn, dyspepsia, flushing, palpitations, migraine, and urinary symptoms were significantly more common in the group with irritable bowel syndrome. Abdominal pain in childhood was more common in the subjects with irritable bowel syndrome (12%) than without (3%). One third of the group with irritable bowel syndrome had sought medical advice during the study period (male:female ratio 1:1.21); consultation behaviour was influenced by age and the presence of associated symptoms, varied considerably among patients registered with different general practitioners, and was poorly correlated with symptom severity. CONCLUSION--Symptoms consistent with a diagnosis of irritable bowel syndrome are present in almost one quarter of the general population and tend to be associated with a number of other complaints and conditions, some of which may reflect smooth muscle dysfunction.

A questionnaire to establish the presence of 15 symptoms thought to be typical of the irritable bowel syndrome (IBS) was given to 109 unselected patients referred to gastroenterology or surgery clinics with abdominal pain or a change in bowel habit or both. Review of case records 17--26 months later established a definite diagnosis of IBS in 32 patients and of organic disease in 33. Four symptoms were significantly more common among patients with IBS--namely, distension, relief of pain with bowel movement, and looser and more frequent bowel movements with the onset of pain. Mucus and a sensation of incomplete evacuation were also common in these patients. The more of these symptoms that were present the more likely was it that the patient's pain or altered bowel habit, or both, was due to IBS. We conclude that a careful history can increase diagnostic confidence and reduce the amount of investigation in many patients with chronic abdominal pain.