Functional diagnostic work-up in patients with irritable bowel syndrome

The first aim of the study was to find a cause of symptoms in patients suffering from "irritable bowel syndrome" using diagnostic tests aimed at functional disorders of lower gut. A second aim was to test, whether the presence of irritable bowel syndrome (or, synonymously, absence of classic organic disease) can be predicted by specific symptoms. 134 consecutive patients (50 +/- 16 SD years, range 17 to 88, 94 women) presenting in our gastroenterological outpatient department with abdominal pain and altered bowel habits were included. A conventional diagnostic work-up aimed at classic organic diseases and, if negative, a functional diagnostic work-up aimed at gastrointestinal malfunction such as dietary fibre trial, functional proctoscopy, defecography, colonic transit of radiopaque markers, anorectal manometry, and lactose tolerance test were done. A classic organic disease was found in only 15 of 134 patients by conventional diagnostic tests. Functional diagnostic work-up yielded a diagnosis in 70 of the remaining 119 patients that else would have been labeled to suffer from IBS (25 slow transit constipation, 20 disordered defecation, nine low fibre intake, and nine lactose intolerance among them). When symptoms were evaluated with a standardized questionnaire, "constipation" and the "necessity of straining to open bowels" were very specific for functional bowel disorder (92% and 100%), but sensitivity of both symptoms was only about 60%. The so-called "Manning criteria" had a very low prevalence in our sample and so were not discriminatory. Since in more than half of the patients with "irritable bowel syndrome" a specific diagnosis can be reached, functional tests should be considered in such patients. The symptom "constipation" in patients with lower gut complaints predicted a functional disorder rather than a classic organic disease with a high specificity.