There is some evidence that, despite attempts to classify them separately, functional bowel disorders are not distinct entities and that such divisions are artificial.
To examine this issue in a large cohort of secondary care patients.
Consecutive, unselected adults with gastrointestinal (GI) symptoms attending out-patient clinics at two hospitals in Hamilton, Ontario were recruited. Demographic data, symptoms and presence of anxiety, depression or somatisation were collected prospectively. We used validated questionnaires, including the Rome III questionnaire, with patients categorised as having irritable bowel syndrome (IBS), functional diarrhoea or chronic idiopathic constipation (CIC). We compared data between these disorders, and measured degree of overlap between them by suspending their mutual exclusivity.
Of 3656 patients providing complete lower GI symptom data, 1551 (42.4%) met criteria for a functional bowel disorder. Diarrhoea-predominant IBS (IBS-D) patients were younger, and more were female, met criteria for anxiety, and reported somatisation-type behaviour, compared with functional diarrhoea. Only loose, mushy or watery stools were more common in functional diarrhoea. When mutual exclusivity was suspended, overlap occurred in 27.6%. Constipation-predominant IBS (IBS-C) patients were younger, and more were female, had never married, reported anxiety type symptoms and exhibited somatisation-type behaviour. One in five CIC patients reported abdominal pain or discomfort. All constipation symptoms were more common in IBS-C. When the mutual exclusivity was suspended, overlap occurred in 18.1%.
There were significant differences in demographics between individuals with functional bowel disorders. Despite this, the Rome III classification system falls short of describing unique entities.