Characteristics of Functional Bowel Disorder Patients

A Cross-sectional Survey Using the Rome III Criteria

A. C. Ford; P. Bercik; D. G. Morgan; C. Bolino; M. I. Pintos-Sanchez; P. Moayyedi


Aliment Pharmacol Ther. 2014;39(3):312-321. 

In This Article

Abstract and Introduction


Background There is some evidence that, despite attempts to classify them separately, functional bowel disorders are not distinct entities and that such divisions are artificial.

Aim To examine this issue in a large cohort of secondary care patients.

Methods 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.

Results 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%.

Conclusions 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.


The functional bowel disorders are chronic conditions in which patients report symptoms referable to the middle or lower gastrointestinal (GI) tract.[1] Irritable bowel syndrome (IBS) is characterised by abdominal pain or discomfort in association with altered stool form or frequency. The prevalence of IBS in community surveys is between 5% and 20%.[2] Chronic idiopathic constipation (CIC) consists of persistently difficult, infrequent or incomplete defaecation in the absence of any physiological abnormality.[1] Again, CIC is common, affecting between 10% and 20% of the general population.[3] Functional diarrhoea is defined by the presence of chronic loose or watery stools, without abdominal pain or discomfort.[1] The prevalence of functional diarrhoea has not been studied extensively, but appears to be slightly lower than that for IBS or CIC, between 2% and 9%.[4–8]

Although the Rome III classification system for the functional GI disorders aims to make these conditions mutually exclusive, there is evidence to suggest that they are not distinct entities. Cross-sectional surveys demonstrate that the functional bowel disorders may fluctuate during extended follow-up, such that individuals with CIC or functional diarrhoea at baseline will go on to report symptoms compatible with IBS at a later date, while those with IBS at study entry may experience a flux of symptoms, such that they meet criteria for CIC or functional diarrhoea.[9,10] In a study based in a health maintenance organisation, Wong et al. demonstrated that one-third of individuals with constipation-predominant IBS (IBS-C) switched to meet criteria for CIC at 12 months, and a similar proportion of individuals with CIC experienced an alteration in their symptoms such that they met criteria for IBS-C at the same time point.[11] In addition, there was considerable overlap between the two conditions when the mutual exclusivity between them was suspended.

Taken together, this suggests that the functional bowel disorders may exist on a continuous spectrum, with functional diarrhoea and CIC at extreme ends, and IBS in the centre. We aimed to test this theory in a large cohort of patients referred from primary to secondary care. Our hypothesis was that the demographic characteristics and psychological symptom profiles of patients with diarrhoea-predominant IBS (IBS-D) and functional diarrhoea, and those with IBS-C and CIC, would be similar, the severity of the individual symptoms of diarrhoea and constipation would be comparable between these groups, and that there would be considerable overlap between IBS-D and functional diarrhoea, and IBS-C and CIC.