Division of the Irritable Bowel Syndrome into Subgroups on the Basis of Daily Recorded Symptoms in Two Outpatient Samples

Background: If subgroups exist in a sample of patients with irritable bowel syndrome (IBS), they may represent different etiologic and pathophysiologic entities. Our aim was to identify subgroups on the basis of symptoms in IBS. Methods: Two independent groups of 56 (sample I) and 52 (sample II) outpatients recorded their abdominal symptoms daily for 6 weeks and 1 week, respectively. The daily records were assessed by using cluster analysis. Results: Similar subgroups appeared in both samples. Three bowel habit subgroups were identified. The first was distinguished by hard stools, varying stool consistency, and highly disturbed stool passage, the second by loose stools and urgency, and the third by normal stools and the least disturbed stool passage. Two pain/bloating subgroups were identified, one distinguished by little and the other by considerable pain and bloating. No relation was found between pain/bloating and bowel habit subgroup membership. Most patients had stool frequency within the normal range regardless of subgroup. In sample I the subgroups had stable symptoms during the study, and subgroup placement was not related to the presence of dyspepsia, smoking habits, or use of bulk agent and/or sporadic intake of loperamide. The degree of pain and bloating was inversely related to illness duration. Conclusions: Subgroups exist in IBS. Division of IBS into bowel habit subgroups should be based on stool consistency, not frequency. Mechanisms mediating pain and bloating may be different from those mediating symptoms at defecation.