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 pathophysiologi c entities. Our aim was to identify subgroups on the basis of symptoms in I BS. Methods: Two independent groups of 56 (sample I) and 52 (sample II) out patients recorded their abdominal symptoms daily for 6 weeks and I week, re spectively. The daily records were assessed by using cluster analysis. Resu lts: Similar subgroups appeared in both samples. Three bowel habit subgroup s were identified. The first was distinguished by hard stools, varying stoo l consistency, and highly disturbed stool passage, the second by loose stoo ls and urgency, and the third by normal stools and the least disturbed stoo l passage. Two pain/bloating subgroups were identified, one distinguished b y little and the other by considerable pain and bloating. No relation was f ound between pain/bloating and bowel habit subgroup membership. Most patien ts had stool frequency within the normal range regardless of subgroup. In s ample I the subgroups had stable symptoms during the study, and subgroup pl acement was not related to the presence of dyspepsia, smoking habits, or us e of bulk agent and/or sporadic intake of loperamide. The degree of pain an d bloating was inversely related to illness duration. Conclusions: Subgroup s 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.