Background: It is unclear how the quality and quantity of abdominal symptoms and anorectal function differ between irritable bowel syndrome (IBS) patients and healthy controls, and whether different anorectal function in patients is associated with abdominal symptoms in IBS.
Methods: Fifty-two outpatients with IBS and 12 healthy controls kept daily symptom records over 1 week. At the end of the week, anorectal function was assessed by manovolumetry before and after a standard fatty meal. Patients were divided into symptom and manovolumetric subgroups using a cluster analysis and also into those below (hypersensitive) and those within (normosensitive) the 95% confidence interval of the controls' mean for maximal tolerable distension (MTD).
Results: Regardless of subgroup, the patients were distinguished from the controls by pain, bloating, straining and incomplete evacuation. Compared with controls, MTD was lower in the pain/bloating subgroup characterized by considerable pain and the bowel habit subgroup characterized by hard stools, variable stool consistency and heavily disturbed stool passage. Preprandial rectal hypersensitivity was highly prevalent in this bowel habit subgroup. No similar association with the pain/bloating subgroup was found. Patients and controls showed a significant and similar postprandial decrease in MTD.
Conclusions: IBS is distinguished from health by pain, bloating, straining and a feeling of incomplete evacuation. Baseline rectal hypersensitivity is associated with constipation-like bowel habit. Increased rectal sensitivity after a meal and/or preceding distension is a normal reaction unimportant in the genesis of symptoms in IBS.