Anorectal function and dyssynergic defecation in different subgroups of patients with irritable bowel syndrome

The purpose of this study was to evaluate anorectal function in different subgroups of patients with irritable bowel syndrome (IBS), including those with mixed bowel habits.

Sixty-six IBS patients selected according to Rome III criteria (39 female and 27 male patients; mean age, 41.5 +/- 15.4) and 20 subjects in the control group (13 female and 7 male patients; mean age, 41.4 +/- 13.7) were examined. The IBS patients were divided into three subgroups according to bowel movement pattern: patients with constipation (27%), patients with diarrhea (27%), and patients with mixed bowel habits (46%). Anorectal manometry and rectal distension test were performed using a four-lumen water-perfused catheter with a polyethylene balloon.

No significant differences in manometric parameters between the subgroups of IBS patients and the control group were found, except for pelvic floor dyssynergia (PFD), which was more frequent in all subgroups of IBS (41% of patients) than in controls (5% of subjects) (p < 0.01). Lower rectal pain threshold was observed particularly in IBS patients with diarrhea and mixed bowel habits (p < 0.01).

Manometric parameters characterizing anal sphincter function are not correlated with the predominant bowel movement pattern in IBS. The features of PFD are significantly more frequent in all subgroups of IBS patients than in controls, suggesting that, in general, IBS patients show changes in the mobility of the pelvic floor. Hypersensitivity to rectal distension is commonly observed in IBS, but it does not seem to be a highly specific marker of the disorder.