Anorectal motility and rectal sensitivity in chronic idiopathic constipation: effect of high-fiber diet.

The rectoanal inhibitory reflex and rectal sensitivity were evaluated in 13 patients with idiopathic chronic constipation and in 13 control subjects. A double balloon probe was used to stimulate and record the rectoanal inhibitory reflex and rectal sensitivity. The results showed a linear relationship between relaxation amplitude and the logarithm of rectal distending volume, and between relaxation duration and the logarithm of rectal distending volume, with a significant reduction of relaxation amplitude in the patient group. The rectal sensitivity thresholds were significantly increased in patients compared with controls. In 10 additional patients with chronic constipation, motility and sensitivity parameters were evaluated before and after 28 days of high-fiber diet. After diet, the values of relaxation amplitude were significantly increased, returning within normal range, but sensitivity parameters did not change. In conclusion, it appears that in adult chronic idiopathic constipation, anorectal motility and rectal sensitivity are altered, and that only motor abnormalities are corrected by a high-fiber diet.