Alteration of recto-anal motility in chronic idiopathic constipation

We studied anorectal function in 10 controls and 13 constipated patients (chronic idiopathic constipation, outlet obstruction and inertia coli). We did not find any difference among the 3 groups as regards the internal anal sphincter (IAS) basal tone, the recto-anal inhibitory reflex (RAIR) and the maximal voluntary contraction, whereas some significant differences were observed in the sensitivity threshold. In fact, we observed that all patient groups required larger volumes in order to perceive the minimum sensation. Moreover, the patients with distal obstruction showed higher threshold for a permanent defecation stimulus. The reduction of rectal sensitivity in these patients was confirmed by the infusion of 1500 cc of saline solution. On the basis of our experience constipated patients are characterized by both normal IAS tone, RAIR appearance, squeezing capacity, and lower rectal sensitivity.