Effect of perineal compression on the rectal tone: a study of the mechanism of action

Digital pressure on the perineum was reported to result in an increase of the rectal tone. This effect has been related to a reflex action named perineorectal reflex but was not verified. The mechanism of action of perineal pressure on the rectal tone was studied.

Eighteen healthy volunteers (mean age +/- standard deviation, 39.7 +/- 11.8 years; 10 males) were studied. The barostat system used consisted of a polyethylene balloon connected to a strain gauge and a computer-controlled, air-injection system. The balloon was introduced into the rectum, and the rectal tone was assessed by recording the balloon volume variations in response to digital pressure on the perineum. The test was repeated after individual anesthetization of perineum and rectum. It was performed again using normal saline instead of Xylocaine.

During perineal pressure, all the volunteers exhibited rectal tone increase with a mean decrease in the balloon volume of 72.3 +/- 14.7 percent. There was no significant difference (P > 0.05) in the rectal tone response between females and males nor between young and elderly patients. The mean latency was 17.3 +/- 1.8 ms. Perineal pressure 20 minutes after individual anesthetization of perineum and rectum effected no significant rectal tone changes. The response returned after the anesthetic effect had waned. The rectal tone response after saline administration was similar to that before administration.

The study has shown that rectal tone increase during digital perineal pressure represents most probably a reflex action. This was evidenced by absence of rectal tone response on individual anesthetization of the assumed two arms of the reflex arc: perineum and rectum. The perineorectal reflex may be of diagnostic significance in rectal motor disorders and has the potential to be used as an investigative tool, provided further studies are performed to prove these points.