The perineorectal reflex The perineorectal reflex in health and obstructed defecation

Many females with obstructed defecation apply digital pressure on their perineum to facilitate defecation. This study investigated the impact of this maneuver on rectal tone.

Forty-five female patients with obstructed defecation were studied. Thirty-four patients (76 percent) regularly applied digital pressure on their perineum to facilitate defecation. Total colonic transit time was normal in 32 patients and prolonged in 13 patients. For comparison, 17 female controls were studied. With the subject in the left lateral position, a thin, "infinitely" compliant polyethylene bag was inserted into the rectum at 10 cm from the anal canal. Rectal tone was assessed by measuring variations in bag volume with a computer-controlled electromechanical air injection system. After an adaptation period of 15 minutes, digital pressure was applied to the anterior perineum by one of the authors (WRS). In a second recording session, the tonic response of the rectum to an evoked urge to defecate was examined.

During the application of perineal pressure, all controls showed an increase in rectal tone (mean value, 52.8+/-19 percent). In the whole patient group, this response was significantly lower (mean value, 24.2+/-19 percent; P < 0.001). Eight of these patients (18 percent) showed no response at all. None of them applied perineal pressure. In the remaining 37 patients (72 percent), the perineorectal reflex was present but was significantly lower (mean value, 29.8+/-17 percent; P < 0.001). Thirty-four of these females (92 percent) stated that they applied perineal pressure on a regular basis to facilitate their defecation. All controls showed an increase in rectal tone during an evoked urge to defecate (mean value, 37.8+/-8 percent). In the patients, this response was significantly lower (16.7+/-6 percent). Eight of these patients showed no increase in rectal tone at all. These patients were the same patients in whom the perineorectal reflex was absent. Regarding the tonic response of the rectum to perineal pressure, no difference was found between patients with a normal colonic transit time and those with a prolonged colonic transit time.

Digital pressure applied on the perineum results in an increase in rectal tone. This perineorectal reflex is present, although significantly lower, in the majority of females with obstructed defecation. This observation might explain why females with obstructed defecation frequently apply perineal pressure to facilitate defecation.