Rectal tone in response to bisacodyl in women with obstructed defecation

This study investigated the tonic response of the rectum to topical application of bisacodyl in women with obstructed defecation. Forty-five women with obstructed defecation, and 15 female controls were studied. Total colonic transit time was normal in 35 patients, and prolonged in 10. For the purpose of this study an "infinitely compliant" polyethylene bag was inserted into the rectum. Rectal tone was assessed by measuring variations in bag volume with a computerized electromechanical "barostat" system. After an adaptation period of 30 min, a suppository containing 10 mg bisacodyl was inserted into the rectum. Recording was continued for 90 min. In a second recording session rectal tone in response to an evoked urge to defecate was assessed. In a third session we investigated rectal sensory perception. After a mean time interval of 30+/-15 min following intrarectal application of bisacodyl, all controls showed a significant increase in rectal tone (mean value: 68.2+/-12%). In patients with a normal transit time, a similar increase was observed. In patients with prolonged transit time, the tonic response of the rectum to bisacodyl was significantly lower (mean 21.1+/-11%; P<0.001). Five of these patients showed no response at all. In the second recording session, all controls showed an increase in rectal tone during an evoked urge to defocate (mean 36.3+/-7%). In both patient groups this tonic response was absent or significantly blunted (mean 19.2+/-6%) (P<0.001). In both patient groups rectal sensory perception was impaired significantly. In conclusion, rectal tone increases significantly after topical application of bisacodyl in controls as well as in patients with obstructed defecation in whom transit time is normal. This tonic response is absent or significantly blunted in patients with a prolonged transit time. Both the tonic response of the rectum to an evoked urge to defecate and rectal sensory perception are significantly impaired in patients with a normal and those with a prolonged transit time.