Pressure profile of the rectum and anus of healthy persons

Summary

This study was undertaken to determine the pressure profile of the rectum and anal sphincter of healthy persons. Open-tip tubes and tiny balloons of various sizes connected to pressure transducers were withdrawn in stages from the lower part of the sigmoid to the exterior in 11 healthy males in the Sims position. Records of the pressures encountered during the withdrawals were made photokymographically. Mean sigmoid and rectal resting pressures were 2 to 5 cm. of water above ambient pressure. A band of elevated pressure about 4 cm. in width was always detected in the anal sphincter. The mean maximal pressure in the sphincter as detected by open-tip tubes was 45 cm. of water; greater maximal pressures were encountered when balloons were withdrawn through the sphincter. Bands or zones of increased pressure were consistently detected in the rectum during withdrawal of even tiny balloons. These zones have been interpreted as being produced by pressure applied to the balloon as it was withdrawn past a bend in the rectum or over folds in the rectum. The suggestion is made that these structures may act as incomplete or feeble valves resisting the analward movement of rectal contents, just as they resisted the analward movement of the balloons.