The measurements help locate anal sphincters, muscle rings that close the anus when they contract. Alternatively, the pressure may be measured with a balloon manometry system, a hollow metal cylinder to which three balloons are attached. You are asked to squeeze the anus as forcefully as possible, while pressure in the sphincters is recorded. A balloon at the tip of the probe is inflated, and you are asked to report whether you have a sensation that your rectum is full and you feel an urge to defecate. After the test You are free to return to previous activities.
Factors affecting results Pressure in the rectum decreases somewhat with age.
On average, the pressure is slightly higher in men than in women. Measurements made at different points in the rectum help locate any problem in the functioning of the rectal muscles or nerves. Abnormal reflexes in the rectum may also signal disease. For example, internal sphincters should relax when the rectum is full. Failure to relax when the rectum is dilated with a balloon may indicate Hirschsprung's disease.