In infants and children with stooling problems, anorectal manometry is used to test for the normal relaxation of the muscles which help to control bowel movements. These muscles are known as sphincters. Normally these muscles are closed to keep stool in the rectum and open when it is time to have a bowel movement.
Anorectal manometry can also test for how the child senses distention or stretching of the rectum. A tube with a balloon on its end is inserted into the rectum. The balloon is slowly inflated to simulate stool in the rectum. As the balloon is inflated the muscles should open. The tube is connected to a computer which will measure how well this happens.