Colonic transit studies are simple x-ray studies that determine how long it takes for food to travel through the intestines. For transit studies, individuals swallow a total of six capsules, each containing 10 barium tablets, two capsules each at 0, 9 and 18 hours. Plain AP radiographs of the abdomen and pelvis are obtained at 27 hours.  Some of the capsules contain small pieces of plastic that can be seen on x-rays. The gelatin capsules dissolve and release the barium tablets (or the radio-opaque plastic pieces) into the small intestine. These then travel (as would digesting food) through the small intestine and into the colon.Each radiograph is divided into three areas namely the right, left and rectosigmoid areas and the markers present in each area are counted. After 5 or 7 days, a repeat x-ray of the abdomen is taken and the radio-opacities in the different parts of the colon are counted. From this count, it is possible to determine if and where there is a delay in the colon. In non-constipated individuals ,all of the  radio-opacities are eliminated in the stool and none remain in the colon. When pieces are spread throughout the colon, it suggests an abnormality of  the muscles and/or nerves throughout the colon, which is typical of colonic inertia. When pieces accumulate in the rectum, it suggests pelvic floor dysfunction or anal sphincter disturbance.