Patient Information
Tests and Treatments: Diagnostic Tests: Function Studies: Transit Time Measurement
A transit time x-ray measures the time it takes for food to go through the colon. The person takes special capsules by mouth twice a day for five days. Each capsule has twelve x-ray markers. Each day, the person takes a total of twenty-four markers. This averages out to one every hour.
On the sixth day, an x-ray of the abdomen is taken and we count the number of markers left in the person's colon. This tells about how long it takes for food to go through the colon. If there are eighty-six markers, it takes eighty-six hours. If there are only twenty-four markers, it takes twenty-four hours.
The average normal transit time is thirty-five hours. The upper limit of normal is seventy-two hours. If it takes more than seventy-two hours to go through the body, and all other tests are normal, then we make the diagnosis of colonic inertia (slow transit).
It is important to avoid the use of all laxatives and enemas during the five days before a transit time x-ray. However, it is fine to continue Natural Vegetable Powder, or other fiber supplements, in a normal dose.