Bowel Transit Time
A bowel transit time test measures how long it takes for food to travel through the digestive tract . After you chew and swallow your food, it moves into your stomach, where it is mixed with acid and digestive enzymes. After your food leaves your stomach, it is squeezed through your small intestine, where nutrients are absorbed for use by your body. The food then goes into your large intestine (colon) where water is absorbed. Whatever hasn't been digested and absorbed by your intestines combines with bacteria and other waste products and becomes stool (feces). Stool is expelled from your body through your anus. The time it takes for food to travel from your mouth through your digestive tract to your anus is your bowel transit time. Sometimes, just the time it takes for food to travel through the colon is measured. This is called the colonic transit time.
Bowel transit time depends on what types of food you eat and how much you drink. For example, people who eat lots of fruits, vegetables, and whole grains tend to have shorter transit times than people who eat mostly sugars and starches. Because different people have different transit times, experts disagree about how useful this test is. Some doctors do not recommend bowel transit time testing.
For this test, you swallow one or more gel capsules filled with markers that will show up on an X-ray. The markers look like white spots or rings in the X-ray pictures. When you will have X-rays depends on the type of test done. Most commonly, you will have an X-ray test 5 days after swallowing the markers. This will show how the markers have moved through your intestines. Or you may swallow multiple capsules full of markers on three days in a row. In this case, you will have X-ray tests on multiple days to check the progress of the markers through your intestines.
Why It Is Done
Bowel transit time tests may be done to:
- Find the cause of constipation or the slow movement of food through the digestive tract.
- See if one place in your intestines is slowing down movement more than the rest of your intestines.
Bowel transit time tests are not done to find the cause of diarrhea.