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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.
Bowel transit time tests may be done
Bowel transit time tests are not done to find the cause of
Tell your doctor if you are or might
be pregnant before having this test.
You may need to change your diet for a few days before having this test. You may also need to stop taking medicines for a short time before having a bowel transit time test. Tell your doctor about all the prescription and nonprescription medicines you are taking.
Talk to your doctor about
any concerns you have regarding the need for the test, its risks, how it will
be done, or what the results will mean. To help you understand the importance
of this test, fill out the
medical test information form(What is a PDF document?).
Your doctor will give you one or more gel capsules filled with markers that will show up on an X-ray. Follow your doctor's instructions about when to take the
capsules. You may take only one capsule. Or you may be told to take one at a certain time for 2 or 3 days in a row.
You will then have X-rays taken of your belly. These are usually done on day 5. The percentage of markers that show up on the X-ray tells your doctor if you have a normal bowel transit time.
Bowel transit time tests do not cause
You will not feel discomfort from the X-rays used for the test. The X-ray table may feel hard and the room may be cool. You may
find that the positions you need to hold are uncomfortable.
This test is not recommended if you are
pregnant because the radiation from the X-ray can harm your developing baby
A bowel transit time test measures how
long it takes for food to travel through the
Bowel transit time depends on what types of food
you eat and how much you drink. Different people have different bowel transit
Fewer than 20% of the markers show up on an X-ray after 5 days (120 hours).
More than 20% of the markers show up on an X-ray after 5 days (120 hours).
You may have an abnormal bowel
transit time if you:
Lembo A, Camilleri M (2003). Chronic constipation. New England Journal of Medicine, 349(14): 1360–1368.
Other Works Consulted
Lembo AJ, Ullman SP (2010). Constipation. In M Feldman et al., eds., Sleisenger and Fordtran's Gastrointestinal and Liver Disease, 9th ed., vol. 1, pp. 259–284. Philadelphia: Saunders.
March 7, 2012
Adam Husney, MD - Family Medicine & Jerome B. Simon, MD, FRCPC, FACP - Gastroenterology
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