Test Overview

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.

How To Prepare

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?).

How It Is Done

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.

How It Feels

Bowel transit time tests do not cause
pain.

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.

Risks

This test is not recommended if you are
pregnant because the radiation from the X-ray can harm your developing baby
(fetus).

Results

A bowel transit time test measures how
long it takes for food to travel through the
digestive tract.

Bowel transit time depends on what types of food
you eat and how much you drink. Different people have different bowel transit
times.

Bowel transit time footnote 1
Normal:

Fewer than 20% of the markers show up on an X-ray after 5 days (120 hours).

Slowed:

More than 20% of the markers show up on an X-ray after 5 days (120 hours).

What Affects the Test

You may have an abnormal bowel
transit time if you:

  • Have an infection in your
    intestines.
  • Do not drink enough fluids (dehydration).
  • Have a disease, such as a
    narrowing (stricture) in your intestine, an underactive thyroid gland (hypothyroidism),
    diabetes, or
    Hirschsprung’s disease.
  • Are eating less
    than you usually do or you are eating different kinds of food than
    usual.
  • Take medicines, such as cold medicines, iron, or medicine
    used to control blood pressure and pain.

What To Think About

  • Bowel transit time also can be done using a dye capsule. You swallow a capsule containing a bright red dye and measure the amount of time until you see the red color appear in your stool. You may also measure the time needed for all of the dye to pass through your colon.
  • Many doctors do not think that bowel transit time testing
    is useful. Different people have different bowel transit times on different
    days.
  • This test is not recommended if you are or might be
    pregnant.
  • You can usually speed up bowel transit time if you increase
    the amount of fruits, vegetables, and whole grains that you eat each day. To learn more, see the topic
    Healthy Eating.
  • It is possible to have a
    daily bowel movement but still have a slow bowel transit time.

References

Citations

  1. 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.

Credits

ByHealthwise Staff
Primary Medical Reviewer Adam Husney, MD – Family Medicine
Specialist Medical Reviewer Jerome B. Simon, MD, FRCPC, FACP – Gastroenterology

Current as ofOctober 9, 2017