Types of Colonic Transit Time Tests

A colonic transit time test is a diagnostic procedure that offers information as to how long it takes for food to travel through your digestive system. It is used to gain a better understanding of how well your large intestine is functioning in terms of moving stool along. The test is particularly useful if you experience constipation on a chronic basis.

Colonic transit time is the amount of time that it takes for a substance to move through your colon. Taking a measurement of this time provides useful information as to the severity of your digestive problem. Colonic transit time measurements are also used in research to assess the effect of treatment on gut motility.

How Colonic Transit Times Are Tested

There are three predominant types of ways in which colonic transit time is tested:

Radiopaque Marker Test

The radiopaque marker test is the most traditional and most widely used of the three options. This is considered to be a relatively simple test. You will be asked to swallow a capsule that contains plastic beads or rings which are used as markers. The capsule will dissolve and the rings will make their way into your colon. This test is known by a few names - colonic transit time study, bowel transit time test, or a Sitz marker study.

There are a few variations of this test. One requires you to swallow a single capsule followed by a series of appointments to have X-rays taken of your abdomen until all of the markers have been passed. Alternately, one X-ray will be taken on day five. Another variation has you swallow one capsule a day for three days. X-rays will be scheduled for days four and seven, or perhaps just on day seven.

One drawback to this type of colonic transit test is that you cannot use laxatives, enemas or take any medication for your constipation until the test has been completed, which as you can see may take up to a week. Another downside is that you are exposed to radiation from the X-ray.

Radionuclide Scintigraphy

Radionuclide scintigraphy, also called colonic scintigraphy, is a nuclear medicine test. You will be asked to swallow a capsule or eat a semi-liquid meal that contains radioactive isotopes. As the isotopes make their way through your digestive system, their progress is noted with the use of a gamma camera.

An advantage of this test is that it also allows for the measurement of gastric (stomach) and small intestine motility. However, this test is not widely available. Images are typically taken at the 24- and 48-hour marks.

Wireless Motility Capsule

The wireless motility capsule for measuring digestive system motility was approved by the FDA in 2006 for the evaluation of delayed gastric emptying (gastroparesis) and chronic idiopathic constipation. The test involves swallowing a small data recording device that transmits information to a wireless data receiver.

This method of testing colonic transit time may be recommended if it appears that you have motility problems in more than one area of your digestive system. It offers the advantages of being well-tolerated and there is no radiation exposure. However, it can be quite expensive.

This test requires that you fast overnight and temporarily discontinue any digestive medication. At your healthcare provider's office, you will swallow a capsule that contains the small data recording device. You will be given something to eat and water to drink with the capsule. You must avoid eating for the next six hours, but then can return to your regular meals.

You will be instructed to avoid strenuous exercise until the test is over. A follow-up appointment will be scheduled three to five days later in which you will return the data receiver. Your healthcare provider will be able to confirm that you eliminated the capsule from your body because there will be a change to the recording signal.​