Colonic transit (pellet) study

A colonic transit study is a test that shows how quickly food passes through the digestive system. This may also be called a pellet study.  It starts when you give your child some pellets to swallow on three consecutive days. On the fourth day, they will need to come into hospital for an x-ray. If there are some pellets seen on this x-ray you might be asked to return for a second x-ray on day 6. This information sheet from Great Ormond Street Hospital (GOSH) explains about the transit study test and what to expect when your child has one.The digestive system is a hollow tube from the mouth to the anus. The walls of the tube contain muscles and nerves that squeeze food rhythmically through the system – this action is called peristalsis.

Your child needs a colonic transit study to show if there are any problems with their digestive system which are causing food to pass too quickly or too slowly between their mouth and the outside world, as faeces (poo).

What happens before the test?

Most children will need to have their large intestine (colon) emptied before the test. This might mean that your child needs to be admitted to the hospital for a few days to be given high dose laxatives. During this time your child will need to follow a low fibre diet.

What does the test involve?

We will give you six small capsules of pellets with instructions for taking them. The pellets are clearly marked to tell you on which day they need to be taken. There are two capsules per day. The pellets for each day are different shapes.

Older children should be able to swallow them with water, but for younger children you can take the pellets out of the capsule and hide them in a small amount of food.

Your child will need to stop taking any laxatives when they swallow the first pellet and not take any laxatives until the last x-ray has been taken.

Your child will have an x-ray that will show up where the pellets are in their digestive system on day 4. If many pellets are seen on this x-ray your child may need a second x-ray a few days later (on day 6).

Are there any risks?

There are no risks to your child linked to taking the pellets needed for this test, and they will pass out of your child in their faeces. They can be flushed away safely.

The x-rays that are taken to see where the pellets are in your child’s digestive system use only a tiny amount of radioactivity and any possible harm from this is extremely small.

However, X-rays may harm developing babies, so if your daughter over 12 years old and is having the test, we will ask her about her periods and may enquire about any possibility that she could be pregnant. We may ask for a urine or blood sample to carry out a pregnancy test.

How long will it take to get the results?

The results will be available after the x-ray has been carried out and you will be given an outpatient appointment to discuss these with your child’s doctor.

Compiled by:
The Gastroenterology Investigation Suite in collaboration with the Child and Family Information Group
Last review date:
August 2020