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Colorectal Physiology Tests

Colorectal Physiology Tests

General Information

Your doctor has arranged for you to have some tests on your lower bowel/back passage.

If instructed (see appointment letter), you may be required to stop all laxative medication and the use of suppositories prior to your appointment. Otherwise, you do not need to do anything before your arrival at the Unit. You can eat and drink as normal and continue to take any medication that you would normally take. You do not need to use any bowel preparation (laxative, enemas). There is no reason why the tests should have any adverse effects. However, you are welcome to bring along somebody for support if you so require.

This test consists of a number of individual tests that allows us to understand the function of your bowel. These include the following:

Colonic Transit: This test allows us to measure the time it takes for you to empty your bowel. For this test, you will be asked to swallow the small capsule that we will send you. This capsule contains 50 markers which can be seen on an x-ray. On the day of your appointment you will have an x-ray of your abdomen, which will show up any markers left in your bowel.

Rectal sensation: This test enables us to measure how much volume your rectum can hold. To do this, a small tube with a small balloon attached to it is passed into your back passage. We then inflate the balloon with air to determine what you can feel and the capacity of your rectum. During the test we also look for the presence of a nerve reflex in your back passage.

Anal Pressure Measurements: This test measures the strength of the muscles in your back passage. To do this, we insert another small tube (only 2mm thick) and ask you either to relax or squeeze the muscles of your back passage. This enables us to tell whether the muscles are functioning correctly.

Pudendal nerve function test: This test studies the function of the nerves in the pelvic floor, which control the muscles in your back passage. This involves inserting a finger-sized probe, with a small electrode on it, through the back passage into the rectum. A very small electric current is then passed over the nerves causing the pelvic floor muscles to twitch. You may feel a pulsing, twitching or prickling sensation in the back passage while we are taking measurements, which can be a little uncomfortable.

Ultrasound: This test can tell if the muscles around your back passage are intact or damaged. To do this, a finger sized probe is inserted into your back passage and gently moved in and out so that we can take scans (pictures) at different positions in your back passage. This procedure may be a little uncomfortable, but is not painful.

Evacuation Proctography: This test is used to investigate any problems that you may have when you try to open your bowels. Barium paste (a chalk-like substance, which shows up on x-ray) is inserted into your rectum via an examining scope until you have the urge to go to the toilet. You will then be asked to sit on a specially designed toilet in front of an x-ray machine and given instructions to open your bowels so as to pass the barium out of your back passage. While you do this, you will be given privacy behind a screen in a darkened room.

What can I expect?

You will be asked some questions relating to how your bowel works and the problems you have been having. We will then explain the procedures to you and you will be asked to sign a consent form, giving us permission to do the tests. Although there are no risks involved in performing the tests, some patients may find they have some mild discomfort. You will then be asked to change into a gown before the tests are done. 

In order for us to carry out the tests, apart from the colonic transit test, you will be asked to lie on a couch on your left side and we will explain to you what we are doing at each stage of the tests.


Are there any risks?

It can be embarrassing and a little uncomfortable to have these tests done on your back passage, but these tests are carried out by professional staff who are committed to ensuring that any discomfort is minimized and that your privacy is maintained at all times.


After the test

After the test you are allowed to rest for a while and then you will be allowed to go home. As sedation is not administered during the tests you do not need anyone to accompany you home but you can ask a family member or friend to pick you up if you would prefer.

You may experience a little discomfort in the lower part of the tummy or back passage after the tests for a few hours but this usually settles down. Bleeding through the back passage is very unusual. However, if you experience any unusual symptoms or more prolonged symptoms then please do not hesitate to contact us using the details given in the contacts section on this website.