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CT Colonography

CT Colonography - What it is

What is CT Colonography?
A CT Colonography (or Virtual Colonoscopy) uses X-rays to obtain an interior view of the colon (the large intestine). It does not require sedation. It is also less invasive than colonoscopy which involves insertion of a camera into the colon.

Why do I need it?
This study looks for growths, such as polyps or cancers, in the large intestines. Some polyps may grow into cancers. Early detection means these growths can be removed.

During the CT scan
The CT scanner is a large ring-shaped structure. You will lie on an examination table that passes through the scanner. You will not come into contact with the scanner, although it produces some noise as the table moves.

You will be fully awake and required to lie in different positions as gas is introduced into your colon. When the scan starts, you will be instructed to hold your breath for about 15 seconds so as to obtain good scan images.

Your radiographer operates the scanner from the console next to the scan room. He will always be able to see and hear you during the scan.

Preparing for your scan
To get a good look at the lining of the colon, it is necessary to clean out any traces of stool. You will be required to follow a restricted diet for two days before the examination to clear your bowel.

The following medications may also be required for your CT Colonography:

  • Colonic Lavage Solution
    A powder sachet to be mixed with two litres of water to help in preparing the bowels by clearing all the residual stools.
  • Bisacodyl Tablets
    A form of tablet laxative to be consumed orally.
  • Tagitol
    A stool tagging agent which is consumed orally and helps to improve radiological assessment by coating any retained stools in your colon.

Two days before procedure
Follow our recommended diet to clear your bowel for accurate diagnosis.

  • Recommended food for a low residue diet

    • Clear soup
    • Lean meat (eg. Chicken breast)
    • Steamed fish
    • Boiled potatoes
    • Porridge

  • Do not take
    Vegetables, fruits, cereal, milk or creamy product, oily/fatty food.

One day before procedure

  • Take only clear soup or fluid for breakfast and lunch
  • No food after 1.00pm
  • Colonic lavage solution
    • From 5.30pm to 8.00pm, take colonic lavage powder ( 2 packs) by dissolving one pack at a time in 1 litre of water and drink 250ml at regular intervals
    • Repeat with second sachet as instructed
    • You may add a little syrup for flavour


On the day of the scan

  • DO NOT take any food before your CT scan
  • Only plain water is allowed
  • You may continue your regular medications any time with sips of water

After the scan
There are usually no restrictions after having a CT scan. You may resume your normal activities unless advised otherwise by the radiographer or your doctor.

Your images will be read and interpreted by radiologists, who are doctors specialised in imaging. They will send your results electronically to your clinician who will discuss them with you at your next appointment.

CT Colonography - Symptoms

CT Colonography - How to prevent?

CT Colonography - Causes and Risk Factors

CT Colonography - Diagnosis

CT Colonography - Treatments

CT Colonography - Preparing for surgery

CT Colonography - Post-surgery care

CT Colonography - Other Information

The information provided is not intended as medical advice. Terms of use. Information provided by SingHealth

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