CT colonography (virtual colonoscopy)

Category: Digestive Tests & Procedures · All digestive tests & procedures

What it is

CT colonography, sometimes called virtual colonoscopy, is a CT scan of the large bowel after it has been gently inflated with gas through a small tube. Computer software builds a fly-through view of the bowel lining to look for polyps and cancers.

Why it is done

It is used to investigate bowel symptoms and for screening in some programmes, particularly when standard colonoscopy is not suitable, was incomplete, or is not wanted.

How to prepare

The bowel must be emptied with diet changes and laxative preparation, as for colonoscopy, and you may drink a special liquid beforehand that labels any remaining stool so it is not mistaken for polyps. Tell the team about allergies and kidney problems.

What happens during the procedure

A small tube is placed in the back passage and gas inflates the bowel, which can feel bloating and crampy. The scanner takes pictures with you on your back and front (or side), a few minutes each. The whole visit is usually 20 to 30 minutes and no sedation is needed.

Afterwards — recovery & results

You can go home and eat normally straight away, and drive yourself. If a significant polyp is found, a colonoscopy may still be needed to remove it. The report goes to your doctor, usually within days.

Risks & considerations

Risks include the radiation dose and discomfort from gas, and a very small risk of bowel perforation from inflation. It cannot remove polyps, and it is slightly less accurate for very small polyps than colonoscopy.

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Frequently asked questions

If it's clear, do I still need colonoscopy?

Usually not — a clear CT colonography is reassuring. Colonoscopy follows only if findings need removal, biopsy or closer inspection.

Can I drive afterwards?

Yes — no sedation is used, so you can drive and return to normal activities immediately.

Related procedures — Digestive Tests & Procedures

Anorectal physiology and manometry Barium enema Colorectal transit study (marker study)Defecating proctogram (evacuation study)Faecal calprotectin and stool tests Gastric emptying study

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Please note: This page is educational information about a medical procedure or test. It does not replace the instructions of your own care team, who know your situation and whose preparation, fasting and medication advice you should follow if it differs from anything here. If you have symptoms that worry you, or an appointment you do not understand, contact your clinical team.