Virtual Colonoscopy for Colorectal Cancer Screening
What is virtual colonoscopy?
Virtual colonoscopy is a test that's used to look for polyps or other growths inside
your colon before they cause problems. (Looking for cancer before it causes symptoms
is called cancer screening.)
Polyps that grow on the inside lining of the colon may turn into colon cancer over
time. Finding and removing them can keep this from happening. Virtual colonoscopy
every 5 years is one of many colon cancer screening options.
The American Cancer Society advises that people at average risk for colon cancer start
screening for it at age 45. If you have a family history of colon cancer or are at
high risk for other reasons, you may need to start screening earlier.
Virtual colonoscopy is also called CT colonography. CT stands for computed tomography.
A CT scanner takes many X-rays of the colon. A computer puts all the X-rays together
to create 3-D images of your colon and rectum. These images can show polyps or other
changes inside your colon and/or rectum.
Why might I need a virtual colonoscopy?
Colon cancer is a common cancer in men and women. Virtual colonoscopy can be used
to find colon cancer at an early stage–when it's small and can be easier to treat.
A regular colonoscopy is also used to screen for colon cancer. For this test, a long,
flexible, lighted tube (called a scope) with a tiny camera on the end is put into
the rectum and slid up into the colon. This lets the healthcare provider look right
at the colon wall and remove any polyps that are found. Colon polyps that are found
by virtual colonoscopy cannot be removed during the test. A regular colonoscopy must
be done to take them out before they turn into cancer.
Virtual colonoscopy has some benefits over regular colonoscopy:
It's less uncomfortable and nothing is put into your body.
You don't need medicine (anesthesia) to get the test.
There's less risk of damaging the large intestine.
It may be able to show areas of the large intestine that regular colonoscopy can't
reach. This may be the case if part of the bowel is very narrow or blocked.
Virtual colonoscopy might be used if you're not able to have regular colonoscopy.
For instance, it may be an option it you have problems with swelling or bleeding,
or breathing problems.
What are the risks of virtual colonoscopy?
Every procedure has some risks and possible problems. For virtual colonoscopy, these
A small, short tube is put into your anus so that air can be pumped into your colon.
This inflates your colon so that polyps or other growths are more easily seen. Pumping
air into the colon carries a very small risk that it may cause a tear (perforation).
But the risk is thought to be far less than with regular colonoscopy.
Polyps or other growths can’t be removed with a virtual colonoscopy. You'll still
need to have a regular colonoscopy if polyps or other growths are found.
This test can miss some polyps if they are smaller than 10 millimeters. Some of these
might be seen by regular colonoscopy.
The test may show problems in other parts of your body (such as your kidneys, liver,
ovaries, spleen, or pancreas) which can lead to more tests.
Unlike most other screening tests, the test uses X-rays to make pictures of the colon
and rectum. The amount of radiation is small. But it may still raise your risk for
cancer slightly. It could also be dangerous for pregnant women. If you are or could
be pregnant, talk with your healthcare provider before the test.
Virtual colonoscopy may not be covered by your health insurance.
You may have other risks, depending on your health. Discuss any concerns with your
healthcare provider before this test.
How do I get ready for a virtual colonoscopy?
Tell your healthcare provider about any medicines you take. This includes prescription
and over-the-counter medicines, vitamins, herbs, or supplements you take. Also tell
them about any implanted medical devices, such as a pacemaker.
Before having a colonoscopy, you'll need to do a bowel prep. This helps empty your
colon so that the CT images will be clear. Here's how bowel prep is often done:
You may need to limit your diet to clear liquids for 1 or 2 days before the test.
These might be water, clear broth, or an electrolyte solution. Follow any directions
you are given for not eating or drinking.
The day before the test, you'll be given a strong laxative in pill or liquid form
to help you empty your colon. Expect to have many loose or liquid bowel movements.
You'll need to stay near a toilet.
Just before the procedure, you may be given a liquid to drink. This is a contrast
dye. It helps coat any stool left inside your colon so it shows up more clearly on
the X-rays. Tell your provider if you've had any reactions to contrast dye in the
What happens during a virtual colonoscopy?
Virtual colonoscopy can be done wherever a CT scanner is used. In most cases it's
done in the radiology department of a hospital or medical center. The scan takes only
about 10 to 15 minutes. This is what happens during the test:
The thin tube will be put in your rectum. It's used to inflate your colon with air.
You may feel a slight fullness.
You'll lie face up on a table that slides into the ring-shaped CT scanner.
The technologist will leave the room. The CT scanner is run from a separate control
room. But you'll be able to hear and talk with the staff the whole time.
The table will slide into and through the scanner. You may hear some whirring and
You may be asked to hold your breath a few times.
The scan may be repeated while you lie face down or on your side.
What happens after a virtual colonoscopy?
In most cases, you should be able to return home without help. You can go back to
your normal diet and activities. You may have gas and cramping right after the test
as you move the air out of your colon.
No medicines or special instructions are needed. Talk with your healthcare provider
and the radiology staff if you have any questions.
Before you agree to the test or the procedure make sure you know:
The name of the test or procedure
The reason you are having the test or procedure
What results to expect and what they mean
The risks and benefits of the test or procedure
What the possible side effects or complications are
When and where you are to have the test or procedure
Who will do the test or procedure and what that person’s qualifications are
What would happen if you did not have the test or procedure
Any alternative tests or procedures to think about
When and how you will get the results
Who to call after the test or procedure if you have questions or problems
How much you will have to pay for the test or procedure