What is a virtual colonoscopy?
colonoscopy uses X-rays and computers (computed tomography [CT] or
magnetic resonance imaging [MRI]) to take two- or
three-dimensional images of the interior lining of your
large intestine (colon) and rectum. A virtual colonoscopy can be used to
screen for precancerous and cancerous growths in the colon or rectum (colorectal cancer), such as
polyps or tumors.
Virtual colonoscopy (also called computed tomographic
colonography, or CTC) is still being studied to determine whether the results
are as accurate as a
regular colonoscopy. Virtual colonoscopy is not yet
Virtual colonoscopy is one of many tests that may be used to screen for colon cancer. Which screening test you choose depends on your risk, your preference, and your doctor. Talk to your doctor about what puts you at risk and what test is best for you.
For more information on screening tests for
colon cancer, see:
Colon Cancer: Which Screening Test Should I Have?
Why is it done?
A virtual colonoscopy may be done
- Screen for colorectal cancer or
- Monitor the growth of polyps.
- Screen for recurrence of colorectal cancer in people who have
had surgery for this disease.
- Evaluate abnormal results from other
- Replace a regular colonoscopy if the thin lighted
scope cannot be inserted in the colon for some reason, such as when a tumor
blocks the passage.
Virtual colonoscopy is not commonly done for other
conditions at this time but may prove to be useful to:
- Detect other problems or diseases of the
anus, rectum, or large intestine (colon).
- Check the source of
- Check the cause of chronic
- Monitor the treatment of inflammatory bowel
How do I prepare for it?
requires the same cleansing colon prep as a regular colonoscopy. Colon prep
takes 1 to 2 days depending on which type of prep your doctor recommends. For
many people, the prep for a colonoscopy is more trying than the actual test.
Researchers are studying methods that could be used to mark (tag) stool in the
colon before virtual colonoscopy so cleansing colon preps would not be
One to two days before a colonoscopy, you will need to
stop eating solid foods and drink only clear liquids, such as water, tea,
coffee, clear juices, clear broths, Popsicles, and gelatin (such as Jell-O).
Some preps, such as taking a prescription laxative tablet or drinking a
laxative solution (such as Nulytely or Golytely), are done the evening before
your colonoscopy. The colon prep causes loose, frequent stools and diarrhea so
that your colon will be empty for the test. Plan to stay home during your prep
time since you will need to use the bathroom frequently. The colon prep may be
uncomfortable, and you may feel hungry on the clear liquid diet. If you need to
drink a laxative solution, be sure to have clear fruit juices or soft drinks to
drink after the prep because the solution tastes salty.