Virtual Colonoscopy - Topic Overview
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
Before this test, you will need to
clean out your colon. The following information gives you a general idea of the
preparation for a colonoscopy. Your doctor will give you specific instructions
before your test.
- One to two days before a colonoscopy, you will stop eating solid
foods and drink only clear fluids, such as water, tea, coffee, clear juices,
clear broths, Popsicles, and gelatin (such as Jell-O).
- Your doctor will recommend a medicine for you to use to prepare for your colonoscopy. It will most likely be a prescription
laxative tablet and/or a laxative solution (such as Nulytely or Golytely) that you drink before your colonoscopy. This solution will be given to you as a powder
that you will mix with
1 gal (3.8 L) of water. You may need to drink this laxative solution over 1 to 2 hours in the evening before the test. Or you may be asked to drink half the solution the evening before your test and the other half the morning of your test. This solution
may taste very salty and may make you feel sick to your stomach. To make your
colon prep easier, you may want to try some of the following tips:
- You may find it easier to drink the solution if you use a straw with the end at the back of your throat (to bypass the taste buds).
- Each time you drink some of the solution,
you may also drink some water or clear fluids (like apple juice) to help get
rid of the salty taste in your mouth.
- You may find it easier to
drink the solution if you chill it in the refrigerator first.
your doctor if it is okay for you to add flavored drink crystals (such as
Crystal Light) to the solution.
- Add lemon juice to the solution or
suck on sliced lemon wedges after you take a drink.
- Your doctor may recommend a different preparation product, such as the
Nutraprep meal kit or sodium phosphate tablets (for example, Visicol). These are other methods
of preparing for a colonoscopy. If you are concerned about the bowel prep, you can ask your doctor whether another method will
work for you.
- Oral sodium phosphate (either tablets or liquid) can cause kidney problems. Make sure you check with your doctor before using a nonprescription sodium phosphate product.
- You will want to stay home while doing the colon prep because it will make you use the bathroom
- Drink plenty of clear fluids during the prep so you will not
dehydrated. This will also help clean out your colon
completely after you finish the colon prep.
- Do not eat any solid
foods after doing the colon prep.
- Stop drinking clear
liquids 6 to 8 hours before the test.
- Your doctor may have
you use an enema 30 to 60 minutes before the test to completely clean out your