Virtual Colonoscopy

Video of Virtual Colonoscopy

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Picture of example of how a polyp may appear to a Radiologist when viewing a Virtual Colonoscopyexample

Pictured above is an example of how a polyp may appear to a Radiologist when viewing a Virtual Colonoscopy

What is Virtual Colonoscopy?

Virtual Colonoscopy is a medical imaging procedure which uses computed tomography (CT), sometimes called a CAT scan, and advanced computer software to produce two- and three-dimensional images of the colon that can be viewed on a video screen.
The major reason for performing virtual colonoscopy is to screen for polyps or cancers in the large intestine. Polyps are growths that arise from the inner lining of the intestine. Some polyps may grow and turn into cancers. The goal of screening with colonoscopy is to find these growths in their early stages, so that they can be removed before cancer has had a chance to develop.

Most physicians agree that everyone older than 50 years should be screened for polyps every seven to 10 years. The American Cancer Society recommends virtual colonoscopy screening every 5 years.
Individuals at increased risk or with a family history of colon cancer may start screening at age 40 or younger and may be screened at shorter intervals (for example, every five years). Risk factors for the disease include a history of polyps, a family history of colon cancer, or inflammatory bowel diseases, such as Crohn’s disease or ulcerative colitis.

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What are the benefits of Virtual Colonoscopy?

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What happens during the test?

Just before CT scan, check that your rectum is empty by attempting one more evacuation. After changing into a gown you will lie on the CT scanner table. The technologist will need to distend your colon by placing a small soft tube into the rectum of the colon and administering CO2 gas. As the gas is administered you may experience a bloated feeling and mild discomfort. Please let us know if you are uncomfortable.

You will be scanned initially lying on your back. We will then ask you to turn onto your stomach and we will scan a second time. You will be asked to hold your breath during each scan for about 10 seconds. If you have to breathe out, do so shallowly. We may need to give additional gas when you turn onto your stomach.

Then you are done! You will need to visit the restroom to change back into your clothes.

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American Cancer Society

 The American Cancer Society estimates that 146,970 men and woman will be diagnosed with colorectal cancer and 49,920 will die of the disease in 2009 - this is the 3rd most common cancer diagnosed and the 2nd leading cause of death from cancer in the United States. 

In 2008 the American Cancer Society approved virtual colonoscopy as an alternative to traditional colonoscopy. 

ACS guidelines for colorectal screening:

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The Stanford Diagnostic Imaging Advantage

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Insurance Coverage

Virtual Colonoscopy as a screening method is not currently covered by Medicare. However, Medicare does reimburse the examination in certain situations.  Additionally, some insurance companies are covering this exam for patients with failed or incomplete traditional colonoscopies. Some private insurers are also reimbursing this exam for screening colonoscopy.  Coverage varies by plan.

For additional information regarding Medicare coverage guidelines, go to:  CMS Medicare

Please call Patient Financial Services at 1-800-794 8978 for cash pricing.

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Virtual Colonoscopy Exam Preparation Kit


875 Blake Wilbur Drive, Suite CC1101
Palo Alto, CA 94305
(inside the Stanford Advanced Medicine Cancer Center)

PHONE: 650-838-0429       FAX: 650-838-0447

Mon-Fri 8am-7pm
Saturday 9am-3pm

  • CTVC-KIT (Bisacodyl® (Dulcolax), EZ CAT, Gastrografin)
  • CTVC-KIT is available at this location only. Pick-Up or Mail Delivery available
  • Magnesium Citrate Over the counter & available at any local pharmacy. Mail delivery not available.

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Virtual Colonoscopy Exam Preparation

For 7 days before the test:

Day before the test:

Step one - 11:00 am: Take two Bisacodyl® (Dulcolax) tablets (5 mg each) with 1 glass of clear liquids.

Step two - 2:00 pm: Drink one bottle (296 mL) of magnesium citrate. Follow this with 6 cups of clear liquids over the next 90 minutes.

Step three 5:00 pm: Mix package of barium sulfate (EZ CAT) with 450 mL of water. Drink.

Step four - 5:30 pm: Drink the second bottle (296 mL) of magnesium citrate. Follow this with 6 cups of clear liquids over the next 90 minutes.

Step five 8:00 pm: Mix 2 bottles (60 mL total) of diatrizoate (Gastrografin) in 1 glass of clear juice, soda, or water. Drink.

12:00 MIDNIGHT: No Food or Liquids

The day of the test be sure to take your blood pressure and heart medicines with a sip of water. Do not eat or drink anything else.

Special Precautions

In general, you can (and should) continue to take any routine prescribed medications during the preparation. However, take them 1 hour before or at least one hour after taking the laxative (magnesium citrate).

In the event that polyps are found on the virtual colonoscopy, certain eligible patients may choose to undergo same day traditional colonoscopy, and removal of polyps (polypectomy) may be performed. For this reason, patient taking anticoagulants, aspirin, NSAIDS (e.g., Advil, Aleve, Motrin), plavix, supplements and/or vitamins should consult with their physician before scheduling a virtual colonoscopy.

If you take blood pressure or heart medications, or prednisone or other steroids, take them before 7 am with a sip of water on the day of the test.

If you are taking INSULIN the dosage may need to be adjusted the day prior and the morning of the test. Contact your physician for instructions regarding dosage.

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Scheduling an Appointment

To schedule an appointment for a virtual colonoscopy, please call:

Stanford Radiology Scheduling Center
Call (650) 723-6855; Fax (650) 723-6036

For more information, go to:


  1. Johnson, C.D., et al., Accuracy of CT Colonography for Detection of Large Adenomas and Cancers. N Engl J Med, 2008. 359(12): p. 1207-1217.
  2. Pickhardt, P.J., et al., Computed tomographic virtual colonoscopy to screen for colorectal neoplasia in asymptomatic adults. N Engl J Med, 2003. 349(23): p. 2191-200.
  3. Jemal, A., et al., Cancer Statistics, 2009. CA Cancer J Clin, 2009: p. caac.20006.
  4. Levin, B., et al., Screening and Surveillance for the Early Detection of Colorectal Cancer and Adenomatous Polyps, 2008: A Joint Guideline From the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. Gastroenterology, 2008. 134(5): p. 1570-1595.

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