Virtual Colonoscopy

Virtual colonoscopy (VC), also known as CT colonography, is equally effective, less invasive and faster than standard colonoscopy for colon cancer screening. Unlike standard colonoscopy, it does not require sedation. You can drive yourself home after the test and return to normal daily activities.

UCSF Medical Center is one of the few centers in California to offer the latest generation of CT technology — the 64-slice CT scanner — for this screening. Centers offering VC have specialized software and specially trained radiologists to read the results.

Virtual colonoscopy is recommended if you:

  • Need colon cancer screening because you're age 50 or older or because of family risk factors
  • Need colon cancer screening due to symptoms such as abdominal pain, blood in stool, as a follow-up to polyps removed in the past, or in place of a biopsy
  • Can't be sedated due to medical conditions, you take anti-coagulants, you're frail or elderly or you failed a colonoscopy due to abdominal surgical scarring or an abnormally shaped colon

Benefits of Virtual Colonoscopy

Benefits of virtual colonoscopy include:

  • Low risk: Unlike colonoscopy, there are no risks associated with sedation and bowel perforation.
  • Faster, less complicated: VC takes about an hour versus a whole day for standard colonoscopy. Patients can return to work and normal daily activities on the same day and do not need someone to take them home.
  • Quick diagnosis: At UCSF, each image receives a same-day, double-reading by two radiologists to ensure the most accurate diagnosis. Reports are returned to your doctor within 24 hours or earlier.
  • Thorough evaluation: Unlike standard colonoscopy, VC can spot cancers and growths beyond the colon because it takes a picture of the entire abdominal cavity and pelvis.

VC is approved by the American Cancer Society and leading gastrointestinal societies as an alternative to standard colonoscopy.

What Happens During the Procedure

  • Virtual colonoscopy requires the same preparation as standard colonoscopy. You must undergo laxative cleansing and a liquid diet for 24 hours prior to the scan.
  • The procedure involves placing a small tube — compared to a 6-foot scope used in standard colonoscopy — in the rectum to inflate the colon. An insufflator injects air or carbon dioxide into the colon to expand it. UCSF Medical Center uses carbon dioxide, which provides better visibility, is more quickly absorbed and causes less cramping and discomfort compared to air.
  • CT scan and cutting-edge imaging software creates 2- and 3-dimensional images of the entire colon, along with other views of the pelvic and abdominal region. UCSF uses the latest generation CT technology — the 64-slice CT scanner.
  • Scanning takes about 10 seconds while you lie on your back and about 10 seconds lying on your stomach. The whole procedure takes about an hour.
  • If polyps are found, a standard colonoscopy must be performed to remove them. You'll complete another bowel preparation, which may be on a different day if an appointment is not available following your VC. Polyps are found in about 10 to 20 percent of patients during colonoscopy.

Research Findings on Virtual Colonoscopy

A study, called the American College of Radiology Imagining Network (ACRIN) trial, found that virtual colonoscopy is accurate in detecting polyps that have the potential to become cancerous. Ninety percent of polyps 1 centimeter or larger were detected and polyps as small as a half centimeter were detected with a high sensitivity.

The trial, sponsored by the National Cancer Institute, included 2,600 participants at 15 centers nationwide. The study, the largest of its kind conducted to date, compared virtual colonoscopy to standard colonoscopy. Previous single-site studies, including those conducted at UCSF, reported varying results regarding VC's accuracy in detecting polyps.

The American Cancer Society (ACS) recommends that VC for healthy men and women 50 or older be repeated every five years if no polyps are found. For standard colonoscopy, the ACS recommends the test every 10 years for healthy patients.

Request an Appointment

You'll need a referral from your specialist or primary care doctor. Call Radiology Scheduling at (415) 353-2573 to request an appointment. Please provide information about existing medical conditions, tests performed related to this condition and your insurance coverage.

Most health insurance plans don't yet cover the cost of a virtual colonoscopy. For information about the fee, please call Radiology Billing at (415) 514-8888.

Once you have made an appointment, instructions will be mailed to you. It is important to follow the instructions carefully. Otherwise, the procedure may have to be rescheduled.


Reviewed by health care specialists at UCSF Medical Center.