Fergus V. Coakley, M.D.
Radiologist and Chief of Abdominal Imaging
UCSF China Bay Imagining Center
Studies show that half of Americans age 50 and older aren't getting colonoscopies as recommended, possibly because it requires sedation and carries a small risk of bowel perforation. Colon cancer remains the second leading cause of cancer deaths in the United States, but it is one of the most curable forms of cancer when detected early. The availability of virtual colonoscopy (VC) — a less invasive and equally effective alternative to standard colonoscopy — may encourage more people to undergo colon cancer screening and save lives.
A recent study found that VC is highly accurate in detecting clinically significant polyps. 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 American College of Radiology Imagining Network (ACRIN) trial, sponsored by the National Cancer Institute (NCI), included 2,600 participants at 15 centers nationwide. The trial, the largest of its kind to date, compared virtual colonoscopy findings with conventional colonoscopy. Results were published in the Sept. 18, 2008 issue of the New England Journal of Medicine. Previous single-site studies, including those conducted at UCSF, reported varying results regarding VC's accuracy in detecting polyps.
The virtual colonoscopy procedure is as follows:
VC requires the same preparation as standard colonoscopy. Patients must undergo laxative cleansing, adhere to a liquid diet and eat no solid food for 24 hours prior to the scan.
It 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 distend it. UCSF Medical Center uses carbon dioxide, which provides better visibility, is more quickly absorbed and causes less patient cramping and discomfort compared to air.
CT scan and cutting-edge imaging software creates 2- and 3-dimensional images of the colon. At UCSF, we use the latest generation CT technology — the 64-slice CT scanner — available at only a few select medical centers nationwide. Centers offering virtual colonoscopy must have specialized computer software and radiologists trained to read the results.
Scanning takes about 10 seconds with the patient lying on his or her back and abaout 10 seconds lying on the stomach. The entire procedure takes about an hour.
If polyps are found, patients must undergo a standard colonoscopy to remove them. Polyps are found in an estimated 10 to 20 percent of patients during colonoscopy.
The American Cancer Society recommends that for healthy men and women age 50 and older, VC is repeated every five years if no polyps are found. For standard colonoscopy, the ACS recommends the test every 10 years for healthy patients.
Perhaps the most significant advantages of VC are that it is much less invasive and does not require sedation. Other benefits include:
Very low risk — Unlike standard colonoscopy, there are no risks associated with sedation and bowel perforation.
Faster, no recovery — VC takes about an hour compared to a whole day for standard colonoscopy. Patients can return to work and normal daily activities on the same day and don't need someone to drive them home after the procedure.
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 referring physicians within 24 hours or sooner.
VC is recommended for patients who:
Require colon cancer screening due to age (over 50 or older) or family risk
Require screening due to symptoms such as abdominal pain and blood in stool, had polyps in the past or have other needs for a biopsy.
Cannot be sedated due to pre-existing medical conditions, take anti-coagulants, are frail or elderly or have failed a colonoscopy due to abdominal surgical scarring or abnormally shaped colons.
Currently, medical insurers rarely cover the cost of VC for standard colon cancer screening and most patients pay for the procedure. However, in June 2008, the Centers for Medicare and Medicaid Services (CMS) called for national coverage of VC, which is expected to lead to reimbursement for the test in 2009.
VC is performed at UCSF's China Basin Imaging Center. For the last decade, UCSF researchers have been at the forefront of studying VC and developing guidelines for the test. We were one of the lead centers in the ACRIN trial.
For more information, contact the Physician Referral Service at UCSF Medical Center:
Phone — (888) 689-UCSF or (888) 689-8273
Email — email@example.com