Wednesday, August 22, 2012
SCOTTSDALE, Ariz. — One of the most unpleasant aspects of colorectal cancer screening for many patients is the amount of laxative they must drink the night before. Some become so anxious about drinking so much liquid that they avoid the entire procedure, putting them at risk of undiagnosed cancer. Under a new practice at Mayo Clinic in Arizona, four pills replace the multiple liters of laxative for people having a CT colonography also known as a virtual colonoscopy.
Colonoscopies, in which a tiny camera is inserted into the body to examine the bowels, and virtual colonoscopies, in which a CT scan is used to provide three-dimensional imaging of the colon and rectum, are commonly performed for early detection of colon cancer in people over 50. Both colon exams require the use of a laxative to empty the colon.
In the new Mayo protocol that began this summer, patients having virtual colonoscopies simply take four tablets of the cleansing agent bisacodyl.
"Our hope is that this will make people less anxious and more likely to get screened and will ultimately result in fewer deaths from colorectal cancer," says C. Daniel Johnson, M.D., chair of the Department of Radiology at Mayo Clinic in Arizona.
The development of the new protocol was based on a study co-by Dr. Johnson and published in Abdominal Imaging journal last year. The study found that the new four-tablet procedure worked as well as the standard liquid laxative for virtual colonoscopies. The new protocol is not intended for standard colonoscopies because the cleansing requirements between the two procedures differ.
Virtual colonoscopy was found to be highly accurate for detection of intermediate (6-9 millimeters) and large (greater than 1 centimeter) polyps. Because the majority of patients will not have a polyp, no further workup is necessary. Only the 12 percent of patients identified with a polyp during a colonography would then need to have a colonoscopy. Because most colon cancer arises from preexisting polyps, detection and removal of these lesions can help eradicate it.
Dr. Johnson says that how people get screened should be an individual decision, based on discussions with their medical providers. Virtual colonoscopies may be considered for patients who:
Despite the known benefits of colorectal screening, studies show that the majority of Americans 50 and older do not have it done. Colorectal cancer is the third most frequently diagnosed cancer and the second-leading cause of U.S. cancer deaths.
Mayo Clinic has been at the forefront in using and studying virtual colonoscopy since the technique began in the 1990s. Mayo published the first report in the scientific literature on the clinical effectiveness of virtual colonoscopy and was the first to offer it for routine care; Mayo has since performed thousands of virtual colonoscopies, and continues to study ways to improve the procedure.
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