Colonoscopy vs. Virtual Colonoscopy: M. D. Anderson Offers Screening Advice for National Colorectal Cancer Awareness Month
Style News Wire | 3/3/2009, 3:58 p.m.
“The most widely used screening exam is colonoscopy, which is an accepted, standard screening test.” said George J. Chang, M.D., M.S., assistant professor in M. D. Anderson’s Department of Surgical Oncology.
However, many people have concerns about colonoscopy-related complications, such as bleeding and/or tearing of the colon. A newer option, virtual colonoscopy, sounds less invasive and may appeal to the public as a more desirable alternate screening tool.
Chang and David J. Vining, M.D., inventor of the virtual colonoscopy procedure and professor in
M. D. Anderson’s Department of Diagnostic Radiology, list advantages and disadvantages of both exams.
Colonoscopy (every 10 years unless polyps are found) – A doctor uses a colonoscope, a lighted tube, to examine the rectum and colon.
Most colorectal cancers begin as a polyp (a small, non-cancerous growth on the colon wall that can grow larger and become cancerous over time). During a colonoscopy, doctors can detect and immediately remove these polyps. Polyp removal is considered the most effective way to prevent the development of colorectal cancer.
This test may not detect all small polyps, nonpolypoid lesions (flat and depressed abnormal pieces of tissue), or cancers, but it is one of the most sensitive tests currently available. Thorough cleansing of the colon is necessary before this test. Patients may take laxatives 24 hours before the test. They also will not be able to eat or drink anything after midnight the night before the test. Some form of sedation is used in most cases. If sedation is used, someone will need to drive the patient home. Although uncommon, sedation or instrument-related complications, such as bleeding and/or tearing of the colon, can occur. “Getting accurate colonoscopy test results depends greatly on the skill of the examiner and the amount of time he or she spends viewing the colon,” Chang said. “The same can be said about virtual colonoscopy test results.”
Virtual colonoscopy (every 5 years) – A health care provider uses specialized CT scan techniques to produce images of the abdomen and pelvis. A computer then assembles these images into detailed three-dimensional pictures of the colon and rectum that can show polyps and other abnormalities.
It is less invasive than standard colonoscopy. Virtual colonoscopy may be as sensitive as standard colonoscopy if performed in experienced centers. Because sedation is not needed, virtual colonoscopy does not have sedation-related risks and does not require someone to accompany the patient to the examination. Risk of instrument-related complications, such as bleeding or tearing of the colon, may be lower than with standard colonoscopy.
Like standard colonoscopy, this test may not detect all small polyps, nonpolypoid lesions and cancers. Thorough cleansing of the colon is necessary before this test, similar to what is done to prepare for a colonoscopy. If an abnormality, such as a polyp, is detected, the patient will need to undergo a standard colonoscopy after the virtual procedure to remove the polyp or lesion, or to perform a biopsy. Because sedation is not used, patients may experience some discomfort during virtual colonoscopy when air is pumped into the colon. Not all insurance providers currently cover the costs of this exam. Virtual colonoscopy exposes the patient to a low dose of radiation (more than a chest x-ray but less than a conventional CT scan). “A frequent argument is that if virtual colonoscopy finds a polyp, then colonoscopy is needed for polyp removal,” Vining said. “However, about 90 percent of patients do not have a significant polyp that needs removal, eliminating the need for a follow-up colonoscopy in the majority of patients.”