In the study, 45 virtual colonoscopy patients out of 500, or 9 percent, were found to have clinically important extracolonic findings ranging from kidney cancers to abdominal aortic aneurysms. In 35 of the patients, or 7 percent, these conditions had not been previously diagnosed.
"That's a fairly large percentage," observes principal investigator and lead author Judy Yee, MD, chief of radiology at SFVAMC. "Depending on the patient population you look at, this finding suggests that it may be more common to find something significant outside of the colon than in the colon with this technique, because there is more likely to be a problem outside the colon." The study is being published in the August 2005 issue of Radiology.
Virtual colonoscopy uses a CT (computed tomography) scanner, which generates a three-dimensional image from a series of two-dimensional X-rays, to screen for cancers and polyps in the colon. It is much less invasive than more conventional screening techniques such as a colonoscopy, in which a flexible tube with an imaging device on the end is inserted all the way through the colon to the lower end of the small intestine, or a lower gastrointestinal (GI) series, in which X-rays are taken of the colon after it has been filled with barium. Unlike these techniques, virtual colonoscopy is not limited to the colon. It is also much quicker -- less than one minute -- versus 30 minutes to an hour for standard colonoscopy and one to two hours for a lower GI series.
"Essentially, we're performing a CT scan of the entire abdomen and pelvis," says Yee, who is also associate professor and vice-chair of radiology at the University of California, San Francisco (UCSF). "This allows us to look
Contact: Steve Tokar
University of California - San Francisco