You may need to come back another day for a colonoscopy. In an ideal world, radiology and gastroenterology programs would coordinate so that on the slim chance that a threatening polyp is found, you can have it removed the same day. That's what happens at the University of Wisconsin, which has offered virtual colonoscopies since 2004. Kim says only about 8 percent of patients need a follow-up colonoscopy, and they have all been able to get one the same day. Other hospitals, however, still need to set up procedures that guarantee same-day follow-up, and it's going to be essential to coordinate radiology and gastroenterology departments if the CT scan is to be more widely used, says Robert Bresalier, a gastroenterologist at M.D. Anderson Cancer Center in Houston. "It's unfair for patients to have to go through two preps." But until such procedures are set up, if you do need a colonoscopy, you may have to schedule it for another day.
It's expensive. Right now, the procedure runs north of $1,000 and isn't usually covered by insurance. (There are exceptions—some people are covered if there's a medical reason, such as a bleeding disorder or anesthesia allergy, for them to avoid conventional colonoscopy.) More widespread coverage will most likely follow on the heels of the consensus endorsement, but until then, it's out of pocket.
Seek out experienced practitioners. Whichever screening test you get, "it's only as good as the quality of performance brought to it," says Winawer. With regular colonoscopy, for example, evidence suggests that the greater the skill of the gastroenterologist and the more time she spends performing the test, the more likely it is to pick up polyps. So avoid walk-in, full body-scan centers and seek out a radiologist who has experience in the procedure and uses the latest in 3-D software and multidetector/multislice CT technology.
Don't hold out for a virtual colonoscopy. If one isn't available in your area, get some other kind of colorectal screening. In addition to colonoscopy, preventive tests include flexible sigmoidoscopy and double-contrast barium enema, either of which can be done every five years. Those are preferable to the tests that look for signs of cancer in the stool, which must be done annually and have their own pluses and minuses. The newly recommended stool DNA test, for example, can be done at home, but requires you to package up an entire bowel movement and send it for testing.
The most important thing is to pick something—don't be overwhelmed by your options. (One small study found that having more choices actually increased the odds that people would forgo colorectal cancer screening.) "The important thing is to talk to a doctor and get screened regularly," says Smith. "The best test is the one you have."