Bowel prep is much more manageable, and CT-based ‘virtual colonoscopy’ may one day allow you to skip that, too.
Public health guidelines urge people 50 or older to undergo colorectal cancer screening. There are a number of options, but the gold standard procedure is colonoscopy: using a flexible, lighted instrument to check for signs of colon cancer or the presence of potentially precancerous growths called polyps. Removing polyps can prevent cancer.
But many people do not take advantage of colonoscopy’s ability to prevent cancer. In fact, a large fraction of Americans avoid or delay colorectal cancer screening altogether. The main reason is fear of the aggressive colon-clearing “bowel prep” required before colonoscopy. But it might be time for people in avoidance mode to reconsider.
“All I can say is the concern of patients about colonoscopy far outweighs the reality in almost all cases,” says Dr. John Saltzman, an associate professor at Harvard Medical School and director of endoscopy at Brigham and Women’s Hospital in Boston. “It’s not nearly as bad as they think.”
At a time when the benefit of colonoscopy has never been clearer, doctors have developed less unpleasant bowel-clearing methods than previous ones. Meanwhile, scientists at Harvard and elsewhere are working to perfect a new type of CT-based “virtual colonoscopy” that will allow many people to avoid bowel prep.
Colonoscopy is considered the gold standard because it allows the doctor to both find and remove polyps, explains Dr. Robert Mayer, an oncologist based at the Dana Farber Cancer Institute in Boston and professor of medicine at Harvard Medical School. “Colonoscopy is diagnostic and therapeutic,” Dr. Mayer says.
Other screening methods can detect cancer or pre-cancer in the colon and rectum, but only colonoscopy allows for thorough removal of polyps (polypectomy). Studies suggest that colonoscopy at age 50 will find precancerous polyps (adenomas) in about 25% of men. The procedures typically offered in the United States include:
Fecal occult blood test: A sample of stool is examined for tiny traces of blood from polyps or colon cancer. The test indicates possible internal bleeding from cancer or polyps, but confirmation requires a colonoscopy.
Sigmoidoscopy: A lighted instrument (sigmoidoscope) enables the doctor to examine the first 24 inches of the colon, or about one-third of the colon that can be visualized. Small polyps can be removed during sigmoidoscopy.
Virtual colonoscopy: A CT scan of the colon is performed and digitally processed to image the colon wall. If abnormalities are observed, a colonoscopy usually follows.
Colonoscopy finds and removes precancerous polyps in one procedure
In colonoscopy, a flexible instrument is used to check for signs of colon cancer or the presence of potentially precancerous growths called polyps. Removing polyps prevent cancer.
Illustration ©Harriet Greenfield
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For all its virtues, colonoscopy has a public relations problem: many of the people it can help don’t want anything to do with it. The latest statistics published by the American Cancer Society dramatize the problem. Delaware leads the nation, with 7 out of 10 people age 50 and older screened for colorectal cancer, but in Oklahoma only 5 in 10 get screened. The good news is that doctors have developed bowel prep approaches that make colonic clearing about as palatable and tolerable as it can be.
The standard bowel prep once came down to two options. The first was drinking about a gallon (four liters) of a liquid called polyethylene glycol (PEG). It works well, but some people have trouble finishing the whole gallon and it can cause nausea. The alternative was ingesting about half as much of a liquid based on sodium phosphate, which sucks large amounts of body fluids into the colon. Vomiting was not an uncommon side effect of this prep, in addition to dehydration, electrolyte imbalances, and, in the worst case, kidney failure. Sodium phosphate preps are not used much anymore, Dr. Saltzman says.
Tastes better, less filling
Today, there are more options. Added flavorings make liquid bowel preps more palatable. Combining liquids and pills reduces the overall volume of fluid that must be consumed to as little as two liters (roughly a half-gallon). At Brigham and Women’s Hospital, Dr. Saltzman says, doctors use a liquid laxative sold over the counter, Miralax, mixed with sweetened soft drinks to produce a total volume of two liters. When consumed chilled, it is both palatable and effective.
“The take-home message is that there are more choices than there were a few years ago, and the preps are more palatable, are lower volumes, and get better results if people take them as directed,” Dr. Saltzman says.
Another approach is called a split prep, which requires you to take a portion of the bowel prep the day before the procedure and the remainder three to five hours before the colonoscopy. “People like not having to take it all at once,” Dr. Saltzman says. “It’s rapidly becoming a standard of care, but there are some practical issues.”
If the colonoscopy or other procedure is scheduled for, say, 7 a.m., the second dose needs to be taken as early as 2 a.m., which is not acceptable to some people. At Brigham and Women’s Hospital, they consider split prep only for procedures scheduled for 11:00 a.m. or later.
The best thing about split prep, according to some studies, is that it clears the colon more effectively, producing a more accurate cancer screening. The colonoscopist can potentially see all worrisome polyps, and that means you don’t have to come back for a follow-up procedure if the prep turns out to be less than complete. About one-quarter of bowel preps are inadequate.
Because so much depends on a good prep, get clear directions from your doctor when you schedule your colonoscopy. “Although it is not that bad,” Dr. Saltzman says, “you don’t want to do it twice if you don’t have to.”