Recent news reports suggest that getting only part of your colon scoped for precancerous lesions might be a good enough way to prevent colon cancer. But the real story is that whatever test you get, there is a wide variation in the quality of the colon examinations that doctors do, and out of hurry or poor training, some doctors miss a lot of lesions that should be taken out.
So if you want to have a safe, effective — and potentially life-saving — exam, you need to do some simple doctor screening to make sure the doctor is right for you.
The good news is it’s not that hard. Research has found that two simple questions will bring out what you need to know to assure that all the trouble you’re going through to get your colon examined will be worthwhile.
Before I lay out the questions, some quick anatomy to make this easy to understand:
The food we eat passes through the stomach and then through nearly thirty feet of small intestine before hitting the large intestine, or colon. The place where the small intestine joins the colon is called the ileocecal valve. It connects the ileum, the final part of the small intestine, to the cecum, the first part of the colon. The cecum is also where your appendix dangles off the end of the colon. In most people, the cecum and the appendix are in the right lower section of your abdomen. Intestinal contents travel from there vertically, in the ascending colon, up your right side toward the liver. The colon then turns 90 degrees to cross your belly from the right to the left. This section is called the transverse colon. Then the colon turns south in the descending colon, which runs down the left side of your abdomen. Finally it moves sideways one more time, in the sigmoid colon, which then reaches the rectum and the anus.
A colonoscopy uses a flexible telescope inserted through your anus to travel the entire length of the colon, to where it ends at the cecum. Most of the visual inspection by the doctor is done while the scope is being pulled back from the cecum to the exit at the anus.
A sigmoidoscopy, by contrast, only inspects the first foot or so of your colon. In some people, that’s enough to find most precancerous growths. But in many, it’s not. African-Americans, for example, have a higher rate of colon cancer in the further reaches of the colon beyond where the sigmoidoscope looks.
So the smart choice is to go with the full colonoscopy, even though the bowel preparation you have to undergo is more burdensome. That’s the recommendation of the American Gastroenterological Association, the doctors’ group that specializes in the intestines.
Now for the two questions to get the best chance of a good colon exam:
First, ask the doctor:
What is your detection rate of precancerous polyps?
(These are technically called adenomas). The rate should be at least 20 percent — or 25 percent in men patients and 15 percent in women patients. A lower rate means the doctor is very likely missing precancerous lesions that are waiting to turn into cancer — when the whole purpose of the colonoscopy is to find them and snip them off before they go bad.
The second question for the doctor:
What is the amount of time you typically take to inspect the entire length of the colon?
This answer should be at least six minutes. It takes that long to adequately inspect all the nooks and crannies.
Both these questions get at the same issue. You want to minimize the chance that a hurried examination will give you a clean bill of health by mistake.
How often does that happen? Frightfully often. In research published this year, the rate of colon cancers in people who had had a colonoscopy within the previous five years was ten times higher when the doctors who did the colonoscopy had a detection rate of ten percent or less, compared to doctors who had a detection rate of twenty percent or more.
Dr. Douglas Rex of Indiana University has written guidelines for his fellow gastrointestinal doctors about how to do an adequate colon exam. Dr. Rex is an advocate for careful comparison shopping by patients. In an article he wrote for fellow practitioners, he estimated that the doctors with the lowest detection rates are missing 75 to 90 percent of precancerous growths in the colon.
That’s a huge number. But patients can do their part to make sure their colon cancers aren’t missed by asking these simple questions before they undergo a colonoscopy.