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While we often say that the colonoscopy is the “gold standard” when it comes to colon cancer screening, no test is perfect. But colonoscopy still offers the most effective screening option.

A recent study by the Huntsman Cancer Institute at the University of Utah found that about 6% of colon cancers are diagnosed within three to five years after a patient receives a clean colonoscopy.

This was especially common in those over age 65, those with a family history of the disease and for patients in whom polyps were previously found. In addition, the cancers were more likely to appear on the right side of the colon.

Why Were Polyps Missed?

There are a couple of factors here. While it is possible in some cases the doctors overlooked a polyp, growth or suspicious tissue, there are some types of colon cancer that grow fast enough to develop between colonoscopies.

"Our first thought was that perhaps doctors did not view the entire colon, or that preparation for the procedure was not complete, which would obscure their view," N. Jewel Samadder, MD, M.Sc., lead author of the study, said. "However, the medical records of the patients with missed cancers showed these problems were seldom present."

In addition, many of the cancers that were found later grew on the right side of the colon with different types of polyps. "These types of polyps are flatter and faster-growing, which may explain why they are not seen during colonoscopy as well as how a cancer could develop even when no polyps were visible," he continued.

How to Make Sure Your Doc Gets it Right the First Time

While there is no guarantee, there are three easy steps you can take to make sure that your colonoscopy is complete (that is, the doctor can finish the exam) and thorough.

1. Ask Questions BEFORE the Exam

Has your doctor been specially trained to perform colonoscopies? How many colonoscopies has he or she performed? What is his or her adenoma detection rate (that is, his or her accuracy for finding polyps)?

Most doctors should find one or more polyps in at least 25% of men and 20% of women age 50 or older, however, some doctors who do colonoscopy still haven’t measured their adenoma detection rate and therefore can’t tell you whether they are careful or not. The only way you can find out is to ask.

2. Pay Attention to Your Prep

We’re not going to lie – colonoscopy prep is generally considered the most difficult part of the entire procedure. The good news? Once you’re done with the prep, the rest is easy!

A good prep means that your colon is empty and clean, ensuring that your doctor can see as much of your colon as possible. Following your prep and doctor’s instructions carefully will get rid of any food or waste residue that polyps can hide behind.

Follow Up Afterwards

3. Follow Up Afterwards

Take charge of your health! Ask questions, even after the exam. Questions to ask your doctor after your colonoscopy:

  • How effective was the bowel prep? (If the prep was not complete the doctor’s view of the colon may have been obscured, limiting the value of the test.)
  • Did you reach the cecum? (Answer should be “Yes”; if they did not reach the cecum, the colonoscopy should not be considered complete.)
  • Did you find any polyps or abnormal tissue while performing the colonoscopy? If polyps were found, how many and did you remove them? If abnormal tissue, was it removed and does a biopsy need to be done to determine if cancer is present?
  • How long did it take you to withdraw the colonoscope? (The colon is actually examined during withdrawal, so moving too quickly can cause the doctor to miss problems. Current studies say that withdrawal time should be 8 minutes or longer.)
  • When do I come for a follow-up appointment?
  • What symptoms might suggest I should come back before my next scheduled colonoscopy?

Download the free full “Questions to Ask Your Doctor about You Colonoscopy” PDF.


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