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Thursday 24th May 2018

Colonoscopies 'miss cancers'

22nd December 2008

A Canadian study shows that colonoscopy misses almost every cancer in the right side of the colon, and 30% of cancers in the left side of the colon.


This is especially significant because the right side of the colon is the place where about 40% of colon cancers occur.

For years, doctors and patients thought that colonoscopies could prevent 90% of cases. But colonoscopies now seem to prevent only 60-70% of them.

David Ransohoff of the University of North Carolina said the result was dramatic. Nevertheless, other experts say patients should go ahead with plans to be tested.

But it is now strongly recommended that patients seek the best colonoscopists when having a colonoscopy. This can be done by asking questions about how many polyps the doctor finds and removes on average.

Experts also say patients should be scrupulous in going through with the bowel cleansing that precedes the test. Patients should report bleeding or other symptoms, even if they occur soon after they have received a colonoscopy.

The American Cancer Society (ACS) says that even if the test has proven less effective than previously thought, it has no plans to modify its suggested intervals between screenings.

The new study matched each of 10,000 people who lost their lives to colon cancer to five others in the same geographic area and of the same age, sex and average yearly income.

The researchers found out how many patients and control subjects had had colonoscopies and whether the doctors had removed polyps.

Then the researchers compared them, calculating the colon cancer death rate for people who had had the screening test.

According to the ACS, this year roughly 148,000 people will learn they have colon cancer and nearly 50,000 will die of the disease.

There are several possible reasons why the tests did not prove to be accurate. It is possible that patients had not properly cleansed their bowels. Cleansing the bowels before testing is a particular problem for the right side of the colon.

One solution is to be sure that only a short time passes between taking strong laxatives and the colonoscopy itself.

Robert Smith of the ACS said there is a possiblity that a satisfactory test for the right side of the colon may never be developed.

It is thought that cancer may develop differently in the right side of the colon, since serrated lesions tend to occur there, and can turn into cancer much more quickly than typical polyps.


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Wednesday 14th January 2009 @ 20:57

Stool DNA testing detects cancers and some pre-cancers across the entire colon. Doctors should consider doing this test as an adjunct to colonoscopy; it can detect missed disease and cancers. Molecular tests are objective and are not subject to bowel preps, dieting, etc. Used in between colonoscopy makes sense, there are no risks.

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