A new Canadian study suggests that colonoscopy may detect polyps and early cancers only 60 to 70 percent of the time, even if colonoscopies have long been considered the gold standard for colorectal cancer screening. It is well known that a colonoscopy is 90 percent effective in detecting the second leading cancer killer of men and women in the US. According to the study, whether a colonoscopy saves a life may depend on exactly where in the colon the cancer starts.

It looks like a colonoscopy prevents two-thirds of the deaths from left sided colon cancer. Unfortunately, the procedure does not prevent any of the deaths from right-sided colon cancer. Why is that? Well, a possible explanation is that polyps on the left side of the colon are more likely to be raised and easy to detect, while those on the right side are flatter and, therefore, easy to miss. However, these results are still debated by doctors, as only about 30 percent of the colonoscopies in this study were performed by gastroenterologists.

Another study about colonoscopies states that doctors who rush through the procedure can miss polyps. In addition, it can be the patient's fault too, if he does not follow the instructions for colon cleansing to the letter. Even if colonoscopies seem to be less accurate than previously thought, they're still the best way to prevent colon cancer, but it's important to know they do not detect some polyps. Colon cancer screenings are recommended for most people starting at age 50, and patients should choose experienced doctors and make sure they follow their doctors' directions to the letter when preparing for the procedure.