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Colon Polyps Part I
As a practicing Gastroenterologist, one of the most common situations that arises relates to the question of colon polyps. Polyps of the colon are extremely important! Therefore my mission today is to try to debunk some of the misconceptions regarding colon polyps, and give a clear understanding of this common condition.
First off, what exactly is a polyp? A colorectal polyp is a fleshy growth lining the wall of the colon or rectum. There are a variety of types of polyps, but I will confine my discussion to the two major types. Adenomatous polyps are the most important type, because they are the principal precursor of colorectal cancer. The other type of polyps are hyperplastic polyps. The vast majority of those are small and insignificant, although as I will discuss later there is a small subset of hyperplastic polyps that do have the potential to become cancerous.
Since adenomatous polyps are the main precursor of colorectal cancer, I will focus most of our attention on them. Just to give you an idea about the magnitude of this problem, consider the fact that in the United States alone in 2010, there were 142,570 cases of colorectal cancer diagnosed(4th leading cause of cancer in the US) and 51,370 deaths from colorectal cancer(2nd leading cause of cancer death). There is a 6% lifetime chance of the average American developing colorectal cancer.The appalling part of these statistics in my opinion is that I believe those numbers are far higher than they need to be. Why? Because if precancerous polyps can be identified and removed, we can effectively reduce the risk of colorectal cancer, and in turn the risk of dying of the disease. We, as a society, are doing a much better job of getting this message out. Since colonoscopy was recognized as an effective screening method, and routine screening colonoscopy began to be covered by Medicare, the death rate from colon colorectal cancer has gradually edged down. However, sadly, only about 50% of Americans of the proper age(50 years and up) is getting routine colorectal cancer screening.
So why aren’t we shouting this from a mountaintop and having everyone checked for polyps? Good question. It is a huge public health problem, and like many things, there are a variety of opinions on how to best screen people for colorectal cancer and colorectal polyps. I could spend hours reviewing the different strategies that have been proposed. Let me just summarize by saying that in my opinion, there is no doubt that colonoscopy is the best screening test to look for colon polyps and cancer. But if you have the time and interest, feel free to look at the conclusions of the U.S. Preventative Services Task Force-which goes into great detail about the various options. http://www.uspreventiveservicestaskforce.org/uspstf/uspscolo.htm
So what are the odds that your routine screening colonoscopy will show adenomatous polyps? It is estimated that approximately 25% of Americans at the age of 50 will have polyps on a routine screening exam. The chances of having polyps increases with age. These polyps come in a variety of shapes and sizes. When it comes to polyps, size does matter. In generally, larger polyps are more likely to harbor cancer cells than smaller polyps. As far as shape goes, they may grow on a stem, almost like a cherry(pedunculated polyps) or they may grow fairly flat, more like moss on a tree(sessile polyps). These differences in polyp shape can have important implications as far as the techniques used to remove them.
Not only do adenomatous polyps vary in the their size and shape, they also vary in the way they look when examined under a microscope. By that, I mean that the polyps can be categorized as tubular adenomas, tubulovillous adenomas, and villous adenomas. Of these, the more villous component, the higher the risk of cancer transformation. Fortunately, about 80% of polyps are tubular adenomas.
Next time we will discuss the management of polyps including methods for removal, safety of removal, and subsequent followup.