COLON POLYPS OVERVIEW
Polyps are abnormal growths in the colon. They can be flat or protruding or mushroom shaped. There are several types of polyps, mainly adenomas and hyperplastic polyps. The concern is that colon cancer usually begins as a polyp and certain types have a greater potential to do so. Adenomas have the potential to become cancerous while hyperplastic polyps are only rarely considered precancerous.
Polyps are common (they occur in 30% or more of adults in their lifetime. It takes many years for a polyp to become cancer and not all polyps will ever become cancer. The good news is that polyps can be completely and safely removed, preventing cancer.
The best course of action when a polyp is found depends upon the number, type, size, and location of the polyp. People who have an adenoma removed will require a follow up examination; new polyps may develop over time that need to be removed.
WHAT CAUSES COLON POLYPS?
Polyps are very common in men and women of all races who live in industrialized countries, suggesting that dietary and environmental factors play a role in their development.
Lifestyle risk factors include: a high fat high red meat diet, a low fiber diet, Cigarette smoking, and obesity.
Polyps and colon cancer tend to run in families, suggesting that genetic factors are also important in their development. Any history of colon polyps or colon cancer in the family should be considered in discussing when an individual should undergo testing, especially if cancer developed at an early age in close relatives, or in multiple family members. As a general rule, screening for colon polyps and cancer begins at an earlier age in people with a family history of cancer or polyps. There are genetic diseases that can cause high rates of colorectal cancer and brought to attention by the important family history.
Colorectal cancer is uncommon before age 40. Ninety percent of cases occur after age 50, with men somewhat more likely to develop polyps than women; therefore, colon cancer screening is usually recommended starting at age 50 for both sexes.
TYPES OF COLON POLYPS
The most common types of polyps are hyperplastic and adenomatous polyps. Hyperplastic polyps are usually small, located in the end-portion of the colon (the rectum and sigmoid colon), and have no potential to become malignant. It is not always possible to distinguish a hyperplastic polyp from an adenomatous polyp based upon appearance during colonoscopy, which means that hyperplastic polyps are often removed or biopsied to allow microscopic examination. A rare form of hyperplastic polyps in other areas of the colon is considered precancerous in some patients.
Adenomatous polyps — Two-thirds of colon polyps are adenomas. Most of these polyps do not develop into cancer, although they have the potential to become cancerous. Adenomas are classified by their size, general appearance, and their specific features as seen under the microscope. As a general rule, the larger the adenoma, the more likely it is to eventually become a cancer.
Malignant polyps — Polyps that contain pre-cancerous or cancerous cells are known as malignant polyps. The optimal treatment for malignant polyps depends upon the extent of the cancer (when examined with a microscope) and other factors. Complete removed with colonoscopy may be adequate if the cancerous part is superficial in the polyp.
COLON POLYP DIAGNOSIS
Polyps usually do not cause symptoms and are usually detected during a colon cancer screening examination such colonoscopy.
Colonoscopy is the best way to evaluate the colon because it allows us to see the entire lining of the colon and remove any polyps that are found. During colonoscopy, a very thin flexible tube with a light source and small camera is inseteed into the anus. The tube is advanced through the entire length of the large intestine (colon). Patients are sedated, alleviating discomfort and any potential embarrassment.
A polyp appears as a lump that protrudes into the inside of the colon. Some polyps are flat (“sessile”) and others extend out on a stalk like a mushroom (“pedunculated”).
Colonoscopy is also the best test for the follow-up examination of polyps. Virtual colonoscopy using CT technology is another test used to detect polyps but involves radiation and can not biopsy or removes any abnormal findings.
COLON POLYP REMOVAL
Colorectal cancer is the second leading cause of cancer deaths in the United States, accounting for 14 percent of cancer deaths. Colorectal cancer is usually preventable if precancerous polyps are detected and removed before they become malignant (cancerous). Polyps develop from a genetic mutation in the colon cells. Over time, small polyps can develop additional mutations and become cancerous. Polyps are usually removed when they are found on colonoscopy.
The medical term for removing polyps is polypectomy. Most polypectomies can be performed through a colonoscope. Small polyps can be removed with an instrument (forceps) that is inserted through the colonoscope and snips off small pieces of tissue. Larger polyps are usually removed by placing a noose, or wire snare, around the polyp base and simultaneously cutting and burning through it with electric cautery. Rarely, a polyp will be too large to remove during colonoscopy, which means that a surgical procedure will be needed at a later time. Polyp removal is not painful because the lining of the colon does not sense pain.
Pedunculated polyp (polyp with a stalk)
Placing wire cutting snare around polyp stalk
Polypectomy has a few potential risks and complications. The most common complications are bleeding and perforation (creating a hole in the colon). Fortunately, this occurs infrequently (less than one in 1000 patients having colonoscopy). Bleeding can usually be controlled during colonoscopy by cauterizing (applying heat) to the bleeding site at that time or later if the bleeding occurs after the colonscopy is completed. Surgery is usually required for perforation.
COLON POLYP PREVENTION
People with adenomatous polyps have an increased risk of developing more polyps and potentially cancer. There is a 25 to 30 percent chance that adenomas will be present on a repeat colonoscopy when done three years after the initial polypectomy. After polyps are removed, repeat colonoscopy is recommended. The timing of the follow-up colonoscopy depends upon several factors such as microscopic characteristics of the polyp, number and size of the polyps, and the quality of visualization during colonoscopy. If the bowel prep was not adequate, feces may remain in the colon, making it more difficult to see small to moderate size polyps.
Studies have shown that people who undergo screening (and re-screening) for colon cancer are much less likely to die from colon cancer. Thus, following screening guidelines is important in the prevention of colon cancer.
Preventing colon cancer can not be accomplished with lifestyle modification or medications. It may be possible to reduce somewhat the risk of colon cancer by eating a diet that is low in fat and high in fruits, vegetables, and fiber, maintaining a normal body weight, avoiding smoking and excessive alcohol use, and taking aspirin regularly (although the risks of daily aspirin may outweigh this potential benefit).
IMPLICATIONS FOR THE FAMILY
First-degree relatives (a parent, brother, sister, or child) of a person who has been diagnosed with an adenomatous polyp (or colorectal cancer) before the age of 60 years have an increased risk of developing adenomatous polyps and colorectal cancer compared to the general population. Thus, family should be made aware if the person is diagnosed with an adenoma or colon cancer.
While screening for polyps and cancer is recommended for everyone (typically beginning at age 50), those at increased risk should begin screening earlier, typically at age 40. Colonoscopy is the recommended test for colon cancer screening.