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Colorectal Polyps
Polyps are an abnormal growth of mucous membrane tissue. There are many types of polyps, which can grow in several locations throughout the body, including the colon, stomach, small intestine, vocal folds, nose, ear, sinus, bladder, uterus, and cervical canal. However, having polyps in the colon does not mean that you are more likely to have polyps in other parts of the body. Colorectal polyps are common, especially in adults older than 50 years of age, but usually don’t cause any symptoms. When they first develop, colorectal polyps are typically non-cancerous (benign); however, there is a potential for some polyps to become cancerous (malignant) over time if a physician does not detect and remove them.
Polyps and Colorectal Cancer
Colorectal cancer affects 6-7% of Canadians at some point in their life. It is the second leading cause of death from cancer in men, and the third leading cause of death from cancer in women. Only a small number of polyps become malignant, but most cases of colorectal cancer begin with polyps. Typically, it takes at least 5-10 years for a polyp to become malignant, which is why screening is important.
Symptoms and Risk Factors
While polyps are usually asymptomatic, very large polyps can cause symptoms such as rectal bleeding, abdominal pain, and changes in bowel habits, such as diarrhea or constipation.
Risk factors include being older than 50 years of age, being male, or having certain genetic conditions, a family history of polyps or colorectal cancer, inflammatory bowel disease, diabetes, or obesity. Lifestyle factors such as smoking, alcohol use, inadequate exercise, and eating too much red meat, or not eating enough fibre, can also increase your risk.
Screening and Treatment for Colonic Polyps
Colonic polyps, some of which can lead to colorectal cancer, are common, and become more likely with age, so all adults between 50 and 74 years of age should be screened. The following are the recommended screening tests:
- Fecal Immunochemical Test (FIT): this involves obtaining a FIT kit from a medical lab, bringing it home, using it to collect a stool sample, and then returning it to the lab for testing. Lab technicians will analyze the stool sample for traces of blood. If the result is positive, your physician will likely perform a colonoscopy to determine the source of blood in the sample.
- Fecal Occult Blood: with this test, your physician will instruct you to gather a stool sample at home and bring it in to a medical laboratory, where a technician will test the sample for any evidence of blood. If it tests positive for blood, then it might be from polyps, but it could also be from other conditions, such as hemorrhoids, so further testing is usually required.
- Colonoscopy: a physician can use this procedure to look for polyps and/or to remove polyps. Generally, your physician will recommend this if you have a positive FIT test or blood in the stool but they might also recommend it based on symptoms, age, or medical history. To perform this test, a physician uses a long, flexible tube with a camera attached to the end to look at the inner lining of your rectum and large intestine (colon). During this process, they can identify and remove any polyps that they find. Larger polyps may require a repeat colonoscopy to ensure complete removal. Your physician will send tissue from removed polyps for testing to determine the type of polyp that it is.
Types of Polyps
Your physician will base follow-up recommendations on the number of polyps present and their size and characteristics. It is important to know the type of polyp, as some carry very little risk while others are more concerning. Once you have developed polyps, your chance of experiencing more increases.
Hyperplastic polyps occur when cells in a section of the mucous membrane of the intestine grow too quickly. There is a low risk of these becoming malignant unless the affected individual has more than 100 hyperplastic polyps.
Adenomatous polyps (adenomas) are defined by the growth of new cells, rather than an excessive reproduction of typical cells, as in hyperplastic polyps. They are the most common type of polyp, and can become cancerous, although it often takes many years for this to happen. There are several different types of adenomas.
Villous adenomas are more likely to become malignant but can be safely removed during a colonoscopy.
Inflammatory polyps are common in individuals with inflammatory bowel disease (primarily Crohn’s disease and ulcerative colitis) and aren’t really polyps. These are actually raised sections of inflamed tissue, and don’t typically carry a risk of developing into colorectal cancer.
Polyp Shapes
While there are several different types of polyps, they generally appear in one of two shapes:
Sessile polyps are flat polyps, in which the unusual cells are grouped as a mound on the bowel wall. These can sometimes be difficult to spot because they don’t stand out much, but the newer high definition colonoscopes make detection easier.
Pedunculated polyps are raised growths that are attached to the bowel wall by long, thin stalks. These have a shape that is similar to mushrooms and are much easier to detect than sessile polyps. It is typically simple for a physician to remove these during a colonoscopy.
Polyp Size
Colorectal polyps can range in size from very small (a few millimetres in diameter) to quite large (several centimetres in diameter). The larger the polyp, the greater the risk that it could become malignant in the future.
Conclusion
Colorectal polyps are a common occurrence, especially in the aging population. While polyps don’t usually cause symptoms initially, some polyps can progress to colorectal cancer if you don’t have them removed. However, regular screening with FIT makes it possible to detect (and then remove) polyps before they have a chance to become malignant.