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. In this article, we will focus on colorectal polyps. When you have polyps in the colon, it 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 and it is the second leading cause of death from cancer in men, and the third leading cause of death from cancer in women.1 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. It is important to have regular colonoscopies, as it is much easier to remove polyps than to treat advanced colorectal cancer.
While most polyps are asymptomatic, very large polyps can cause rectal bleeding or changes to stool consistency and frequency, such as constipation and diarrhea.
Diagnosis and Treatment
Physicians primarily detect polyps during routine tests, such as to screen for colorectal cancer or look for other signs of illness.
The fecal immunochemical test (FIT) involves obtaining a FIT kit from a medical lab, bringing it home, using it to collect a stool sample, then returning it to the lab for testing. Lab technicians will then 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 the blood in the sample.
Colonoscopy involves your physician using 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. However, you may need a separate surgery to remove especially large polyps. Your physician might send tissue from removed polyps for testing to see if there is any sign of malignancy.
Once you have developed polyps, your chance of experiencing future polyps increases. In this case, your physician might recommend more frequent screening, such as having a colonoscopy every three to five years, rather than every ten years. They will base the frequency for screening on the type, size, and number of polyps they find in your colon.
Types of 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 the most likely to become malignant. These typically have a cauliflower-like appearance and often require surgery to remove.
Hyperplastic polyps occur when the number of cells in a section of the mucous membrane of the intestine grows too quickly. There is a low risk of these becoming malignant, unless the affected individual has more than 100 hyperplastic polyps.
Inflammatory polyps are common in individuals with inflammatory bowel disease (including 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.
While there are several different types of polyps, these can 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, and are more likely to require surgery to remove.
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 than sessile polyps to detect. It is typically simple for a physician to remove these during a colonoscopy.
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.
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, with regular screening, it is possible to detect and remove polyps before they have a chance to become malignant.