Bowel polyps are growths that occur on the inner lining of the colon or rectum. Bowel polyps are caused by an abnormal production of cells. Mutations in certain genes can cause cells to continue dividing even when new cells aren’t needed. In the colon and rectum, this unregulated growth can cause polyps to form. Polyps can develop anywhere in your large intestine.
There are two main categories of polyps, nonneoplastic and neoplastic. Nonneoplastic polyps include hyperplastic polyps, inflammatory polyps and hamartomatous polyps. Nonneoplastic polyps typically do not become cancerous.
Neoplastic polyps include adenomas and serrated types. These polyps have the potential to become cancer if given enough time to grow. Most of these colon polyps are called adenomas. Serrated polyps may also become cancerous, depending on their size and location in the colon. In general, the larger a polyp, the greater the risk of cancer, especially with neoplastic polyps.
The exact cause of bowel polyps is not fully understood, but several factors may increase the risk of developing them, including:
- Age. Most people with colon polyps are 50 or older.
- Having inflammatory intestinal conditions, such as ulcerative colitis or Crohn’s disease of the colon. Although the polyps themselves are not a significant threat, having ulcerative colitis or Crohn’s disease of the colon increases your overall risk of colon cancer.
- Family history. You’re more likely to develop colon polyps or cancer if you have a parent, sibling or child with them. If many family members have them, your risk is even greater. In some people, this connection isn’t hereditary.
- Smoking and excess alcohol use. An analysis of eight studies showed an increased risk of developing colon polyps for people who consumed three or more alcoholic drinks per day. Alcohol intake combined with smoking also appears to increase the risk.
- Obesity, lack of exercise and fat intake. Studies show that all of these factors can increase your risk of developing polyps. On the other hand, including more fiber in your diet and exercising regularly can reduce your risk.
- Race. Black Americans have a higher risk of developing colon cancer.
Hereditary polyp disorders
Rarely, people inherit genetic mutations that cause colon polyps to form. If you have one of these genetic mutations, you are at a much higher risk of developing colon cancer. Screening and early detection can help prevent the development or spread of these cancers.
Hereditary disorders that cause colon polyps include:
- Lynch syndrome, also called hereditary nonpolyposis colorectal cancer. People with Lynch syndrome tend to develop relatively few colon polyps, but those polyps can quickly become malignant. Lynch syndrome is the most common form of inherited colon cancer and is also associated with tumors in the breast, stomach, small intestine, urinary tract and ovaries.
- Familial adenomatous polyposis (FAP), a rare disorder that causes hundreds or even thousands of polyps to develop in the lining of your colon beginning during your teenage years. If the polyps aren’t treated, your risk of developing colon cancer is nearly 100%, usually before age 40. Genetic testing can help determine your risk of FAP.
- Gardner’s syndrome, a variant of FAP that causes polyps to develop throughout your colon and small intestine. You may also develop noncancerous tumors in other parts of your body, including your skin, bones and abdomen.
- MUTYH-associated polyposis (MAP), a condition similar to FAP that is caused by mutations in the MYH gene. People with MAP often develop multiple adenomatous polyps and colon cancer at a young age. Genetic testing can help determine your risk of MAP.
- Peutz-Jeghers syndrome, a condition that usually begins with freckles developing all over the body, including the lips, gums and feet. Then noncancerous polyps develop throughout the intestines. These polyps may become cancerous, so people with this condition do have an increased risk of colon cancer.
- Serrated polyposis syndrome, a condition that leads to multiple serrated adenomatous polyps in the upper part (right side) of the colon. These polyps have the potential to become cancerous and require surveillance and removal.
NOTE:
Some colon polyps may become cancerous. The earlier polyps are removed, the less likely it is that they will become cancerous.