Overview

A colon polyp is a small clump of cells that forms on the lining of the colon. Most colon polyps are harmless. But over time, some colon polyps can develop into colon cancer, which may be fatal when found in its later stages.

Anyone can develop colon polyps. You're at higher risk if you're 50 or older, are overweight or a smoker, or have a personal or family history of colon polyps or colon cancer.

Colon polyps often don't cause symptoms. It's important to have regular screening tests, such as a colonoscopy, because colon polyps found in the early stages can usually be removed safely and completely. The best prevention for colon cancer is regular screening for and removal of polyps.

Symptoms

Because most people with colon polyps do not experience any symptoms, you might not know you have a polyp until your doctor finds it during an examination of your colon.

However, some people with colon polyps may experience:

  • Rectal bleeding. This can be a sign of colon polyps or cancer or other conditions, such as hemorrhoids or minor tears of the anus.
  • Change in stool color. Blood can show up as red streaks in your stool or make stool appear black. A change in color may also be caused by certain foods, medications or dietary supplements.
  • Change in bowel habits. Constipation or diarrhea that lasts longer than a week may indicate the presence of a larger colon polyp or cancer. However, a number of other conditions also can cause changes in bowel habits.
  • Pain. A large colon polyp can partially obstruct your bowel, leading to crampy abdominal pain.
  • Iron deficiency anemia. Bleeding from polyps can occur slowly over time, without visible blood in your stool. Chronic bleeding robs your body of the iron needed to produce the substance that allows red blood cells to carry oxygen to your body (hemoglobin). The result is iron deficiency anemia, which can make you feel tired and short of breath.

When to see a doctor

See your doctor if you experience:

  • Abdominal pain
  • Blood in your stool
  • A change in your bowel habits that lasts longer than a week

You should be screened regularly for polyps if:

  • You're age 50 or older.
  • You have risk factors, such as a family history of colon cancer. Some high-risk individuals should begin regular screening much earlier than age 50.

Causes

Healthy cells grow and divide in an orderly way. 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.

Risk factors

Factors that may contribute to the formation of colon polyps or cancer include:

  • 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.

Complications

Some colon polyps may become cancerous. The earlier polyps are removed, the less likely it is that they will become cancerous.

Prevention

You can greatly reduce your risk of colon polyps and colorectal cancer by having regular screenings. Certain lifestyle changes also can help:

  • Adopt healthy habits. Include plenty of fruits, vegetables and whole grains in your diet and reduce your fat intake. Limit alcohol consumption and quit all tobacco use. Stay physically active and maintain a healthy body weight.
  • Talk to your doctor about calcium and vitamin D. Studies have shown that increasing your consumption of calcium may help prevent recurrence of colon adenomas. But it isn't clear whether calcium has any protective benefits against colon cancer. Other studies have shown that vitamin D may have a protective effect against colorectal cancer.
  • Consider your options if you're at high risk. If you have a family history of colon polyps, consider having genetic counseling. If you've been diagnosed with a hereditary disorder that causes colon polyps, you'll need regular colonoscopies starting in young adulthood.