Colon polyps

This page was reviewed under our medical and editorial policy by

Toufic Kachaamy, MD, Chief of Medicine, City of Hope Phoenix

This page was reviewed on January 17, 2022.

A colon polyp is a small growth of tissue inside the colon, or large intestine. Although most colon polyps are harmless, some may turn into colorectal cancer or already be cancerous.

Screening tests, including a colonoscopy, can help detect colon polyps.

This article will cover:

What causes colon polyps?

Although researchers don’t know the exact cause of colon polyps, certain factors may increase a patient’s risk of developing them. These risk factors include:

  • Being older than age 45
  • Having a family member who has had colon polyps or colon cancer
  • Having had a previous diagnosis of colon polyps

What percentage of colon polyps are cancerous?

The percentage of colon polyps that are cancerous or become cancerous depend on a variety of factors, including the type and size of the polyp and when it formed. It may take up to 10 years for some polyps to become cancerous.

Size and types of colon polyps

Colon polyps come in various shapes and sizes. They range from several millimeters to a few centimeters in size, and may also be raised or flat.

Types of colon polyp shapes

Colon polyps may grow into several distinct shapes, as listed below.

Sessile polyps: Colon polyps that may look like small bumps.

Pedunculated polyps: Raised colon polyps that may look like small cauliflower or mushrooms and grow on short stalks.

Serrated polyps: Colon polyps that have an appearance similar to a serrated utensil, with saw-toothed edges.

Colon polyps symptoms

Colon polyps often develop silently, which means they usually don’t cause symptoms. In some cases, the patient may notice signs such as:

  • Blood in stool
  • Constipation or diarrhea that persists longer than a week
  • Feeling tired due to anemia and lack of iron, which can happen if there is bleeding from the colon
  • Rectal bleeding, which could show up on toilet paper or in underwear

How colon polyps are diagnosed

Doctors may diagnose colon polyps by using a screening test for colorectal cancer. Expert groups recommend that everyone with an average risk for developing colorectal cancer undergo screening regularly, beginning between the ages of 45 and 50 and continuing through age 75. Between ages 75 and 85, the doctor can help patients decide whether it would be beneficial to continue screening. Patients who are older than 85 no longer need to receive colorectal cancer screening.

Patients who are at a high risk for developing colorectal cancer may need to begin screening before turning 45. The following factors raise a person’s risk for developing colorectal cancer:

  • Certain types of polyps or colorectal cancer run in the family
  • Hereditary colorectal cancer syndromes run in the family, including Lynch syndrome, and familial adenomatous polyposis
  • A personal history of certain polyps or colorectal cancer  
  • Radiation therapy to the abdominal area or pelvic area for the treatment of an earlier cancer
  • Crohn’s disease or ulcerative colitis (UC), which are inflammatory bowel diseases

Types of colorectal cancer screening tests:

Colonoscopy, which involves using a tool called a colonoscope to see the colon and rectum

Sigmoidoscopy, which involves using a tool called a sigmoidoscope to assess the rectum and sigmoid colon, or the portion of the colon that is shaped like an “S” and attaches to the rectum

Stool tests, which test for blood in the stool (which can happen if the patient has polyps or colorectal cancer) or cell changes

Virtual colonoscopy, which is a noninvasive method involving the use of X-ray tools to provide images of the colon and rectum

How are colon polyps treated?

The care team will treat colon polyps by removing them, either through colonoscopy or flexible sigmoidoscopy. Both colonoscopes and sigmoidoscopes have a light and a lens (inserted into the colon) to view the lining of the patient's colon and rectum, as well as a tool to remove colon polyps.

Patients undergoing colon polyp removal should alert the doctor if any of the following issues occur afterward:

  • Dizziness
  • Fever
  • Persistent bloody stools
  • Persistent rectal bleeding
  • Severe abdominal pain
  • Weakness

Colon polyps can grow back. Research indicates that as many as 60 percent of polyps may grow back within three years. Also, about 30 percent of patients who've had polyps removed develop new ones. This is why it is important to talk to the care team about follow-up screening within five years after the polyps are removed.

What happens if a colon polyp is cancerous?

After removing colon polyps, the care team submits the polyps to a lab so they can be analyzed. If cancerous cells are found, the next step is to evaluate whether all of the cancer was removed and the margins (the area around the polyps) are free of cancer cells. If all of the cancer was removed during the polyp removal, then the patient may not require any additional treatment.  


However, if any cancer cells remain following the polyp removal, the care team performs further testing to determine whether the cancer has spread to the lining of the colon, the colon wall or areas outside the colon into nearby or distant tissue. If the patient is diagnosed with colon cancer, the care team stages the cancer and advises the patient about the best treatment options moving forward.

How to lower the risk of colon polyps

Eating a healthy diet may reduce the risk for developing colon polyps. Specifically, research suggests that eating a diet rich in fruits, vegetables and fiber-containing foods such as bran cereal and beans may help prevent colon polyps.

Additionally, it’s important to limit certain foods in order to lower the risk of developing colon polyps. This includes reducing consumption of high-fat foods such as:

  • Fried foods
  • Red meats, including beef and pork
  • Processed meats, such as lunch meats, sausage, bacon and hot dogs

For patients who are overweight, losing weight can help lower the risk for developing colon polyps. Patients who are already at a healthy weight should try to maintain their weight and avoid weight gain.

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