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 is often 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 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 polyps.
There are several types of colon polyps, including:
- Adenomatous. About two-thirds of all polyps are adenomatous. Only a small percentage of them actually become cancerous. But nearly all malignant polyps are adenomatous.
- Serrated. Depending on their size and location in the colon, serrated polyps may become cancerous. Small serrated polyps in the lower colon, also known as hyperplastic polyps, are rarely malignant. Larger serrated polyps — which are typically flat (sessile), difficult to detect and located in the upper colon — are precancerous.
- Inflammatory. These polyps may follow a bout of 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.
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. In general, the larger a polyp, the greater the likelihood of cancer.
Colon polyps often cause no symptoms. You might not know you have a polyp until your doctor finds it during an examination of your bowel.
But some people with colon polyps experience:
- Rectal bleeding. This can be a sign of colon polyps or cancer or other conditions, such as hemorrhoids or minor tears in your 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 foods, medications and supplements.
- Change in bowel habits. Constipation or diarrhea that lasts longer than a week may indicate the presence of a large colon polyp. But a number of other conditions can also cause changes in bowel habits.
- Pain, nausea or vomiting. A large colon polyp can partially obstruct your bowel, leading to crampy abdominal pain, nausea and vomiting.
- 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.