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.
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.
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.
Factors that may contribute to the formation of colon polyps or cancer include:
- Age. Most people with colon polyps are 50 or older.
- Inflammatory intestinal conditions, such as ulcerative colitis and Crohn's disease.
- 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.
- Tobacco and alcohol use.
- Obesity and lack of exercise.
- Race. African-Americans are at higher risk of developing colon cancer.
- Type 2 diabetes that isn't well-controlled.
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 much higher risk of developing colorectal 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 ovary.
- 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 percent, 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.
- MYH-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 malignant, so people with this condition have an increased risk of colon cancer.
- Serrated polyposis syndrome, a condition that leads to multiple serrated adenomatous polyps in the upper part of the colon. These polyps may become malignant.
Some colon polyps may become cancerous. The earlier polyps are removed, the less likely it is that they will become malignant.
You may be referred to a doctor who specializes in digestive diseases (gastroenterologist).
What you can do
- Be aware of any pre-appointment restrictions, such as not eating solid food on the day before your appointment.
- Write down your symptoms, including any that may seem unrelated to the reason why you scheduled the appointment.
- Make a list of all your medications, vitamins and supplements.
- Write down your key medical information, including other conditions.
- Write down key personal information, including any recent changes or stressors in your life.
- Ask a relative or friend to accompany you to help you remember what the doctor says.
- Write down questions to ask your doctor.
Questions to ask your doctor
- What's the most likely cause of my symptoms?
- What kinds of tests do I need? Do these tests require any special preparation?
- What treatments are available?
- What are the chances these polyps are malignant?
- Is it possible that I have a genetic condition leading to colon polyps?
- What kind of follow-up testing do I need?
- Should I remove or add any foods to my diet?
- I have other health conditions. How can I best manage these conditions together?
In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask other questions during your appointment.
What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to answer them may make time to go over points you want to spend more time on. You may be asked:
- When did you first begin experiencing symptoms, and how severe are they?
- Have your symptoms been continuous or occasional?
- Have you or has anyone in your family had colon cancer or colon polyps?
- Has anyone in your family had other cancers of the digestive tract, the uterus, ovaries or the bladder?
- How much do you smoke and drink?
Screening tests play a key role in detecting polyps before they become cancerous. These tests can also help find colorectal cancer in its early stages, when you have a good chance of recovery.
Screening methods include:
- Colonoscopy, the most sensitive test for colorectal polyps and cancer. If polyps are found, your doctor may remove them immediately or take tissue samples (biopsies) for analysis.
- Virtual colonoscopy (CT colonography), a minimally invasive test that uses a CT scan to view your colon. Virtual colonoscopy requires the same bowel preparation as colonoscopy. If a polyp is found, you'll need colonoscopy to have it removed.
- Flexible sigmoidoscopy, in which a slender, lighted tube is inserted in your rectum to examine it and the last third of your colon (sigmoid). If a polyp is found, you'll need colonoscopy to have it removed.
Your doctor is likely to remove all polyps discovered during a bowel examination. The options for removal include:
- Removal during screening. Most polyps can be removed with biopsy forceps or a wire loop that snares the polyp. This may be aided by injecting a liquid under a polyp to lift it off the wall for removal. If a polyp is larger than 0.75 inches (about 2 centimeters), a liquid may be injected under it to lift and isolate the polyps from surrounding tissue so that it can be removed (endoscopic mucosal resection).
- Minimally invasive surgery. Polyps that are too large or that can't be reached safely during screening are usually removed using minimally invasive surgery.
- Colon and rectum removal. If you have a rare inherited syndrome, such as FAP, you may need surgery to remove your colon and rectum (total proctocolectomy).
Some types of colon polyp are far likelier to become malignant than are others. But a doctor who specializes in analyzing tissue samples (pathologist) usually must examine polyp tissue under a microscope to determine whether it's potentially cancerous.
If you have had an adenomatous polyp or a serrated polyp, you are at increased risk of colon cancer. The level of risk depends on the size, number and characteristics of the adenomatous polyps that were removed.
You'll need follow-up screenings for polyps. Your doctor is likely to recommend colonoscopy:
- In five years if you had only one or two small adenomas
- In three years if you had more than two adenomas, adenomas measuring 0.4 inches (about 1 centimeter) or larger, or adenomas with a broad base (villous)
- Within three years if you had more than 10 adenomas
- Within six months if you had a very large adenoma or an adenoma that had to be removed in pieces
It's important to fully prepare your colon before colonoscopy. If stool remains in the colon and obstructs your doctor's view of the colon wall, you will likely need a follow-up colonoscopy sooner than the guidelines specify.
You can greatly reduce your risk of colon polyps and colorectal cancer by having regular screenings. Certain lifestyle changes also can help:
- Eat fruits, vegetables and whole grains.
- Reduce your fat intake.
- Limit alcohol consumption.
- Don't use tobacco.
- Stay physically active and maintain a healthy body weight.
- Talk to your doctor about calcium. 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.
- Talk to your doctor about aspirin. Regular aspirin use may reduce your risk of polyps. But aspirin use can increase your risk of gastrointestinal bleeding, so check with your doctor beforehand.
- 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 colonoscopy starting in young adulthood.