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Colorectal Cancer Screening

Cross section of sigmoid colon, rectum, and anus showing cancer and polyp.

Colorectal cancer is cancer in the colon or rectum. It's a leading cause of cancer deaths in the U.S. But when this cancer is found and removed early, the chances of a full recovery are very good. Because colorectal cancer rarely causes symptoms in its early stages, screening for the disease is important. It’s even more crucial if you have risk factors for the disease. Learn more about colorectal cancer and its risk factors. Then talk to your healthcare provider about being screened.

Risk factors for colorectal cancer

Your risk of having colorectal cancer increases if you:

  • Are 50 years of age or older, but it can occur in people younger than 50

  • Have a family history or personal history of colorectal cancer or polyps

  • Have a personal history of type 2 diabetes, Crohn’s disease, or ulcerative colitis

  • Have an inherited genetic syndrome like Lynch syndrome (HNPCC) or familial adenomatous polyposis (FAP)

  • Are very overweight

  • Are not physically active

  • Smoke

  • Drink a lot of alcohol

  • Eat a lot of red or processed meat

The colon and rectum

Waste from food you eat enters the colon from the small intestine. As it travels through the colon, the waste (stool) loses water and becomes more solid. Intestinal muscles push it toward the sigmoid colon. This is the last section of the colon. Stool then moves into the rectum, where it’s stored until it’s ready to leave the body during a bowel movement.

How colorectal cancer starts

Polyps are growths that form on the inner lining of the colon or rectum. Most are benign, which means they aren’t cancer. But over time, some polyps can become cancer (malignant). This happens when cells in these polyps start growing abnormally. In time, malignant cells invade more of the colon and rectum. The cancer may also spread to nearby organs or lymph nodes or to other parts of the body. Finding and removing polyps can help prevent cancer from forming.

Your screening

Screening means looking for a health problem before you have symptoms. During screening for colorectal cancer, your healthcare provider will ask about your health history, examine you, and do 1 or more tests. To start, you may have:

  • Health history questions to answer. Your healthcare provider will ask about your health history. Mention if a family member has had colon cancer or polyps. Also mention any health problems you have had in the past.

  • Digital rectal exam (DRE). During a DRE, the healthcare provider inserts a lubricated gloved finger into the rectum. The test is painless and takes less than a minute. This test alone is not enough to screen for colorectal cancer. You will also need one of the below tests.

Screening test choices

Some expert groups generally advise that people at average risk for colorectal cancer start screening at age 50. But the American Cancer Society (ACS) recommends starting screening at age 45.

For those who are 45 years old and of average risk for colorectal cancer, the ACS recommends:

  • A fecal occult blood test (FOBT) or fecal immunochemical test (FIT) every year, or

  • A flexible sigmoidoscopy every 5 years, or

  • A colonoscopy every 10 years, or

  • A CT colonography (virtual colonoscopy) every 5 years, or

  • A stool DNA test every 3 years

If you have a family history of colon cancer or are at high risk for other reasons, you may need to have screening even earlier. Talk with your provider to find out about your risk factors. Screening recommendations vary among expert groups

Fecal occult blood test (FOBT) or fecal immunochemical test (FIT)

These tests check for blood in stool that you can’t see (hidden or occult blood). Hidden blood may be a sign of colon polyps or cancer. A small sample of stool is tested for blood in a lab. Most often, you collect this sample at home using a kit your healthcare provider gives you. Follow the instructions carefully for using this kit. You might need to not eat certain foods and not take certain medicines before the test, as directed.

Stool DNA test

This test looks for DNA changes in cells in the stool. These DNA changes might be signs of cancer. It also looks for hidden blood in stool. For this test, you collect an entire bowel movement. This is done using a special container put in the toilet. The sample is then sent to a lab for testing.

Visual exams

Colonoscopy

This test can be used to find and remove polyps anywhere in the colon or rectum.

The day before the test, you will do a bowel prep. This is a liquid diet plus a strong laxative solution or an enema. The bowel prep will cleanse your colon. You will be given instructions for this.

Just before the test, you are given a medicine to make you sleepy. Then the healthcare provider getnly puts a long, flexible, lighted tube (colonoscope) into your rectum and guides it through the entire colon. The provider looks at images of the colon on a video screen. Any polyps that are found are removed and sent to a lab for testing. If a polyp can’t be removed, a sample of tissue is taken. The polyp might be removed later during surgery.

You will need to bring someone with you to drive you home after this test.

Colonoscopy is the only screening test that lets your healthcare provider see the entire colon and rectum. This test also lets your healthcare provider remove any pieces of tissue that need to be looked at by a lab. If something suspicious is found using any other tests, you will likely need a colonoscopy.

Sigmoidoscopy

This test is similar to colonoscopy. But it focuses only on the sigmoid colon and rectum. As with colonoscopy, bowel prep must be done the day before this test. It might not need to be as complete as the bowel prep for a colonoscopy.

You are awake during the procedure, but you may be given medicine to help you relax. During the test, the healthcare provider guides a thin, flexible, lighted tube called a sigmoidoscope through your rectum and lower colon. The images are displayed on a video screen. Polyps are removed, if possible, and sent to a lab for testing.

Virtual colonoscopy

This exam is also called a CT colonography. It uses a series of X-ray photographs to create a 3-D view of the colon and rectum.

The day before the test, you will need to do a bowel prep to clean out your colon. Your healthcare provider will give you instructions on how to do this. During the procedure, you will lie on a table that is part of a special X-ray machine called a CT scanner. A small tube will be placed into your rectum to fill the colon and rectum with air. This can be uncomfortable for some people. Then, the table will move into the machine and pictures will be taken of your colon and rectum. A computer will combine these photos to create a 3-D picture. Because the test uses X-rays, it exposes you to a small amount of radiation. This test can be done without sedation. If polyps or any suspicious areas are seen, you will need a follow-up colonoscopy to further investigate.

Talking with your healthcare provider

Talk with your healthcare provider about which tests might be right for you. No matter which test you choose, the most important thing is that you get screened. Keep in mind that if cancer is found at an early stage during screening, treatment is more likely to be work well. Many cancers can even be prevented with these tests

Note. If you choose a test other than a colonoscopy and have an abnormal test result, you will need to follow-up with colonoscopy.

Some people should be screened using a different schedule because of their personal or family history of colorectal cancer. They may also need a different schedule because of polyps or certain inherited conditions. These include familial adenomatous polyposis (FAP), Lynch syndrome (hereditary non-polyposis colon cancer, HNPCC), or inflammatory bowel disease such as Crohn's or ulcerative colitis. Talk with your doctor about your health history.

When to call your healthcare provider after a test

Call your healthcare provider if you have any of the following after any screening test:

  • Bleeding

  • Fever of 100.4°F (38°C) or higher, or as directed by your healthcare provider

  • Abdominal pain

  • Vomiting

Online Medical Reviewer: Alteri, Rick, MD
Online Medical Reviewer: Gersten, Todd, MD
Date Last Reviewed: 1/27/2019
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