Colonoscopy and Other Screening Tests for Colorectal Cancer
Overview
Colorectal cancer screening means getting routine tests to find colon or rectal cancers even before you have any signs or symptoms. The goal of regular screening is to prevent or find cancer early, when it’s easier to treat.
There are a few types of colorectal cancer screening tests. The most common screening test is a colonoscopy (KOH-luh-NOS-koh-pee).
A colonoscopy is the only test that can both find and remove polyps. These are small growths on the inner lining of the colon or rectum. They’re not cancer, but can become cancer. Your doctor can remove polyps during a colonoscopy. It’s the only test that can both find and prevent colorectal cancers.
Your healthcare provider may recommend other screening tests, based on your personal choices.
MSK's Ralph Lauren Center offers free or lower cost cancer care, including colorectal cancer screening referrals. Some people do not get screened because they’re worried about the cost, say MSK researchers. New York residents who are uninsured or underinsured may be able to get screened with no out-of-pocket costs.
Screening for Colorectal Cancer
What is a colonoscopy?
A colonoscopy is a test that lets your doctor see inside your colon and rectum. Your doctor will use a colonoscope (koh-LAH-noh-SKOPE). This is a flexible tube with a camera on the end. The images will appear on a video monitor.
Watch our video to see what happens during a colonoscopy.
Your doctor can see if you have any polyps. Polyps are small growths on the inner lining of the colon or rectum. Polyps are not cancer but can become cancer over time.
During your procedure, your doctor can:
- Remove polyps, to prevent cancer.
- Do a biopsy to remove a small sample of tissue for testing.
- Explore inside your colon or rectum and take photos.
Your colon and rectum must be empty for your procedure. Your doctor will not be able to see polyps or other problems if there’s stool (poop) inside your colon. You may need to have the procedure again if this happens.
You'll need to get ready days before the test to be sure your colon is empty. Your doctor will give you instructions on how to get ready for the test.
For a colonoscopy, you’ll need sedation (medicine to make you drowsy or sleep). Someone must be with you after the procedure to take you home. You should not go to work the same day.
Are there other ways to screen for colorectal cancer?
A colonoscopy is the most common way to screen for colorectal cancer. There are other tests for colon and rectal cancer. Many people have questions about how to test for colorectal cancer, including which test is right for them.
Here are the types of colorectal cancer screening tests.
Endoscopic (en-doh-SKAH-pik) tests: These tests use a flexible tube with a camera on the end to look inside the colon and rectum. Examples are a colonoscopy, anoscopy, proctoscopy (rigid sigmoidoscopy), and flexible sigmoidoscopy (sig-MOY-DOS-koh-pee).
Radiology tests: These tests use imaging technology called computed tomography (CT) scan. This test takes a fast series of X-ray pictures, which are put together to create 3D images of the rectum and colon. This test is also called a virtual colonoscopy or CT colonography. CT scans can show polyps and cancer, but your doctor cannot remove them during the scan. If they see a polyp, you may need to have a colonoscopy to remove it.
Stool tests: They analyze a sample of your stool (poop) for signs of cancer and polyps inside the colon and rectum. Cologuard is the brand name of one type of stool test, but there are others.
- Flexible sigmoidoscopy
-
A flexible sigmoidoscopy is like a colonoscopy, but uses a shorter tube. A sigmoidoscope (sig-MOY-doh-skope) is a thin, tube-like instrument used to look inside the lower colon. Your doctor can remove polyps or take a tissue sample during this procedure.
You get ready for a sigmoidoscopy in the same way as a colonoscopy. Most often, you’ll get sedation (medicine to make you drowsy or sleep). The procedure takes about 15 to 30 minutes.
If you’re sedated, someone must be with you after the procedure to take you home. You should not go to work the same day.
- Anoscopy
-
During an anoscopy (ay-NOS-koh-pee), your doctor will use a small tool with a light at the end to see inside the rectum. They’ll look for any lumps or tissue that’s not normal. You will not need sedation (medicine to make you drowsy or sleep).
- Proctoscopy (rigid sigmoidoscopy)
-
During a proctoscopy (prok-TOS-koh-pee), your doctor will use a proctoscope to look inside the rectum. This is a small tool with a light at the end. It may also have a tool to remove a tissue sample. You will not need sedation (medicine to make you drowsy or sleep).
- Virtual colonoscopy
-
A virtual colonoscopy (VC) is also known as a CT colonography. It creates images that can find polyps and cancer. You will not need sedation (medicine to make you drowsy or sleep). You may have to drink contrast dye before your scan.
A virtual colonoscopy needs you to have an empty colon and rectum, just like a colonoscopy. If a VC shows a polyp, you may need a colonoscopy to remove it. VC can sometimes miss small or flat polyps.
The test is done in 15 to 20 minutes. You can go back to work the same day.
- Fecal occult blood test
-
A fecal occult (FEE-kul uh-KULT) blood test (FOBT) finds blood in stool (poop). Occult blood is when there’s blood you cannot see by looking at your stool.
Bleeding in your colon or rectum can be a sign there are polyps or colorectal cancer. This test is done for 3 days in a row. You put small samples of your poop on a special card. Then, you send the cards to a lab for testing. During the 3 days, you must follow a special diet so the test results are accurate.
- Fecal immunochemical test
-
A fecal immunochemical (FEE-kul IH-myoo-noh-KEH-mih-kul) test, or FIT, checks for blood in your feces (poop). You do not have to follow a special diet. FIT is also called an immunochemical fecal occult blood test.
- Stool DNA test
-
A multitarget stool DNA (MTsDNA) test looks for gene changes (mutations or variants). It analyzes DNA for mutations and other genetic changes caused by polyps or colorectal cancer. It also looks for blood in your stool. You do not need to follow a special diet.
Common questions
Some screenings are covered by health insurance. There also are programs that provide low or no-cost screenings.
A colonoscopy is covered by most insurance plans. Contact your health insurer to get more information. For some tests, you’ll need to buy the test or low-cost items to get ready for the test.
MSK offers referrals to low or no-cost colorectal cancer screenings at our Ralph Lauren Center in New York City.
For the multitarget stool DNA (MTsDNA) test, Medicare and some insurers cover 1 test every 3 years.
For some tests, you must first prepare your bowel so there is no stool (poop).
You’ll need to get ready for all of these tests. Here’s information about how to get ready before a:
- Colonoscopy using MiraLAX
- Colonoscopy using Sutab
- Colonoscopy using SUPREP Bowel Prep Kit
- Virtual colonoscopy
- Flexible sigmoidoscopy
- Fecal occult blood test (FOBT)
- Fecal immunochemical test (FIT)
MSK recommends people at average risk for colon or rectal cancer start getting screened at age 45.
MSK recommends people at higher risk for colorectal cancer talk with their healthcare provider about when to start screening.
You can learn more about screening guidelines for colon cancer and rectal cancer.
A colonoscopy procedure can take from 15 to 60 minutes. But it can take about 2 to 3 hours to get ready for the colonoscopy and recover from sedation.
Someone will have to escort you home after the procedure. Your care team will tell you how long it will take, so someone can come get you. You will not be able to drive yourself home.
If you work, plan to take the day off.