Colorectal Cancer Screening Tests

Colorectal cancer screening tests check for colorectal cancer before you have any symptoms. Colorectal cancer is a type of cancer that affects the colon or rectum. The colon makes up most of the large intestine.

The rectum is at the end of the large intestine and connects to the anus. Colorectal cancer screening can help to: Find colorectal cancer early, when treatment is most effective.; Prevent cancer from developing. Some screening tests let your health care provider find and remove abnormal growths, known as colorectal polyps.

Cancer in the colon or rectum often starts as a polyp. Most of these polyps are benign (not cancerous) but could become cancerous if not removed.; Find bleeding that you can't see, which may mean you have a polyp. ;

Why this test is done

Regular screening can detect colon polyps and colorectal cancer. If you aren't at higher risk for colorectal cancer, your provider will likely recommend you start screenings at age 45. If you are at higher risk, you may need to start getting screened for colorectal cancer earlier.

Talk with your provider about when to start, how often to get screened, and which type of test you should have.

You may need to be screened at a younger age, or more often, if you have certain risk factors, including:

• A family history of colorectal cancer
• A personal or family history of ovarian cancer
• An inflammatory bowel disease such as ulcerative colitis or Crohn's disease
• Being overweight or having obesity
• Smoking tobacco products
• Alcohol misuse

Some of the tests used to screen for colorectal cancer may also be used as diagnostic tests. They can help your provider make a diagnosis when you are having symptoms of a colonic disease.

How to prepare

There are no special preparations needed for a FIT or stool DNA test. The typical preparations for other colorectal cancer screening tests are below.

For a colonoscopy and virtual colonoscopy, you will need to do a bowel prep. Your provider will give you specific instructions on how to do your bowel prep, but steps for bowel prep may include:

• Following a liquid diet for one to three days before the test.
• Drinking plenty of clear liquids one to three days before the test. Clear liquids include water, black coffee or tea, fat-free broth, and sports drinks without added color. Avoid red or purple drinks or gelatin; the dye in those can look like blood in the colon.
• Drinking a strong liquid laxative (a medicine used to cause a bowel movement), taking laxative pills, and/or using an enema on the evening before your test.

The laxative or enema will cause diarrhea. Be prepared to stay close to a bathroom. Bowel prep can be inconvenient and uncomfortable, but if the colon is not thoroughly cleaned out, your provider may not be able to get a complete picture of your colon and rectum.

They might not be able to see if you have polyps and other abnormal areas.

Also, you may need to stop taking certain medicines before these tests, so tell your provider about everything you take. But don't stop taking any medicines unless your provider tells you to.

For a sigmoidoscopy, before the test, you may need to:

• Follow a clear liquid diet one or more days before the procedure. This isn't always required, so be sure to talk to your provider before the test.
• You may be asked to fast (not eat or drink) on the morning of the procedure.
• You may need to take a laxative (a medicine used to cause a bowel movement) the night before the test.
• You should empty your bowels with an enema about one hour before the procedure. A second enema is sometimes needed.
• Also, you may need to stop taking certain medicines before these tests, so tell your provider about everything you take. But don't stop taking any medicines unless your provider tells you to.

For a g(FOBT) test, you may need to avoid the following foods and medicines for several days before your test:

• Nonsteroidal, anti-inflammatory drugs (NSAIDs), such as ibuprofen, naproxen, or aspirin
• Vitamin C daily from supplements, fruit juices, or fruit
• Certain vegetables, such as broccoli and turnips
• Red meat, such as beef, lamb, or pork

Your provider will give you full instructions on how to prepare for your screening test.

Sample type

Blood Stool Tissue/Biopsy

Other names for this test

colon cancer screening