Colorectal Cancer Screening

Colorectal cancer is one of the easiest cancers to treat when caught early. Regular screenings are the best way to do this. Screening methods range from simple tests you can do at home to more involved procedures that must be performed by a doctor.

The most accurate and comprehensive way to screen for colorectal cancer remains the colonoscopy. This is a procedure that can detect cancer as well as treat it in its earliest stages. However, if you are unable to undergo a colonoscopy, your physician can recommend alternative screening methods.

What are the screening guidelines for colorectal cancer?

Patients who carry an average risk of colorectal cancer usually begin regular screenings at age 45. An “average risk” of colon cancer generally means that:

  • You have never been diagnosed with colorectal cancer or colon polyps
  • You have no family history of colorectal cancer
  • You don’t have an inflammatory bowel disease (such as Crohn’s or ulcerative colitis)

Patients who have a higher risk of colorectal cancer start screenings earlier. Higher-risk patients are typically individuals who:

  • Have a strong family history of colorectal cancer
  • Have been diagnosed with a hereditary colorectal cancer syndrome
  • Have an inflammatory bowel disease

Generally, for higher-risk patients, screenings begin ten years before the earliest age at which cancer was diagnosed in one of their family members. For instance, a patient whose father developed colorectal cancer at 45 would start screenings at 35.

You should talk to your physician about your screening options.

What tests are used to screen for colorectal cancer?

Your physician will likely recommend a particular type of screening based on your age, risk factors, and health. The most common options are listed below. Keep in mind that some screening methods must be repeated more frequently than others.

Stool-based tests

These tests are a convenient way to learn if you are passing blood in your stools. Blood in the stool can be a key indicator of colorectal cancer, but it’s not always visible to the eye. Your physician may recommend that you take one of these tests as a simple screening for colorectal cancer.

To perform the test, you will collect multiple samples of a bowel movement and send them off to a laboratory. There, they will be tested for hidden blood.

If the test indicates that you do have blood in your stool, you will need to undergo a colonoscopy. This will identify the source of the bleeding and rule out possible colorectal cancer. Furthermore, if you choose to use stool-based tests as your primary method of colorectal cancer screening, you’ll need to complete one every year.

Stool-based screening tests include:

  • Fecal occult blood test (FOBT)
  • Fecal immunochemical test (FIT, or iFOBT)
  • Colo Gard DNA test 


A colonoscopy is an imaging procedure that can locate pre-cancerous or cancerous growths, called polyps, on the interior lining of the colon. If the polyps are small enough, they can be removed during the test. This prevents them from developing into cancer. Tissue samples can also be collected for biopsies.

The colon must be entirely clear of stool for the procedure to be accurate. The night before undergoing a colonoscopy, patients must “prep” their colons by drinking a laxative solution.  Though inconvenient and sometimes uncomfortable, completing the prep is critical for the quality of the colonoscopy. Most patients tolerate the prep very well.

During the colonoscopy, the patient will be sedated. The doctor threads a thin, flexible tube with a small camera at the end through the full length of the colon. The colon will be inspected for polyps or other suspicious areas, which will be removed as necessary. Any tissue removed during the procedure will be tested for cancerous cells.

Because a colonoscopy is such a thorough method of screening, patients only need to have one every ten years.

Virtual colonoscopy

This is a type of CT scan that creates a 3D image of the inside of the colon. During the test, a small tube is inserted into the rectum to gently inflate the colon with air and scan it. Patients must still complete a colon prep before undergoing a virtual colonoscopy.

Virtual colonoscopies offer several advantages. They’re not invasive, and the patient doesn’t need to be sedated during the procedure. They can be a good option for patients who take blood thinners. However, because the imaging takes place from outside the colon, the physician is unable to remove any polyps or tissue. If polyps are discovered, the patient will need a colonoscopy or other follow-up procedure to take them out.

Patients who are screened with virtual colonoscopies are advised to have them every five years.

Flexible sigmoidoscopy 

This exam uses a small flexible tube to examine only the lower part of the colon. Patients do not need to be sedated. The test should be repeated every five years.

Barium enema

This is an X-ray of the colon taken after barium liquid is put into the rectum and colon to check for polyps or other abnormal areas in the colon and rectum. In large part, barium enemas have been replaced by virtual colonoscopy.

Where can I get a screening for colorectal cancer?

Colorectal cancer screenings are usually performed by gastroenterologists – physicians who specialize in treating the digestive system. But most people don’t see a gastroenterologist regularly, and it’s not always easy to access screenings. It’s important to know who to talk to and where to go to get these important tests.

For many patients, the path to screening begins with their primary care doctor. Their doctor will recommend a screening method – usually a colonoscopy – and suggest a few gastroenterologists who could perform it. The patient then contacts the gastroenterologist’s office to set up the procedure. Typically, patients meet their gastroenterologist at a regular office appointment first to discuss the test and how to prepare for it.

Washington University’s Division of Gastroenterology is made up of a team of dedicated doctors who are exceptionally skilled at performing colonoscopy. If you have concerns about your colon health and wish to schedule a colonoscopy, fill out this form on their website.

How do I get a screening if I don’t have health insurance?

Colonoscopies are expensive medical procedures, and it’s natural to worry that you won’t be able to afford one if you aren’t insured.

One option for patients without insurance is to contact their local community health center and ask about colonoscopy screening. Staff should be able to assist you.

In addition, hospitals sometimes offer financial assistance for colonoscopies for patients who qualify. Reach out to the hospitals in your area and ask if there are any funds available.