Colon Cancer

Which Colon Cancer Screening Is Right for Me?

Originally published September 12, 2019

Last updated April 26, 2024

Reading Time: 3 minutes

There are four different ways to be screened for colon cancer. Read on to find out which test might be a good choice for you.

So you’ve reached a birthday milestone — and surprise! — it’s time to begin screening for colon cancer. If the thought of colon cancer screening makes you shudder, you’re likely not alone: About one-quarter of eligible American adults haven’t been screened. Since colon cancer is the second-leading cause of cancer death in the country (and the third most-diagnosed), this is a serious problem.

Add to this the fact that recent guidelines from the American Cancer Society have lowered the age at which people should start getting screened for colon cancer, if they are at average risk. Now it’s recommended that people begin screening at age 45 (previously, the recommended age was 50).

It turns out there’s good reason the guidelines recommend screening at a younger age.

“We know from our experience as health care providers — and there is plenty of emerging evidence to support this — that people are being diagnosed with colorectal cancers at an increasingly young age,” says Christine Hsieh, MD, a colorectal surgeon at Keck Medicine of USC and assistant professor of clinical surgery at the Keck School of Medicine of USC.

So, before you think of skipping screening altogether, familiarize yourself with the different types of tests, and talk to your doctor about which one makes the most sense for you.

1. Stool test

This test looks for blood and/or DNA changes in your stool that may indicate cancer. For this test, you’ll get a kit with instructions on how to take a sample. The test is easy to do at home and must be done every year. (The DNA test may be done once every three years.)

“If you opt to have a stool test, you should be aware of the diet restrictions that need to be followed before the test; otherwise, you might have a false positive,” Dr. Hsieh advises.

If anything is found in your stool test, you’ll need to have a colonoscopy.

2. Colonoscopy

A colonoscopy is a procedure done under sedation, which means you’ll need someone to take you to your appointment and stay with you afterward. The night before, you’ll have to drink liquids, take a pill and/or use an enema to completely empty your bowels. During the procedure, the doctor will look at your entire colon and remove any potentially precancerous polyps. Since colonoscopies are very thorough, they need to be done only once every 10 years.

3. Virtual colonoscopy

Known as CT colonography, this is a specialized CT test that requires a full bowel prep but does not require sedation. During the test, air is injected into your colon to push the walls of the colon apart, before a CT scan is done.

“Virtual colonoscopy is best for detecting polyps that are larger than 5 millimeters, but sometimes errant pieces of stool can cause a false positive,” Dr. Hsieh says.

If anything is found during this test, you’ll need a follow-up colonoscopy.

4. Flexible sigmoidoscopy

This test is similar to a colonoscopy but only examines the lower third of the colon. It requires a bowel prep (often with a laxative and an enema) and typically isn’t done under sedation. Flexible sigmoidoscopy needs to be repeated every five years (or every 10 years, if it’s combined with an annual stool test). If anything is found during a sigmoidoscopy, a follow-up colonoscopy will be required.

So, which test is best?

There’s no test that’s best for everyone; however, some doctors consider colonoscopy to be the gold standard for screening, because it can look at the entire colon.

“Colorectal surgeons tend to favor full colonoscopy, as it’s both diagnostic and therapeutic,” Dr. Hsieh says.

Also, if anything abnormal is found with a stool test, virtual colonoscopy or flexible sigmoidoscopy, a colonoscopy will be required, which will mean some people will need to have two tests, Dr. Hsieh adds.

Each test has pros and cons, so be sure to discuss them with your doctor. Ultimately, the decision is yours, but your best bet may be to pick the test you’re most likely to actually get done.


Tina Donvito
Tina Donvito is a freelance writer covering health, culture, travel and parenting.