Colonoscopy is one method of screening for colorectal cancer. Other methods are also effective and available.

Alternatives to colonoscopy include sigmoidoscopy, which is a less invasive form of colonoscopy, and noninvasive methods, such as stool sample testing.

According to colorectal cancer guidelines published in BMJ, doctors should help people decide on the best screening method and frequency based on their risk of developing this type of cancer.

Below, we look at the various tests that doctors use to check for colorectal cancer. We also outline the official recommendations for screenings.

a woman talking to a doctor about colonoscopy alternativesShare on Pinterest
Getty Images

Medical professionals use colonoscopy to check the large intestine for abnormalities, often when screening for colorectal cancer.

During the procedure, a healthcare professional inserts a long tube, called a colonoscope, into the rectum and along the length of the colon. This tool creates images that help identify colon polyps, and it can also remove them using a small wire loop attached to the tube.

Colonoscopy can be costly, cause uncomfortable side effects, and require substantial preparation and sedation.

Health experts once considered colonoscopy to be the best screening tool for colorectal cancer. More recent guidelines acknowledge that other methods can be just as effective, depending on a person’s level of risk and other factors.

Guidelines from the American College of Physicians (ACP), published in 2019, recommend that adults with an average risk of colorectal cancer undergo screenings between the ages of 50 and 75 years.

According to the guidelines, a person and a doctor should decide on the method of screening based on a discussion of:

  • the benefits of each technique
  • possible complications
  • costs
  • availability
  • the recommended frequency of screenings
  • the individual’s preferences

In the sections below, we discuss seven alternative screening methods for colorectal cancer.

Fecal immunochemical testing (FIT) involves analyzing stool samples. FIT is a popular screening choice in many areas of the world, and the Food and Drug Administration (FDA) approves its use.

FIT uses antibodies to detect traces of blood in the sample, which indicates bleeding in the gastrointestinal (GI) tract.

To help avoid inaccurate results, a person should let a doctor know if they have hemorrhoids or anal fissures or are menstruating before giving the stool sample.

For this test, the person collects a stool sample at home and brings it to the doctor. Most insurance companies cover FIT, and it is low in cost.

A person usually needs to repeat FIT every 1–2 years, depending on the doctor’s recommendations.

If FIT results suggest bleeding in the GI tract, the doctor may recommend colonoscopy for further diagnosis.

A fecal occult blood test involves analyzing a stool sample and is an alternative to FIT. The ACP particularly recommends high-sensitivity guaiac-based fecal occult blood tests (gFOBT).

For gFOBT to screen effectively, a person should undergo it every 2 years.

A doctor may recommend having a colonoscopy if the test indicates that there could be an abnormality in the GI tract.

This test checks for blood and specific DNA in a stool sample, which could indicate the presence of colon cancer. A doctor may use a stool DNA test alongside FIT.

If the test detects any abnormality, a person may need to undergo colonoscopy.

A sigmoidoscopy is similar to a colonoscopy, but it checks a smaller portion of the large intestine.

Sigmoidoscopy is an invasive procedure that requires preparation, including fasting and taking pills to induce diarrhea or having an enema to clear the colon.

This method carries fewer risks than colonoscopy, and it is often less expensive. However, it does not evaluate the whole of the colon.

A doctor can detail the benefits and risks of colonoscopy and sigmoidoscopy for each individual.

CT colonography involves taking detailed images of the colon.

The procedure does not require sedation. However, as with colonoscopy, a person will need to use medications or an enema to clear the colon beforehand.

During the procedure, a healthcare professional will inflate the colon with air to provide a better view.

If the test detects an abnormality, a colonoscopy is necessary.

A double contrast barium enema is a type of X-ray that helps a doctor examine the colon. The barium helps create clear images of the colon.

Doctors rarely use this method, because — unlike colonoscopy — it does not detect small polyps and tumors. However, it is an option for people at risk of colonoscopy complications.

Some doctors collect a single stool sample during a routine rectal examination and analyze it with gFOBT.

However, research has not shown this to be an effective method of screening for colorectal cancer.

Researchers agree that fecal testing, colonoscopy, and sigmoidoscopy are all effective at detecting colorectal cancer.

The most appropriate screening method varies, depending on a person’s risk factors and preferences.

According to BMJ guidelines, yearly FIT or regular sigmoidoscopy or colonoscopy has reduced the incidence of the cancer. However, the incidence reduction of FIT is small compared with those of sigmoidoscopy and colonoscopy.

Colonoscopies and sigmoidoscopies can help prevent colorectal cancer by finding adenomas, which appear before a tumor develops.

Stool sample tests, on the other hand, cannot prevent colorectal cancer. They can only help a doctor detect it once it is present.

The ACP recommends the following options for adults aged 50–75 years with an average risk of colorectal cancer:

  • fecal testing every 2 years, either by FIT or gFOBT
  • a colonoscopy every 10 years
  • a sigmoidoscopy every 10 years plus FIT every 2 years

A range of screening methods can help detect colorectal cancer, including colonoscopy, stool sample testing, sigmoidoscopy, and CT scans of the colon.

If any tests detect abnormalities in the colon, a person will likely need a colonoscopy to help identify the issue.

A doctor will recommend a method and frequency of screening based on a person’s risk factors and preferences.