Regular colon cancer screening leads to early detection, making the disease easier to treat. Screening also enables your healthcare provider to find and remove any growths before they become cancerous. A colonoscopy is a standard screening tool for colon cancer, but there are other screening methods too.

This article will discuss what happens during a colonoscopy and other screening methods, selecting the proper test, and current screening guidelines.

What Happens During a Colonoscopy?

A colonoscopy is a procedure that looks inside the colon, using a long, flexible tube with a camera called a colonoscope. It is used to screen for colon cancer and other colon problems.   

A clean colon is necessary for a successful colonoscopy. You will need to restrict your diet for at least 24 hours before your appointment. This means a completely clear liquid diet, which can include things like coffee, water, broth, and sports drinks.

You will also need to empty your bowel. Your doctor might suggest a laxative or enemas. You will need to do this the night before the colonoscopy. Be sure to follow all your doctor’s directions closely.

Make arrangements for someone to take you home after the colonoscopy. You will be sedated for the procedure (given medication to make you groggy and relaxed) and it won’t even be safe for you to drive for at least eight hours after the colonoscopy.

The colonoscopy is performed by a gastroenterologist, a doctor specializing in disorders of the digestive tract. The procedure lasts about 30 to 60 minutes. You will be given sedation medication through a vein in your arm. You will be connected to a monitor that will record blood pressure, blood oxygen levels, and heart rate.  

During the colonoscopy, the gastroenterologist will use the colonoscope to view the lining of your colon and examine it for abnormalities.

The colonoscope is inserted through the rectum and advanced to the colon. It bends so it can be moved around to examine the colon. It also blows air into the colon to help the colon expand so it can be viewed more clearly.

If doctors see anything abnormal during the colonoscopy, they will take a small sample for analysis (a biopsy). If any polyps are discovered, they are removed during the procedure.

Colon Cancer Screening Methods  

A colonoscopy is not your only option for screening for colon cancer. Other screening methods are sigmoidoscopy, virtual colonoscopy, a fecal immunochemical test, a fecal occult blood test, or a stool DNA test.  

Sigmoidoscopy  

A sigmoidoscopy is a diagnostic test used to check the sigmoid colon, the lowest part of the colon responsible for holding and voiding feces. A sigmoidoscopy may be used to take a tissue sample and to remove polyps or hemorrhoids (swollen veins in the rectum and anus). It can also screen for colon and rectal cancers.  

The sigmoidoscopy uses a thin, flexible tube called a sigmoidoscope that has a tiny light and camera. The sigmoidoscope is inserted in the anus and moved slowly through the rectum to the lower part of the colon. The tube is also used to blow air into the colon to make it swell up and improve visibility.  

Much like a colonoscopy, you will need to prepare in advance of the procedure. You should stop eating solid foods for at least eight hours before. You will also need to clear out your colon using the enema before the procedure. You will need someone to drive you home because you will be sedated for the procedure.

Virtual Colonoscopy  

A virtual colonoscopy helps your doctor see the inside of the colon and rectum. It is used to look for polyps and check for colon and rectal cancers. Virtual colonoscopy uses a computerized tomography (CT) scanner and X-rays to take 3-D images of the colon that can be seen on a computer screen.

This test doesn’t involve sedation, but some preparation is necessary. To prepare, your doctor may recommend some diet changes. Before the procedure, you will also need to drink contrast medium, a liquid that makes the colon and rectum easier to see on the scans.

Fecal Immunochemical Test  

The fecal immunochemical test looks for antibodies to detect the presence of hemoglobin (the oxygen-carrying protein in red blood cells) in the stool, which can be an early sign of colon cancer.

This test is becoming more popular because it is noninvasive and can be collected in the privacy of your home. Unfortunately, the test is not always accurate, and a positive test might require a follow-up colonoscopy.  

Fecal Occult Blood Test  

A fecal occult blood test looks for hidden (occult) blood in the stool. The source of blood can be anywhere in the gastrointestinal tract, and it can be related to many different conditions, including colon cancer.

This test is used less than other screening methods for colon cancer, and there are newer stool testing methods that yield better results, including the fecal immunochemical test.

Stool DNA Test

The stool DNA test is a noninvasive tool for adults aged 45 and older with an average risk for colon cancer. The stool DNA tests look for microscopic blood in stool and DNA changes and mutations in the stool that might include precancerous polyps and/or cancerous tumors. 

The stool test is done by collecting a stool sample at home and sending it to a lab for testing. The stool DNA analysis will look for multiple DNA markers and mutations using sensitive methods for detection. Stool DNA testing has high detection rates for colon cancer in its earliest stages.

In 2014, the Food and Drug Administration (FDA) approved Cologuard, making it the first DNA stool test for screening colon cancer. Since then, it has become a preferred screening method for colon cancer.

Selecting the Right Colon Cancer Test  

Your healthcare professional is in the best position to give you advice on which colon cancer screening method might be best for you. They know your personal and family history with cancer and any additional risk factors. They will recommend you start getting screened at age 45.  

If you have an average risk for colon cancer, your healthcare provider might recommend an at-home screening method. The stool DNA test, fecal occult blood test, and fecal immunochemical test can all be collected in the privacy of your bathroom.

These home-collected tests are convenient, easily accessible, and effective. But if these tests detect anything, you will need a follow-up colonoscopy.

A full colonoscopy is the most accurate screening method. But it requires preparation, sedation, and one or two days away from work.

Depending on what part of the colon your doctor wants to see, a sigmoidoscopy might be considered. A sigmoidoscopy is less invasive because it only looks at the lower part of the colon whereas the colonoscopy looks at the entire colon.

If time is a problem for you, a virtual colonoscopy might be an alternative to a full colonoscopy. This procedure images the rectum and colon and can be as accurate as a colonoscopy. But if this test reveals polyps or other abnormal growths, you will need a colonoscopy to remove them.

Current Screening Guidelines

The ACS recommends people who have an average risk for colon cancer start regular colon cancer screenings at age 45. If you have risk factors, screening might start earlier.

Considering the Pros and Cons

There is no best screening method for colon cancer. Each test has benefits and drawbacks. Your healthcare professional can educate you on the pros and cons of each test and help you todecide based on your preferences, overall health, availability, and financial resources for testing and follow-up.

People in good health and who have a life expectancy of more than 10 years should continue their screenings until age 75.

After age 75 and through age 85, screening is based on personal preference, prior screening history, health, and life expectancy. Colon cancer screening is not recommended after age 85.  

Screening frequency depends on the testing method or combination of tests. According to the Centers for Disease Control and Prevention (CDC), stool tests should be repeated yearly. A sigmoidoscopy can be done every five or 10 years with a yearly fecal immunochemical test.

A virtual colonoscopy is good for five years, while a full colonoscopy can be done every 10 years if you do not have increased risk factors for colon cancers.

Summary  

Screenings are your best preventive method for colon cancer. Testing can detect polyps and abnormal tissue early and long before you develop symptoms.

A wide range of screening options can spot abnormalities of the colon, including a full colonoscopy, stool sample testing, sigmoidoscopy, and virtual colonoscopy. Your doctor can recommend a screening method based on your risk factors and preferences.

A Word From Verywell

It can be stressful and scary if you are diagnosed with colon cancer. Fortunately, colon cancer is treatable, especially if it is found early and has not spread past the colon and rectum.

Your treating doctor can discuss typical outcomes for your cancer. It is important to keep in mind that information on cancer survival and outcomes is based on the general population and often is years behind, so it doesn’t account for the latest treating methods. It cannot predict your specific prognosis or outlook.

Additionally, because of advanced and improved treatment methods, the outlook for colon cancer is improving every day.

Frequently Asked Questions

  • Are at-home colon cancer tests accurate?
  • Studies have found at-home stool tests for colon cancer to be reliable. You have different options for at-home testing and each of these has its unique level of accuracy. Your doctor is in the best position to advise you on the benefits of at-home testing for your unique health situation.
  • Learn More:
  • Best At-Home Colon Cancer Tests
  • What are the signs that you should have a colonoscopy?
  • Your doctor might recommend a colonoscopy if you have reported frequent gastrointestinal symptoms, including constipation, irregular stools, frequent diarrhea, blood in the stool, sudden weight changes, and/or abdominal pain.
  • Learn More:
  • Symptoms of Colon Cancer
  • Can a colonoscopy detect irritable bowel syndrome?
  • A colonoscopy cannot detect irritable bowel syndrome (IBS) because IBS is a functional disease that causes symptoms but doesn’t affect bowel tissue. A diagnosis of IBS is usually based on symptoms (crampy abdominal pain and altered bowel habits) and the ruling out of other conditions that cause similar symptoms.
  • Learn More:
  • How Irritable Bowel Syndrome (IBS) Is Diagnosed

Studies have found at-home stool tests for colon cancer to be reliable. You have different options for at-home testing and each of these has its unique level of accuracy. Your doctor is in the best position to advise you on the benefits of at-home testing for your unique health situation.

Your doctor might recommend a colonoscopy if you have reported frequent gastrointestinal symptoms, including constipation, irregular stools, frequent diarrhea, blood in the stool, sudden weight changes, and/or abdominal pain.

A colonoscopy cannot detect irritable bowel syndrome (IBS) because IBS is a functional disease that causes symptoms but doesn’t affect bowel tissue. A diagnosis of IBS is usually based on symptoms (crampy abdominal pain and altered bowel habits) and the ruling out of other conditions that cause similar symptoms.