Colon cancer screening

Colon cancer is the growth of abnormal cells in the colon. These abnormal cells are harmful and can spread to various organs causing damage.

Types of polyps

A colon polyp can lead to cancer, it takes about 10 years to transform from a bad polyp to full blown cancer.

Hyperplastic polyps are good polyps that do not transform to cancer.

Adenomatous polyps are bad polyps that can be defined by their histological appearance as tubular, villous, or tubulovillous. These polyps can transform into cancer and are removed during colonoscopy.

What is a screening colonoscopy?

The purpose of a screening colonoscopy is to identify polyps in people without any gastrointestinal symptoms. When polyps are found, they are removed during the colonoscopy. Depending on the type of polyp a repeat colonoscopy may be done in 3 years, 5 years or 10 years. The gastroenterologist will best advise as to the frequency of the colonoscopy.

A screening colonoscopy is generally performed starting from age 45 years in black people and every 10 years if normal up to age 75 years.

Screening colonoscopy is offered to people at age 40 years if there is a family history of adenomatous polyp or colon cancer at age 60 years or less in a first-degree relative.

Screening colonoscopy is also offered at 10 years younger than the earliest diagnosis of cancer in a first-degree relative. For instance if a parent had colon cancer at age 50 years, then their offspring should start screening colonoscopy at age 40 years (50 years minus 10).

There are hereditary syndromes that predispose a person to colon cancer, these are genetic conditions, such as familial adenomatous polyposis and hereditary nonpolyposis colon cancer. In these genetic conditions, screening would start at much earlier ages.

Other conditions that cause an increased risk for colon cancer include inflammatory bowel disease (ulcerative colitis and Crohn’s disease) and primary sclerosing cholangitis (a condition of the bile ducts).

What is a diagnostic colonoscopy?

If a person has gastrointestinal symptoms, such as rectal bleeding, weight loss, low iron, abdominal pain, pelvic or rectal pain, or change in bowel habits and a colonoscopy is performed, the term is called diagnostic colonoscopy. A diagnostic colonoscopy is done at any age.

In a patient who does not have any gastrointestinal symptoms having a colonoscopy, the term is called screening colonoscopy, and this is determined by age and family history.

Are there any other things to know?

Yes. A colonoscopy is a procedure performed by a gastroenterology with an anesthesiologist administrating sedation. There are risks with this procedure as well as over-diagnosis and under-diagnosis. There are anesthetic risks also.

The adenoma detection rate is a rating of how effective the colonoscopist is to detect polyps. A low adenoma detection rate means that the colonoscopist misses adenomas. While a high adenoma detection rate means that the colonoscopist is good at finding polyps.

I don’t want to have a colonoscopy. Are there other ways to screen?

Colonoscopy is the gold standard test because it is possible to remove a polyp or polyps during the procedure whereas polyp removal is not possible with the other testing methods listed below. If any of these tests is abnormal then a colonoscopy will need to be performed.

  • Fecal immunochemical test (FIT) every year. In Nigeria FIT test is available at
  • High-sensitivity guaiac-based fecal occult blood testing (FOBT) every year
  • Barium enema every 5 years
  • Flexible sigmoidoscopy every 5 years
  • Ct scan colonography/ virtual colonoscopy every 5 years

Where can I find a colonoscopist in Nigeria?

Major teaching hospitals in Nigeria have Gastroenterologists.

Private hospitals also have Gastroenterologists.

How can I prevent colon cancer?

Let’s review the risk factors for colon cancer, these are

  • Poor diet, including consumption of processed and red meat, alcohol, and low consumption of nonstarchy vegetables and fruits;
  • Lifestyle factors; smoking and sedentary lifestyle.

In fact, we have often heard that sedentary lifestyle or sitting for prolonged periods has become the new smoking.

By modifying these risk factors, we may be able to reduce our risk for colon cancer through healthy eating and lifestyle.

Photo by Godaddy

Summary by Dr. Onuoha.

Disclaimer: This post is for general health education. Kindly consult with your doctor to determine what is best for you. The mention of services or external links is not endorsement.

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