What Are the Different Types of Colorectal Cancer Tests?

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  • Written By: A.M. Boyle
  • Edited By: PJP Schroeder
  • Last Modified Date: 08 October 2019
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There are several colorectal cancer tests commonly used to screen individuals for colorectal cancer. These include simple tests, such as the fecal occult blood test (FOBT), digital rectal exam, and barium enema imaging. Other complex colorectal cancer tests, such as sigmoidoscopy, colonoscopy, and virtual colonoscopy provide a patient with more comprehensive screening.

A digital rectal exam is one of the most common of all colorectal cancer tests and is usually performed as part of a person’s routine physical. A doctor lubricates his glove, then inserts his finger into a patient’s rectum and feels for any abnormalities. This exam only encompasses the lower part of the rectum and is not considered to be a comprehensive screening. If any abnormalities are detected, a doctor generally recommends that a patient undergo further testing.

The FOBT is a simple test that checks for signs of blood in a person’s stool. While not diagnostically specific, blood in the fecal matter can indicate problems warranting further evaluation. An FOBT is often used as a preliminary means to determine whether more extensive testing is needed.

Another type of test called a barium enema uses X-rays to detect abnormalities. Prior to the X-ray, a liquid solution of barium sulfate is inserted into the patient’s rectum. The silver-white compound coats the inside of the lower gastrointestinal tract, making it easier for polyps and other abnormal areas to be visualized.


Sigmoidoscopy and colonoscopy are two more advanced types of colorectal cancer tests. These tests are similar, and both require that a patient prepare beforehand by thoroughly cleansing his or her colon. Typically, a patient is given a strong laxative to use at home prior to testing so that the colon is completely empty when the test is administered.

During a sigmoidoscopy, a sigmoidoscope, a thin, flexible tube, is threaded into the patient’s rectum and lower colon. The sigmoidoscope is lighted and typically has a lens attached so that the doctor can view the interior of the rectum and lower colon. It may also have a tool attached to remove or biopsy any growths that are found during the procedure.

A colonoscopy is much like a sigmoidoscopy, except that the entire colon is visualized. The patient is usually sedated during the procedure. The instrument used, called a colonoscope, is very similar to a sigmoidoscope. The colonoscope generally has a tiny camera attached to the tip so that an image can be projected onto a video screen for the doctor to evaluate.

One of the least invasive of all colorectal cancer tests is the virtual colonscopy, also known as the computerized tomographic colonography. During this procedure, a specialized type of X-ray is used to generate images of a patient’s colon, and those images are used to create a detailed computerized picture that can show abnormalities. Although less invasive than other colorectal cancer tests, this type of screening might not be as accurate as some of the other tests.


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