Colorectal Cancer Screening Methods

The American Cancer Society recommends that all adults be screened for colorectal cancer by the age of 50 by one of several screening methods. Some of the colorectal cancer screening methods are considered more accurate than others and some are less comfortable than others. What is most important is that you get screened, no matter which method you decide to use.

Screening Methods

Fecal Occult Blood Testing (FOBT)

With this exam, the stool is inspected for blood cells. Blood in the stool, even in microscopic amounts, can be an indicator of a bleeding tumor or polyp in the colon.

Barium enema / Double Contrast Barium Enema (DCBE)

With a barium enema, liquid barium is instilled into an empty colon through a tube inserted into the rectum. While the barium is administered, x-ray images of the colon are taken. These images are examined for abnormalities. With a double contrast barium enema, air is pumped into the colon and a second set of x-ray images are taken.

Sigmoidoscopy

A sigmoidscope (a thin, lighted tube with a camera on the end) is inserted into the sigmoid, or lower colon, for this exam. Polyps, tumors and other abnormalities can be found in the rectum and lower portion of the colon, but not in the remainder of the colon.

Conventional Colonoscopy

This exam is performed similarly to a sigmoidoscopy, but the tube is extended through the entire length of the colon to look for polyps, tumors and other abnormalities. The camera images are displayed on a computer monitor for the physician to see during the procedure. If any abnormalities are found, they can be removed or biopsied at that time.

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Virtual Colonoscopy

Like a conventional colonoscopy, a virtual colonoscopy examines the rectum and entire colon. However, rather than using a tube and camera to see the colon, a CT scanner takes images of the abdomen. A virtual reality software program combines the images to form three dimensional models of the colon and rectum, similar to what is seen by camera in a conventional colonoscopy. A radiologist then examines these images for abnormalities. A virtual colonoscopy requires that a small tube be inserted only 4 inches into the rectum so the colon can be filled with carbon dioxide prior to the CT images being taken.

Stool DNA Test (Under Development)

Colorectal cancers occur as a result of accumulated genetic mutations or malfunctioning genes. The stool DNA test analyzes the DNA in a stool sample for many of the genetic abnormalities associated with current, active colorectal cancer. Initial studies of this test are promising; however, it is still under development.

Comparison of Screening Methods

The following chart compares the accuracy of several screening methods for detecting the presence of colorectal cancer and polyps of different sizes.

Test Colorectal Cancer Colorectal Polyp
> 1cm 		Colorectal Polyp
5-9mm
FOBT
40-90%
10-25%
DCBE
85-90%
75-80%
50-80%
Virtual Colonoscopy
95-98%
90-95%
80%
Conventional Colonoscopy
95-98%
90-95% GI
87% Non-GI
85%

Virtual Colonoscopy Results

Virtual colonoscopies are nearly as effective as conventional colonoscopies and more effective than other screening methods for identifying colorectal cancer and polyps of varying sizes.

Whether you choose a virtual colonoscopy or another screening method, the important thing is that you get screened!

 

During a virtual colonoscopy, a CT scanner rapidly takes images of the abdomen which are then constructed into 3D images of the colon. With a barium enema, liquid barium is administered into the colon while x-ray images are taken.