Virtual Versus Traditional Colonoscopy: What Are The Risks?

News reports in the past couple of days have hit on part two of the CT radiation overexposure inquiry. Before, the issue was whether certain CT devices because of manufacturing, design, or technician error, provided too much radiation to patients. A secondary question was whether patients were receiving too much radiation through scans over the course of their lives (the FDA reports that the average person’s radiation exposure has doubled in the last thirty years).

Now, the question is focused on whether CT scans are a good idea for screening purposes where a patient has no indication that they have any disease—the three that have been most mentioned are whole-body CTs (to see if there is anything wrong); CT colonoscopy (to detect colon cancer), and CT scans of the heart (to detect heart disease).

Most of the debate has been centered around the colonoscopy procedure.

Traditional Colonoscopy

On one side are those who believe that traditional methods—a colonoscopy, are best to detect colon cancer. Proponents (including the American College of Gastroenterology, who come out on the side of their financial interests in the question) state that CT colonoscopies are not as certain as the traditional visual colonoscopy; that removal of polyps would require a second procedure with a CT colonoscopy (versus being done at the same time in the traditional procedure), and those incidental findings on a CT scan may lead to unnecessary procedures. Additionally, repeating these scans increases patient exposure to radiation.

Virtual Colonoscopy

A virtual colonoscopy, also known as a CT colonography, is a non-invasive medical imaging test used to screen for colorectal cancer and other abnormalities in the colon and rectum. It uses computed tomography (CT) technology to create detailed, three-dimensional images of the inside of the colon.

Unlike a traditional colonoscopy, which uses a flexible tube with a camera attached to it to examine the colon, a virtual colonoscopy does not require sedation or the insertion of a tube. Instead, the patient lies on their back on a table while a radiologist uses a CT scanner to take images of the colon.

To prepare for a virtual colonoscopy, the patient must follow a special diet for a day or two before the test and take laxatives to clear the colon of stool. The day of the test, the patient will be asked to drink a contrast material that helps to highlight the colon on the CT scan.

During the virtual colonoscopy, the patient lies on a table that moves through a CT scanner. The scanner takes images of the abdomen and pelvis, which are then processed by a computer to create a three-dimensional image of the colon. The radiologist will examine the images for any abnormalities, such as polyps or other growths, that could be signs of colorectal cancer.

If a polyp or other abnormality is detected, the patient may need to undergo a traditional colonoscopy to remove the growth or take a tissue sample for biopsy. The virtual colonoscopy can also detect other conditions, such as diverticulitis or inflammatory bowel disease.

Pros and Cons of Virtual Colonoscopy

A virtual colonoscopy is a safe and effective way to screen for colorectal cancer, and it has several advantages over a traditional colonoscopy. First, it is non-invasive and does not require sedation, which means the patient can resume normal activities immediately after the test. Second, it is less expensive than a traditional colonoscopy and may be covered by insurance in some cases.

However, there are some potential drawbacks to a virtual colonoscopy. For example, it may not be as accurate as a traditional colonoscopy in detecting small polyps. Additionally, if a polyp or other abnormality is detected, the patient will need to undergo a traditional colonoscopy for further evaluation and treatment.

Detractors, those who support the “virtual colonoscopy” (including the American College of Radiology, who likewise come out on the side of their financial interests in the question) state that virtual colonoscopies are less invasive and more people will probably use them; that there is less chance of perforated bowel or anesthesia risks.

Even the FDA is undecided—there is a fight there about whether the procedure, which General Electric wants to have approved (it manufactures scanning equipment), should be approved (meaning GE would be able to market the virtual colonoscopy to patients and doctors). Some doctors and scientists believe the extra radiation exposure would cause actual harm, when even now between 1.5 and 2 percent of cancers are caused by CT scan radiation exposure.

Why You Still May Want to Have a Traditional Colonoscopy

While virtual colonoscopy, also known as CT colonography, is a safe and effective way to screen for colorectal cancer, it has some limitations compared to traditional colonoscopy. Here are some reasons why regular colonoscopy is generally considered a better screening method:

1. Ability to remove polyps during the procedure: During a traditional colonoscopy, if polyps or other abnormalities are detected, they can be removed or biopsied during the same procedure. This allows for both diagnosis and treatment in one procedure, which can be particularly important for individuals who have a higher risk of developing colorectal cancer.
2. Higher accuracy in detecting polyps: Traditional colonoscopy is considered the gold standard for detecting polyps and other abnormalities in the colon. While virtual colonoscopy can detect most large polyps, it is less accurate at detecting smaller polyps, which can still be precancerous or cancerous. For this reason, traditional colonoscopy is still recommended for people with a higher risk of developing colorectal cancer.
3. Ability to examine the entire colon: Traditional colonoscopy allows for a thorough examination of the entire colon, whereas virtual colonoscopy may miss certain areas. This can be particularly important for people who have a higher risk of developing colorectal cancer or have a history of polyps or other abnormalities.
4. Ability to biopsy suspicious areas: During a traditional colonoscopy, if the physician sees any suspicious areas in the colon, they can take a biopsy for further examination. This can help to determine whether the area is cancerous or not.
5. More frequent screening not required: Traditional colonoscopy is generally recommended every 10 years for people who have a normal exam and no increased risk factors. However, virtual colonoscopy may need to be repeated more frequently, potentially increasing the overall cost and inconvenience of the screening.

Final Analysis

A virtual colonoscopy is a safe and effective screening method for colorectal cancer.  Traditional colonoscopy is still considered the gold standard due to its ability to remove polyps during the procedure, higher accuracy in detecting polyps, ability to examine the entire colon, ability to biopsy suspicious areas, and less frequent screening requirement.  Is the conventional wisdom outdated?  Talk to your doctor about your individual risks and preferences and figure out what works best for you.