Dr. Oz and the Polyp: Part 2 Virtual Colonoscopy

Last week, we did a story about Dr. Mehmet Oz’s cancer scare. On routine screening colonoscopy, doctors found and removed an benign tumor called an adenomatous polyp. Dr. Oz underwent the traditional method of colonoscopy with a flexible colonoscope. However in February of this year, President Obama underwent a virtual colonoscopy during his annual physical exam. So, what are the pros and cons of tradition vs. virtual colonoscopy?

Virtual colonoscopy uses either a CT or MRI scanner to develop a 3-D image of the colon. Like traditional colonoscopy, a thorough bowel clean-out is necessary. Before the exam, a CT-scan patient drinks a liquid contrast media. To start the exam, a thin tube is inserted through the anus and into the rectum. For CT, carbon dioxide gas is pumped through the tube expanding the large intestine for better viewing. For MRI, contrast media will be given rectally to expand the large intestine.

What are the advantages of virtual colonoscopy? Source: NIDDK

Virtual colonoscopy has several advantages over other procedures:

• Virtual colonoscopy does not require the insertion of a colonoscope into the entire length of the colon. Instead, a thin tube is inserted through the anus and into the rectum to expand the large intestine with air.
• No sedation is needed. A patient can return to usual activities or go home after the procedure without the aid of another person.
• Virtual colonoscopy provides clearer, more detailed images than a conventional x-ray using a barium enema — sometimes called a lower GI series.
• Virtual colonoscopy takes less time than either conventional colonoscopy or a lower GI series.
• Virtual colonoscopy can see inside a colon that is narrowed due to inflammation or the presence of an abnormal growth.

What are the disadvantages of virtual colonoscopy?

Virtual colonoscopy has several disadvantages:

• As with conventional colonoscopy, virtual colonoscopy requires bowel prep and the insertion of a tube into the rectum for expanding the large intestine with gas or liquid.
• Virtual colonoscopy does not allow the doctor to remove tissue samples or polyps.
• Virtual colonoscopy does not detect precancerous polyps smaller than 10 millimeters.
• Many health insurance plans, including Medicare, do not pay for virtual colonoscopy cancer screening.
• Virtual colonoscopy is a newer technology and is not as widely available as conventional colonoscopy.

According to a May MedPage Today article, even when insurance companies cover virtual colonoscopy many people will decide to undergo the traditional colonoscopy. Reseacher Patrick Pfau, MD postulated that :” When doctors tell patients about the undiminished need for bowel preparation with CT colonography, as well as its lower sensitivity for certain lesions and the requirement that patients undergo a regular colonoscopy to confirm and treat positive findings, their enthusiasm for initial CT colonoscopy often wanes.

This video shows a virtual colonoscopy of the rectosigmoid colon performed in a retrograde fashion. There is a 10-mm colonoscopically-proven polyp in the sigmoid colon seen at the top of the frame at the midpoint of the movie. The movie concludes at the tip of the rectal tube which was used to insufflate the colon. CT dataset courtesy of C. Daniel Johnson, MD, Department of Radiology, Mayo Clinic, Rochester, MN, and was found on the National Institute of Health Clinical Center website.

Virtual colonoscopy images of a colon: left, with the patient scanned supine (face up) ; right, with the patient scanned prone(face down). The red colored area indicates a polyp detected by computer-aided detection (CAD). Images courtesy of Dr. Ronald M. Summers, Diagnostic Radiology Department, Clinical Center, National Institutes of Health.