Print PageEmail Page
 

Virtual Colonoscopy


Virtual Colonoscopy

There are new colon imaging procedures that the American Cancer Society feels are not yet ready for routine care.

We are interested in the development of virtual colonoscopy. 

  • It is an evolving field, at this time we are not recommending it as a screening test. 
  • We advise patients to check carefully with their insurance carrier before having a virtual colonoscopy because the majority of insurance carriers do not pay for it at this time. 
  • There are concerns that if the patient has a virtual and a polyp is found, they may need to have a traditional colonoscopy which will incur costs for a second procedure. The traditional colonoscopy may often not be able to be performed on the same day requiring the patient to prep again. 
  • If a patient has further questions they can talk with their physician to determine the best option for them.

Covered Colorectal Screenings 

Medicare covers tests to check for colon cancer, including colonoscopies, sigmoidoscopies, and fecal occult blood tests. Talk to your doctor about which test is right for you. Medicare doesn’t cover computed tomographic colonography (also called "virtual colonoscopy") at this time.  Get details on these and other covered Medicare Part B screenings at www.medicare.gov

Computed Tomographic Virtual Colonoscopy

Source:  American Society of Colon and Rectal Surgeons  
The premier society for colon and rectal surgeons and other surgeons dedicated to advancing and promoting the science and practice of the treatment of patients with diseases and disorders affecting the colon, rectum and anus.

Submitted by: Dr. Anthony Senagore

Virtual computed tomographic virtual colonoscopy (VCT) utilizes radiographic images obtained by CT technology for the purpose of rendering two and three-dimensional images of the colon. The technique is rapidly evolving and appears promising and an adjunct method to perform screening examinations for colorectal cancer. Patients still require a mechanical bowel preparation to remove solid stool and a period of time on a clear liquid diet. The colon is insufflated via a transanally placed tube using room air.

The patient is imaged and a computerized software program extracts the images of the insufflated colon, generates an automated centerline for navigation and subtracts the opacified residual fluid in the lumen. The observer is then able to perform a virtual "fly-thru" of the colon. Use of both two and three-dimensional visualization optimizes identification of polyps and other lesions.

Early evaluations of VCT have been limited, based primarily upon the use of two dimensional views. The recent study by Pickhardt et al (NEJM 2003; 349:2191-2200) reported a sensitivity of 93.8% for polyps >7mm and 88.7% for adenomatous polyps at least 6mm in diameter. The sensitivity and specificity in this study was equivalent to optical colonoscopy. VCT identified two malignant polyps, one of which was missed at optical colonoscopy. The authors also commented that the rate of extra-colonic lesions in an average risk patient is <50% of high risk groups which reduces the potential for unnecessary investigations as a result of the VCT. Another report by Iannaccone et al (Radiology 2003; 229:775-781) reported 100% sensitivity for cancers, 100% for polyps >1cm, and 83% for polyps 6-9 mm. These authors were able to reduce the radiation exposure by using a multi-detector device (1.8-2.4 mSv compared to 4.4-6.7 mSv in other studies). Taylor et al (Radiology 2003; 229:782-790) reported an absence of hemodynamic changes during VCT compared to a 30 fold increase in hypotension and a higher rate of bradycardia with optical colonoscopy.

VCT appears to offer significant promise as a screening modality in moderate risk populations. It avoids the need and risks for sedation, avoids the risk of instrument perforation with optical colonoscopy, and compares favorably for time consumption (15 minutes for image acquisition and at best, under ideal circumstances, 15 minutes for interpretation). Optimal VCT requires a multidetector CT scanner for high speed and better resolution. The downside is that patients require mechanical bowel preparation and those with a suspected lesion will either need to be referred for an optical colonoscopy or arrangements will need to be made for on-demand colonoscopy of positive tests. Further data is required to support full transition of screening for colorectal cancer to VCT. The additional CT resources, technicians and radiologists will be significant as well.