Lake Side Surgical Associates, S.C.

Colon Rectal Cancer is the third most commonly diagnosed cancer in men and women and the second leading cause of cancer related deaths in the United States and Western Europe!

Virtual Colonoscopy is a method (under medical study) to examine the colon by taking a series of x-rays (called a CT scan) and then using a high-powered computer to reconstruct 2-D and 3-D pictures of the interior surfaces of the colon. The pictures can be saved, manipulated to better viewing angles, and reviewed after the procedure.

Standard Colonoscopy is a test to look into the rectum and colon through a long, flexible, narrow tube with a light and tiny lens on the end. This tube is called a colonoscope. The patient is under sedation and feels no discomfort during the procedure.

Is there discomfort with a virtual colonoscopy versus a standard colonoscopy?

Yes, there is discomfort during the procedure with a virtual colonoscopy. Why? Because a tube filled with air is inserted into the rectum and the colon is filled with air so it can be viewed on the CT scanner.

There is no sedation used on a virtual colonoscopy. Air is also insufflated during a standard colonoscopy, but the patient is sedated during this procedure and feels no discomfort. Prior to the end of the standard colonoscopy, air is removed through the colonoscope resulting in less discomfort after the procedure.

If the physician finds a polyp during the virtual procedure, then the patient will have to schedule a colonoscopy using the standard method, repeat the bowel prep and have the polyp removed. Studies have shown that more than ten percent of virtual colonoscopies will “see” polyps that aren’t there, triggering an unnecessary procedure.

Because the virtual colonoscopy is new and is still being debated regarding its accuracy in detecting lesions, most insurance companies will not pay for this procedure. However, insurance companies and Medicare will pay for the standard colonoscopy. Virtual Colonoscopy is ideal for patients that cannot complete the standard colonoscopy due to health risks.

Conclusion: Standard Colonoscopy remains the gold standard for screening purposes.

Shaun Melarvie, MD, FACS has been practicing general surgery and gastroenterology in Sturgeon Bay, WI since 1994. He has performed thousands of colonoscopies over the past eleven years and hundreds of colectomies for benign and malignant disease. He is joined by Kurtis D. Scheer, MD, FACS who also has a wealth of experience in colorectal cancer.

It is the third most common cause of new cancer cases and deaths for both men and women. In 2004, there were a combined total of 146,940 cases of colorectal cases (CANCER FACTS AND FIGURES, AMERICAN CANCER SOCIETY, 2004).

Historically, screening for colon cancer has consisted of some combination of Fecal Occult Blood Testing (FOBT), flexible sigmoidoscopy and barium enema. Since 2000 Medicare has been providing for a low risk screening every ten years as per current National Cancer Society recommendations. There is some current debate as to whether this interval is too long. In the high risk screening population, i.e. those with a family history in first degree relatives or a personal history of adenomatous polyps, the recommended follow-up is between 3 and 5 years. It may that a more optimal follow-up for the low risk population falls somewhere between 5 and 10 years. Some third party payers provide for a low risk screen colonoscopy; however, some do not provide for even a high risk screening, such as a positive family history.

Recently, a new imaging modality, CT colonography or Virtual Colonoscopy (VC), has become available. VC is being marketed as an alternative to screening for colorectal cancer, the current gold standard being conventional colonoscopy (CC), and there currently is an ongoing debate in that regard. At this point in time medicare does not cover VC for screening purposes, but does provide for VC in selected cases such as an incomplete colonoscopy or in a patient with co-morbidities in which a CC would be considered high risk. Clearly, there is concern on part of the federal and private insurers regarding the costs, standardization of technique and redundancy of VC followed by CC.

The first study trumpeting the success of VC was published in the New England Journal of Medicine in 2003 in which Pickhardt et al applied three dimensional software, elaborate stool tagging oral contrast, and healthy compliant patients. Sensitivity of 94% and specificity of 96% were reported for detecting lesions > 1cm (1). On the heels of this was a study out of the Medical University of South Carolina in which Cotton et al were unable to duplicate the results of the former study. The study involved 9 major hospital centers and 600 participants. A total of 827 lesions were identified in 308 of the participants. The sensitivity of VC for detecting lesions at least 6mm was 39%, and for lesions at least 10mm in size, 55%. The results for conventional colonoscopy were sensitivities of 99% and 100%, respectively. Also in this study was demonstrable variation of accuracy between centers that did not improve as the study progressed and the participants expressed no clear preference for either technique (2).

There is of yet no widespread agreement on the “endpoints” of VC, or specifically, which polyps should be removed. Polyps greater than 1cm will progress to colorectal cancer at a rate of about 1% per year (3). Polyps of this size are found in up to 2% of the screened population while smaller polyps are present in up to 30% or more (4,5). The clear advantage to colonoscopy is that all polyps, or at least those judged to be significant in regards to size, or appearance are removed at the time of colonoscopy. The question is what to do with the polyps less than 1cm. Do you tell a patient that they have an 8mm growth or polyp that will monitored with a repeat VC in one year, or two, or should the follow-up study be a CC? What percentage of those 30% or more should be referred on for colonoscopic examination and how much will this add to the total cost? Any endoscopist of experience can relate anecdotal experiences of small insignificant lesions that proved to be quite significant histologically; however, this is only statistically significant to the particular patient with the small, insignificant appearing lesion.

VC and CC have similar sensitivities for polyps as small as 7mm, but for the smaller lesions the false positive of VC increases to 13% (1). False positives could arise from an incomplete prep or poorly distended colon. Imagine the difficult position of the endoscopist in pursuing a “phantom” polyp. The patient has been told he, or she has a growth that needs to be removed and that it is in the area of the hepatic flexure. From the standpoint of an endoscopist, the only sure thing is the beginning, and the end. It is relatively easy to accurately localize a lesion within site of the ileocecal valve or some small distance from the rectal vault. Everything in between is more or less an educated guess, unless the colonoscope can be transilluminated through the abdominal wall (although a redundant transverse colon could be anywhere), or you might see the bluish tinge of the spleen, or liver—but, is it the liver, or the spleen? Perhaps the patient has a tortuous colon and is already a challenging case. How long do you look for the “polyp” that never was—30minutes…60? How much risk does this add to the procedure for the patient? How do you explain this to the patient and what should the protocol be—another colonoscopy or VC in one year, or two, or five?

The purpose of this article is not to segue into the economics of medicine, but simply to address which is best for the patient. Medicine is big business today more than ever and the technology is a big part of that. There have been billions of dollars spent on the development of sophisticated imaging techniques, of which VC is one, and these are being marketed aggressively for purposes perhaps ahead of their time.

There is a role for VC today, as utilized under the medicare guidelines discussed above, namely, as a supplement to conventional colonoscopy. At the current time, there is no role in my estimation for VC as a diagnostic exam (an exam in a symptomatic patient) as there is a high likelihood of biopsy for histological study, or polypectomy. Whether there will be a role for VC as a general screening study, remains to be seen. There needs to be careful consideration of the points raised above and some standardization not only in regards to the technique of VC itself, but also some consensus on the “target” and intervention or follow-up to be recommended. This will only follow further study and cooperation across specialties.

As the technology matures there may come a time when there may be a role for VC as a screening tool—perhaps for low risk patients, or even high risk patients (family history). If it occurs there should be a mechanism in place such that the patient would not have to suffer through two separate preps or remain on a clear liquid diet for more than a day. As a veteran of five colonoscopies myself I can assure you that twenty four hours of jello and juice is more than enough for my corpus. I see the ideal as consisting of close cooperation between the radiologist and endoscopist. This could be as simple as scheduling the VC in the morning during which there is an endoscopist is available that day to proceed with a colonoscopy, if needed. I think this would be a reasonable goal and one that would be accomplished, relatively easily, even at my own rural institution.

1) Pickhardt PJ, Choe JR, Hwang I, et al. Computed tomographic virtual colonoscopy to screen for neoplasia in asymptomatic adults. N Engl J Med. 2003;349:2191-2200.

2) Cotton PB, Durkalski VL, Pineau BC, et al. Computed tomographic colonography (virtual colonoscopy) multicenter comparison with standard colonoscopy for detection of colorectal neoplasia. JAMA. 2004;291:1713-1719.

3) Stryker SJ, Wolff BG, Culp CE, et al. Natural history of untreated colonic polyps. Gastroenterology. 1987;93:1009-1013.

4) Lieberman DA, Weiss DG, Bond JH, et al. Use of colonoscopy to screen asymptomatic adults for colorectal cancer. N Eng J Med. 2000;343:162-168.

5) Imperiale TF, Wagner DR, Lin CY, et al. Risk of advanced proximal neoplasms in asymptomatic adults according to the distal colorectal findings. N Engl J Med. 2000;343:169-174.