Virtual Colonoscopy: Time for Some Tough Questions for Radiologists and Gastroenterologists

The study by Kay and colleagues in this issue of Endoscopy [1], when published in abstract form [2] [3] was the first blinded prospective study (to my knowledge) to demonstrate a sensitivity of computed tomographic (CT) colonography of ≥ 90 % for polyps ≥ 1 cm in size. Prior to publication of this study in manuscript form, others have reported similar sensitivity for CT [4] [5] [6] or magnetic resonance (MR) [7] colonography, and perhaps extended this level of sensitivity to 6 - 9 mm polyps [8]. CT and MR colonography are continuing to evolve rapidly and improve. Image acquisition will be faster and better with multislice scanners, which are being installed in the United States at a remarkable pace. Image rendering and display have improved, and will improve, at an even more rapid pace. lt seems all but certain that CT and MR colonography will achieve sufficient sensitivity and specificity to become important options in colorectal neoplasia screening, diagnosis, and surveillance.

In fact, considering performance characteristics alone, CT and MR colonography could now legitimately enter clinical practice. There would be several potential advantages to the use of these techniques right now: 1) a performance almost certainly better than that of barium enema; 2) a better safety profile than diagnostic colonoscopy; 3) a very rapid scan time; and, most importantly, 4) the potential for acceptance as a screening test by a substantial segment of the population that will not accept current screening modalities. The last advantage likely depends significantly on calling the technique “virtual colonoscopy”, since the word “virtual” has an almost magical attractiveness for the lay public and many physicians. Although I was earlier opposed to using this term because it is not as accurate a descriptor as “CT (or MR) colonography”, I now favor it, solely because it seems to improve dramatically the marketability of the techniques.

The equipment and software needed to perform virtual colonoscopy are, in fact, readily available at this time. Radiologists seem eager to learn and to introduce virtual colonoscopy, and one frequently reads that virtual colonoscopy may obviate the need for diagnostic colonoscopy [9] [10] [11] . The enthusiasm of radiologists certainly arises in part from the very low reimbursement for double-contrast barium enema (DCBE) relative to that for abdominal-pelvic CT or MR scans. In Indiana the combined professional and technical fee allowed by Medicare for DCBE is $ 122. This puts DCBE in a situation analogous to that of flexible sigmoidoscopy, where reimbursement is often less than the cost of doing the procedure.

As virtual colonoscopy begins to enter the marketplace, there are several tough questions that appear unanswered at this time, but which should soon be directly confronted by radiologists. As the technique evolves, the answers to these questions may change. To the extent that the techniques are considered investigational, these questions may be premature. However, the answers will be needed soon enough, and the need for answers will be in direct proportion to the extent that the techniques enter practice. The answers to these questions will be prominent among the factors defining the appropriate use of, indications for, and cost-effectiveness of virtual colonoscopy.

References

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