Controversies in Documentation
C-RADS is a system based on a consensus recommendation that was put forth by an international body of experts in CT colonography. It is still not considered a generally applicable guideline, but rather is included as an optional guideline by the American College of Radiologists. CT colonography has already been added to the guidelines of the American Cancer Society as a possible examination technique for the early detection of colorectal cancer.
In a few European countries, and at some centers in the United States, C-RADS has been integrated in the interpretation of findings and has also been adopted by some national radiological guidelines. The implementation of C-RADS in a hospital unit requires its acceptance by referring physicians, however. The divergence of opinions on this system is also evident in the recommendations of the American Gastroenterological Association (AGA) on documentation (see above).
C-RADS is primarily intended for the management of screening patients. The underlying system of ignoring all small polyps (<6 mm) and following up medium-sized polyps (6–9 mm) is particularly criticized by gastroenterologists. The argument is that 95% of all colonic polyps are smaller than 1 cm, and this would mean leaving the overwhelming majority of colorectal polyps in place. This recommendation would appear, then, to directly contradict the fact that the incidence of colorectal carcinoma can be reduced only by colonoscopic removal of detected precancerous polyps. Another point that is criticized is the recommendation that polyps measuring 6–9mm in size should be followed up with CT colonography rather than removed. The recommended interval is 1–3 years. This not only increases the associated costs, but also theoretically increases the risk of cancer and the patient radiation dose. Some argue that insufficient data exist to define and recommend a follow-up interval and whether follow-up should be by CT colonography or by optical colonscopy. In addition, one must take into account the views of the patient. It is conceivable that a patient who knows that he or she has a potentially “dangerous” lesion in the colon would prefer to have it colonoscopically removed rather than wait for follow-up.
Opinions also diverge with regard to lesions smaller than 6 mm. The documentation of diminutive polyps may unnecessarily create the impression among both patients and referring physicians that a lesion has been identified which requires treatment. Many of the small polyps that are detected at CT colonography are not identified at follow-up colonoscopy, either because the CT colonography results were false-positive or because the optical colonoscopy was false-negative. In addition, the overall sensitivity of CT colonography for small polyps is methodologically limited; the possibility of differentiating them from stool particles adhering to the colon wall on the basis of typical morphological CT colonographic criteria is limited (see Chapter 4, “Polypoid Lesions of the Colon,” pp. 91 ff). Colonoscopic follow-up of diminutive polyps in a screening program would lead to high costs and an increase in the rate of colonoscopy-related complications (due to perforation and bleeding). Higher costs and more complications appear unwarranted given the large number and low clinical significance of these lesions. However, different opinions also exist among the gastroenterologists about the treatment of diminutive colonic lesions. While some gastroenterologists have suggested that colonoscopy referral might be considered for isolated diminutive lesions detected at CT colonography, a large volume of scientific data indicates that clinicians may need to shift their attention away from simply detecting and removing all diminutive colorectal adenomas toward strategies that allow the reliable detection of the much less common, but much more dangerous, advanced adenoma (Bond 2001).
Finally, some experts in CT colonography believe that the clinical decision or recommendation as to whether a polyp needs to be resected or not, should not be made primarily by a radiologist. The decision should be made by the endoscopist, who is responsible for the procedure and who knows about the personal history and the personal risk of the patient.
These opposing views make it clear that when a model for documentation is introduced, in particular with regard to the management of small and medium-sized polyps, consensus must be obtained with the referring gastroenterologist and surgeon. There is a need for standardized guidelines from radiology societies that have been developed together with gastroenterologists and surgeons. Referrals for CT colonography can then be made by physicians in full knowledge of the limitations relating to small polyps. Some radiologists add to their reports a note on the limitations of CT colonography as well as a remark that small polyps are not reported.