[Virtual colonoscopy--and then? Relevance of small colorectal polyps]

Colorectal carcinomas are the second most frequent malignant tumors in Germany and originate predominantly from benign polyps (adenoma-carcinoma sequence). Optical colonoscopy is still the gold standard for diagnosis and treatment colorectal polyps. However, CT colonography ("virtual colonoscopy") provides an alternative procedure with similar diagnostic performance but without the possibility of endoscopic polypectomy. Because of the high prevalence (approx. 30 %) of colon polyps in the screening population, virtual colonoscopy is useful for screening only, if a small number of the lesions must be subsequently removed endoscopically. Most of these lesions must represent such a low risk of malignant transformation in order for a control examination to be sufficient. According to a comprehensive review of the literature, the risk potential of small polyps up to a size of 5 - 6 mm can be summarized as follows: Up to 75 % of all polyps found in screening programs belong to the group of "small polyps". Only approx. 1.5-2 % of these contain advanced atypia and less than 0.05 % are carcinomas. Growth speed lies in the range of approx. 0.4 mm in 2 years, but regression can be observed as well. The very few existing growth studies cannot provide reliable information about how quickly these small lesions may turn malignant.

The risk potential of small polyps can be considered to be low. Nevertheless, because only poor data is available, a definitive statement cannot be made about the spontaneous course of these lesions. Therefore, further studies examining the natural growth behavior of small polyps are necessary, before control examinations (in intervals of two to three years) rather than immediate endoscopic polypectomy can be recommended as an adequate approach in screening programs.