Department of Diagnostic Radiology, Institution for Molecular Medicine and Surgery, Karolinska University Hospital, Karolinska Institute, Stockholm, Sweden.
BACKGROUND: The size of colorectal polyps is important in the clinical management of these lesions. When using a conventional ruler (the tool of pathologists worldwide), we have previously found unacceptably high intra- and inter-observer variations in assessing the size of phantom polyps. The aim of this study was to assess the size of 12 phantom polyps by computed tomography (CT). MATERIALS AND METHODS: The size of phantom polyps as assessed by CT was compared to the gold standard size (GSS) measured at The Royal Institute of Technology, Stockholm, Sweden. RESULTS: In 33.3% (n=4) of the 12 polyps and in 41.7% (n=25) of the 60 measurements, the mean CT size under- or overestimated the GSS by more than 1 mm. In 15%, or in 9 of the 60 measurements, the CT size was under- or overestimated by more than 2 mm. In polyp #5 the GSS size was 8.41 mm where the expected cancer-risk in adenomas is 1%. But 3 out of 5 CT measurements were >10 mm, where the expected cancer-risk in adenomas is 10%. In polyp #10 the GSS size was 10.20 mm where the expected cancer-risk is 10%. But 2 out of 5 CT measurements were