Background: Accurate measurement of polyp size during colonoscopy is important because of the direct correlation of size with colon cancer. Major studies of colorectal neoplasms have measured polyp size differently. It is also well documented that endoscopists underestimate polyp size frequently. The goal of this prospective study was to determine which one of the five methods of estimating polyp size during colonoscopy is most accurate.
Methods: One hundred colon polyps were measured by means of visual estimation, open biopsy forceps methods, linear probe, a ruler immediately after excision, and after fixation in formalin. The size of the polyps measured outside the body immediately after excision was considered the "gold standard" against which all measurements were compared.
Results: Forty-seven polyps were 5 mm or less in diameter, 33 polyps were 5.01 mm to 10 mm, and 20 polyps were more than 10 mm in size. For all polyps the mean difference versus the actual size of the polyps was 3.4% for linear probe, 6.4% for visual estimation, and 12.3% for the forceps.
Conclusion: Measurement of polyp size by linear probe agreed best with the actual polyp size, followed closely by visual estimation. The open biopsy forceps method was the least accurate.