Usefulness of a novel calibrated hood to determine indications for colon polypectomy: visual estimation of polyp size is not accurate

Accurate measurement of polyp size during colonoscopy is important because the size is a surrogate marker of cancer, but a standardized measurement technique to measure polyp size has yet to be determined. We have developed a new device a novel calibrated hood. We assessed polyp size by visual estimation and measurement using the calibrated hood. Patients who underwent polypectomy from November 2012 to September 2013 and who had received screening colonoscopy within 6 months prior to the polypectomy were included in this study. Polypectomy was performed attaching the calibrated hood. The endoscopist measured the polyp size using the calibrated hood. Polyp size was compared between visual estimation and measurement using the calibrated hood. Seventy-five patients with 157 polyps were included. Seventy-seven polyps fulfilled the selection criteria. Mean polyp size by visual estimation was 6.57 +/- 2.15, and by using calibrated hood was 5.94 +/- 1.73 (p = 0.005). There was a significant difference between measurements using the calibrated hood vs. visual estimation by inexperienced trainees; however, there was no difference in case of well-experienced endoscopists. By visual estimation, 11 of 19 polyps were decided for a parts per thousand yen5 mm despite being less than 5 mm, and 5 of 58 polyps were decided for < 5 mm despite being 5 mm or larger in diameter. Visual estimation of polyp size is not accurate. It is important to measure the size by an objective way, and the calibrated hood is useful in measuring polyp size, from the standpoint of accurately determining indication for polypectomy.