Use of a novel polyp “ruler snare” improves estimation of colon polyp size

Abstract

Prior studies have demonstrated that endoscopists' estimates of polyp size are imprecise. The aim of this study was to determine whether a modified polypectomy "ruler snare" improves the accuracy of assessment of polyp size in real time without the use of additional devices. Ten artificial polyps of predetermined sizes (4 to 25 mm) were affixed to the inside of a colon model. A standard polypectomy snare was modified by adding 5-mm graduated markings to the distal end of the plastic sheath. Study participants estimated the sizes of the artificial polyps during simulated colonoscopies, first using a standard snare and then with the modified ruler snare. Thirty-four private practice and academic gastroenterologists participated in the study. Endoscopists' ability to accurately classify polyps by size (diminutive, small, or large) improved from 48.5% to 60.3% with the ruler snare (P = .002). The greatest improvement in precision was seen among the large polyps, where accuracy increased from 35.9% to 58.2% with use of the ruler snare (P < .0001). Participants underestimated polyp size by a mean of 3.6 mm (interquartile range, -5 to -2 mm) with the standard snare and 1.8 mm (interquartile range, -3 to 0 mm) with the ruler snare, which corresponded to a 44.2% improvement in accuracy with the ruler snare (P < .05). The modified ruler snare improved polyp size assessment compared with a standard snare, particularly with large polyps. Overall, although size estimation continues to be imprecise, the addition of calibrated markings to a polypectomy snare is a simple and likely low-cost means to improve neoplasia surveillance recommendations.