Use of a novel polyp "ruler snare" improves estimation of colon polyp size.

Publication Type:

Journal Article


Gastrointestinal endoscopy (2015)


BACKGROUND AND AIMS: 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.

METHODS: Ten artificial polyps of predetermined sizes (4 mm-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, then with the modified ruler snare.

RESULTS: 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=0.002). 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<0.0001). Participants underestimated polyp size by a mean of 3.6 mm (interquartile range (IQR) -5 mm to -2 mm) with the standard snare and 1.8 mm (IQR -3 mm to 0 mm) with the ruler snare, which corresponded to a 44.2% improvement in accuracy with the ruler snare (p<0.05).

CONCLUSIONS: 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.