Accurate assessment of colorectal polyp size is crucial for determining treatment and surveillance policies. However, visual estimation of lesion diameter is often inaccurate, making simple and effective educational tools essential. We aimed to evaluate the learning effects of virtual scale endoscopy (VSE).

Thirty-three endoscopists first watched prelearning videos for SET1. They then estimated the diameters of 20 lesions and referred to instructional videos with VSE for self-study. Subsequently, they watched the postlearning videos for SET2 and estimated the lesion diameters. The error between the estimated and correct lesion sizes of both sets was compared. To evaluate longer-term learning effects, participants answered SET3 and SET4, which consisted of the same questions as SET2 and SET1, respectively, but 2 to 3 months later without watching the instructional video for SET2.

The error in the participants’ estimation of the correct lesion diameter improved from SET1 to SET2 (34.7 ± 6.6 mm vs 30.7 ± 7.7 mm, P = .048), with a significant learning effect and error improvement specifically among nonexperts (35.2 ± 5.3 mm vs 30 ± 6.8 mm, P = .028). In SET3 and SET4, participants’ errors indicated that the learning effect was well maintained (SET2 vs SET3: 30.7 ± 7.7 mm vs 28.6 ± 7.2 mm [P = .1]; SET1 vs SET4: 34.7 ± 6.6 mm vs 31.7 ± 7.1 mm [P = .025]).

VSE videos are a valuable learning tool for estimating lesion diameter, particularly for novice endoscopists, both in the short and longer term.