ASGE Masterclass: Expert Performance Approach to Colonoscopy (Live/Virtual) | February 2026-How Experts Detect Nonpolypoid Colorectal Lesions

Video Transcription

Video Summary

The speakers teach a systematic method for detecting subtle, flat colorectal lesions during colonoscopy. The core approach is to first identify “normal” mucosa—smooth folds, consistent color, visible vessels, and regular innominate grooves/crypt patterns—then look for any disruption. Once a disrupted “patch” is noticed, the endoscopist should define its borders and compare it with surrounding normal tissue to judge size and significance, building a mental classification map (neoplastic vs serrated patterns).<br /><br />They walk through multiple examples, narrating visual cues that draw attention: missing or interrupted vessels, localized redness, thickness or elevation within a fold, deformity of the wall, loss/interruption of grooves, and texture changes. Experts often act on just one or two prominent abnormalities rather than requiring every criterion.<br /><br />For sessile serrated lesions (SSLs), key features include mucus cap, cloud-like or “layered” surface texture, indistinct borders, and “O-sign” (dilated/open crypts). Neoplastic (adenomatous) lesions are emphasized as a different mental map from serrated lesions.<br /><br />They advise avoiding biopsy of resectable flat lesions because it can cause fibrosis and hinder later removal. Accurate size estimation matters for management and surveillance; tips include using known device diameters (cap, snare size, sheath) and measuring before submucosal injection because lifting—especially in serrated lesions—can enlarge apparent size. A “cookie monster” sign (a fold that looks “bitten out”/missing) is highlighted as concerning and may be more obvious with partial desufflation.

Keywords

colonoscopy

flat colorectal lesions

subtle lesion detection

normal mucosa assessment

mucosal pattern disruption

sessile serrated lesions (SSL)

mucus cap

O-sign (dilated crypts)

adenomatous neoplastic lesions

lesion size estimation