Expert Endoscopist Agreement for Size Measurement of Large (> 2 cm) Colorectal Laterally Spreading Tumors: A...

Accurate size estimation of large (≥ 20 mm) colorectal laterally spreading tumors (LSTs) is essential for procedural planning, risk stratification, and predicting technical difficulty. Yet, the reliability of visual LST size assessment among endoscopists has not been systematically evaluated.

46 LSTs were recorded during colonoscopy. Twenty-four international expert endoscopists independently reviewed de-identified videos and provided visual estimates for (1) maximal diameter, (2) oral-anal axis, (3) left-right axis, and (4) percentage of colonic circumference involved. Each lesion was assessed twice in randomized order. Fleiss's kappa, Krippendorff's alpha, and intraclass correlation coefficients (ICC) were used to evaluate inter- and intra-rater agreement.

A total of 1104 measurements were collected. Inter-endoscopist kappa agreement for maximal diameter was poor (κ = 0.16), with similarly poor agreement for the oral-anal (κ = 0.15) and left-right axes (κ = 0.14). The percentage of circumferential involvement demonstrated moderate reproducibility (ICC 0.74 and 0.70 across rounds). Subgroup analyses showed consistently poor agreement for larger lesions for diameter-based methods, whereas circumferential percentage estimation ranged from poor to good depending on LST size and morphology. Intra-endoscopist agreement for diameter- and axis-based approaches showed wide variability (κ range 0.01-0.67), while circumferential estimates achieved good to excellent agreement for most endoscopists.

Visual estimation of large colorectal LST size is highly variable among expert endoscopists. Maximal diameter and axial lengths demonstrate poor inter- and intra-observer reliability. Circumferential extent is the most reproducible descriptor and may be the preferred approach for reporting LST size in clinical practice and research.