Introduction Colonic polyp size is a factor in determining management and prognosis of patients. Polyp diameters greater than 9 mm require ongoing colonoscopic surveillance.¹ Accurate endoscopic estimation of polyp size can be affected by depth perception and parallax errors. We compared endoscopic versus histological size assessments to determine if accurate estimation was operator-dependent.

Methods Symptomatic and asymptomatic (bowel screening) patients were identified from hospital databases. Endoscopic and histological polyp diameters were reviewed. Agreement levels between these were analysed by deriving intraclass correlation coefficient (ICC) using SPSS software (Version 20).

Results Sixteen colonoscopists were included: 5 bowel screening, 7 non-bowel screening and 4 trainees. Five hundred and ten polyps (n = 510) were found among 299 patients (186 males, 104 females). Two hundred eighteen polyps were enbloc resected, retrieved whole and analysed. Overall accuracy of polyp size assessment was good (ICC > 0.70) with variability between skill levels (Table 1).

Accuracy was best among polyps ≥20 mm diameter (ICC 0.99, p < 0.001); all removed by bowel screening colonoscopists. Polyps between 8 to 12 mm demonstrated poor correlation (ICC (absolute agreement) 0.535, P = 0.002).

Conclusion While endoscopic estimation of polyp diameter is accurate, variability exists. Estimations are more accurate among bowel screening endoscopists suggesting experience and/or colonoscopy workload contribute to this skill. Poor diameter estimations among polyps 8–12 mm has implications for polyp surveillance intervals. Standardising diameter using against closed or open biopsy forceps (width 2.2 and 8 mm respectively) to optimise accuracy should be used.

Reference 1 Cairns, et al. Guidelines for colorectal cancer screening and surveillance in moderate and high risk groups (update from 2002). Gut 2010;59:666–690

Disclosure of Interest None Declared.