Association Between Colonoscopy Withdrawal Time and Adenoma Detection: Evidence of a Continuous Dose-Response...

Background/Objectives: Colonoscopy withdrawal time is an established quality indicator, but ongoing debate exists regarding whether its relationship with adenoma detection follows a fixed threshold or a continuous dose-response pattern. Methods: We retrospectively analyzed 31,780 colonoscopies from a multicenter endoscopy database to evaluate the relationship between withdrawal duration and lesion detection. Withdrawal time was assessed as both a continuous and categorical variable, and adenoma detection rate (ADR) and polyp detection rate (PDR) were examined across quartiles and clinically relevant intervals. Results: ADR increased progressively from 7.72% in the shortest withdrawal-time quartile to 36.47% in the longest quartile, while PDR increased from 21.22% to 67.86% (both p for trend <0.001). In the multivariable analysis adjusted for age, sex, and bowel-preparation quality, each additional minute of withdrawal time was independently associated with higher odds of adenoma detection (adjusted OR 1.14, 95% CI 1.13-1.15; p < 0.001). Although the confidence interval was narrow, reflecting the large sample size, the effect was clinically appreciable: model-predicted adenoma detection increased from 13.6% at six minutes to 21.0% at eight minutes and 28.2% at ten minutes, corresponding to approximately seven and fifteen additional adenoma-positive examinations per hundred procedures, respectively. The association remained consistent across age and sex strata. Receiver operating characteristic analysis showed moderate discrimination (area under the curve 0.701), with a Youden-optimal region of approximately 7 to 8 min. Because recorded withdrawal time incorporates interventional time, the principal analysis of inspection effort was conducted at the level of the endoscopist, using withdrawal time measured exclusively in the 14,611 examinations in which no polyp was detected and no tissue was sampled. Among 107 endoscopists contributing 26,793 procedures, inspection time was associated with adenoma detection (Spearman ρ = 0.46; p < 0.001), corresponding to an absolute increase of approximately 1.5 percentage points per additional minute, with attenuation of the gradient beyond approximately seven minutes. Conclusions: The procedure-level findings above describe the association with recorded withdrawal duration as captured in routine practice and are reported as supportive rather than as estimates of inspection effort. Together these analyses indicate that inspection time is associated with adenoma detection in a graded manner extending beyond the historical 6 min benchmark.