The adenoma detection rate (ADR) is an important colonoscopy quality parameter. A longer withdrawal time is associated with increased adenoma detection; however, the effect of cecal insertion time on adenoma detection is unclear. The aim of this study was to evaluate if cecal insertion time is associated with adenoma detection.

The study included 50- to 89-year-old subjects undergoing an elective outpatient colonoscopy as part of a randomized trial on cap-assisted colonoscopy. The primary outcome was the adjusted mean number of adenomas per patient across quartiles of lengthening patient insertion times. Secondary outcomes included the mean number of advanced adenomas, ADR, and advanced ADR. Adjusted regression analysis was applied to assess for a possible trend.

Among 1043 included study subjects, the median cecal insertion time was 5.3 minutes (interquartile range [IQR], 3.5-8.1) and the median withdrawal time was 8.6 minutes (IQR, 7.1-10.7). Cecal insertion time was not associated with withdrawal time (P = .950). The mean number of adenomas per patient decreased across increasing insertion time quartiles from 1.1 to .7, corresponding to a 11% decline per quartile (P = .031). Similarly, the number of advanced adenomas decreased from .15 to .06, corresponding to a 7% decline per quartile (P = .013). The observed decrease in adenoma detection was similar for proximal and distal adenomas. Endoscopists’ individual insertion times were not associated with adenoma detection.

A longer cecal insertion time was associated with a decreased detection of adenomas and advanced adenomas. A long insertion time may be a marker for a more difficult examination that requires a longer withdrawal time to assure adequate examination and adenoma detection. (Clinical trial registration number: NCT01935180.)