1. The study was a multicenter, prospective,single-blind, randomized controlled study involving patients who underwent a colonoscopy from February 2016 to December 2016. It was conducted according to the Declaration of Helsinki Principles and was approved by the institutional review board of our hospital (2016LL001). The study was reported according to the CONSORT guidelines and was registered at www.clinicaltrials.gov. Written informed consent for this study was obtained from all patients.