Bowel preparation and colonoscopy
Eligible participants were randomly assigned to the experimental group or the control group. The experimental group was given a 3 L split-dose regimen (1 L PEG was taken at 8:00 pm one day before the colonoscopy date, and 2 L PEG was taken 4-6 h before the colonoscopy). The control group was given a single dose regimen of 2 L PEG, taken 4-6 h before the colonoscopy.The laxative was PEG electrolyte powder (specification: 68.56 g/bag or 137.15 g/bag, Shenzhen Wanhe Pharmaceutical Co., LTD.), whose main component was PEG 4000. Once enrolled, each participant received a uniform education both verbally and in writing. Participants were guided to consume a low-residue diet one day before the colonoscopy (Supplementary Table 