Inclusion Criteria:  Patients aged 18 to 75 years for unsedated colonoscopy for colorectal cancer screening, polyp surveillance, or polyp resection were enrolled.  Exclusion Criteria:  Patients who underwent sedation or analgesia before colonoscopy, and were reluctant to cooperate or provide informed consent. Those who were suffering from too serious diseases to tolerate the examination. The intestinal segment was incomplete or the colonoscopy did not reach the cecum.