Evaluating the Clinical Value of Transparent Cap-Assisted Second Examination of the Sigmoid Colon for Improving Colorectal Adenoma Detection Rates

Inclusion Criteria: * aged 45-75 years Exclusion Criteria: * Patients scheduled for therapeutic colonoscopy as postoperative surveillance after colorectal surgery, post-polypectomy follow-up, or treatment of histologically confirmed polyps * Patients with highly suspected or pathologically confirmed colorectal cancer * Patients presenting with alarm symptoms or signs (hematochezia, melena, unexplained anemia or weight loss, palpable abdominal mass, or a positive digital rectal examination) * Pregnant or breastfeeding women * Patients with gastrointestinal obstruction * Patients with inflammatory bowel disease, familial adenomatous polyposis, or serrated polyposis syndrome * Patients who have taken anticoagulants (e.g., aspirin, warfarin) within 7 days before colonoscopy or who have coagulation disorders * Patients currently enrolled in another clinical study or who participated in any clinical trial within the past 60 days * Insertion failure for any reason (e.g., scope cannot pass an obstruction, patient cannot tolerate the procedure) or colonoscopy not reaching the cecum * A Boston Bowel Preparation Scale (BBPS) score \< 6 at scope insertion (inadequate preparation requiring repeat bowel cleansing) * Use of non-guideline-recommended bowel preparation agents * Patients undergoing emergency colonoscopy * Inadequate withdrawal time (defined as a withdrawal time \<6 minutes during the first examination or \<2 minutes during the second examination)