AIM: To evaluate association(s) between withdrawal time and polyp detection in various bowel preparation qualities. METHODS: Retrospective cohort analysis of screening colonoscopies performed between January 2005 and June 2011 for patients with average risk of colorectal cancer. Exclusion criteria included patients with a personal history of adenomatous polyps or colon cancer, prior colonic resection, significant family history of colorectal cancer, screening colonoscopy after other abnormal screening tests such as flexible sigmoidoscopy or barium enema, and screening colonoscopies during in-patient care. All procedures were performed or directly supervised by gastroenterologists. Main measurements were number of colonic segments with polyps and total number of colonic polyps.RESULTS: Multivariate analysis of 8331 colonosco-pies showed longer withdrawal time was associated with more colonic segments with polyps in good(adjusted OR = 1.16; 95%CI: 1.13-1.19), fair(OR = 1.13; 95%CI: 1.10-1.17), and poor(OR = 1.18; 95%CI: 1.11-1.26) bowel preparation qualities. A higher number of total polyps was associated with longer withdrawal time in good(OR = 1.15; 95%CI: 1.13-1.18), fair(OR = 1.13; 95%CI: 1.10-1.16), and poor(OR = 1.20; 95%CI: 1.13-1.29) bowel preparation qualities. Longer withdrawal time was not associated with more colonic segments with polyps or greater number of colonic polyps in bowel preparations with excellent(OR = 1.07, 95%CI: 0.99-1.26; OR = 1.11, 95%CI: 0.99-1.24, respectively) and very poor(OR = 1.02, 95%CI: 0.99-1.12; OR = 1.05, 95%CI: 0.99-1.10, respectively) qualities.CONCLUSION: Longer withdrawal time is not associated with higher polyp number detected in colonoscopies with excellent or very poor bowel preparation quality. AIM: To evaluate association (s) between withdrawal time and polyp detection in various bowel preparation qualities. METHODS: Retrospective cohort analysis of screening colonoscopies performed between January 2005 and June 2011 for patients with average risk of colorectal cancer. Exclusion criteria included patients with a personal history of adenomatous polyps or colon cancer, prior colonic resection, significant family history of colorectal cancer, screening colonoscopy after other abnormal screening tests such as flexible sigmoidoscopy or barium enema, and screening colonoscopies during in-patient care. All procedures were performed or directly supervised by gastroenterologists. Main measurements were number of colonic segments with polyps and total number of colonic polyps .RESULTS: Multivariate analysis of 8331 colonosco-pies showed longer withdrawal time was associated with more colonic segments with polyps in good (adjusted OR = 1.16; 95 % CI: 1.13-1.19), fair (OR = 1.13; 95% CI: 1.10- A higher number of total polyps was associated with longer withdrawal time in good (OR = 1.15; 95% CI: 1.13-1.18), and poor (OR = 1.18; 95% CI: 1.11-1.26) fair (OR = 1.13; 95% CI: 1.10-1.16), and poor (OR = 1.20; 95% CI: 1.13-1.29) bowel preparation qualities. Longer withdrawal time was not associated with more colonic segments with polyps or greater number of colonic polyps in bowel preparations with excellent (OR = 1.07, 95% CI: 0.99-1.26; OR = 1.11, 95% CI: 0.99-1.24, respectively) and very poor OR = 1.05, 95% CI: 0.99-1.10, respectively) qualities. CONCLUSION: Longer withdrawal time is not associated with higher polyp number detected in colonoscopies with excellent or very poor bowel preparation quality.