According to American Cancer Society guideline, screening total colonoscopy every 10 years or sigmoidoscopy every 5 years is recommended for average risk people above 50 years old. However,study in Taiwanese population demonstrated that 37.8% of colorectal lesions were beyond reach of sigmoidoscope, and in cases with lesions with advanced pathology, 66.7% did not have distal colorectal lesion. However, many people think colonoscopy is more painful and choose sigmoidoscopy for screening. However, according to experience in a self-payed health check-up center,unsedated total colonoscopy is not inferior or may be better than unsedated sigmoidoscopy in terms of pain and patients' acceptance.
According to experience in a self-payed health check-up center,unsedated total colonoscopy is not inferior or may be better than unsedated sigmoidoscopy in terms of pain and patients' acceptance.~Hypothesis: Unsedated total colonoscopy is not inferior to unsedated sigmoidoscopy in terms of pain and patients' acceptance.