A prospective study of the frequency and the topographical distribution of colon neoplasia in asymptomatic average-risk Chinese adults as determined by colonoscopic screening

Background: The goal of this study was to determine the frequency of colorectal neoplasia in an asymptomatic Taiwanese population and the topographic distribution of lesions relative to age and gender. Methods: Colonoscopy was performed in 1846 consecutive asymptomatic adults undergoing a health evaluation in 2003. Neoplastic lesions were considered advanced if they exceeded 10 mm in size, had a villous component, or contained moderately or severely dysplastic tissue or invasive cancer. Lesions at and proximal to the splenic flexure were considered proximal in location; those distal to the splenic flexure were classified as distal in location. Results: Of 1741 (94.3%) patients (1041 men, 700 women; mean 52.5 years) enrolled, 1708 (98.1%) underwent total colonoscopy. Of these patients, 263 (15.4%) had colorectal neoplasia; 51 (3.0%) had advanced lesions. A total of 331 lesions were detected; 125 (37.8%) were proximal in location. Two thirds of patients with proximal advanced lesions (66.7%, 10/15) had no distal lesion. The proportion of patients with proximal or proximal plus distal lesions increased with age (p = 0.027). Conclusions: Colonoscopy is an effective primary screening modality for colorectal neoplasia in asymptomatic Chinese patients. Many lesions would be missed, especially in the elderly, if only sigmoidoscopy was used for initial screening.