Abstract:Objective To review the following colonoscopy of negative baseline screening colonoscopy crowd, and to explore the risk of colorectal tumor at different time intervals in different gender, age and risk levels. MethodsWith bicohort study design, selfmade questionnaire was used to survey the following colonoscopy of the asymptomatic averagerisk population with negative baseline screening colonoscopy from January 1, 1995 to December 31, 2005. The survey contents included all the following colonoscopy, the risk stratification factors of colorectal cancer (age, gender, smoking status, history of diabetes, green vegetables intake, pickled food intake, fried smoked food intake, white meat intake). The life table survival analysis method was used to study the cumulative risk of colorectal tumor in different gender, age, risk levels. ResultsFour hundred and fiftyfive cases were included, and there were 91 cases of colorectal polyp, 24 cases of adenoma and 9 cases of advanced tumor. The cumulative prevalence rates of colorectal polyp, adenoma and advanced tumor during 5 years for negative baseline screening colonoscopy crowd were 11.9%, 4.2% and 2.0% respectively. The cumulative prevalence rate of advanced tumor during 12 years was 3.9%. The risk of colorectal polyp of men was higher than that of female (χ2=8.142, P=0.004). The risk of colorectal polyp of ≥60 years group was higher than that of ＜60 years group (χ2=6.321, P=0.012). The risk of colorectal polyp of high risk group was higher than that of low risk group (χ2=4.082, P=0.043). ConclusionIn the negative baseline screening colonoscopy crowd, 5year cumulative prevalence rates of colorectal polyp, adenoma, advanced tumor are low, and 12year cumulative prevalence rate of colorectal advanced tumor is low too.

Key words:Colorectal neoplasms,Colonoscopes