Colonoscopic screening of an average-risk population for colorectal neoplasia

Background and study aims: The role of screening colonoscopy in an asymptomatic, average-risk population remains to be determined. Moreover, the value of screening colonoscopy in individuals older than 75 years and for right-sided lesions has recently been questioned. The aims were to assess: (i) the risk of colorectal neoplasia in a large consecutively screened asymptomatic average-risk population, aged 40 – 85 years; (ii) whether colonoscopy is better than sigmoidoscopy for primary screening; and (iii) the prevalence of right-sided lesions at different ages.

Patients and methods: This prospective study, analyzed data from 1563 consecutive, asymptomatic, average-risk individuals, aged 40 – 85 years, who underwent screening colonoscopy.

Results: Overall, neoplastic lesions were detected in 262 individuals (17 % of the study population), of whom 75 had advanced lesions (5 % of population) and nine had colorectal cancers (CRC) (0.6 % of population). The prevalence of all lesions increased with age, with the highest percentages in the > 75 age group (26.5 % with neoplastic and 6 % with advanced lesions). Higher age was also associated with relatively more right-sided lesions. In particular the prevalence of proximal neoplasia, without concurrent distal neoplasia, increased from 5 % in those < 50 years to 24 % in those > 75 years. Those with distal lesions had a higher overall risk for proximal lesions (odds ratio [OR] 3.2); nevertheless flexible sigmoidoscopy alone would have missed up to 40 % of all lesions and up to 3.5 % of advanced neoplastic lesions in this patient subgroup.

Conclusions: Screening colonoscopy in asymptomatic, average-risk individuals is mandatory, as noteworthy numbers of advanced colorectal neoplasias have been detected in all age groups, especially in those aged > 75. Most importantly, many of the detected lesions were proximal and would not be revealed by sigmoidoscopy alone.

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