Flexible sigmoidoscopy or colonoscopy as a screening modality for colorectal adenomas in older age groups? Findings in a cohort of the normal population aged 63-72 years.

Background: Most cases of colorectal cancer originate from adenomas. Removing adenomas has been shown to reduce the incidence of colorectal cancer. The design of cost effective endoscopic screening programmes requires a knowledge of the distribution of adenomas in different age groups.

Aim: To investigate the distribution of colorectal adenomas in older age groups in the normal population.

Method: A total of 356 men and women selected randomly from the population register were offered a colonoscopic screening examination to detect and remove polyps.

Results: In all, 241(68%) subjects, mean age 67.4 years (range 62-73), attended. The caecum was intubated in 193 (80%), and in this group 32 (38%) women and 51 (47%) men had adenomas. One hundred and ten (54%) of the adenomas and 11 (39%) of the "high risk adenomas" (adenomas larger than 10 mm in diameter, adenomas containing villous components, and adenomas with severe dysplasia) were found proximal to the sigmoid colon. In 36 (43%) of the subjects with adenomas, the adenomas were only found proximal to the sigmoid colon. Twenty two (11%) subjects had more than two adenomas. Of 203 adenomas discovered, 189 (93%) were less than 10 mm in diameter.

Conclusion: More than half of the adenomas were localised proximal to the sigmoid colon, and, in nearly half of the adenoma bearing subjects examined, the adenoma was proximal to the descending colon. This indicates that a sigmoidoscopic screening examination in this age group would miss a substantial number of adenomas, but this may be acceptable as the vast majority of proximal adenomas do not progress to clinical cancer within the life expectancy of this age group.