Colon Polyps : Prevalence
The prevalence of adenomatous polyps in a population is related to the risk of developing colon cancer. The prevalence rates are lower than 12% in populations at low-risk for colon cancer. In moderate or high-risk populations, adenomatous polyps are found in 30% to 40% of the individuals. A population of asymptomatic, healthy individuals over age 50 years and with an average risk of colon cancer will show adenomas in 27% to 32% on screening colonoscopy. About 6% to 10% of these will be adenomas with advanced pathology (one or more of: size > 1cm, villous component, high-grade dysplasia or carcinoma). Men have a slightly higher prevalence of adenomas as well as adenomas with advanced pathology (relative risk of 1.5) as compared to age-matched women. African-Americans show slightly higher rate of larger polyps as well as more proximal locations as compared to age-matched whites. Age is the single most important factor influencing adenoma prevalence. Advanced age is associated with higher prevalence rate of adenomas, greater likelihood of multiple polyps, greater degree of dysplasia, and larger size of adenomas. The prevalence of adenomas is greater in individuals with a family history of colorectal carcinoma and adenomas, particularly if multiple family members are affected or affected at young age. This specimen photograph shows a large tubular adenoma.