Location of colorectal adenomas and serrated polyps in patients under age 50

Background The incidence of colorectal cancer, especially located in distal colorectum, is rising markedly in young patients. Conventional adenomas and serrated polyps have been widely recognized as precursors of colorectal cancer. Aim To investigate the correlation of polyp feature with polyp location in patients under age 50. Method Patients under age 50 who had received colonoscopy were included from 2010 to 2018. Clinical data including number, location, size, and histopathology of polyps were collected. Odd ratios and 95% confidence interval of adenomas with their location were calculated. Result In total, 25,636 patients aged 18-49 were enrolled, among which 4485 patients had polyps, with polyp detection rate of 17.5%. A total of 2484 and 2387 patients had conventional adenomas and serrated polyps, respectively. 76.0% advanced adenomas and 69.5% >= 10-mm serrated polyps were located in the distal colorectum. The detection rate of advanced adenomas was higher in patients aged 45-49. Patients with adenomas especially advanced adenomas in the distal colorectum were more likely to have advanced adenoma in the proximal colon. Conclusion Among patients under age 50, advanced adenomas and >= 10-mm serrated polyps were predominantly in the distal colorectum. Advanced adenomas tended to be found in patients aged 45-49. Our results might explain the rising trend of distal colorectal cancer and emphasize the necessity for colonoscopy screening among these populations.