To investigate the risk factors of advanced colorectal adenoma(ACA)and high-risk adenoma.

A retrospective analysis was conducted on the data of 4 573 patients with 10 653 adenomas, who received endoscopic polypectomy at the Day Surgery Center of West China Hospital of Sichuan University from January 2014 to December 2019. Patients were divided into advanced adenoma group (1 205 patients with 1619 adenomas) and non-advanced adenoma group (3 368 patients with 9 034 adenomas) according to the diameter, the villous component or high-grade dysplasia of the adenoma. Age, gender, body mass index of patients, distribution, morphological classification of the colorectal adenoma polyps, melanosis coli and family history of colorectal cancer(CRC) in first-degree relatives(FDRs) were compared between two groups at the perspective of polyps and patients, separately. Besides, we divided the subjects into high-risk adenoma group(2 141 patients) and non-high-risk adenoma group(2 432 patients) based on the number of adenoma and pathological characteristics. The differences in age, gender, body mass index, melanosis coli and family history of CRC in FDRs were compared between the two groups. Risk factors of ACA and colorectal high-risk adenoma were analyzed by multivariate Logistic regression model.

Advanced colorectal adenomas accounted for 15.2% of all colorectal adenomas in this study. For a single adenoma, the distribution (distal colon)and the morphological classification (pedunculated and sessile adenomas) were significantly different between two groups(P<0.05), which were confirmed to be the independent risk factors of ACA. ACA counted 1.244 times in the distal colon than which in the proximal colon. Compared with flat adenomas, the risks of ACA for pedunculated and sessile adenoma were significantly higher, which were 23.948 times and 3.426 times than which for flat adenomas. For a single patient, there were statistically significant differences between the two groups in age (41-60 years old, >60 years old), gender (male), melanosis coli and family history of CRC in FDRs(P<0.05), which were independent risk factors for patients with high-risk adenomas. The risks of high-risk adenoma in patients aged 41-60 and over 60 were 1.733 times and 2.489 times than who under 40. The risk of high-risk adenoma in men was 1.294 times than that in women. Colorectal adenoma patients with melanosis coli and with family history of CRC in FDRs had increased risk of high-risk adenomas to 1.972 times and 1.765 times, respectively. There were no statistically difference in BMI between two groups(P>0.05)and it was not an independent risk factor for high-risk adenoma.

Distal colonic adenoma, pedunculated and sessile adenoma were independent risk factors of ACA. Ages beyond 40, males, melanosis coli, family history of family history of CRC in FDRs were independent risk factors for high-risk adenoma. This study has great clinical significance for the risk stratification of colorectal adenomas cancerization and it aims to further promote the early diagnosis and treatment of precancerous lesions for colorectal tumors as well as the prevention and treatment of colorectal cancer.