As a good niche for bacterial growth, appendix plays a very important role in maintaining and protecting intestinal symbiotic flora. Appendectomy will lead to intestinal microecological disorders. Therefore, we put forward the hypothesis that "appendectomy leads to intestinal microecological disorders and then increases the risk of colorectal cancer". In this study, the feces of normal controls, appendectomy and patients with colorectal cancer were collected, and the specific changes of intestinal flora after appendectomy were explored in detail from the level of family, genus and species by macrogenomic sequencing. Then through functional gene analysis, metabolic pathway analysis and other methods to explore the molecular mechanism of colorectal cancer risk changes and the changes of microflora involved, and verified by mouse fecal bacteria transplantation animal experiment.

Inclusion Criteria:

• Patients undergoing appendectomy due to appendicitis;
• 6-36 months after appendectomy;
• Patients with no obvious abnormality observed by colonoscopy;
• Age between 20 and 85.

Exclusion Criteria:

• A. Any history of malignancy or disease
• Any inflammatory bowel disease (IBD) prior to study inclusion;
• Antibiotics and hormone drugs taken within the last three months;
• Patients with severe systemic diseases (severe diabetes, hypertension or autoimmune diseases, etc.);
• Severe clinical symptoms of digestive tract (severe diarrhea, constipation, purulent disease, etc.) within half a year.

Patients with an appendectomy and meet the above conditions