Briefly introduce the operation principle and common operation methods of rectal cancer.

The main surgical methods of rectal cancer are: ① local resection, which is suitable for patients with early rectal cancer, small tumor, limited to mucosa or submucosa and high tumor differentiation, and can be through anus or sacrum; (2) Abdominal perineum combined with Miles operation is suitable for rectal cancer below peritoneal folds in principle; ③ Abdominal rectal excision (Dixon operation) is suitable for rectal cancer more than 5cm away from anal margin; ④ Abdominal resection, proximal stoma and distal closure (Hartmann operation) for rectal cancer is suitable for patients who can't tolerate Miles operation due to poor general condition, or rectal cancer complicated with acute intestinal obstruction is not easy or suitable for Dixon operation.