The upper end of rectum is in the plane of the third sacral vertebra, connected to the sigmoid colon, and the lower end is connected to the anal canal at the dentate line, which is about 12-15 cm long; the surgical anal canal is from the dentate line to the anal verge, which is about 1.5-2 cm long; middle and lower rectal cancer refers to cancer tumors located in the middle and lower 2/3 of the rectum. Usually, clinical examination (rectal examination) is used to determine that rectal cancer within 10 cm from the anal verge is middle and lower rectal cancer, and above 10 cm is upper rectal cancer. The surgical methods and resection scope of middle and lower rectal cancer that can be resected can be divided into two categories: anus-preserving and non-anus-preserving. Anal-preserving surgery mainly includes anterior resection (Dixon surgery), local resection (transanal, transabdominal and sacrococcygeal routes) and drag-out resection (Bacon surgery); non-anal-preserving surgery mainly includes transabdominal perineal proctocolectomy (Miles surgery) and Hartmann surgery. The main points of the surgery and the scope of resection are explained by the example of transabdominal perineal proctocolectomy (Miles surgery) and anterior resection (Dixon surgery). I. Transabdominal perineal proctocolectomy (Miles surgery) is suitable for low rectal cancer, which cannot guarantee the removal of 3cm of normal intestinal canal distal to the tumor even after adequate freeing of the rectum during surgery; or the tumor invades the anorectal ring and other surrounding tissues; or the operation of low anastomosis in the pelvis is difficult due to pelvic stenosis, patient obesity, etc. 1.Stone amputation position. Sterilize the towel, insert the catheter and suture the anus closed. 2.Median incision in the lower abdomen, around the right side of the umbilicus. 3.Probe the abdominal cavity, pay attention to explore the upper abdomen first, especially the liver, and do intraoperative ultrasound if necessary to exclude liver metastases; then check the colon to understand whether there are multiple primary lesions: finally check the rectum to clarify the primary site and decide whether to use Miles surgery. 4.Ligate the lower part of sigmoid colon and inject anti-cancer drug 5-fluorouracil 1000-1500mg in the intestinal cavity. 5.Open the peritoneum in front of the abdominal aorta, free and remove the lymphatic fatty tissue next to the inferior mesenteric artery until the superior rectal artery, ligate and cut at the second branch of the sigmoid artery, or ligate and cut at the root of the inferior mesenteric artery. 6.Lift the sigmoid colon, cut its left posterior peritoneum, and free the sigmoid mesentery from the posterior abdominal wall. Then peel off the adipose tissue in front of the left common iliac artery and vein. The right posterior peritoneum of the sigmoid colon was incised and separated to the lateral side of the right ureter and cleared of adipose lymphatic tissue. Care should be taken not to free and damage the bilateral ureters and their surrounding tissues, and to pay attention to their orientation. 7.The rectum should be separated according to the principle of TME, which is performed within the gap between the intrinsic fascia of the rectum and the fascia of the pelvic wall, without damaging the inferior abdominal nerve, the presacral venous plexus and the pelvic nerve plexus. Separate its posterior and lateral parts first, down to the tip of the coccyx and the plane of the levator muscle on both sides, and then separate the rectum anteriorly to the plane of the tip of the prostate. 8. Separate male patients along the posterior wall of the bladder, vas deferens, seminal vesicles, and prostate, and female close to the posterior wall of the vagina. The separation should be far from the rectum to avoid perforation of the anterior rectal wall. Be careful not to damage the ureter. 9.Cut the ligaments on both sides with the electric knife and free the rectum downward near the pelvic wall to remove the fatty lymphatic tissue of the two pelvic walls. 10.The sigmoid colon was cut off according to the aseptic technique, and an abdominal wall stoma was made at the appropriate position in the left lower abdomen, and the sigmoid colon was properly sutured to the lateral abdominal wall to avoid internal hernia. 11.The perineal group can start the operation when the abdominal exploration decides that Miles operation can be performed. Double purse-string sutures are required for the anus. A skin shuttle incision is made around the anus, and the fatty tissue of the colorectal fossa should be excised more extensively. 12. The caudal ligament is severed in front of the coccyx, and the levator muscle is separated and severed on both sides near the pelvic wall. Pull the anal canal forward, cut the superior levator muscle transversely and enter the posterior pre-sacral space of the rectum. Cut and enlarge the superior levator muscle on both sides and pull out the free and severed sigmoid colon and rectum from the pre-sacral area to facilitate the separation of the anterior rectal wall. 13.Cut the deep forward crossed fibers of the external anal sphincter and place the index finger and middle finger into the pelvis between the posterior prostate (posterior vaginal wall) and the rectum. The rectum is excised by cutting the muscle attached to the anterior rectum. When separating the anterior rectal wall, it is necessary to prevent damage to the urethra and the posterior vaginal wall, and pay attention to avoid penetration of the anterior rectal wall and contamination of the wound. 14.After rectal resection, the pelvic cavity was rinsed with a large amount of sterile water or anti-cancer drug solution via the abdomen several times to thoroughly stop bleeding, the abdomen was sutured to the posterior peritoneum of the pelvic floor, gauze and instruments were counted, and the abdomen was closed. The perineal incision was sutured in layers and drainage was placed, etc. For contaminated wounds, the perineal incision is not easily closed completely and should be filled with oil gauze or iodoform gauze.