1.Preoperative judgment ability Rectal cancer anal preservation refers to the evidence: anal preservation surgery requires radical removal of tumor specimens to reduce the postoperative local recurrence rate in the pelvis and reduce the possibility of the intestinal canal being compressed in the pelvis. In a broad sense, surgeons try not to wrongfully take the blame for local recurrence brought by anal preservation surgery. In a narrower sense, there is still a surgical anal canal in addition to the specimen after radical excision. (1) Tumor condition: Generally, preoperative rectal finger examination and pathological examination can be considered for anal preservation surgery for rectal cancer if the following conditions are met: a. the lower edge of the tumor base is 5 cm or more from the anus (1 cm or more from the upper edge of the surgical anal canal), b. the tumor is a limited type of augmentation or ulcerative lesion, c. the tumor base has good mobility, d. the tumor pathology is rectal adenocarcinoma. The pathology of the tumor is adenocarcinoma of the rectum. In addition, intracavitary ultrasound, CT and MRI are of great help in judging tumor extravasation and lymph node metastasis. (2) Anal function: preoperative rectal finger examination to determine whether the anal sphincter function is good? Elderly patients, especially those over 75 years old, with poor anal sphincter function are not suitable for anal preservation surgery. (3) Systemic condition: a. What is the patient’s tolerance for surgery? If poor tolerance is not suitable for anal preservation. b. Is it worthwhile to perform anal preservation surgery for patients with distant metastases? Because it usually takes six months to one year to recover the defecation function after anal preservation surgery. The author does not advocate anal preservation surgery for such patients. Only by skillfully freeing the rectum to the upper edge of the surgical anal canal can we remove the maximum specimen of rectal cancer 5 cm from the anus or even early rectal cancer 3-5 cm from the anus, which is consistent with the radical nature of surgery. For this reason, the surgeon must: ① be familiar with the anatomical features of the pelvis, especially the anatomical structures of Waldeyer’s fascia, lateral ligaments, Denonvilliers’ fascia, rectosacral fascia, and anterior sacrococcygeal ligament. ② Must have some surgical instruments to expose and maintain tension separation such as: open right angle pull hook, open rigid suction tube, open blocking forceps, laparoscopic “pug”, etc. ③ Adept at directing assistants on how to perform effective exposure. ④Master the use of scissors, electric knife and ultrasonic knife. ⑤ Optimize pelvic separation procedures whether open surgery or laparoscopic surgery. Laparoscopic surgery should focus more on the method of apt separation. A group of specialized surgeons performing anus-preserving surgery, the abdominal group of surgeons can free the rectum to the pelvic floor or the upper edge of the surgical anal canal by open or laparoscopic freeing, and the pelvic freeing should be effortless and time-consuming and should take only a fraction of the time of the whole operation. For early rectal cancer which is 3-5 cm from the anus, not only the abdominal group doctors are required to free the rectum to the pelvic floor; the perineal group doctors also have to start from the dentate line and free upward to the pelvic floor through the internal and external sphincter gap, and then remove the specimen from the anus after meeting with the abdominal group doctors. 3. Keep the colon with good blood supply long enough For the radical nature of the tumor, at least the base of the sigmoid mesentery is removed along with the lower 1/3 of the intestinal canal of the sigmoid colon. After removing the specimen, sometimes the length of sigmoid colon is not long enough to reach the pelvic floor, some surgeons are often unwilling or afraid to free the colon further to the proximal end, so that the colon cannot be extended to the pelvic cavity and the anus-preserving surgery is abandoned halfway and lost, and the stoma surgery is done instead. Surgeons must overcome this mentality in order to go to the next level. Pulling down the colon with good blood supply without tension is the basic requirement for anal preservation surgery. For this reason, ① the surgeon should have the ability to free the splenic flexure of the colon or the left hemicocele during surgery and pull down the sigmoid or descending colon with good blood supply to the pelvis or outside the anus. ② If necessary, the surgeon should have the determination and vigor to free the right hemicocele and pull the hepatic flexure of the colon with good blood supply to the pelvic cavity or outside the anus by rotating 90 degrees counterclockwise. As long as the skill of freeing the splenic flexure of the colon is mastered in laparoscopic surgery, the operation becomes easier. 4, master the method of establishing continuity between colon and rectum (or anal canal) The surgeon should first consider radical resection of the specimen before considering the anastomosis method, and should not make the lower margin resection range insufficient for the sake of anastomosis. ① For rectal cancer that is more than 7 cm from the anus, double anastomosis with anal preservation is used, and anastomotic fistula is less likely to occur after surgery. ②For rectal cancer 6-7 cm away from the anus, an anastomotic anus-preserving operation should be performed. In order to prevent postoperative anastomotic fistula, the technique of using protective ileostomy should be mastered. ③For rectal cancer 5-6 cm away from the anus (except for tumors located in the posterior wall), anastomotic fistula is more likely to occur if anastomosis is forcibly performed by anastomosis-protective surgery (in women, even rectovaginal fistula occurs). In such cases, even if a protective ileostomy is done, it cannot prevent the occurrence of anastomotic fistula. For rectal cancer 5-6 cm away from the anus (except for tumors located in the posterior wall), it is best to cut the intestinal canal below the tumor as close as possible to the upper edge of the anal sphincter, i.e., to remove the intestinal canal below the tumor to the maximum extent possible, so as to avoid the possibility that the lower cut edge of the tumor is not clean. After the resection of the specimen, the connection between the large intestine and the anus can not be completed by the anastomosis, so the end of the large intestine can be pulled out from the anus for 3-5 cm, which can completely prevent the occurrence of anastomotic fistula, and there is no need to make a protective ileostomy. 1 month later, after the adhesion between the large intestine and the pelvic cavity is healed, the excess large intestine outside the anus can be removed, and the patient can resume defecation from the anus. This surgical approach is both radical and safe, and is known as the modified Bacon procedure developed and perfected by the Chinese. ④ For early rectal cancer of 3-5 cm from the anus, the specimen is removed to the dentate line, the specimen is removed from the anus, and the extra large intestine outside the anus is retained for about 3-5 cm. 1 month later, the extra large intestine outside the anus is removed after the adhesions between the large intestine and the pelvis have healed. This procedure is called modified trans-sphincteric gap rectal resection for anal preservation. The extent of resection for modified trans-sphincteric gap proctocolectomy is lower than that for modified Bacon’s procedure, but the method of establishing continuity between the colon and the anal canal is similar. In conclusion, anal preservation surgery for rectal cancer is a therapeutic process and an engineering project. Rectal cancer anus-preserving surgery should not be treated as an appendectomy or gallbladder stone removal in one fell swoop. This treatment process cannot be completed by a surgeon working hard alone, but by the joint efforts of the patient, family and medical staff, all three are indispensable.