In the second half of the 20th century, local excision of rectal cancer has attracted attention because of its low surgical trauma, rapid postoperative recovery, low complication rate and death rate, avoidance of permanent colon stoma, normal bladder function and sexual function, and similarity of postoperative physiological activities to those of normal people. In the second half of the 20th century, local resection of rectal cancer attracted attention because of its advantages such as less invasive surgery, faster postoperative recovery, lower complication rate and mortality, avoidance of permanent colostomy, normal bladder function and sexual function, and similar physiological activities to normal people after surgery. If the case selection is appropriate, the long-term outcome is not significantly different from that of transabdominal and transabdominal perineal radical resection. It should be noted that local excision of rectal cancer refers to complete removal of tumor and surrounding normal tissues, not palliative surgery, which is of great significance in preserving the function of anal sphincter and avoiding overtreatment on the premise of ensuring radical treatment. 1. Indications for local resection of rectal cancer Strictly mastering the indications for surgery and carefully selecting suitable cases are the keys to successful local resection of rectal cancer, on the basis of which the purpose of reducing surgical trauma, improving life quality and ensuring long-term efficacy can be achieved. At present, most scholars believe that the following conditions should be considered for case selection: (1) low to medium rectal cancer, tumor diameter of 3 cm, invading 40% of the circumference of the intestinal wall; (2) good tumor activity on rectal finger diagnosis, no basal infiltration, and the general type of tumor is augmentation, polyp or superficial ulcer; (3) lesions limited to the mucosa or submucosa (Tis/T1), and lesions invading the muscular layer (T2) are still controversial; (4) lesions that invade the muscular layer (T2); and (5) lesions that invade the muscular layer (T1). (4) good histological type, highly or moderately differentiated adenocarcinoma or villous adenoma malignancy, no lymph node metastasis or distant metastasis, and no lymphovascular or vascular invasion. In addition, local excision is a safe and anus-preserving method for patients of advanced age, poor physical condition, with vital organs (heart, lung, liver, kidney, etc.) that cannot tolerate transabdominal surgery or patients who refuse to undergo Miles. However, local resection should be abandoned in favor of conventional radical resection when the patient has: (1) poorly differentiated adenocarcinoma; (2) mucinous adenocarcinoma or indolent cell carcinoma; (3) intraoperative confirmation of tumor penetration through the muscular layer (T3); (4) intraoperative confirmation of vascular invasion; and (5) intraoperative confirmation of local lymph node metastasis. 9~125) months, 15 cases of local recurrence, and the mean time to recurrence was 12 months. The local recurrence rate was closely related to the depth of infiltration, in which T1 recurrence rate was 13 ％, T2 recurrence rate was 24％ and T3 recurrence rate was 71％. The poorer the histological differentiation, the higher the recurrence rate (12% for highly differentiated, 24% for moderately differentiated, and 44% for poorly differentiated). The recurrence rate of margin-positive patients was as high as 50%, which was significantly higher than that of margin-negative patients (16%). The recurrence rate after local resection was 16% for 3cm diameter tumors, which was significantly lower than that of 47% for >3cm tumors. The local recurrence rate was 9% (1/11) in T2 patients treated with adjuvant radiotherapy and up to 36% (5/14) in those without radiotherapy. 3 out of 4 T3 patients treated with adjuvant radiotherapy and 2 out of 3 without radiotherapy had local recurrence. The study concluded that local resection is an alternative treatment for well-differentiated rectal cancer with tumor diameter of 3 cm and T1, and postoperative adjuvant radiotherapy is recommended for T2 patients; T3 patients with high recurrence rate after local resection should undergo radical resection with or without radiotherapy. Most scholars now believe that potential lymph node metastasis and residual cancer at the incision margin are important causes of recurrence after local resection. In the literature, the depth of infiltration and the degree of tumor differentiation are closely related to lymph node metastasis in rectal cancer, and the rates of lymph node metastasis in T0, T1 and T2 are 1.8%, 6.3% and 19%, respectively; the rate of lymph node metastasis in G1 tumor is 1.8%, which is significantly lower than that in G2 tumor, which is 24.1%. The local recurrence rate of T1 patients was 17.9% (5/28), which was significantly lower than that of T2 patients (25%) (1/4); the local recurrence rate of highly differentiated adenocarcinoma was 12.5% (3/24), which was significantly lower than that of medium differentiated adenocarcinoma (37.5%) (3/8). Borschitz et al. reported a local recurrence rate of 29% after local R0 resection for low-risk T2 rectal cancer. Zhao Hongbing et al. concluded that patients with T2 rectal cancer should undergo radical resection because the former can obtain a higher survival rate than local resection. 2. Diagnosis of early rectal cancer Preoperative diagnosis should be made through the joint application of such examinations as endoluminal ultrasound, CT, MRI, and rectal diagnosis to make a more objective and accurate preoperative staging (clinicalstage) of the tumor, and the selection of suitable patients for local resection is the key to ensure the curative effect. Among them, endorectal ultrasound is a reliable means to diagnose early rectal cancer. Lin Guole et al. reported that the accuracy of endorectal ultrasound in detecting the depth of rectal cancer infiltration was as high as 86.7%; Landmann et al. reported that the accuracy of detecting lymph node metastasis in rectal cancer was 70%, the false positive rate was 16%, and the false negative rate was 14%. In addition, CT and MRI have been reported in the literature to further improve the accuracy of rectal cancer staging. The combination of rectal palpation and endoscopic morphology is also of great value in the diagnosis of early rectal cancer. If the tumor is still soft and can be pushed up and down, it can be judged as intra-mucosal cancer or sub-mucosal cancer. As for the distinction between the two, the morphology and size of the tumor should be taken into consideration. Those with a bulging tumor and a diameter of about 1 cm are mostly intra-mucosal carcinoma; those with a wider or inconspicuous tumor and a diameter of 1.5~3 cm are mostly sub-mucosal carcinoma. In addition, the clinical index staging advocated by York Mason to determine the depth of lesion infiltration is also of considerable practical value, which is consistent with 80% of postoperative pathology, i.e. stage I: freely moving, mucosal or submucosal cancer; stage II: well moving, lesion invading the muscular layer; stage III: poorly moving, lesion involving the outer bowel wall; stage IV: fixed, inactive, lesion involving the pelvic wall. Among them, stage I rectal cancer is the main indication for local resection. Folkesson et al. reported that local resection was performed in 643 (6.3%) of 10,181 cases of rectal cancer in Switzerland between 1995 and 2005, and the efficacy of local resection for early-stage rectal cancer was consistent with that of transabdominal resection. The 5-year survival rate after local resection was 95.3% (confidence interval: 91.5% to 99.1%) in 256 cases of stage I rectal cancer, and the local recurrence rate was 7.2%. The surgical methods of local resection of rectal cancer include: transanal excision (Parks), transoccygeal excision (Kraske), transsphincteric excision (Mason) and transana lendoscopicm i crosurgery (TEM), etc. The surgical methods of local resection of rectal cancer include: transanal excision (Parks), transoccygeal excision (Kraske), transsphincteric excision (Mason) and transana lendoscopicm i crosurgery. TEM surgery), etc. The specific surgical approach and surgical method should be selected reasonably according to the distance of the tumor from the anal verge and the familiarity of the operator with a certain surgical method, so as to ensure the radicality of local excision, improve the 5-year survival rate, reduce recurrence, and preserve normal defecation, urination and sexual function, and improve the quality of life. For tumors >7cm from the anal verge, transabdominal resection is preferred; for tumors 5-7cm from the anal verge, transsacrococcygeal resection is preferred; for tumors less than 5cm from the anal verge, transanal or transsphincter resection is indicated. 3.1 Transanal resection General anesthesia or sacral canal anesthesia is chosen for the operation. Depending on the location of the tumor, a juck knife position is used for tumors located in the anterior wall, and a lithotomy position is used for tumors located in the posterior wall. The anus is fully dilated to 5~6 fingers and maintained for 5 min until the anal sphincter is completely relaxed. The anal canal was retracted through the anoscope or spreader to fully reveal the tumor. The tumor was then injected with 1/200,000 epinephrine saline into the submucosa and surrounding area at the base of the tumor, followed by traction sutures at 1.5~2 cm from the upper, lower, left and right sides of the tumor, and total dissection with an electric knife at 1 cm from the edge of the tumor (for polyp malignancy, only the muscle layer can be cut). The tumor was completely excised and closed with 3.0 vicryl absorbable sutures in a continuous manner. The excised specimen was sent for rapid freezing examination to determine whether the tumor was completely excised. Finally, the wound was checked for active bleeding, and if there was no abnormality, the operation was ended by compression with oil gauze to stop bleeding. Stamos et al. reported that the transanal resection rate of T1 rectal cancer patients increased from 26% in 1989 to 44% in 2003. Several retrospective studies have shown recurrence rates as high as 18% and 47% after local excision for T1 and T2 rectal cancer, while a few prospective studies have shown recurrence rates of 4% to 5% and 14% to 16% after local excision for T1 and T2 rectal cancer, respectively. The reason for this may be related to the strict selection of patients enrolled in the prospective studies, and Fenech et al. reported a significant improvement in quality of life after transanal local excision in patients with early-stage rectal cancer. The median number of lymph nodes cleared by EPMR was 71-22, which was slightly lower than the 11(2-36) cleared by transabdominal low anterior rectal resection. The difference was not statistically significant (P = 0.132); the study concluded that EPMR in the second stage after transanal local excision is a safe and effective treatment for T1 rectal cancer, and has the advantage of lower postoperative complication rate than transabdominal low anterior resection, and can reduce the local recurrence rate after transanal local excision alone. 3.2 Transsacrococcygeal resection The operation is performed with subarachnoid anesthesia or sacral canal anesthesia. A folding incision is made in the mid-sacrococcygeal position, from the sacrococcygeal joint upward to above the external anal sphincter, and the subcutaneous fatty tissue of the skin is incised and part of the gluteus maximus muscle is cut. If the tumor is close to the peritoneal fold, the caudal bone often needs to be removed to achieve full exposure. If the tumor is close to the anus, the anal levator muscle and puborectalis muscle need to be cut. In order to have adequate tumor margins, the rectum must be adequately freed up and down. The rectum is separated between the anterior sacral fascia and Waldeyer’s fascia to the level of the retroperitoneum, and the posterior wall of the rectum is adequately freed. The rectum is separated bluntly to the right and left to reach Denonvilliere’s fascia, and the anterior rectal wall is fully freed. If necessary, the anterior superior peritoneum can be opened to free the rectum from above and downward to reconstruct the Douglos fossa. If the tumor is located in the anterior wall, the posterior wall of the rectum is incised to reveal the lesion. Total resection includes the tumor and 1 cm of surrounding normal tissue. The rectal incision is closed with interrupted transverse sutures. “Anal gas injection test” is performed to check for air leakage and repair accordingly. The anal levator and puborectalis muscles were carefully sutured, drains were routinely placed, and subcutaneous tissues and skin were sutured. In China, Fu Tao et al. reported 12 cases of early rectal cancer using transsacrococcygeal local excision, with a mean hospital stay of 14.2 d. Postoperative incisional infection occurred in 2 cases, which healed after dressing change, and none of them had urinary retention or sexual dysfunction. The average follow-up time was 38( 2~110) months, and two cases (16.7%) of local recurrence occurred at the 7th and 14th months after surgery, respectively, and the former was re-operated by Miles. The study concluded that local transsacrococcygeal resection is a safe and effective treatment option for low-grade malignant early rectal cancer. 3.3 Transsphenoidal resection General anesthesia was chosen for the procedure, with the prone position. The incision is about 12 cm long, starting 3~4 c m above the sacrococcygeal joint and going down to the anal verge. The skin and subcutaneous tissues were incised, the caudal ligament was cut with an electric knife, and the sacrococcygeal joint was interrupted to remove the coccyx. The external anal sphincter, anal levator and puborectalis muscles were cut in groups and marked. The rectum was fully freed, and the posterior wall of the rectum was incised from the anal margin upward, and the lesion was exposed by a large papillary retractor to prop up the incision. Depending on the tumor site, size and circumference of the invasive bowel wall, localized total rectal wall resection or rectal segmental resection or recto-rectal end-to-end anastomosis is performed. The M ason procedure has the following advantages: a superficial and straightforward surgical approach, a spacious field, and clear exposure; a wide range of surgical indications, and most patients with lower and middle rectal cancer can be locally resected by this procedure; and an adequate resection area to reduce local recurrence after surgery. The disadvantage of this surgery is that the external anal sphincter must be severed during surgery, and postoperative anal incontinence is likely to occur. However, Qiu Huizhong et al. reported that this complication rarely occurred because the external anal sphincter of each group was correctly cut and anatomically repaired during surgery to avoid postoperative incisional infection. In this study, 30 cases of lower and middle rectal cancer (Tis 5, T1 13, T2 10, and T3 2) were treated with Mason’s surgery, with a mean follow-up time of 52(4-108) months, a 5-year survival rate of 93%, no local recurrence, normal postoperative defecation and control function, and no anal incontinence. The study concluded that the Mason procedure should be used as the procedure of choice for local excision of middle and lower rectal cancer. 3.4 TEM surgery TEM surgery is a safe and effective minimally invasive treatment for benign rectal tumors and early rectal cancer, first pioneered by German surgeon Bues. The patient’s preoperative preparation is the same as for transanal resection. The technique uses a specially designed 40 mm diameter, 25 cm long endoscopic instrument that can remove benign rectal tumors and early rectal cancers up to 10 cm (anterior wall tumors), 15 cm (lateral wall tumors) and 20 cm (posterior wall tumors) from the anus. TEM has the advantage of being able to reach distances that cannot be reached by transanal resection, while offering a higher safety profile than open surgery; magnification of the field, which facilitates accurate tumor removal; and a short hospital stay with a low complication and mortality rate of less than 20% and 1.3% respectively. The main complications are bleeding and perforation. the disadvantages of TEM surgery are the expensive equipment, the steep learning curve, and the inability to remove draining lymph nodes for pathological staging. 15 cases of rectal intraepithelial neoplasia and early rectal cancer underwent TEM surgery with an average operative time of 57 (40-90) min, bleeding volume of 35 (10-60) mL, and hospital stay of 4.5 (2-9) d. Kreissler et al. found that the incidence of bleeding and other complications was significantly higher after TEM for masses in the lateral rectal wall, >2 c m in diameter and >8 c m from the anal verge. Lozoche et al. retrospectively studied the clinical data of TEM surgery, in which 24 cases (17.8%) of T0, 66 cases (48.8%) of T1, and 45 cases (33.4%) of T2; the median follow-up time was 78 (36 ~ 125) months, and the tumor-free survival rates of T1 and T2 rectal cancer patients were 100% and 93%, respectively, which were consistent with the efficacy of conventional surgery. Four cases of postoperative local recurrence and two cases of distant metastasis were reported by Bretagnol et al. 52 TEM procedures were performed, including 31 T1, 17 T2 and T34 cases, with 7 (13% ) additional remedial procedures. The median follow-up time was 34 ( 1-102) months, and postoperative local recurrence occurred in 8 cases ( 15% ). 4. Precautions for local resection of rectal cancer Adequate preoperative bowel preparation, preventive antibiotics, nutritional support, as well as careful intraoperative hemostasis and reliable suturing techniques are important means to avoid postoperative complications such as incisional infection, dehiscence, bleeding or intestinal fistula. Female patients should have vaginal douching 2 d before surgery, and intraoperative disinfection should be performed vaginally, which is especially important for anterior rectal wall tumors. Intraoperatively, the concept of tumor free should be emphasized. 0.5g of 5-FU can be used to soak the surgical area after rinsing with iodophor to prevent implantation metastasis and recurrence. Before removing the tumor, 1/200,000 epinephrine saline should be injected into the submucosa of the tumor base to separate the tumor from the basal tissue for easy removal and to reduce intraoperative bleeding. The posterior rectal wall should be separated between the anterior sacral fascia and Waldeyer’s fascia to avoid damaging the anterior sacral vein from causing hemorrhage during surgery. Tumor removal from the anterior wall should avoid damage to the posterior vaginal wall as well as the seminal vesicle gland and prostate gland, which may cause rectovaginal fistula and bleeding. After resection of tumor, pathological section is routinely sent for examination, and intraoperative frozen pathological examination is feasible if available, and judgment on the depth of tumor infiltration, circumferential margin and possible local lymph node metastasis is required to decide whether to perform additional remedial surgery. Postoperative follow-up should be closely followed up once every 3 months, including liver ultrasound, chest X-ray, rectal examination and proctoscopy, etc. The recurrence of rectal cancer after local resection may still be cured by remedial surgery.