The surgical treatment of rectal cancer has undergone nearly a century of development so far, evolving from the initial classical Miles surgery to the TME technique, standard lymph node dissection and the application of neoadjuvant therapy, which have been widely used in recent years and have greatly improved in terms of therapeutic effects . However, the treatment outcome and prognosis of rectal cancer, especially tumors below the peritoneal fold, are still a major challenge for colorectal surgery due to the anatomical scope located in the restricted space of the pelvis and the lack of the barrier structure of the plasma membrane layer. It is still worthwhile to further clarify and explore how to maximize the curative effect of low and intermediate rectal cancer, to ensure that the risk of recurrence is reduced to a minimum, and how to take the most appropriate surgical countermeasures after recurrence occurs. I. Risk factors of rectal cancer recurrence and prevention Postoperative recurrence of rectal cancer has always been a major problem for surgeons and an important factor affecting the average postoperative mortality and survival rate. We usually discuss the recurrence of rectal cancer mainly refers to the tumor recurrence in the local area of surgical operation or nearby lymphatic flow area and adjacent organs, so the recurrence of rectal cancer is usually divided into two kinds of recurrence in the intestinal cavity and extra-intestinal recurrence. For distant metastases such as liver and lung, we will not discuss them here. The factors leading to the recurrence of rectal cancer are: tumor stage, biological characteristics, surgeon’s factors, post-surgical comprehensive treatment, therapeutic response and immune function status, etc. From the analysis of the above factors, the most important factor that can be controlled is that the surgical operator should be more strict in the specification of surgical operation, the choice of surgical method and the use of comprehensive treatment for high-risk patients. In this regard, we summarize three main elements: first, the choice of surgical approach, second, the use of various specific techniques in the surgical process, and third, the continued treatment after the surgery, including close and standardized follow-up. In terms of the choice of surgical modality, for medium and low rectal cancer with late staging, ulcerative growth, poor biological characteristics such as hypofractionated or mucinous adenocarcinoma and intraoperative judgment of vascular invasion, extensive radical resection should be adopted in general, i.e., combined abdominoperineal resection, at this time, if anastomosis and anus preservation surgery is chosen, special care should be taken. The distal margin should be at least 3.5 cm or more. In addition, special attention should be paid to the adoption of appropriate extended radical and debridement techniques. During surgery, more emphasis should be placed on the adoption of tumor-free techniques, reasonable and standardized regional lymph node dissection techniques, etc. for high-risk patients. For example, the metastasis rate of lateral lymph nodes in rectal cancer below the peritoneal reflex line is about 10%-20%, and the general rectal cancer resection and Miles procedure may cause metastatic lymph nodes to remain in about 10% of cases, leaving a hidden danger for regional lymph node recurrence after surgery. Of course, we would like to emphasize that the technical standard of total mesorectal excision (TME) should be strictly followed during the surgical operation. Pre- and postoperative radiotherapy for rectal cancer can reduce the postoperative recurrence rate, but it can also increase some complications, so some scholars suggest that radiotherapy should only be used selectively for high-risk groups prone to recurrence after surgery. The results of multicenter studies have clearly confirmed that preoperative radiotherapy for rectal cancer can reduce the local recurrence rate. In addition, it is important to emphasize that the presence or absence of cancer cells in the resected tumor margin is significantly associated with postoperative recurrence of rectal cancer (10% recurrence rate in the group without cancer cells in the margin and 78% recurrence rate in the group with cancer cells in the margin). Therefore, surgeons should avoid palliative resection when radical resection of rectal cancer can be performed. The most ideal is to remove the recurrent foci through surgery again to achieve the effect of radical treatment again. The most ideal is to remove the recurrent foci through surgery to achieve radical treatment again. If it is combined with distant metastasis, it will be more difficult to achieve radical treatment. Therefore, here we emphasize the indications for reoperation for local recurrence of rectal cancer after surgery. To determine the extent of recurrent lesions and the presence of distant metastases with the help of various adjuvant examinations is extremely important for the selection of patients suitable for reoperation, i.e. the key depends on accurate preoperative assessment. In clinical practice, we usually use physical examination, hematological examination and imaging examination. Physical examination here we again emphasize anal canal rectal examination, inguinal lymph node examination, etc. Anal finger examination can often visually determine the extent of local recurrence foci and the degree of invasion. Hematological examinations mainly include CEA and CA19-9 to exclude distant metastases. Imaging examinations include intracavitary ultrasound, endoscopy and CT scan, and PET scan for evaluation if necessary. In some cases, intravenous pyelogram is required to clarify whether the ureter is compressed, and cystoscopy is required to clarify whether the bladder is involved if necessary. Clinically, we generally classify recurrences into the following three categories. 1. Local and distant recurrence It is usually considered that distant metastasis is a contraindication to re-surgery. However, this is not absolute, and there are cases where neoadjuvant treatment can be used to turn unresectable distant metastases into resectable ones, which can also be reoperated. For patients with multiple local recurrences, resection of multiple local lesions can be performed in some centers. However, because of the high surgical mortality rate, it is not advisable to do so in hospitals that do not have surgical experience, and it can be regarded as a contraindication to surgery. 2. Unresectable local recurrence For patients with symptomatic local multiple recurrence, it is generally considered that radical resection is no longer possible. Palliative surgery, however, does not improve survival, but it is inappropriate to assess the efficacy of surgical resection only from the viewpoint of reducing mortality. Some palliative resections may improve quality of life and relieve patients of painful symptoms. Surgical treatment for symptomatic relief requires only the removal of a large recurrence of tumor tissue. Radiotherapy combined with chemotherapy is usually the usual method after palliative surgery because it can relieve pain, reduce bleeding and improve quality of life. Selective chemotherapy of the pelvic vessels has a tumor-reducing effect on unresectable tumors. If the recurrent lesion is close to the anus, an endoluminal stent or colostomy is required. Other treatment options for patients with bleeding symptoms are laser ablation, electrocautery, and vascular embolization. Local excision For perineal recurrence, abdominal perineal combined with proctocolectomy is an option, but it can lead to pelvic spread and poor prognosis. 3.resectable local recurrence For resectable local recurrence without distant metastasis, surgical resection is the only treatment option. The surgical procedure for postoperative pelvic recurrence of rectal cancer is determined by the site and scope of recurrence, and the goal of resection is to have no cancer cells at the edge of the microscopic incision, i.e. R0 resection. If cancer cells are visible microscopically at the edge of the incision then it is R1 resection. R1 and R2 resections have much worse survival rates than R0 and are considered to be a palliative procedure. Resection of adjacent pelvic organs and sacrum may be required to achieve R0 resection, but a subset of patients may not be able to undergo R0 resection. Patients with advanced disease include peripelvic lateral wall tumor infiltration, iliac vessel involvement leading to lower extremity edema, bilateral ureteral obstruction leading to bilateral hydronephrosis, sciatic nerve invasion leading to bilateral lower extremity muscle weakness, tumor invasion of the sciatic notch and peri-abdominal aortic lymph node metastasis. Localized lateral pelvic wall invasion and sacral invasion above S2 are considered as relative contraindications because the possibility of adequate resection is small. III. Surgical treatment of local recurrence after rectal cancer Before performing surgery, we again emphasize the importance of adjuvant therapy. Especially for cases with more drastic local invasion and judged to be less likely or more difficult to be surgically resected, appropriate radiotherapy treatment can be administered before surgery according to the patient’s specific condition. The possibility of resection should be evaluated after the end of treatment and should not be given up lightly. Due to individual differences, preoperative treatment plans are often developed by urologists, obstetricians and gynecologists, plastic surgeons and radiologists in conjunction with colorectal surgeons. The initial surgical procedure and the ligation of the inferior mesenteric artery need to be defined before surgery. Intraoperatively, the patient’s caudal tip is fixed at the bed edge using the Lloyd-Davis device. Usually a catheter or ureteral catheter is left in place. The presence of distant metastases, peritoneal metastases, and evaluation of tumor resectability need to be excluded before complete resection of the lesion. Approximately 25% to 50% of cases are extensively metastatic or unresectable. The incision should be made away from the recurrent foci, and easily resectable lesions and known lesions should be resected first, followed by less resectable lesions and unknown lesions. If the extent of resection involves the iliac vessels of the pelvic floor, this will make surgical access to the pelvis very difficult. In this case, incision of the top of the bladder to access the pelvic floor is an option. Intraoperatively, the bladder can be repaired or removed directly. The specific operation style should vary according to the type of recurrence and the extent of tumor invasion. 1. Central recurrence Central recurrence includes anastomotic recurrence and mesorectal recurrence. This type of recurrence is becoming less common with the widespread implementation of total rectal mesorectal resection. This type of recurrence is most often performed with combined abdominal perineal proctocolectomy, although preserving anal surgery can be considered. With the initial surgery and postoperative radiation therapy, the reoperative field exposure is often not as complete and clear as the initial surgery. It is usually required to remove as much tissue as possible around the tumor to ensure that no tumor tissue remains. Although preoperative radiotherapy can damage the anal sphincter, low anterior rectal resection + colonic storage pouch can reduce the occurrence of postoperative functional problems. 2. Anterior type recurrence Anterior pelvic recurrence may invade structures such as uterus, vagina, prostate, seminal vesicles or bladder. The posterior and lateral tissues should be released first when assessing the extent of anterior recurrence. In female patients, the chance of bladder involvement may be reduced due to the obstruction of organs such as the uterus and vagina, which makes it possible to remove the remaining rectum, uterus, and part or all of the vagina from anteriorly. Depending on the extent of vaginal resection, the decision to require intraoperative repair or vaginal reconstruction with a flap is made. For limited invasion of the bladder wall superiorly, wedge resection of the bladder and repair of the bladder is possible. If the lesion invades further into the bladder triangle or prostate, total cystectomy and reconstruction of the urethra is required. 3. Lateral recurrence Lateral recurrence is difficult to achieve radical cure because of the involvement of the ureter and iliac vessels. Of course, unilateral ureteral resection and displacement as well as combined resection of internal iliac vessels can also be considered during surgery in an effort to remove the recurrent foci. In addition, some soft tissues such as uterus, iliac branches and pear-shaped muscle can be appropriately resected and repaired. Effective identification of bilateral ureteral involvement is a guide to assess the severity of lateral recurrence. If the extent of the lesion involves the lateral pelvic wall and sciatic nerve, it is usually unresectable. In this case, the cut edge of the lesion that cannot be completely resected can be treated with intraoperative chemotherapy. 4.Posterior recurrence When the recurrent tumor invades into the sacral fascia posteriorly, it can be removed along the periosteum as a whole. However, if the sacrum is involved, sacrocolpopexy is required. The segment of the sacrum involved is an important factor in the prognosis. Lesions involving sacral 3 and below can be resected as a whole from the involved segment and its distal sacrum, but intraoperative bleeding is usually greater. When the lesion involves sacral 2 and above, it is considered a contraindication to sacral resection because of its high mortality rate, and it requires resection of the anterior sacral plane and careful separation of the nerve roots. Lesions involving sacral 3 and below rarely result in voiding dysfunction. When the lesion involves the S1 or S2 segments unilaterally, it often leads to mild bladder dysfunction. When bilateral S1 segments are involved, it leads to complete bladder dysfunction. Many scholars have reported on total sacrocolpopexy, and since Wanebo and Marcove reported transabdominal surgery for postoperative recurrence of rectal cancer, many reports with large sample sizes have appeared one after another. Intraoperative mortality rate is 0%-8.5%, but postoperative recurrence rate is as high as 42%-82%. the best outcome is achieved in patients with R0 resection, but the 3-year survival rate is only 17%-62% and 5-year survival rate is 31%-42%. moriya et al. reported a 5-year survival rate of 35% in all patients who underwent pelvic recurrent lesion resection, which is similar to the survival rate of liver lesion resection in colorectal cancer with liver metastasis. However, the former had a higher postoperative recurrence rate. Perineal recurrence The pelvic floor defect caused by combined abdominal perineal proctocolectomy is obvious and more pronounced after total sacrocolpopexy. Most of these patients still need to receive radiotherapy, causing difficulty in healing the pelvic floor incision. In this case, myocutaneous flaps can be used to repair the defect and fill the residual dead space in the pelvic cavity, and can also be used for reconstruction after vagotomy. The commonly used sources of myocutaneous flaps are the femoralis, gluteus, rectus abdominis and latissimus dorsi muscles. The use of myocutaneous flaps significantly reduces postoperative complications compared with direct suturing of the pelvic floor incision. Surgery for recurrent rectal cancer is challenging for the surgeon, as the altered local anatomy caused after the first surgery, combined with the varying degree of local tumor invasion and the effects of radiation therapy, requires careful surgical separation techniques and precise determination of the location of adjacent vital structures to avoid collateral damage during the procedure. For example, for ureteral protection, it is usually necessary to place ureteral catheters before surgery, and the ureteral course can be judged according to the catheters found during surgery to avoid damage to the ureter.