Lower-limb lymphedema (LLL) is one of the common complications after pelvic lymph node dissection. The reported incidence varies widely, from about 1% to 49%, due to the type of tumor, degree of disease, diagnostic criteria, surgical technique, extent of lymph node dissection, whether postoperative adjuvant therapy is provided, and the duration of follow-up [1-3]. The standard surgical treatment for common gynecologic malignancies such as ovarian, endometrial, and cervical cancers includes pelvic lymph node dissection, and as the survival rate of patients with gynecologic malignancies increases, the occurrence of complications associated with postoperative pelvic lymph node dissection is detrimental to cancer survivors.LLL, once it occurs, is long-lasting and difficult to cure, and impaired lower extremity function and impaired body image in appearance seriously affect patients’ postoperative quality of life. Therefore, both gynecologic oncologists and cancer survivors should pay high attention to the prevention and management of LLL. 1, anatomical characteristics of lymphatic drainage in the lower limbs Lymphatic drainage in the lower limbs is divided into two groups: superficial lymphatic vessels receive lymph from skin and superficial fascia, travel along superficial veins and inject into local superficial lymph nodes; deep lymphatic vessels receive lymph from muscles, tendons, fascia, bones and joints, travel along deep blood vessels and inject into local deep lymph nodes. Both types of lymphatic vessels eventually inject directly or indirectly into the inguinal lymph nodes. The superficial and deep lymphatic vessels have interlocking traffic branches. The inguinal lymph nodes are located below the inguinal ligament and within the femoral triangle. They are divided into two groups, superficial and deep, the superficial group being called superficial inguinal lymph nodes and the deep group being called deep inguinal lymph nodes. The superficial inguinal lymph nodes, located in the subcutaneous tissue on the superficial surface of the broad fascia, receive most of the superficial lymphatic vessels of the lower anterior abdominal wall, buttocks, perineum, external genitalia, and lower extremities, most of which feed into the deep inguinal lymph nodes and some into the external iliac lymph nodes; the deep inguinal lymph nodes, located around the root of the femoral vein, receive the output vessels of the superficial inguinal lymph nodes and the deep lymphatic vessels of the lower extremities, whose output vessels feed into the external iliac lymph nodes. The external iliac lymph nodes receive lymph from the ipsilateral lower extremities, anterior abdominal wall, bladder, uterus, and vagina. The medial group of the common iliac lymph nodes receives lymph from the pelvic organs, while the lateral group of the common iliac nodes receives lymph from the lower extremities and the pelvic wall. 2. Factors associated with the occurrence of lower limb lymphedema after pelvic lymphadenectomy Tumor site The site of tumor is closely related to the occurrence of LLL after pelvic lymphadenectomy. Among patients with gynecologic malignancies, the incidence of postoperative LLL is highest in patients with vulvar cancer, followed by patients with cervical cancer and endometrial cancer, and lowest in patients with ovarian cancer [4]. The incidence of postoperative LLL in gynecologic malignancies was reported to be 5.6%-20.7% for ovarian cancer, 1.2%-27.6% for endometrial cancer, 1.2%-47% for cervical cancer, and 9%-70% for vulvar cancer [1,4-6], and the variability in reports is mainly due to the inconsistent criteria for diagnosing LLL and different postoperative adjuvant therapies. Treatment-related factors During pelvic lymph node dissection, lymphatic pathways are easily broken, anatomical structures are disrupted, and the ability of the lymphatic system to absorb excess water and cells from tissue fluid is reduced; if the transport capacity of the lymphatic system is so low that it cannot handle the increased lymphatic fluid, underfunctioning of the lymphatic system and lymphoid cysts or lymphedema will occur.Todo et al [7] reported that intraoperative removal of lymph nodes number of more than 31, rotary iliac lymph node dissection and postoperative adjuvant radiotherapy are independent risk factors for the development of LLL. It has also been reported that the occurrence of LLL is only associated with the application of postoperative adjuvant radiotherapy [6]. In addition, prolonged standing, hot weather and long-distance travel (long-distance airplane) may induce the development of LLL. 3, Prevention of lower limb lymphedema after pelvic lymphadenectomy LLL is superficial edema, and the International Lymphatic Society classifies lymphedema into grades 0 to 3: grade 0 is occult (subclinical) lymphedema, in which the patient has no visible sunken edema and may have a local feeling of heaviness or tightness months or years before the appearance of edema; grade 1 is early lymphedema, in which there is local edema with or without sunkenness, and the edema can be reduced or even disappeared by elevating the limb; grade 2 is early lymphedema. Grade 2 is moderate lymphedema, with localized depressed edema, which cannot be reduced by elevating the limb, with thickened and hardened skin and tissue, or without depression if fibrosis is severe; Grade 3 is severe lymphedema (elephantiasis), with localized non-depressed edema, thickened and hardened skin and tissue, and extravasated lymphatic fluid if the skin is broken [8]. several years, mostly occurring within 12 months postoperatively [4]. The earliest onset and highest incidence of postoperative cervical cancer have been reported, which may be due to the fact that surgical treatment of cervical cancer involves removal of not only pelvic lymph nodes but also parametrial tissue and part of the vagina, and adjuvant radiation therapy is required after surgical treatment if there are high-risk factors, and radiation therapy itself can cause lymphedema because it prevents the formation of collateral circulation in the lymphatic system and accelerates fibrosis of the skin. Therefore, choosing the appropriate surgical scope, appropriate intraoperative management and early observation of the corresponding symptoms that appear are the keys to reducing LLL after pelvic lymph node dissection. 3.1 Intraoperative preservation of the spinous iliac lymph nodes has been reported in several studies suggesting that in the surgical treatment of patients with endometrial cancer, those with more than 11 total lymph nodes resected have better survival, but more than 31 total resections again aggravate the occurrence of LLL [6]. Therefore, gynecologic oncologists are often in a dilemma between removing more lymph nodes to improve prognosis or less lymph nodes to reduce the incidence of LLL. However, for the most distal of the external iliac lymph nodes, the so-called spinocerebral lymph nodes, which are almost always visible intraoperatively and are a direct extension of the deep inguinal lymph nodes or Cloquet’s lymph nodes draining the lower extremity, its resection is likely to increase the risk of postoperative LLL [9]. Moreover, most of the literature reports that the spinocerebral lymph nodes never metastasize in patients who do not have lymph node metastasis elsewhere.Todo et al [10] reported that in 508 patients with intermediate-risk or high-risk endometrial cancer requiring pelvic lymph node dissection and para-aortic lymph node dissection, only 2.8% had spinocerebral lymph node involvement, and among patients with highly or moderately differentiated pelvic lymph node negativity There were no patients with positive spin-iliac lymph nodes. In another report, among 329 patients (85 with cervical cancer, 108 with endometrial cancer, 127 with ovarian cancer, 3 with oviductal cancer, and 6 with endometrial cancer with ovarian cancer) who underwent pelvic lymph node dissection and para-aortic lymph node dissection, 189 had the spinous iliac lymph nodes removed and 140 had the spinous iliac lymph nodes preserved, and the incidence and severity of LLL were significantly lower in the group with the spinous iliac lymph nodes preserved than in the resected group. The incidence and severity of LLL were significantly lower in the preserved spinocerebral lymph node group than in the resected group, with an incidence of 37% in the resected group and only 6.4% in the preserved group [2]. Therefore, to reduce the incidence of LLL, it is safe and feasible to recommend preserving the spinocerebral lymph nodes. 3.2 Intraoperative omentoplasty and opening of the retroperitoneal greater omentum is rich in circulation, has a high regenerative capacity, and has good resorption, which makes it very easy to adhere to surrounding tissues and form extensive collateral circulation. Successful reports include omentoplasty (J-flap), simple omentoplasty and omental fixation [11]. Another intraoperative preventive measure is to open the retroperitoneum after pelvic lymph node dissection to reduce lymphatic fluid collection and to allow smooth passage of leaking lymphatic fluid into the peritoneal cavity to be absorbed by the peritoneum, thus reducing the incidence of lymphatic cysts. The incidence of LLL was reported to be 39.1% in 184 patients who underwent hysterectomy and retroperitoneal lymph node dissection, of which the incidence in the retroperitoneal open group was 25.3% (21/83), which was significantly lower than that in the retroperitoneal closed group, which was 50.5% (51/101) [12]. 3.3 Postoperative placement of abdominal drains To drain postoperative exudate and reduce the formation of postoperative lymphatic cysts, drains are often placed after pelvic lymph node dissection. There are three methods of drainage tube placement: transvaginal, transabdominal, and combined transvaginal and transabdominal. In general, if the transvaginal drain is not removed in time after the patient starts to defecate after surgery, there is a risk of retrograde infection. In this way, transabdominal drainage is much more convenient and can achieve adequate drainage. In the early years, it was shown that lymphadenography after pelvic lymphadenectomy showed no visualization of the pelvic cavity, but the tissue spaces and microscopic lymphatic vessels in the abdominal wall and dorsum were visualized, especially the proliferation of the lateral circulation that travels subcutaneously to the abdominal wall. However, pelvic infection will seriously affect the formation and establishment of lymphatic collateral circulation, causing local lymphatic vessels to increase in internal pressure and dilate, resulting in lymphedema. Transabdominal drainage can not only achieve adequate drainage and prevent infection, but also stimulate the establishment of lymphatic collateral circulation in the abdominal wall. It is generally believed that the different postoperative drainage methods are related to the severity of lymphedema that occurs within 3 months after surgery, and transabdominal drainage is a better way to prevent LLL [11]. 3.4 Strict control of the indications for postoperative adjuvant radiotherapy Postoperative radiotherapy can increase the risk of lymphedema, and factors such as the dose, duration, and extent of radiation exposure can also affect the occurrence of LLL. In one study, the incidence of LLL was 44.4% and 15.8% for postoperative adjuvant radiotherapy and surgery alone, respectively [12], whereas postoperative chemotherapy did not increase the risk of LLL. Therefore, some authors suggest that to reduce the incidence of LLL, adjuvant radiotherapy should be avoided postoperatively if there is an alternative treatment available [7]. 3.5 Implementation of targeted health education for patients Prevention guidelines are proposed for people at high risk of lymphedema, including postoperative review on time; timely reporting of subjective changes in the limb; weight control; moderate exercise; reasonable application of elastic bandages; prevention of infection and clarification of signs and symptoms of cellulitis in the skin; avoidance of trauma, such as falls, burns or injections; keeping the skin clean and applying moisturizer after bathing; avoiding prolonged sitting or standing, using prophylactic compression measures such as elastic bandages when flying long distances as appropriate; avoid limb restriction, such as wearing tight leggings or tights; and avoid excessive high or low temperatures. In conclusion, patients are advised to self-protect the affected limb, avoid risk factors, maintain skin integrity, prevent infection, and reduce damage to the lymphatic system and venous vessels, thereby preventing lymphedema. 4 .Management of lower limb lymphedema after pelvic lymph node dissection LLL is mainly caused by the destruction of lymphatic vessels after lymph node dissection. LLL usually starts in the thigh and extends to the foot, and in some cases, the edema starts in the ankle. As the disease progresses, the limb thickens and hardens, the skin and subcutaneous tissues become fibrotic, the swelling becomes severe, the epidermis becomes rough and even warty, and eventually elephantiasis develops, or even the joint function decreases and walking becomes difficult. Before diagnosis, other causes of secondary lymphedema should be excluded, for example, pelvic CT examination for tumor recurrence and color multispectral ultrasound examination for deep vein thrombosis (DVT). 4.1 Comprehensive physiotherapy Comprehensive physiotherapy, including elevation of the affected limb, manual lymphatic drainage, multilayer bandages, exercise therapy, and skin care, has become the standard of care for lymphedema and can significantly reduce the high pressure in the microscopic lymphatics and reduce edema [8,13]. Elevation of the affected limb can alleviate edema to some extent in the early stage, but the effect decreases gradually as the disease progresses. Artificial lymphatic drainage is performed by centripetal massage of the edematous limb from the distal to the proximal end to enhance the function of the residual lymphatic vessels, allowing lymphatic fluid to enter the lymphatic vessels that have been emptied by massage and are functional, while in the collecting lymphatic vessels it increases the flow of lymphatic fluid, increases local blood flow, increases the lymphatic concentration rate, and improves protein reabsorption, thus reducing limb swelling. Multi-layer bandage dressing is to use cotton pad or high-density foam pad under the affected limb, and then wrap multiple layers of low-stretch bandage, continuous bandage, requiring the number of bandage layers to gradually decrease from distal to proximal, to ensure that the pressure from distal to proximal gradually decreases, in order to reduce the formation of excessive inter-tissue fluid, prevent lymphatic fluid reflux, and enhance the role of muscle pump. Motor function exercises include resistance exercises, static exercises, stretching exercises, active joint mobility exercises, etc. The therapeutic effect varies depending on the type of exercise, duration and duration of treatment. In addition, attention should be paid to reducing friction on the skin and avoiding infection caused by scratches. If the skin breaks down or suddenly appears red, swollen, hot, painful and other signs of infection should immediately seek medical attention and active anti-infection treatment. 4.2 Pneumatic Compression Therapy (PCT) is more effective in the early stage of lymphedema, especially before the onset of subcutaneous fibrosis, and intermittent pneumatic compression is often used to remove the accumulated tissue fluid. Attention should be paid to moderate pressure during treatment to avoid complications such as lymphangitis and peroneal nerve paresis [14]. 4.3 Drug therapy Phenylpyridines and coumarins bind to proteins deposited in the tissue interstitium and induce protein degradation, but some patients experience gastrointestinal reactions after their use. Phenylpyridones alone for lymphedema have slow onset and unstable effect, so they are only used as an adjunct to limb lymphedema treatment [15]. Some scholars in China have also applied bactrim and mai zhi ling for the treatment of LLL, and achieved good results [16]. 4.4 Surgical treatment Surgical treatment can be used after the failure of conservative treatment. The lesion tissue excision method is now mostly used in combination with other methods for the treatment of advanced and severe cases due to the disadvantages of large trauma, obvious scarring and poor wound healing. Surgery to reconstruct lymphatic drainage channels, such as lymphatic venous system anastomosis and lymphatic vessel grafting, mainly aims to reopen the lymphatic vessels below the patient’s obstruction site and restore the return flow function [17]. In conclusion, LLL is a common complication after pelvic lymphadenectomy and there is no satisfactory treatment so far, early detection of relevant signs and symptoms, early definitive diagnosis, and early preventive and therapeutic measures in order to improve the quality of life of patients.