Veins are the channels through which blood flows back to the heart from the surrounding tissues, and the veins of the lower extremities include superficial veins and deep veins, with the deep veins being the main veins of the lower extremities and the superficial veins eventually converging into the deep veins. Lower extremity deep vein thrombosis is caused by abnormal blood clotting in the deep veins of lower extremities, which leads to obstruction of blood return to the lower extremities, clinically manifested as sudden onset of significant swelling of one lower extremity, accompanied by mild distension and pain, and difficulty walking. The main causes include slow blood flow, venous wall damage and hypercoagulable state, among which slow blood flow and blood stasis caused by prolonged bed rest and lower limb braking are the most common causes. The main danger of lower extremity deep vein thrombosis is that the thrombus is dislodged and returns to the heart through the venous system, and finally enters the pulmonary artery through the right heart, leading to pulmonary embolism (referred to as pulmonary embolism), which is the most critical emergency and can lead to sudden death and often ineffective in resuscitation. The acute phase of lower extremity deep vein thrombosis (within two weeks of onset) is the high incidence of thrombus dislodgement, after which the chance of thrombus dislodgement decreases significantly with thrombus mechanization and fibrosis. Although lower extremity deep vein thrombosis does not lead to serious consequences such as limb necrosis and amputation, it can lead to serious sequelae if it is not treated actively and regularly, especially in the acute stage, which is manifested by the swelling of the affected limb cannot completely subside and is aggravated after moving on the ground. Moreover, deep vein thrombosis in the lower limb is easy to recur and form new thrombosis again, and the repeated attacks lead to serious lower limb deep vein reflux obstruction, which is manifested by high swelling of the affected limb, skin thickening, pigmentation (skin darkening) and cracking in the boot area (distal calf and foot), and finally forming chronic ulcers of the lower limb that never heal, which seriously affects the work and life of patients. Figure 1 Old deep vein thrombosis of the left lower extremity without formal treatment, the patient is highly swollen, with thickened skin, cracked skin and obvious hyperpigmentation in the foot and boot area. Figure 2 Chronic ulcer of the lower extremity caused by untreated old deep vein thrombosis of the lower extremity, which has been prolonged for 15 years. Having been engaged in vascular surgery for many years and having accumulated rich experience in the treatment of lower extremity deep vein thrombosis, we believe that for acute lower extremity deep vein thrombosis, it should be actively treated formally. To treat acute lower extremity deep vein thrombosis, first of all, fatal pulmonary embolism should be targeted. Conservative treatment measures include absolute bed rest (diet, urination and defecation without going to bed) for two weeks and avoid squeezing and massaging the affected extremity, but fatal pulmonary embolism cannot be completely prevented. Currently, an advanced weapon has been invented to prevent fatal pulmonary embolism, namely the inferior vena cava filter, which is implanted into the inferior vena cava (located in the abdomen, the thickest vein in the body, and blood from the lower half of the body flows back into the inferior vena cava) through interventional treatment (puncture at the root of the healthy thigh or neck, i.e. puncture of the healthy femoral vein or the right internal jugular vein), and the filter can effectively stop larger blood clots while allowing blood to pass through The effectiveness of the filter in preventing fatal pulmonary embolism is almost 100%, and the filter implantation is simple and minimally invasive. Inferior vena cava filters have been used in China for at least a decade, and their safety and effectiveness in preventing fatal pulmonary embolism have long been confirmed by clinical trials, and are now covered by medical insurance. In general, permanent filters are implanted in elderly patients, and there is no discomfort caused by the long-term implantation of the filter. In younger patients younger than 50 years of age, a temporary filter can be implanted and then removed three weeks after implantation when the risk of fatal pulmonary embolism is significantly reduced. Figure 3 Permanent filter implanted in the inferior vena cava (mesh in the inferior vena cava). For the treatment of deep vein thrombosis in the lower extremity itself, the currently preferred pharmacological treatment is anticoagulant thrombolytic therapy, which is comparable in efficacy to open surgical removal of the thrombus and is generally no longer required. Anticoagulant drugs can only prevent the further growth and spread of thrombus, and are ineffective for the already formed thrombus. Only thrombolytic drugs can dissolve the already formed thrombus, but thrombolytic drugs are more likely to dislodge the thrombus in the process of dissolving the thrombus, so it is generally recommended to implant the inferior vena cava filter and then carry out thrombolytic therapy, otherwise only anticoagulant therapy can be carried out. The most commonly used thrombolytic drug in clinical practice is urokinase, which has obvious efficacy, few side effects of bleeding at conventional doses, and is inexpensive. The longest used anticoagulant drugs are low-molecular heparin and warfarin. Generally, low-molecular heparin is injected subcutaneously for 1~2 weeks first, and then transition to long-term oral warfarin, during which the coagulation function needs to be tested regularly, so that the prothrombin time international standard ratio (PT-INR) is extended to 1.5~2.5 (normal is 0.8~1.2), within which the recurrence of thrombosis can be effectively prevented without serious bleeding occurs. Long-term anticoagulation therapy is important after the clinical cure of lower limb DVT, because it is easy to recur after the formation of lower limb DVT, and repeated attacks can lead to serious complications such as highly swollen lower limbs and chronic ulcers, and long-term effective anticoagulation therapy can effectively prevent the recurrence of thrombosis. Finally, after the clinical cure of lower limb deep vein thrombosis, medical elastic stockings should be worn for a short or long time according to whether there is swelling in the lower limb after activity. Medical elastic stockings have pressure gradient, which can effectively prevent the swelling of the lower limb caused by the activity on the ground, and can prevent the recurrence of thrombosis to a certain extent. After years of working in vascular surgery, we have accumulated rich experience in the treatment of lower limb deep vein thrombosis and believe that we should take active and regular treatment measures, i.e. anticoagulation and thrombolysis after implantation of inferior vena cava filter, long-term oral warfarin anticoagulation after clinical cure, regular monitoring of coagulation function, and wearing medical elastic stockings for a short or long time according to the situation. After the above treatment, the swelling of the affected limb has completely subsided rapidly and effectively prevented the recurrence of thrombosis, reducing the sequelae to a minimum and restoring normal work and life. 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