Lower extremity venous disease is the most common disease in vascular surgery, and it is reported that venous disease accounts for 8.72% of the cases, of which 65% are blood reflux disease and 30% are reflux-impaired disease. Vascular endoluminal technology for the treatment of lower extremity venous diseases has been rapidly developed, but there are still many problems and controversies in endoluminal treatment of venous diseases. I. Inferior vena cava filter Pulmonary embolism (PE) is a serious complication of deep vein thrombosis (DVT) in the lower limbs and one of the main causes of cardiovascular death. In recent years, the incidence and detection rates of PE have been increasing year by year with better understanding of PE, and the use of vena cava filters to prevent PE has become more common. It is important to note that vena cava filters can only prevent PE, neither treat DVT nor prevent the occurrence of DVT. In addition, there are still many controversies in the application of vena cava filters. Classification of vena cava filters: The nature of existing filters can be divided into three categories: (1) Permanent filters: implanted and left in the vena cava for a long period of time. This category includes Greenfield, Trapeasy, Simon and others. (2) Temporary filters: Temporarily implanted in the vena cava and must be removed from the vena cava after the risk of PE has passed, usually after 2 weeks. (3) Convertible filters: they can be retrieved after implantation in the vena cava, but can be converted to permanent implantation when they are not needed, or cannot be removed, for various reasons. 2. Indications for vena cava filters: This is the most controversial issue. According to evidence-based medicine, the 7th edition of Rutherford Vascular Surgery suggests that the absolute indications for the application of vena cava filter include: thromboembolism (VTE) anticoagulation is contraindicated; VTE anticoagulation has complications; anticoagulant treatment process is still appearing PE; VTE can not achieve effective anticoagulation. However, the indications for relative indications have greatly increased compared with the past, such as floating thrombus in the iliac vena cava, venous thrombolysis or surgical thrombolysis before thrombolysis, VTE patients with concurrent tumors, burns, pregnancy, etc., as well as some prophylactic measures, such as high-risk surgical procedures, trauma, and medical diseases. As far as the current situation is concerned, due to the emergence of retrievable filters, the indications for prophylactic use of filters and clinical applications have greatly increased compared with the previous ones. Recovery of vena cava filters: The purpose of the use of retrievable filters is that some patients who are at high risk of PE can have the filters removed after passing the danger period, and with a view to preventing or reducing the complications that may occur in the distant future of permanent filters, such as vena cava thrombosis occlusion, filter rupture, filter dislocation, and filter perforation of the wall of the vena cava. Filter retrieval occurs after the high risk of PE has passed, typically about 2 weeks after filter implantation. The indications for recall are, for patients with VTE, therapeutic anticoagulation should be used for 2-3 weeks without clinical evidence of VTE progression or recurrence; for prophylactic filter users, after prophylactic anticoagulation, the risk of PE has been lifted, and the deep veins of the lower extremities are normal as assessed by imaging. 4, Complications of vena cava filter: Overall incidence 4-11%, including puncture point thrombosis; vena cava thrombosis; recurrent DVT; filter displacement; vena cava wall puncture, injury; vena cava occlusion. Second, acute lower extremity DVT thrombolytic therapy Acute lower extremity DVT traditional treatment is surgical thrombus extraction, in recent years the efficacy of the application of thrombolytic catheter direct thrombolysis (CDT) has reached a consensus. The purpose of the treatment is to dissolve DVT and restore DVT patency in order to reduce DVT pressure and lower lower limb edema for the purpose of preventing the sequelae of DVT (PTS). CDT must follow some principles: 1, case selection: central or whole-limb DVT; 2, age: because the chance of thrombolytic bleeding complications increases with age, so the age of patients with CDT is generally controlled within 60 years; 3, there is no contraindication to thrombolysis; 4, the duration of the disease of DVT to 2 weeks or less is appropriate; 5, it is recommended that prophylactic implantation of vena cava filter before thrombolysis, preferred retrievable filter, and after the end of thrombolysis, the filter can be recovered. After the end of thrombolysis, the filter should be recovered. Thrombolytic method: 1, access selection: thrombolytic catheter can be used through the small saphenous vein, N vein, contralateral femoral vein, jugular vein, etc., but the small saphenous vein and N vein are most commonly used. 2, the choice of thrombolytic catheter, its thrombolytic work length to cover the entire thrombus range is appropriate. 3, choice of thrombolytic drugs: at present, the thrombolytic drugs available are urokinase, streptokinase and tissue plasminogen activator (t-PA), with urokinase being the most commonly used. According to the experience of our hospital, the dosage of urokinase is 250,000 U dissolved in 50-100 ml of saline every 4 hours, and injected from the thrombolytic catheter by microinjector pump. In order to increase the efficiency of thrombolysis, a pigtail catheter can be used to fragment the thrombus before thrombolysis, or some mechanical thrombus removal devices such as Rotarex can be used. 4, thrombolytic time and monitoring: pay attention to bleeding complications, bleeding tendency should be discontinued. In addition, after thrombolysis every 4 hours to determine the blood fibrinogen (Fg), such as Fg fell to 1.5mg / dl, urokinase should reduce the amount of Fg fell to 1mg / dl, the drug should be discontinued; every day should be carried out in the lower limbs of venography, observation of the effect of thrombolysis; the time of thrombolysis is generally within 3 days, the longest not more than 1 week. 5.If there is iliac vein compression syndrome (Cockette syndrome), it should be treated together. III. Iliac vein compression syndrome Iliac vein compression syndrome refers to the left common iliac vein by the right common iliac artery riding, and the 5th lumbar vertebrae and sacral scapula clamp produced by the venous reflux obstruction, and lead to a series of clinical manifestations. It is also known as Cockette syndrome or May-Thurner syndrome. IVCS is common in young and middle-aged women, and manifests as chronic venous insufficiency or DVT. Lower extremity venous cisternography is the most commonly used method of screening, and the direct signs of its X-ray manifestation are the compression and interruption of the common iliac vein, and the indirect signs are the internal iliac vein, the lumbar ascending vein, the pelvic lateral branches, the contralateral common iliac vein, the affected common iliac vein, the common iliac vein, and the common iliac vein, and the common iliac vein, and the common iliac vein. CT cross-sectional and three-dimensional reconstruction can better reflect the manifestation of iliac vein compression; ordinary ultrasonography is not recommended to be used because the imaging of iliac vein is greatly affected by the influence of abdominal organs; endoluminal ultrasound has a very good value and has been popularized to be used. In addition to detecting compression, it can show intraluminal changes, such as adhesive structures, spurs, and so on. IVCS need not be treated if asymptomatic, but surgical treatment is indicated if there are symptoms of venous insufficiency of the lower limbs, including lower limb edema, varicose veins, etc., and there is imaging evidence of iliac vein compression. Surgical balloon dilatation is possible/not feasible but requires placement of a vascular stent; simple balloon dilatation is contraindicated. Although no venous stent was introduced, Wallstent is the stent of choice in clinical practice. The proximal end of the stent should be anchored into the vena cava for more than 1 cm when releasing the stent to avoid poor anchoring of the stent to the distal side of the common iliac vein. According to the Wallstent stent release characteristics, even if the stent is released 3/4 of the time when the stent is inaccurately positioned, the stent can still be recovered and repositioned for release. Treatment of deep vein thrombosis (PTS) About 25-60% of patients with acute DVT turn into PTS even with anticoagulation + ECS treatment; if the symptoms of PTS are still not relieved after conservative treatment, endoluminal treatment can be considered. Aim of treatment: to open the occluded segment of the lesion, to restore venous blood flow, to reduce venous pressure and the severity of PTS. Patient selection: iliofemoral vein occlusion with severe symptoms of PTS about 1 year after DVT. The ipsilateral femoral vein and the N vein are the most commonly used access routes. It is generally considered appropriate to use a loach guidewire with a catheter to open the occluded segment, but the ability of the guidewire catheter to cross the occluded segment is the key to success. Even in chronic occlusions, thrombolysis may still be required in some cases. Currently, the stent of choice is the wallstent, but the supera stent is also used. It must be emphasized that the stent length must be selected and released with complete coverage of the diseased segment. If the inflow tract lesion involves the femoral vein, the stent must be inserted into the femoral vein across the joint to ensure good inflow tract blood flow and to avoid immediate postoperative stent occlusion. Postoperatively, the affected limb should be supported with elasticity and anticoagulated with low molecular heparin for 3 months.