What is lower extremity deep vein thrombosis? Deep vein thrombosis (DVT) is the abnormal clotting of blood in the lumen of the deep veins, blocking the venous lumen and causing venous return obstruction, resulting in varying degrees of deep vein insufficiency. Lower limb and inferior vena cava thrombosis is the most common, especially iliac-femoral vein thrombosis. If patients do not receive timely and effective treatment, it will lead to lower limb bruising and swelling, pigmentation, and in serious cases, it may cause femoral cyanosis, limb ischemic necrosis, and patients will lose part or all of their labor force, and more than 50% of patients will be left with lower limb deep vein insufficiency affecting the quality of life for a long time, and even pulmonary embolism causing death, which has become a common disease with great danger to human health. Acute DVT occurs in the gastrocnemius plexus, called peripheral type; occurs in the iliofemoral vein, called central type; both are called mixed type when the whole limb is involved by proximal and distal expansion. Why does DVT occur in the lower extremity? The etiology of DVT consists of three main factors: intimal damage, slow blood flow, and hypercoagulable blood. Each of these factors is closely related to thrombosis, but a single factor is not sufficient to cause thrombosis; rather, it is the result of a combination of factors. Common risk factors for venous thrombosis include: old age, surgery, limb braking, fracture, puerperium, malignancy, limb paralysis, and oral contraceptives. Certain genetic factors that cause abnormal formation of blood clots can also trigger thrombosis. How to diagnose lower extremity DVT? The most common clinical signs and symptoms of DVT in the lower extremities are swelling and pain throughout the lower extremities. For patients with clear predisposing factors and triggers, the diagnosis is not difficult. However, the lack of typical signs and symptoms in some patients after the onset of the disease is highly likely to lead to misdiagnosis. Therefore, the diagnosis of DVT also needs to be combined with objective auxiliary examinations: 1.Color Doppler ultrasound: It is the preferred examination method for the diagnosis of DVT, and its sensitivity and specificity are 95% and 98% respectively; 2.Venography: Venography is the gold standard for the diagnosis of DVT, and it is an invasive examination, and the use of this method has tended to decrease; 3.D-dimer: Plasma D-dimer detection has an important value for the diagnosis of DVT; 4.D-dimer: Plasma D-dimer detection has an important value for the diagnosis of DVT. 4.Nuclear magnetic and CT angiography: It is non-invasive, comparable with venography and ultrasonography, and less dependent on the operator, and can obtain good images of inferior vena cava and iliofemoral vein. 5.Nuclear imaging of lower extremity: the accuracy of detecting thrombosis is 85%-90%, which is suitable for patients suspected of pulmonary embolism or with a history of contrast allergy. What are the treatment methods for lower extremity deep vein thrombosis? Drug therapy: It includes thrombolytic and anticoagulant therapy. The main drugs used in thrombolytic therapy are urokinase and rt-PA, whose side effects mainly cause bleeding. Traditional thrombolytic route is mostly superficial vein, thrombolytic drugs flow throughout the body with the blood to dissolve the thrombus; regional thrombolytic therapy is to dissolve the thrombus in a certain area after injecting the drugs into the blood vessel through interventional cannula; thrombolytic therapy in the thrombus is to use intravascular technology to insert the thrombolytic catheter into the thrombus and inject the drugs directly to dissolve the thrombus, which can make the high concentration of thrombolytic drugs infuse directly into the thrombus to achieve the best effect. Anticoagulation therapy: The application of low molecular heparin makes anticoagulation therapy more convenient and safe. Surgical thrombectomy is suitable for deep vein thrombosis within 3 days of onset, when there is no obvious adhesion between the thrombus and the endoluminal surface of the vein, and the endothelial damage of the vein is light after thrombectomy. Compared with simple anticoagulation therapy, venous thrombectomy can improve venous patency and reduce venous reflux and thrombotic sequelae. Interventional treatment: Vena cava filters can be easily inserted percutaneously as a thrombus stopper with a low complication rate. Follow-up is good, and permanent or retrievable filters can be used depending on the characteristics of the disease and the actual need. In addition, with the advancement of endovascular minimally invasive treatment techniques, endovenous mechanical thrombus ablation, negative pressure thrombus aspiration and balloon dilation and stenting have been used to treat DVT in the lower extremities in recent years.