Key Points of Guidelines for Diagnosis and Treatment of Deep Venous Thrombosis (Third Edition) (2017) Deep venous thrombosis (DVT) is a venous reflux disorder caused by abnormal coagulation of blood in deep veins, which occurs mostly in lower limbs. Thrombosis can cause pulmonary embolism (PE). DVT and PE are collectively called venous thromboembolism (VTE).It is the manifestation of the same disease in different stages.The main adverse reactions of DVT are PE and PTS, which can significantly affect the quality of life of patients and even lead to death. I. Etiology and risk factors The main causes of DVT are venous wall injury, slow blood flow and hypercoagulability.Risk factors include primary factors (Table 1) and secondary factors (Table 2).DVT is commonly seen in patients with major surgery or severe trauma, long-term bed rest, limb movement, cancer, etc. Table 1 Primary risk factors for deep venous thrombosis Antithrombin deficiency/congenital abnormal fibrinogenemia/hyperhomocysteinemia/anticardiolipin antibody positive/excessive plasminogen activator inhibitor/prothrombin 20210 gene mutation/_, _, factor_increase/protein C deficiency/factor V Leiden mutation (activator protein C resistance)/plasminogen deficiency/abnormal plasminogenemia/protein S deficiency/_causeSub deficiency Table 2 Secondary risk factors for deep venous thrombosisTable 2 Secondary risk factors for deep venous thrombosis Iliac vein compression syndrome/injury/fracture/stroke, paralysis or long-term bedridden/elderly/central venous catheter/lower extremity venous insufficiency/smoking/pregnancy/postpartum/Crohn disease/nephrotic syndrome/hypercoagulable state of blood (polycythemia, Waldenstrom macroglobulinemia, myelodysplastic syndrome)/platelet abnormality/surgery and braking/long-term useEstrogen/Malignant Tumor Yao Chemotherapy Patient/Obesity/Heart, Pulmonary Failure/Long Time Transportation/Oral Contraceptive/Lupus Anticoagulant/Artificial Vascular or Intravascular Graft/VTE History/Severe Infection II. Clinical manifestations According to the time of onset, DVT can be divided into acute, subacute and chronic stages.Acute stage refers to within 14 days of onset; subacute stage refers to 15-30 days of onset; after 30 days of onset enters the chronic stage; early DVT It includes acute and subacute stages. Acute lower extremity DVT mainly manifested as sudden swelling and pain of affected limbs. Physical examination showed depressed edema of affected limbs, increased soft tissue tension and skin temperature, and tenderness in posterior leg and/or medial thigh, femoral triangle and iliac fossa of affected side.After 1 to 2 weeks of onset, superficial veins may be exposed or dilated in affected limbs.The Homans sign and Neuhof sign were positive when the thrombus was located in the muscular venous plexus of the leg. Severe lower extremity DVT, patients can appear bruises, is the most serious DVT of the lower extremity.The clinical manifestations were extremely swollen lower extremities, severe pain, blue-purple skin shining, low skin temperature with blisters, disappearance of dorsal pedal artery pulsation, strong systemic reaction and elevated questions.Shock and venous gangrene can occur if not treated in time. Once the venous thrombosis falls off, it may drift with blood flow, block the main or branch of pulmonary artery, and cause the clinical manifestations of PE according to the degree of pulmonary circulation disorder. Chronic stage can develop to PTS, generally refers to the clinical manifestations of chronic venous insufficiency of lower limbs after 6 months of acute DVT, including the heavy limbs, swelling and pain, varicose veins, pruritus, pigmentation, eczema and so on. Severe cases appear high swelling of lower limbs, liposcleroderma, prolonged ulcers.In the first two years of diagnosis of DVT of lower extremities, even after standard anticoagulation therapy, there are still about 20%-55% patients with PTS, of which 5%-10% patients develop severe PTS, which seriously affects the quality of life of patients. Three. Diagnosis For the diagnosis of DVT of lower limbs, whether the clinical manifestations are typical or not, further laboratory and imaging examinations are needed to make a definite diagnosis so as to avoid missed diagnosis and misdiagnosis. (1) Auxiliary examination 1. Determination of plasma D-dimer: D-The sensitivity and specificity of dimer assay were high and poor.It can be used for screening of acute VTE