Venous thrombosis mostly occurs in the deep veins of the lower extremities and is relatively common clinically, with less than ideal treatment results, often leaving deep vein obstruction or venous valve insufficiency in the lower extremities. I. Etiology In the mid-20th century (1946-1956), Virchow proposed three major factors of venous thrombosis, namely, venous blood flow stagnation, venous wall damage and blood hypercoagulation. In recent years, through a large number of clinical and experimental observations, not only the specific content of each factor, but also the test method can be confirmed. However, among the above three factors, any single factor is often not enough to cause the disease; it must be a combination of various factors, especially slow blood flow and hypercoagulable state, that may cause thrombosis. Second, pathology The pathological changes of venous thrombosis are mainly due to the thrombosis caused by the hypercoagulable state of blood and slow blood flow. The thrombus is usually only mildly adherent to the tubular wall and can easily dislodge, which can cause pulmonary embolism. The thrombus can also be more tightly adhered to the vessel wall after stimulating an inflammatory response. According to the composition of the thrombus, there are three types of venous thrombosis: 1. red thrombus: the most common, the composition is relatively uniform, platelets and white blood cells are scattered within the gelatinous mass of red blood cells and fibrin; 2. white thrombus: basically composed of fibrin, white blood cells and lamellar platelets, only a very small amount of red blood cells; 3. mixed thrombus: composed of white thrombus in the head, lamellar red thrombus and white thrombus constitute the body, red thrombus or lamellar thrombus constitutes the tail. Venous thrombosis causes venous return obstruction, the extent of which depends on the size and location of the involved vessels, as well as the extent and nature of the thrombus. Elevated venous pressure at the distal end of the obstruction, capillary stasis, and endothelial cell hypoxia increase capillary permeability and cause swelling in the limb distal to the obstruction. Elevated deep venous pressure and venous reflux obstruction cause the traffic branch veins to dilate and open, and the blood flow at the distal end of the obstruction enters the superficial veins through the traffic branch, and superficial venous dilatation occurs. The thrombus may follow the direction of venous blood flow to the proximal end, and the thrombus in the lower leg may continue to extend into the inferior vena cava, or even to the opposite side. When the thrombus completely obstructs the venous trunk, the thrombus may also extend retrogradely distally. The thrombus can be dislodged and embolized in the pulmonary artery via the right heart with blood flow, which can lead to pulmonary embolism. On the other hand, the thrombus can be mechanized, re-tubularized and re-endothelialized so that the venous lumen can regain some degree of patency. Because the lumen is affected by the contraction of fibrous tissue and the destruction of the valve itself, it can lead to venous valve insufficiency. Clinical manifestations Deep vein thrombosis of the lower extremities can occur in any part of the deep veins of the lower extremities. There are two common clinical types: calf muscle plexus thrombosis and iliofemoral vein thrombosis. The former is located in the terminal area and is called peripheral; the latter is located centrally and is called central. Both peripheral and central types can involve the whole limb by proliferation or retrograde expansion, which is called mixed type and is most common clinically. (1) peripheral type; (2) central type; (3) mixed type. Types of lower extremity deep vein thrombosis The calf muscle plexus thrombosis (peripheral type) is a good site for deep vein thrombosis after surgery. Because of the small extent of the lesion and the mild degree of inflammatory response stimulated, the clinical symptoms are not obvious and can be easily ignored. It is usually felt as pain or swelling in the lower leg, with pressure pain in the gastrocnemius muscle and mild swelling in the foot and ankle. If the foot is sharply dorsiflexed in the knee joint extension position, the gastrocnemius muscle and the flounder muscle are elongated, which can stimulate the inflammatory pain caused by the thrombus, and the pain in the gastrocnemius muscle appears, which is called positive Homans sign. The superficial venous pressure does not generally increase because it does not affect blood return. If the thrombus continues to multiply proximally, the clinical manifestations become more pronounced, with swelling of the calf, dilatation of the superficial veins, and pressure pain along the N vein in the N fossa. Iliofemoral vein thrombosis (central type), which is more common on the left side, may be related to the right common iliac artery crossing the left common iliac vein, with some compression of the left common iliac vein. It has an acute onset; local pain and tenderness; swelling of the affected limb below the inguinal ligament; dilatation of superficial veins, especially in the inguinal region and lower abdominal wall; in the third interval of the femur, a thrombus-filled stripe of the femoral vein may be palpable; fever is present, but usually does not exceed 38.5°C. The inferior vena cava may be invaded by the cascade. If the thrombus is dislodged, pulmonary embolism can be formed, with cough, chest pain, dyspnea, cyanosis, shock, and even sudden death in severe cases. Regardless of the retrograde spread of iliofemoral vein thrombosis or the prograde expansion of calf muscle plexus thrombosis, as long as the whole lower limb deep vein system is involved, it is called mixed type. The clinical presentation is an addition of both manifestations. However, the latter has an insidious onset, and the symptoms are mild at the beginning until the iliofemoral vein is involved, and then the varicose manifestations appear. Whenever the onset of the disease is rapid, regardless of the retrograde expansion of the iliofemoral vein thrombus or the proliferation of the thrombus in the intramuscular plexus of the lower leg, as long as the thrombus grows, so that the entire venous system of the affected limb is almost completely in a state of obstruction, and at the same time causes strong spasm of the artery, it is specifically called femoral cyanosis. The pain is severe, the whole limb is widely and obviously swollen, the skin is tense, shiny, cyanotic, and some blisters may occur, the skin temperature is significantly lower, and the dorsal foot and posterior tibial artery pulsations disappear. The systemic reaction is obvious, the body temperature often reaches 39℃ or more, shock and venous gangrene of the limb may occur. Fourth, the auxiliary examination calf muscle plexus thrombosis, the symptoms are obscure and atypical, often difficult to confirm the diagnosis. Iliofemoral vein thrombosis, mixed type and femoral cyanosis, have more typical clinical manifestations, and generally have no difficulty in diagnosis. However, in order to determine the diagnosis and clarify the scope of lesions, the following auxiliary examinations can be used: 1. Radioisotope examination currently has two methods: isotope venography and radioactive fibrinogen test. The former is in the experimental research stage and has not yet been applied clinically; the latter is the application of 125 iodine-labeled human fibrinogen, which can be taken up by the forming thrombus, and the content per gram of thrombus is more than 5 times higher than the equivalent amount of blood, thus forming the phenomenon of radioactive dilution, which can be scanned in the lower limb to determine whether there is thrombus formation. This method is easy to operate, non-invasive, with a high correct rate, and can detect small venous occult thrombosis. 2.Ultrasonic examination uses the Doppler effect and places the probe on the surface of the larger vein, which can smell or trace the venous blood flow sound, and if there is no blood flow sound in this part, it can indicate the venous embolism. With the application of the new imaging instrument, the diameter and lumen of the vein can be directly observed, and the size of the embolism and its location can be understood. 3.Electrical impedance volume tracing examination adopts various volume tracing instruments to determine the degree of increase in calf volume after the balloon band blocks the femoral venous return and the rate of decrease in calf volume after the removal of the block, so that the lower limb venous patency can be judged to determine whether there is venous thrombosis. 4.Venous pressure measurement: the normal pressure of dorsal foot vein in standing position is generally 130cmH2O, when the ankle joint is extended and flexed, the pressure generally drops to 60cmH2O, and after stopping the activity, the pressure rises back up, and the time of rising back up is more than 20 seconds. When there is thrombosis in the trunk vein, the pressure rises significantly in the standing position whether at rest or during activity. The rebound time increases faster, generally for about 10 seconds. 5.Venogram is the most accurate examination method, which can make the veins directly visualized and can effectively determine the presence or absence of thrombus, and can determine the size, location, shape and side branch circulation of thrombus. Later retrograde angiography can also understand the function of venous valves. V. Treatment 1.Non-surgical treatment Applicable to peripheral type and more than 3 days of central type and mixed type. (1) Bed rest and elevation of the affected limb: bed rest for 1 to 2 weeks, avoid activities and forceful defecation to avoid dislodging the thrombus. Elevate the foot of the bed 20 to 25 cm to make the lower limb higher than the heart level, which can improve venous return and reduce edema and pain. When you start to get out of bed, you need to wear elastic stockings or use elastic bandages, and the time of use varies according to the embolism site: 1~2 weeks for calf muscle plexus thrombosis; no more than 6 weeks for N vein thrombosis; 3~6 months for iliofemoral vein thrombosis. (2) Thrombolytic therapy: commonly used drugs are urokinase, streptokinase and fibrinolytic enzymes. Streptokinase: extracted from the culture of Streptococcus haemolyticus. The first dose for adults is 500,000 IU, dissolved in 5% glucose solution, intravenous drip within 30 minutes, and then at a maintenance dose of 100,000 IU/hour, continuous intravenous drip until clinical symptoms disappear, and then continue to maintain 3-4 hours, the course of treatment is generally 3-5 days. During the drug administration, prothrombin time and fibrinogen content should be monitored. The prothrombin time is normally about 15 seconds, so that the control is 2 to 3 times the normal value. Fibrinogen normal 2 to 4g/L, should not be lower than 0.5 to 1g/L. Urokinase: extracted from human urine, little side effects, better than streptokinase. Foreign dose is larger, the first dose of 3000-4000IU/Kg, intravenous drip in 10-30 minutes, maintenance amount of 2500-4000IU/Kg/hr, the course of treatment is generally 12-72 hours. Most domestic use of small doses, generally 30,000 to 50,000 IU / time, 2 to 3 times a day. Shanghai Zhongshan Hospital usage: 80,000 IU/dose, dissolved in 5% glucose solution, intravenous drip, 2 times daily. Later, according to the monitoring of fibrinogen and euglobulin lysis time, if fibrinogen is lower than 2g/L, or euglobulin lysis time is less than 70 minutes, all need to suspend the drug once, can continue to apply 7-10 days. Fibrinolytic enzyme (fibrinase, plasma enzyme) The first injection dose is 50,000 to 150,000 IU, intravenous drip, and then 50,000 Iu every 8 to 12 hours for 7 days. (3) Anticoagulation therapy: often used as a follow-up to thrombolytic therapy and surgical thrombectomy, commonly used anticoagulants are heparin and coumarin derivatives. Heparin is a very effective anticoagulant drug, the general adult dose of 1 ~ 1.5mg/Kg, every 4-6 hours intravenous or intramuscular injection once, and monitor the test tube method of clotting time, to control 20-25 minutes is appropriate, if less than 15 or more than 30 minutes, the dose should be increased or reduced. Coumarin derivatives Commonly used are Warfarin (Warfarum), new anticoagulation and new double coumarin, etc., generally 24 to 48 hours after the drug began to take effect, so often used in combination with heparin. Generally, after 2 days of combined use, the application of heparin is stopped and the maintenance amount of this drug is used. The duration of maintenance anticoagulation therapy should be determined by the condition and the site of thrombosis. For calf deep vein thrombosis, 4-7 weeks are required for maintenance; for iliofemoral vein thrombosis, 3-6 months are required. During the period of medication, the prothrombin time should be monitored so that it is controlled at about 20-30 seconds. Currently, warfarin is commonly used clinically, generally 10-15mg on the first day, 5mg on the second day, and later apply maintenance dose, about 2.5mg daily. (4) Exfoliation therapy: clinically used are low-molecular dextrose, aspirin and pentoxifylline, etc. (5) Chinese herbal medicine: the use of antithrombotic and pulsatile soup (Danshen, Chuanxiong, Angelica, Sanshou, Niu Xi, leech, Tu Beifeng, and Andrographis) with flavor. 2.Surgical treatment (1) Venous thrombectomy: Applicable to central type and mixed type within 3 days of disease. Nowadays, Fogarty catheter with capsule is mostly used to remove the embolus, which is easy to operate. ①Insert the first Fogarty catheter to the inferior vena cava through the right lower limb saphenous vein branch and inflate the balloon to prevent embolism; insert the second catheter from the left lower limb femoral vein incision to reach the proximal side of the thrombus. ②After deflating the balloon of the second catheter on the left side, together with the balloon, slowly pull it out. The balloon of the first catheter is deflated to restore blood return. (2) Inferior vena cava ligation or strainer: suitable for deep vein thrombosis of the lower extremity extending proximally to the inferior vena cava with pulmonary embolism. Inferior vena cava ligation, sudden reduction of cardiac output after surgery, may cause death and complicate lower extremity venous reflux obstruction, nowadays, it is not advocated to apply it, but to replace it with various kinds of strainer. Sixth, the sequelae The main and common sequelae of lower limb deep vein thrombosis is the syndrome after lower limb deep vein thrombosis. According to the different types of original lesions, the syndrome after lower limb deep vein thrombosis is also divided into three categories: 1. Peripheral type (distal inguinal ligament type): the thrombosis of the breeding and reproduction range, terminating in the distal side of the N vein, with a late passage rate of 95%, the main lesions are valve destruction and ankle traffic branch insufficiency, with rapid dystrophic changes in the foot and boot area. Treatment should be less standing, elevate the affected limb, apply elastic stocking force or elastic bandage to support compression, and perform traffic branch ligation. 2.Central type (inguinal ligament proximal type): The thrombosis is limited to the iliofemoral vein and does not extend to the distal part of the inguinal ligament, and the thrombus is rarely recanalized, mainly manifesting as distal venous reflux obstruction, and the main venous valve and ankle traffic branch function are not damaged. Treatment is appropriate for saphenous vein graft diversion. 3, mixed type (inguinal ligament proximal and distal type): the most common, clinical manifestations have both the above two types of characteristics, both venous reflux obstruction, and deep vein and traffic branch valve insufficiency. If reflux obstruction is the main type, various diversions are feasible for treatment; if reflux is the main type, transplantation of venous segment with valve, superficial femoral (distal) – deep femoral vein or saphenous vein (proximal) transposition diversion and hemitendinosus – biceps N vein valve replacement are feasible.