I. Definition
Deep venous thrombosis (DVT) refers to the abnormal clotting of blood in the deep venous lumen, blocking the venous lumen; resulting in venous reflux obstruction, if not treated in time, it will cause chronic deep venous insufficiency of varying degrees, affecting life and work ability, and if the thrombus is dislodged, it can cause pulmonary embolism, resulting in life-threatening. The whole body trunk veins can develop, especially in the lower limbs.
Etiology and pathology
In 1946, Virchow proposed that damage to the vein wall, slow blood flow and hypercoagulable blood are the three major factors causing deep vein thrombosis, which are still in use today. The external causes of slow blood flow are: prolonged bed rest, intraoperative, postoperative and braking state such as limb immobilization and sedentary. At this time, due to slow venous blood flow, vortices are formed in the valve sinus, which not only activate the endogenous coagulation system, but also cause platelets to move from axial flow in the blood stream (axial flow) to close to the endothelium (side flow), contributing to thrombosis. Hypercoagulable blood is seen in pregnancy, postpartum or postoperative period, trauma, long-term use of contraceptives, and tumor tissue lysis products, which increase the number of platelet loss and increase the content of coagulation factors while decreasing the activity of anticoagulation factors, leading to abnormal clotting and thrombosis in blood vessels.
After thrombus formation, the thrombus can be dissolved and dissipated under the action of fibrinolytic enzymes, and sometimes the disintegrated and broken thrombus can become embolus and enter the pulmonary artery with blood flow to cause pulmonary embolism.
Third, risk factors
Prolonged bed rest, joint braking, advanced age, obesity, high LDH, trauma, heart failure, etc.
IV. Clinical manifestations and typing
Deep vein is the main pathway of venous blood return, once the lumen is blocked by thrombosis, it will definitely cause the symptoms of distal venous return obstruction.
1.Typing according to the anatomical site of thrombosis in acute stage.
(1) Central type
The main clinical features are acute onset, obvious swelling of the whole lower limb, pain and pressure pain in the iliac fossa and femoral triangle on the affected side, dilated superficial veins, and increased skin temperature and body temperature of the affected limb. Left-sided onset is more frequent than right-sided.
(2) Peripheral type
(2) Peripheral type includes femoral vein thrombosis and deep vein thrombosis of the lower leg. The main clinical feature of thrombosis limited to femoral vein is swelling and pain in the thigh, but the swelling in the lower limb is often not serious because the iliac-femoral vein is open. Deep vein thrombosis confined to the calf is characterized by sudden onset of severe pain in the calf, inability of the affected foot to land on the ground, and worsening of symptoms when walking; swelling and deep pressure pain in the calf, and ankle hyperextension test can lead to severe pain in the calf (positive Homans sign).
(3) Mixed type
(3) Mixed type, i.e. total lower limb deep vein thrombosis. The main clinical manifestations are: generalized swelling and severe pain in the whole lower extremity, and pressure pain in the femoral triangle, N fossa and calf muscle layer, often accompanied by increased body temperature and accelerated pulse rate (white swelling of the femur). If the disease continues to progress, the limbs become extremely swollen, causing compression of the arteries in the lower extremities and arterial spasm, resulting in impaired blood supply to the lower extremities and loss of pulsation of the dorsalis pedis artery and posterior tibial artery, which often results in blisters on the calves and dorsalis pedis, and a marked decrease in skin temperature and bruising (femoral cyanosis); if not treated in a timely manner, venous gangrene may occur.
2.Typing according to the evolution of clinical course: After the formation of deep vein thrombosis in lower limbs, with the prolongation of the disease, it gradually enters the chronic stage from the acute stage. According to the course of disease, it can be divided into the following four types.
(1) Occlusive type
Early stage of the disease, the main feature: intracavernous obstruction of the deep veins, characterized by severe swelling and distension of the lower extremities, accompanied by extensive superficial venous dilatation, generally without dystrophic changes in the lower legs.
(2) Partial recanalization type
In the middle stage of the disease, the main feature is that the deep veins are mainly occluded, accompanied by early recanalization. At this time, the swelling of the limb is reduced, but the superficial venous dilatation is more obvious; there may be pigmentation of the distal calf.
(3) Recanalization type
(3) late stage of the disease, the main features: most or complete recanalization of the deep veins, clinically reduced swelling of the lower limbs but aggravated by activity; marked superficial varicose veins, extensive pigmentation of the lower legs and chronic recurrent ulcers.
(4) Recanalization
The main feature is the recurrent acute deep vein thrombosis in the already recanalized deep vein lumen.
V. Examination and diagnosis
1.Signs and symptoms
(1) Sudden swelling of one limb.
(2) Swelling or pressure pain, superficial venous dilatation.
(3) Positive Homans sign: when the foot is bent sharply to the dorsal side, it can cause pain in the deep calf muscle. Homans’ sign is often positive in case of deep vein thrombosis in the lower leg.
All of the above signs and symptoms should be suspected of lower extremity deep vein thrombosis. The following tests can help to confirm the diagnosis and understand the scope of the lesion.
2.Auxiliary examination
(1) Ultrasound Doppler examination: To determine the maximum venous outflow rate, use the pressure cuff to block the limb vein, and record the maximum venous outflow rate after release, which can determine whether there is obstruction in the main veins of the lower limbs, but it is not very sensitive to small vein thrombosis.
(2) Radionuclide examination: intravenous injection of iodine-125 fibrinogen can be taken up by fresh blood clot, and the content is more than 5 times of the equivalent blood uptake, so it can detect early thrombosis, and is used for screening examination of high-risk patients.
(3) Phlebography: It can directly visualize the veins and make a definite diagnosis of the deep vein pattern in each area. The main x-ray signs are.
(1) Occlusion and interruption: the main trunk of the deep vein is completely blocked by a thrombus without visualization, or there is a sign of sudden obstruction of the contrast agent in a certain plane. Generally speaking, it is seen in the acute phase of thrombosis.
(ii) Filling defect: persistent, cylindrical or cylindrical-like areas of reduced contrast density in the static lumen of the trunk, i.e., filling defect shadow, is a direct sign of venous thrombosis and is the diagnostic basis for acute deep vein thrombosis.
(iii) Recanalization: the lumen of the vein is irregularly narrowed or finely multibranched, and some of them may show dilatation or even dilatation and distortion. The above signs are seen in the middle and late stages of thrombosis.
④Collateral circulation formation: around the adjacent obstructed veins, there are irregularly arranged collateral veins showing.
Prevention and treatment
Deep vein thrombosis of lower extremity is most closely related to surgery, braking and blood hypercoagulation, therefore, anticoagulation and antiplatelet aggregation drugs should be given for prevention, which can be injected with 2000-2500 AXaIU of low molecular heparin under the abdominal wall once a day for 10-14 days or until the risk of thrombosis disappears. Encouraging patients to make frequent active movements of the extremities and to leave the bed early, to elevate the foot of the bed appropriately, to apply functional muscle electrical stimulation, or to circulate pressure apparatus in the extremities, and to wear long elastic stockings (up to the femur) are the main preventive measures.
Deep vein thrombosis of the lower limbs is important for prevention. For the deep vein thrombosis that has occurred, the treatment methods can be divided into two categories: non-surgical treatment and surgical embolization, which should be determined according to the type of lesion and the actual disease period.
1.Non-surgical treatment
(1) General treatment.
Absolute bed rest, elevation of the affected limb, braking for 2-3 weeks, the patient should be elevated above the level of the heart, about 20-30cm from the bed, and the knee joint should be placed in a slightly flexed position. Use diuretics as appropriate to reduce swelling of the limb. When the systemic symptoms and local pressure pain are relieved, light activities can be performed. When getting up and moving, elastic stockings or elastic bandages should be worn.
Duration of use of elastic stockings.
①For thrombophlebitis of the deep or superficial veins of the calf, it is generally not necessary to use, but if edema appears in the ankle and lower calf, it can be used for several weeks.
(ii) For N and femoral vein thrombosis, it is generally used for no more than 6 weeks.
(3) For iliofemoral vein thrombosis, it is used for 3 months first and then removed intermittently for no more than 6 months in general, but if edema appears, it should be continued.
(2) Thrombolytic therapy.
Thrombolytic therapy can be given to patients whose disease duration does not exceed 72 hours. The commonly used drug is urokinase, and the dose is usually 80,000 units each time, dissolved in 5% glucose solution 250-500ml intravenously twice a day for 7-10 days. If necessary, the dosage can be adjusted according to the measurement of fibrinogen and euglobulin dissolution time.
(3) Anticoagulation therapy.
Indications.
(i) Within 1 month after venous thrombosis.
②When there is a possibility of pulmonary embolism after venous thrombosis.
③After thrombus removal.
Contraindications include
① bleeding tendency.
②After abortion.
③Subacute endocarditis.
④Ulcer disease.
⑤ hepatic and renal insufficiency.
Commonly used anticoagulants are heparin and coumarin derivatives. The former is usually started, followed by the latter. Heparin can be administered intravenously by continuous drip or intermittent injection, or subcutaneously to maintain the clotting time about two times above normal. Among the coumarin derivatives, warfarin can be used in adult doses of 5 mg per dose three times daily on the first day, 5 mg per dose twice daily on the second day, and 2.5 mg or 5 mg per dose once daily starting on the third day, with a maintenance dose of about 2.5 mg adjusted according to coagulation function. Controlled by International Normalized Ratio (INR) of 2-3. generally maintained for 2-3 months. Treatment with low molecular heparin sodium (4000 units, qd. or 150 units/kg qd.) or low molecular heparin calcium (85 IU/kg, qd. for established DVT) is applied. The most serious complication of anticoagulant drugs is bleeding, and the dose varies greatly among individuals and must be used under close supervision.
(4) Anti-platelet aggregation therapy.
Anti-aggregation drugs include dextran, aspirin, dipyridamole (Pansentin) and salvia, etc. They can expand blood volume, dilute blood, reduce viscosity and prevent platelet coagulation, and thus are often used as adjuvant therapy.
2.Surgical therapy
It is often used in patients with deep vein thrombosis of lower limbs, especially iliac-femoral vein thrombosis. For those whose condition continues to aggravate, or those who have already shown signs of femoral cyanosis, even if the disease period is long, surgical extraction of the embolus is used as much as possible to save the limb. The main surgical method is Fogarty catheter embolization, and postoperative adjunctive anticoagulation and expectoration therapy for 2 months to prevent recurrence.
VII. Complications and sequelae
Deep vein thrombosis can cause pulmonary embolism if it dislodges into the pulmonary artery, and large pulmonary embolism can be fatal, which should be paid great attention. Through the peripheral vein route, a metal stent with a filter is placed into the inferior vena cava using a specially designed delivery device, which can stop the dislodged thrombus in the deep veins of the lower limbs from entering the inferior vena cava and prevent the occurrence of pulmonary embolism.