Lower extremity deep vein thrombosis, also known as lower extremity deep vein thrombosis, is a common condition that refers to the clotting of venous blood in the deep veins of the lower extremities. This disease may leave lower limb edema, secondary varicose veins, dermatitis, hyperpigmentation, and stasis ulcers.
Etiology
In the mid-19th century (1946-1956), Virchow proposed three major factors for 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 factors have specific content, but also can be confirmed by testing methods.
1.Venous blood flow stagnation
There are many causes of blood stagnation, such as prolonged braking, bed-ridden due to illness, sedentary, varicose veins, etc. In surgical patients, spinal anesthesia or general anesthesia causes the peripheral veins to dilate and slow down the venous flow; in surgery, the lower limbs are completely paralyzed due to anesthesia and lose the contraction function; after surgery, the muscles of the lower limbs are in a relaxed state due to incision pain and other reasons for bed rest, which causes the blood flow to stagnate and induces the formation of deep vein thrombosis in the lower limbs.
2.Venous wall damage
(1) Chemical injury intravenous injection of various irritant solutions and hypertonic solutions, such as various antibiotics, organic iodine solution, hypertonic glucose solution, etc. can stimulate the venous lining to varying degrees, leading to phlebitis and venous thrombosis.
(2) Mechanical injuries to veins local contusions, lacerations or fracture fragment trauma can cause venous thrombosis. Fractures of the femoral neck can damage the common femoral vein, and pelvic fractures can often damage the common iliac vein or its branches, both of which can be complicated by iliofemoral vein thrombosis.
(3) Infectious injury septic thrombophlebitis caused by perivenous foci of infection, less common, such as infectious endometritis, can cause septic thrombophlebitis of uterine veins.
3, blood hypercoagulation state
This is one of the basic factors that cause venous thrombosis. The causes of congenital hypercoagulable state include lack of thrombosis inhibitor, abnormal blood fibrinogen, abnormal fibrinolysis, etc. The causes of acquired hypercoagulable state include trauma, shock, surgery, tumor, long-term use of estrogen, pregnancy, etc. Platelet adhesion capacity is enhanced after various major surgeries; postoperative serum levels of inhibitors of both pre-fibrinolytic activators and fibrinolytic enzymes are elevated, resulting in reduced fibrinolysis. Blood coagulability can be increased after splenectomy due to the sudden increase in platelets, and blood concentration due to burns or severe dehydration. Advanced cancer such as lung cancer, pancreatic cancer, others such as ovarian, prostate, stomach or colon cancer, when cancer cells destroy tissues at the same time, they often release many substances, such as mucin coagulant, etc. The activity of certain enzymes increases and reduces the level of antithrombin III, which increases blood coagulation. The application of large doses of hemostatic drugs can also cause the blood to be in a hypercoagulable state.
The two main causes of venous thrombosis are stagnant venous blood flow and hypercoagulable blood. A single factor cannot cause the disease independently yet, but often the combination of two or three factors causes deep vein thrombosis. For example, the high incidence of postpartum DVT is the result of a combination of factors. The ability of placental abruption in the uterus after delivery to stop bleeding rapidly in a short period of time without causing postpartum hemorrhage is closely related to the hypercoagulable state of the blood. The placenta produces a large amount of estrogen during pregnancy, peaking at term, and the amount of estriol can increase to 1000 times that of non-pregnancy. Estrogen promotes the production of various coagulation factors by the liver, and at the same time, the fibrinogen in the body also increases greatly at the end of pregnancy, resulting in a hypercoagulable state of blood, which, together with bed rest after delivery, causes blood flow to stagnate in the lower extremities and thus has a tendency to develop deep vein thrombosis. The stagnant blood flow alone is not sufficient to produce the disease, but sometimes there is damage to the vessel wall, such as direct injury, chronic disease, or distant tissue damage, which produces leukocyte tropism factors that cause leukocytes to move to the vessel wall. Similarly, fissures in the endothelial cell layer and the exposure of subendothelial collagen in the basement membrane can cause platelets to move toward the intima, leading to the onset of the coagulation process.
Clinical manifestations
1.Symptoms
The most common main clinical manifestation is the sudden swelling of one limb. Patients suffering from deep vein thrombosis of the lower extremity feel localized pain, which increases when walking. In mild cases, only local heaviness is felt, and the symptoms are aggravated when standing.
2.Signs
Physical examination has the following features: ① The development of swelling of the affected limb is reliable only if it is measured accurately with a tape measure every day and compared with the thickness of the healthy lower limb, which is unreliable simply by visual observation. This sign is of high value to confirm the diagnosis of deep vein thrombosis, which often leads to increased tissue tension when the swelling of the lower leg is severe; ② pressure pain is often present at the site of venous thrombosis. Therefore, the lower limbs should be examined for calf muscles, N fossa, adductor canal and femoral vein below the groin; ③Homans sign can cause deep pain in calf muscles when the foot is sharply bent to the dorsal side. Homans sign is often positive in the case of deep calf vein thrombosis. This is caused by the passive extension of gastrocnemius and flounder muscles, which stimulates the blood all veins of the calf; ④ superficial varicose veins deep vein obstruction can cause superficial vein pressure to rise, and superficial varicose veins can be seen 1 or 2 weeks after the onset.
Examination
It should be noted that some patients may not have typical clinical manifestations, and the following examinations can be used to confirm the diagnosis of venous thrombosis which is difficult to diagnose, and the lower limb venous ultrasound examination is generally preferred, taking care not to miss the iliac veins and intermuscular veins.
1.Vascular non-invasive examination method
In recent years, there has been great progress in the examination method for the diagnosis of deep vein thrombosis, and the vascular non-invasive examination method is used, including radioactive fibrinogen test, ultrasonic examination, electrical impedance volume tracing method, etc. The radioactive fibrinogen test is more sensitive to check the calf deep vein thrombosis, and ultrasound examination is most valuable to check the iliofemoral vein thrombosis. If the above two examination methods are used, the diagnosis is not clear yet, and venography is still needed. So far, there is no non-invasive examination method that can completely replace the traditional venography. Continuously explore and improve the non-invasive examination method, is the direction of future efforts.
2.Upstream venography
The site and scope of thrombosis can be understood. The patient lies supine in a semi-erect position with the head end 30°~45° high. First, tie a rubber tube tourniquet at the ankle to compress the superficial vein, and then use a 12-gauge puncture needle to directly puncture into the superficial vein of the dorsal foot percutaneously, and inject 80-100ml of 40% pantothenic glucosamine within one minute, and take X-rays of the calf first, then the thigh and pelvis under the guidance of TV screen. After the injection of contrast agent, saline is then quickly injected to flush the lumen of the vein, reduce the stimulation of contrast agent and prevent the occurrence of superficial phlebitis.
3.Contrast X-ray
It often shows spherical or sinuous filling defect in the vein, or the main trunk of the vein does not appear, and the distal vein is dilated, and there are abundant lateral branch veins nearby, which all suggest thrombosis in the vein.
Venous pressure is measured by puncturing a superficial vein of the foot or ankle or a superficial vein of the arm with a continuous needle of a glass measuring device filled with saline. The value is checked against the venous pressure of the healthy side. This test is used in the early stage of the lesion before the establishment of the collateral vessels to have diagnostic value.
4.Laboratory tests
D-dimer (D-dimer) test, D-dimer mainly reflects fibrinolytic function. Increased or positive D-dimer is seen in secondary fibrinolytic hyperfunction, such as hypercoagulable state, diffuse intravascular coagulation, renal disease, organ transplant rejection, thrombolytic therapy, etc. As long as there is activated thrombosis and fibrinolytic activity in the body’s blood vessels, D-dimer will be elevated. D-dimer negativity generally excludes lower extremity deep vein thrombosis, and D-dimer positivity requires further imaging.
Diagnosis
1.Most commonly seen in postpartum, post-pelvic surgery, trauma, advanced cancer, coma or patients who are bedridden for a long time.
2.The onset is acute, with swelling and hardness and pain of the affected limb, which is aggravated after activity, often accompanied by fever and rapid pulse.
3.The thrombus site is painful, cords can be found along the blood vessels, the limb distal to the thrombus or the whole limb is swollen, the skin is blue-purple, the skin temperature is reduced, the dorsal foot and posterior tibial artery pulsation is weakened or disappeared, or venous gangrene appears. When the thrombus extends into the inferior vena cava, edema is evident in both lower extremities, buttocks, lower abdomen, and external genitalia. When the thrombus occurs in the muscular plexus of the calf, Homans’ sign and Neuhof’s sign are positive.
4.Late thrombus absorption mechanization, often left venous insufficiency, birth superficial varicose veins, pigmentation, ulceration, swelling, etc., called deep vein thrombosis after syndrome.
5.Thrombus dislodgement can lead to pulmonary embolism.
6.Radiofibrinogen test, Doppler ultrasound and venous hemogram can help to diagnose. Venography can confirm the diagnosis.
Treatment
1.Bed rest and elevation of affected limbs
Leg elevation and initial bed rest may relieve pain in patients with deep vein thrombosis with acute leg swelling. The traditional approach of recommending strict bed rest for 1 to 2 weeks to prevent pulmonary embolism has been questioned, and lung scans have shown that bed rest does not reduce the incidence of pulmonary embolism. In addition, early movement out of bed resulted in faster improvement in pain and swelling compared to bed rest.
Wearing compression stockings in patients with deep vein thrombosis improves pain and swelling long-term wear may inhibit thrombus growth and reduce post-thrombotic syndrome.
2.Anticoagulation therapy
This is one of the most prominent modern treatments for deep vein thrombosis. The correct use of anticoagulants can reduce the complication rate of pulmonary embolism and the sequelae of deep vein thrombosis. Their role is to prevent the continued growth of established thrombi and the formation of new thrombi elsewhere, and to promote more rapid re-tubulation of thrombosed veins. Heparin or low-molecular heparin is generally used in the acute phase, and the transition to oral anticoagulants, such as warfarin, requires monitoring because of the complex drug- or food-related effects of warfarin, the large variation in individual doses, and the risk of bleeding. In recent years, many new oral anticoagulants have been developed, such as rivaroxaban. Rivaroxaban is rarely affected by drugs or food, and generally does not require testing and is easy to use.
3.Thrombolytic therapy
Including systemic thrombolysis and catheter contact thrombolysis, the drugs used are mostly urokinase and so on. Systemic thrombolysis via intravenous systemic thrombolysis: systemic administration of drugs through superficial veins, so that the drugs are evenly distributed in the body with blood circulation to achieve the purpose of thrombolysis. Interventional thrombolysis mostly refers to contact thrombolysis with catheter: also called CDT, which is inserted retrogradely into the distal deep vein of the limb through the proximal deep vein, firstly, the outflow tract obstruction is partially relieved by the physical opening of the vessel lumen with the guide wire and catheter, and then the drug is directly contacted with the thrombus through the placement of thrombolytic catheter to dissolve the fresh thrombus in the acute stage, and the main vein is restored to patency in time. Some scholars believe that catheter thrombolysis for iliofemoral vein thrombosis can improve the quality of life than simple anticoagulation.
4.Long-term treatment of deep vein thrombosis
The duration of anticoagulation therapy for DVT is still controversial. Long-term anticoagulation helps to reduce the recurrence of DVT and post-thrombotic syndrome. For DVT caused by simple factors such as surgery or immobilization, the duration of anticoagulation needs to last 3 months, for idiopathic DVT, it is recommended that the duration of anticoagulation needs to last 6 to 12 months, for patients with malignancy, low molecular heparin due to warfarin, the duration of medication is 3 to 6 months. For the first episode of DVT but with anticoagulant antibodies or two or more risk factors for thrombosis, it is recommended that anticoagulation should be continued for at least 12 months, while for patients with two histories of DVT, lifelong anticoagulation should be administered.
6. Prevention
For patients with high risk factors, comprehensive preventive measures should be taken. Such as preoperative and postoperative necessary drug prophylaxis for surgical patients. During intraoperative operations, operations around adjacent extremities or pelvic veins should be performed gently to avoid endothelial injury. Avoid postoperative pillows under the calf to interfere with deep calf venous return. Encourage the patient’s feet and toes to move frequently and encourage more deep breathing and coughing movements. Get out of bed as early as possible and wear medical elastic stockings for the lower limbs if necessary. Special attention is paid to elderly, cancer or heart disease patients after thoracic, abdominal or pelvic greater than surgery, after femur fracture, and postpartum women.