Published May 17, 2023 by

What is Deep Vein Thrombosis (DVT): Symptoms, Causes, Treatments


General Discussion 

Deep vein thrombosis is clotting of blood in a deep vein of a limb (usually calf, thigh) or pelvis. Acute deep vein thrombosis is the main cause of pulmonary embolism. It happens as a result of conditions that impair venous return, cause endothelial dysfunction or damage, or increase coagulability. It may be asymptomatic or cause pain and swelling of the limb; Pulmonary embolism is an immediate complication. The diagnosis is made using the patient's medical history, physical examination, and objective testing, often duplex ultrasonography.When deep vein thrombosis is suspected, D-dimer tests are done; a negative result aids in the exclusion of deep vein thrombosis, whereas a positive result is vague and need further testing to confirm deep vein thrombosis. Treatment involves the use of anticoagulants. Prognosis is generally good with prompt and adequate treatment. Long-term complications include venous insufficiency, with or without postphlebitic syndrome.

The lower limbs or pelvis are where acute deep vein thrombosis most frequently manifests itself (see image Deep veins of the legs).It can also develop in the deep veins of the upper limbs (4 to 13% of deep vein thrombosis cases).

Deep venous thrombosis of the lower limb is much more likely to cause pulmonary embolism, possibly because of the greater amount of clot. The superficial femoral and popliteal veins of the thighs and the fibular and posterior tibial veins of the calf are the most frequently involved. Deep venous thrombosis of the calf veins is less likely to be a source of large emboli, but can spread to proximal thigh veins and from there trigger pulmonary embolism. About 50% of patients with deep vein thrombosis have occult pulmonary embolism, and at least 30% of patients with pulmonary embolism have demonstrable deep vein thrombosis.

Pathophysiology and risk factors 

The pathophysiology of the disease is related to three factors (Virchow's Triad): venous stasis, hypercoagulable states and endothelial injury. These factors lead to the recruitment of activated platelets, which release pro-inflammatory mediators, triggering a cascade of reactions that result in platelet aggregation and platelet-dependent thrombin synthesis. Venous thrombi form in an environment of stasis, low oxygen tension and increased expression of pro-inflammatory genes. 

Risk factors can be classified as: 

– Hereditary: resistance to activated protein C (mainly factor V Leiden); mutation of the prothrombin gene G20210A; antithrombin deficiency; protein C deficiency; protein S deficiency; hyperhomocysteinemia; increased factor VIII; increased fibrinogen. 

РAcquired: antiphospholipid antibody syndrome; cancer; paroxysmal nocturnal hemoglobinuria; age > 65 years (age is the biggest risk factor for thrombosis); obesity; pregnancy and puerperium; myeloproliferative diseases (polycythemia vera; essential thrombocythemia, etc.); nephrotic syndrome; hyperviscosity (Waldenstr̦m's macroglobulinemia; multiple myeloma); Behcet's disease; trauma; surgeries (the ones with the highest risk are neurosurgeries and orthopedics, with a focus on the hip and knee); immobilization; extended air travel (>6 hours); estrogen therapy.

Clinical condition 

Clinical findings are related to the disease in only 50% of cases. When present, they may consist of: pain, edema (mainly unilateral and asymmetrical), erythema, cyanosis, dilation of the superficial venous system, increased temperature, muscle swelling and pain on palpation. Homans' sign (pain on foot dorsiflexion) may be present but has little diagnostic value. When the difference in diameter between the two calves is greater than 3 cm, the likelihood of DVT increases significantly. 

Clinical findings alone show unsatisfactory performance for the diagnosis of DVT, requiring the use of specific criteria. Among these criteria, the Wells score for DVT (Table 1) is the best validated.

Common Risk Factors 

•Genetic predisposition; 

•Age over 40 years; 


•Pregnancy and postpartum; 


•Use of contraceptives; 

•Hormone therapy; 

•Difficulty walking; 


•Varicose veins; 


•Long-term surgeries; 

•Heart and/or respiratory failure; 

•Air or land travel that requires the passenger to sit for many hours; 



There are several responsible causes DVT. These can be grouped into three categories. These groups and the associated risk factors consist of: 

•Damage to deep veins causing clot formation: 

individuals with trauma, those who just underwent surgery (particularly orthopedic surgery and cancer surgery), 

•Immobility causing blood stagnation and clot formation: 

patients who are hospitalised, post-operative patient (other surgeries), long-term travel (low risk) 

•Conditions and diseases that increase the risk of forming clots: 

cancer, pregnancy, advanced age, personal history of DVT, genetic conditions increasing the risk of forming clots, oral contraceptives and hormone replacement therapy.


The most common symptoms of a DVT are calf pain and swelling in the leg. It is well established, however, that patients with these symptoms do not necessarily have DVT and that patients with proven DVT will not necessarily have these symptoms. The initial presentation may also be that of a pulmonary embolism. Associated symptoms are shortness of breath (dyspnea), chest pain and palpitations. 

Several years after a DVT, up to 20% of patients may develop post-phlebitic syndrome. Leg swelling, heaviness, soreness, and skin changes are symptoms of this condition. These are explained by a chronic obstruction of the deep veins causing complications related to the increase in pressure in the veins.

How is Deep Vein Thrombosis diagnosed? 

The doctor will ask the patient questions about his symptoms, medical history and examine him. Signs and symptoms alone are usually not enough to diagnose DVT, and the doctor may recommend some tests. 

•D-dimer test: D-dimers are parts of a protein found in the blood when a clot is broken down by fibrinolysis, if its concentration is found to be elevated above a threshold in a blood test, it is possible that the patient has a clot in a vein.

•Ultrasound: this type of test can detect clots in veins, and also determine the speed of circulation in a vein. If the doctor knows that the flow has slowed, he can detect the clot if it is present. A Doppler ultrasound can tell us how fast the blood is flowing.

•Venography: this diagnostic test may be used if ultrasound and D-dimer testing are not diagnostic. The doctor injects contrast into a vein in the patient's leg. Radioscopically we can watch the contrast as it moves and reveals the location of the clot because the contrast won't be able to bypass it – it's imaged as a void in the blood vessel.

•Other imaging tests: magnetic resonance imaging (MRI) or computed tomography (CT) may reveal clots. Often such clots are discovered incidentally when these tests are ordered for another reason.

Treatments for deep vein thrombosis

The doctors' goal when treating a patient with deep vein thrombosis is to stop the clot from growing, preventing it from breaking off and traveling to the lungs and causing a pulmonary embolism, preventing recurrence of deep vein thrombosis, and minimizing the risk of other complications.

★Thrombolysis:– called the breaking up of blood clots. Medicines that break up blood clots are called thrombolytics. Patients with more severe DVT or pulmonary embolism may need to be treated with these. TPA (or tissue plasminogen activator) is an example. Because there is a risk of side effects - mainly bleeding - it is only used when the patient's life is in danger.

★Inferior vena cava filter:- is a tiny umbrella-like device placed in the vein to collect clots and prevent them from reaching the lungs while allowing circulation to continue. It is located in the inferior vena cava, a large vein. 

★Antithrombotic compression stockings:- worn to reduce calf pain, swelling and prevent ulcers. Stockings can protect the patient from

postthrombotic syndrome: 

This is a long-term complication of DVT that affects 20 to 50% of DVT patients – the tissues in the calf are destroyed and this results in pain, itching, ulceration, skin discoloration and swelling. 

A patient with DVT must wear stockings for at least 24 months. They must be worn constantly.

Complications of Deep Vein Thrombosis

There are two possible complications: 

•Pulmonary embolism (PE):

The most frequent complication, and also often life-threatening. A piece of clot breaks off and travels through the circulation to the lungs where it lodges. The clot affects blood circulation in a blood vessel of the lung. In mild cases the patient may not even notice it. A medium-sized clot can cause breathing problems and chest pain. In more severe cases, the lungs can collapse, heart failure and even death can occur.

•Postthrombotic syndrome:

Is more common in patients with recurrent DVTs. The patient may experience persistent swelling in the calf area, pain, bleeding into the skin (purpura), ulcers, itching, eczematous dermatitis and cellulitis.