Deep Venous Thrombosis – Causes, Risk Factors, Symptoms And Diagnosis

Deep Venous Thrombosis

Deep venous thrombosis is represented by the formation of a blood clot (thrombus) in the deep veins of the lower limbs, pelvis or upper limbs. Thrombi can form in the superficial veins ( the condition is called thrombophlebitis or more simply, phlebitis) or in deep veins. Thrombi in superficial veins rarely cause problems, while those in the deep veins require immediate medical evaluation.

Thrombi from deep veins can be large in size and may move into the blood torrent up to the lungs, causing pulmonary embolism, which can be life-threatening. Deep venous thrombosis may have other long-term complications. In about 25% of cases, deep venous thrombosis can cause venous wall damaging, leading to chronic post-thrombotic syndrome. This syndrome is responsible for the appearance of pain, leg swelling, abnormal pigmentation of the leg skin (depigmentation) and limb injuries. Most of the thrombi develop in lower leg and thigh veins and less frequently in the upper limb or in pelvic veins.

Deep Venous Thrombosis

Deep Venous Thrombosis Causes

There are three major causes that increase the risk of developing deep venous thrombosis:

• Slowed blood flow. After certain surgical procedures or after a period of inactivity (for example after prolonged period of immobilization in bed or in long time airplane flights), blood flow from the veins of the legs is slowed and this represents a factor which can favor the formation of thrombi.
• Damage to the blood vessels. Blood vessels can be damaged by certain surgical procedures or by trauma.
• Changes in blood composition. Cancer or certain inherited disorders can cause the formation of clots faster than usual.

Deep Venous Thrombosis Risk Factors

There are several factors that increase the risk of developing deep venous thrombosis. Some risk factors can not be modified (eg. congenital disorders), while others are transiently and depend on certain circumstances (eg. pregnancy). The risk factors for deep venous thrombosis can be divided in major and minor.

Major risk factors for deep venous thrombosis are:

1. Bed rest for a period longer than 3 days.
2. Coagulation disorders (hypercoagulable state, in which clots forms faster), as a result of inherited genetic disorders, like deficiency of S protein, C protein deficiency, antithrombin III deficiency and factor V Leiden deficiency.
3. Major trauma.
4. Surgical procedures, especially for the knee or hip, neurosurgery or thoracic or abdominal surgical intervensions.
5. Procedures and therapies used for cancer treatment.
6. Paralysis due to spinal cord damage.
7. Introduction of a central venous catheter.

Deep Venous Thrombosis causes

Minor risk factors for deep venous thrombosis are:

Most of these factors have minimal effect if they appear alone, but in combination increase the risk for developing deep venous thrombosis. The risk of developing deep venous throbosis is increased by:

1. Certain diseases: varicose vein, myocardial infarction, heart failure or stroke.
2. A long journey by plane or by car, because of prolonged immobilization.
3. Pregnancy, especially after normal birth or after cesarean section.
4. Age. People older than 40 years have a higher risk of developing deep venous thrombosis.
5. Obesity.
6. The use of contraceptives. A recent study showed that the risk of pulmonary embolism as a complication of deep venous thrombosis is higher in women who are taking birth control pills. Contraceptive used before the appearance of thrombosis seems not to increase the risk of pulmonary embolism.
7. Hormonal therapies, such as estrogen substitutes, raloxifene for osteoporosis or tamoxifen for breast cancer treatment. Some studies have shown that the estrogen-progesterone combination have a lower risk for developing deep venous thrombosis.
8. Smoking.

Deep Venous Thrombosis Symptoms

In general, deep venous thrombosis causes minimal symptoms. If the symptoms appear, it may include:

• Edema, which can be generalized or localized to the affected limb, or only to the affected blood vessel and will give the aspect of a inflamed cord, which can be felt on palpation.
• Increased local temperature.
• Pain or tenderness. Pain may be continuous in the lower limb or in thigh, or can be present only at the palpation of the area or can appear in walking.
• Erythema (skin redness).

Deep Venous Thrombosis causes

There are several disorders which can have symptoms that are similar to deep venous thrombosis symptoms, such as Baker cyst or cellulitis, and can make the diagnosis to be difficult.

Sometimes the appearance of a pulmonary embolism, will raise the suspicion of a deep venous thrombosis. Pulmonary embolism is a sudden blocking of arteries in the lungs. Thrombi from deep veins of the legs are the most common cause of pulmonary embolism. Symptoms of pulmonary embolism include:

• Sudden dyspnea (shortness of breath);
• Chest pain that gets worse in inspiration;
• Cough that can be bloody (with streaks of blood);
• Tachycardia (increased heart rate).

Pulmonary Embolism

Deep Venous Thrombosis Diagnosis

Deep venous thrombosis is suspected by history of the patient and by physical examination. The data obtained after the initial investigations will allow the physician to determine if the risk of developing deep venous thrombosis is low, medium or high. Establishment of risk will help the physician to determine the appropriate investigations to diagnose deep vein thrombosis.

Investigations commonly used in the diagnosis of deep vein thrombosis are:

Ultrasound represents the most used test to diagnose deep venous thrombosis. This test allows the visualization of blood flow in the veins. Sequence of investigations for deep venous thrombosis is influenced by risk level and by ultrasound results. If further investigations are need, these include:

• Ultrasound repetition, usually after a period of several days;
• Venography. This test involves injecting a contrast substance in the veins, which allow their visualization on X-ray examination.

Venography is useful if ultrasound examination does not provide an accurate diagnosis of deep venous thrombosis. Ultrasound examination does not provide accurate results if it is performed to determine the existence of a thrombus in deep veins of the lower leg. Although, thrombi at this level are not, usually, dangerous, they can grow in size and can extend to the thigh and can become dangerous. Thrombi from the leg veins have increased risk for the occurrence of pulmonary embolism. For this reason are needed  repeated ultrasound examinations, venographies or other tests to identify thrombi that can be overlooked in one ultrasound.

Additional tests:

Aditonale tests are useful in cases in where the ultrasound results are unclear, venography is not available or the result of venography can not establish the diagnosis of deep venous thrombosis. These additional tests can diagnose a thrombus or can exclude a deep venous thrombosis, but are not usually used.

Additional tests may include:

• Determination of D-dimers. This blood test is done before or after the ultrasound examination, if results are not clear enough to exclude deep venous thrombosis in individuals at low risk.
• MRI;
• Computed tomography (CT).
• Certain blood tests can diagnose a inherited coagulation disorders that can increase the risk of thrombus formation. However, screening of these diseases is not usual.

Deep Venous Thrombosis Ultrasound

Screening is indicated in individuals who had one or more of the following events:

1. Thrombus in a vein that has a precise cause.
2. Thrombosis occurred in a person younger than 45 years.
3. Presence of  deep venous thrombosis in a first degree relatives (mother, father, brother, sister). Family history of clots in the arteries does not increase the risk of developing deep venous thrombosis.
4. Thrombus with unusual location, such as: gastrointestinal region, brain or upper limbs.

Some experts believe that routine screening can prevent the onset of a deep venous thrombosis in patients with high risk or who are in a situation with high risk, for example, are subjected to a major surgical intervention.

People treated with anticoagulants need regular blood tests to monitor the effects of anticoagulants.These tests include:

• The activated partial thromboplastin time (APTT) for monitoring therapy with unfractionated standrad heparin;
• Prothrombin time for monitoring warfarin therapy;
• If pulmonary embolism is suspected, will be performed chest X-ray, computed tomography or pulmonary angiogram.