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Deep venous thrombosis

(Redirected from Deep vein thrombosis)
DVT can also refer to Driving Van Trailer

Deep venous thrombosis (or DVT) is the occlusion of a deep vein by a blood clot ("thrombus"). It generally affects the leg veins, such as the femoral vein or the popliteal vein , or occasionally the veins of the arm ("Paget-von Schroetter syndrome").

Contents

Signs and symptoms

Classical symptoms of DVT include pain, swelling and redness of the leg, starting with the calf and progressing upwards. In many patients, the symptoms are more insidious. In up to 25% of all hospitalised patients, there may be some form of DVT, which often remains clinically inapparent (unless pulmonary embolism develops).

There are several techniques during physical examination to increase the a priori likelihood of DVT. These include measuring the circumference of the affected and the contralateral limb at a fixed point (to objectivate oedema), and palpating the venous tract, which is often tender.

A careful history has to be taken considering risk factors (see below), including the use of the oral contraceptive pill, recent long-haul flying, a history of miscarriage (which is a feature of several disorders that can also cause thrombosis). A family history can reveal a hereditary factor in the development of DVT.

It is very important that the possibility of pulmonary embolism is excluded in the history, as this may warrant further investigation (see pulmonary embolism).

Diagnosis

In a low-probability situation, current practice is to commence investigations by testing for D-dimer levels. This fibrin degradation product is an indication that thrombosis is occurring, and that the blood clot is being dissolved by plasmin. A low D dimer level should prompt other possible diagnoses (such as a ruptured Baker's cyst, if this has not been considered as part of the history).

Other blood tests usually performed at this point are:

In cases of higher suspicion, compression ultrasound scanning of the leg veins, combined with duplex measurements (to determine blood flow), can reveal a blood clot and the extent of it (i.e. whether it is below or above the knee).

When all the above remains inconclusive, the gold standard is intravenous venography, which involves injecting a peripheral vein of the affected limb with a contrast agent and taking X-rays, to reveal whether the venous supply has been obstructed. Impedance plethysmography can also be used as a non-invasive alternative.

Therapy

Anticoagulation is the only relevant treatment in DVT. Thrombolysis is generally reserved for serious pulmonary embolism.

Generally, patients are initiated on heparin treatment while they start on a 3- to 6-month course of warfarin (or related vitamin K inhibitors). Often, low molecular weight heparin is substituted for the regular heparin. In patients who have had recurrent DVTs (two or more), anticoagulation is generally "life-long".

Pathogenesis

Main article: thrombosis

Thrombosis is a multifactorial process, caused by the nature of blood flow, the consistency of the blood, and qualities of the vessel wall (Virchow's triad). Amongst the plethora of risk factors, immobilisation, female sex, use of oral contraceptives and air travel ("economy class syndrome") are some of the better-known causes. Censored page (tendency to develop thrombosis) often expresses itself with recurrent thromboses.

It is recognised that thrombi usually develop first in the calf veins, "growing" in the direction of flow of the vein. DVTs are distinguished as being above or below the popliteal vein . Very extensive DVTs can extend into the iliac artery or the inferior vena cava. The risk of pulmonary embolism is higher in more extensive clots.

Epidemiology

DVT's occur in about 1 per 1000 persons per year. About 1-5% will die from the complications (i.e. pulmonary embolism).


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Last updated: 04-25-2005 03:06:01