Deep venous thrombosis
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").
| Table of contents |
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2 Diagnosis 3 Therapy 4 Pathogenesis 5 Epidemiology |
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:
- full blood count
- coagulation studies: PT, APTT, thrombin time, INR
- liver enzymes
- renal function and electrolytes
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.
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
Epidemiology
DVT's occur in about 1 per 1000 persons per year. About 1-5% will die from the complications (i.e. pulmonary embolism).
| Health science - Medicine - Hematology |
| Hematological malignancy and White blood cells |
| Lymphoma (Hodgkin's disease;, NHL) - Leukemia (ALL, AML, CLL, CML) - Multiple myeloma; - MDS - Myelofibrosis - Myeloproliferative disease; (Thrombocytosis, Polycythemia) - Neutropenia |
| Red blood cells |
| Anemia - Hemochromatosis - Sickle-cell anemia; - Thalassemia - other hemoglobinopathies |
| Coagulation and Platelets |
| Thrombosis - Deep venous thrombosis; - Pulmonary embolism; - Hemophilia - ITP - TTP |