How is Deep Vein Thrombosis (DVT) Diagnosed?
Investigations for deep vein thrombosis inculde:
- Blood tests– A particular test called a D-Dimer is performed which measures a breakdown product of clots. If this test is negative it can rule out DVT. However, a positive test result is not always reliable because other things like infection, pregnancy and cancers can also cause it to rise. Therefore if the test is positive more specific investigations are needed such as:
- Venography– This is probably the most reliable test for detecting clots in the veins. For this procedure a radiologist will inject contrast material into a vein on the top of the foot. This spreads through the veins and shows up on an x-ray. The clot area will be seen as a defect in the contrast. The venography is reasonably accurate, but it is also a costly and painful procedure. Moreover, the irritation of the vein by the contrast material may in itself contribute to the formation of new clots.
- Ultrasonography is a less invasive test that is also quite reliable detecting clots. Ultrasound works by emitting sound waves that can determine the flow of blood within the vessels. The clogged veins are easily distinguished on color pictures produced by this method. This method is painless, no foreign material is injected, and no radiation is required. The method is also cheaper than venography, but it is less accurate at detecting thrombi in smaller veins within the calf.
- CT or Magnetic Resonance Imaging may also occasionally be used.
The doctor may do additional tests to determine if you have a clotting disorder. This involves a series of blood tests looking for abnormal levels of some proteins in the blood. This is particularly important for patients with recurrent deep vein thrombosis family history of DVT or cases where there is no obvious cause (such as recent surgery or immobilisation) for the clot forming.
Prognosis of Deep Vein Thrombosis (DVT)
The majority of deep vein thrombosis will disappear without any complications, however there is a significant risk for recurrence. Pulmonary embolus is uncommon when deep vein thrombosis are treated properly but they can occur and can be life threatening.
- If left untreated, deep vein thrombosis can cause a lot of pain and discomfort.
- DVT can also lead to varicose veins and certain other irreversible changes in the skin and the tissue.
- If the thrombus gets detached from the site it can lead to pulmonary embolism.
- Deep vein thrombosis can lead to non-healing venous ulcers.
How is Deep Vein Thrombosis (DVT) Treated?
Treatment of deep vein thrombosis largely aims to prevent the development of a pulmonary embolus (a clot in the lung) as this can be a life-threatening condition. To do this doctors will aim to reduce the size of the clot using anticoagulant (blood thinning) medications.
The first main deep vein thrombosis treatment is called heparin which can be given through a vein in the arm. This results in almost immediate anticoagulation and treatment of the clot. For this treatment you need to stay in hospital so your APTT can be measured in the blood. This basically is a measure for how well your blood clots which indicates if the drug is working or not.
Heparin is also available as an injection under the skin and this can be given on an out-patient basis. This type of heparin is called low-molecular- weight heparin (such as enoxaparin) and has the advantage of more predictable actions. A standard dose can be given based on your weight and monitoring is not needed.
Along with heparin an oral medication called warfarin is given. Because warfarin usually takes several days to reach effectiveness (until it reaches a therapeutic level), the heparin is continued until the warfarin is able to be effective. The effect of warfarin is also monitored using another blood test called the INR. When this reaches approximately 2.5 for two days in a row, the heparin can be stopped. Heparin needs to be given for at least five days. Warfarin is continued for around 3-6 months to prevent further clot formation. INR needs to be continually monitored because there is a risk of bleeding when the dose gets too high.
Other treatments for DVT included pressure stockings and early mobilisation. These help prevent pooling of blood within the legs. In some patients who have pulmonary emboli or that can’t take anticoagulant medications, a filter may be need to be inserted into the inferior vena cava. This is the main vein returning blood from the lower part of the body to the heart and lungs. The filter traps blood clots before they can enter the lungs. All patients who are at risk for DVT (e.g. pregnant, elderly, clotting disorder) will require special preventative methods during hospital visits or surgery. This includes wearing the pressure stockings, physiotherapy, early ambulation and calf compressors during surgery. Around the time of surgery patients will also be given regular heparin to prevent clot formation.