To diagnose DVT, your doctor will examine your legs to check for swelling and tenderness. He or she will ask about your symptoms and risk factors.
Based on the findings, your doctor may order an ultrasound of your legs to look for blood flow problems in your veins. This procedure is called a lower extremity non-invasive test, or LENI. If the LENI shows evidence of a blood clot, your doctor will diagnose DVT. If the test is negative, it does not mean that there is no clot: It may be too early to see the full effect of the clot. In this situation, your doctor may ask that you return in three to four days for a repeat LENI.
If your doctor suspects you have a pulmonary embolism, he or she will first try to determine if you have DVT. If the LENI shows one or more blood clots in your leg veins and you have symptoms of a pulmonary embolism, an embolism is the most likely diagnosis. Other possible tests include a computed tomography (CT) scan of the chest and a special type of lung scan that uses a small amount of radioactive tracer to detect differences in lung blood flow. If your doctor is still unsure about the diagnosis after these tests have been done, he or she may order a test called a pulmonary angiography. In this procedure, a small tube is threaded into the arteries of the lung and dye is injected to help identify blood clots.
Your doctor may order a blood test called a D-dimer test, which tests for levels of a chemical (D-dimer) that increases when blood clots are being formed in the body. An abnormally high level of D-dimer does not automatically mean a diagnosis of pulmonary embolism. However, when a D-dimer blood test is normal in someone at low risk for pulmonary embolism, the test indicates that pulmonary embolism is very unlikely.
If you have a DVT or pulmonary embolism, your symptoms should improve within a few days after starting treatment with blood-thinning medication. However, you will need to take medication for at least three to six months to prevent more blood clots from forming. Most people recover completely, but some people who had a very large pulmonary embolism, or who already had lung disease, will continue to have lung problems. Some people who have had a DVT develop a long-term problem with swelling of their legs called post-phlebitic syndrome. These people often need to wear special stockings that help squeeze blood back toward the heart.