How to diagnose Deep Vein Thrombosis ?
Your doctor will diagnose deep vein thrombosis (DVT) based on your medical history, a physical exam, and test results. He or she will identify your risk factors and rule out other causes of your symptoms.
                
For some people, DVT might not be diagnosed until after they receive emergency treatment for pulmonary embolism (PE).
                
Medical History
                
To learn about your medical history, your doctor may ask about:
                
Your overall health
                
Any prescription medicines you're taking
                
Any recent surgeries or injuries you've had
                
Whether you've been treated for cancer
                
Physical Exam
                
Your doctor will check your legs for signs of DVT, such as swelling or redness. He or she also will check your blood pressure and your heart and lungs.
                
Diagnostic Tests
                
Your doctor may recommend tests to find out whether you have DVT.
                
Common Tests
                
The most common test for diagnosing deep vein blood clots is ultrasound. This test uses sound waves to create pictures of blood flowing through the arteries and veins in the affected leg.
                
Your doctor also may recommend a D-dimer test or venography (ve-NOG-rah-fee).
                
A D-dimer test measures a substance in the blood that's released when a blood clot dissolves. If the test shows high levels of the substance, you may have a deep vein blood clot. If your test results are normal and you have few risk factors, DVT isn't likely.
                
Your doctor may suggest venography if an ultrasound doesn't provide a clear diagnosis. For venography, dye is injected into a vein in the affected leg. The dye makes the vein visible on an x-ray image. The x ray will show whether blood flow is slow in the vein, which may suggest a blood clot.
                
Other Tests
                
Other tests used to diagnose DVT include magnetic resonance imaging (MRI) and computed tomography (to-MOG-rah-fee), or CT, scanning. These tests create pictures of your organs and tissues.
                
You may need blood tests to check whether you have an inherited blood clotting disorder that can cause DVT. This may be the case if you have repeated blood clots that are not related to another cause. Blood clots in an unusual location (such as the liver, kidney, or brain) also may suggest an inherited clotting disorder.
                
If your doctor thinks that you have PE, he or she may recommend more tests, such as a lung ventilation perfusion scan (VQ scan). A lung VQ scan shows how well oxygen and blood are flowing to all areas of the lungs.
                
For more information about diagnosing PE, go to the Health Topics Pulmonary Embolism article.