As there are many causes of leg pain, a doctor cannot diagnose deep vein thrombosis (DVT) by symptoms alone. The doctor will ask you some questions and do a blood test (called D-dimer), and will then decide if further tests are required [1].

Before performing any tests, a doctor will establish the likelihood of a blood clot by asking questions, performing a physical examination, and completing a formalised risk score. If the probability of a DVT is low, a blood test, called a D-dimer test, is performed to rule out the diagnosis. If these tests show the probability of a DVT is high, additional tests, like an ultrasound will be performed to confirm the diagnosis [1].

Figure: compression ultrasonography involves pressing the ultrasound probe to the vein to check if it is open or obstructed by a thrombus.

Further imaging tests include taking X-rays of the veins with the use of contrast agents, as well as more sophisticated imaging such as computed tomography (CT) and magnetic resonance imaging (MRI) [1].


A doctor will make a diagnosis of PE using a similar approach to diagnosing a DVT. Step 1 involves asking questions, assessing clinical signs and then completing a clinical decision rule. Step 2 is performing a D-dimer test, and Step 3 involves imaging the lungs to see if a clot can be seen [2].

The following imaging tests are used to diagnose PE [2]:

  • Computed tomography (CT) scan. Doctors use this test to look for blood clots in the lungs and legs. Dye is injected into a vein to make the blood vessels visible on X-ray image. This test allows doctors to detect PE in most patients. The test only takes a few minutes. Results are available shortly after the scan is completed [2].
  • Ventilation–perfusion lung scan (VQ scan). Doctors use this test to detect PE. The VQ scan uses a radioactive material to show how well oxygen and blood are flowing to all areas of the lungs [2].

VTEMatters offers general information only. Please see a healthcare professional for medical advice.


1. Ho WK. Deep vein thrombosis. Australian Family Physician 2010; 39:468-74.
2. Skinner S. Pulmonary embolism: assessment and imaging. Australian Family Physician 2013; 42:629-32.