Diagnosis

The signs and symptoms of deep vein thrombosis (DVT) and pulmonary embolism (PE) can be difficult to detect and diagnose correctly as they are not specific and are similar to those associated with other conditions, including muscle strains and skin infections.

If, following orthopaedic surgery, your doctor suspects that you may have a DVT or PE, he/she will carry out a physical examination and ask you several questions to try to determine the time course of your symptoms. He/she may also carry out some blood tests or other procedures to help with the diagnosis. These may include:

For deep vein thrombosis

• Ultrasonography: this safe, painless and non-invasive procedure is often the first test for DVT. A gel is wiped over an area of skin on the leg and a hand held device is then passed back and forth over it. This forms a picture of the blood vessels and can measure the rate of blood flow through the veins.

• Venography: a procedure in which a small and harmless amount of radioactive material (as a dye) is injected into a vein in the foot and an X-ray is taken. This procedure is carried out in hospital under local anaesthetic so you will not feel any pain.
  
  
• D-dimer assay: D-dimers are fragments of a blood clot. This simple laboratory test measures the levels of D-dimers in the blood. Elevated levels of D-dimers are found in nearly all patients with venous thromboembolism (VTE).
  
  
• Impedance plethysmography: a simple, safe and painless test, which measures blood volume changes in the affected leg. The test can be done at the patient's bedside and is easily repeated over a period of time.
  

For pulmonary embolism

• Ventilation/perfusion scan: this test uses radioactive material to measure breathing (ventilation) and blood circulation (perfusion) in all areas of the lungs. These tests are painless and use a harmless amount of radioactive material.
  
  
• Computed tomography (CT): a spiral CT scan is a quick and painless procedure in which a dye is injected into a vein in the arm or leg and a special machine rotates rapidly around the body, taking a series of pictures of the blood supply to the heart and lungs.
  
  
• Pulmonary angiography: this is the most accurate method for diagnosing PE. It involves inserting a long, narrow, flexible tube called a catheter into a vein, usually in the groin. The catheter is then guided into the blood vessel that leads to the lungs. A dye can then be injected and X-rays are taken. The procedure is carried out under local anaesthetic so you will not feel any pain.