Diagnosis of DVT & Pulmonary Embolism

Diagnosis of DVT and pulmonary embolism involves taking a medical history and performing a physical examination and diagnostic tests. Blood tests also can be used to help in the diagnosis. A medical history includes information about risk factors for DVT, including blood clotting disorders, use of hormones (birth control pills), obesity, and varicose veins.

During physical examination, the physician looks for signs such as tenderness, swelling, discoloration, and warmth on one side of the body (e.g., in one leg); checks blood pressure; and listens to the heart and lungs. In some cases, the physician is able to feel a cord-like vein and tenderness occurs along the length of the vein involved.

Duplex ultrasound is the most common test used to diagnose DVT. In this test, sound waves are transmitted from a device called a transducer and are used to evaluate blood flow. The sound waves are then converted into an image on a computer screen that shows the flow of blood through the veins and can detect blood clots.

If the results of ultrasound are not conclusive, venography may be performed. Venography involves taking x-rays of the veins (called venograms) after a dye is injected to make them visible on x-ray. Venography can show reduced blood flow and detect blood clots.

Another imaging test that may be used is magnetic resonance imaging (MRI scan). This test uses electromagnetic radio waves to produce images of the veins and provides more information than x-rays. In rare cases, computed tomography (CT scan) also is used. In this test, x-rays are taken from different angles to create three-dimensional images of blood vessels.

There are a number of diagnostic tests available to help diagnose pulmonary embolism. These tests include the following:

  • Ultrasound
  • Spiral CT scan (produces images of the blood vessels in the legs and lungs)
  • CT angiography (uses CT scan and a contrast agent to produce images of the blood vessels)
  • Ventilation-perfusion lung scan (VQ scan; uses radioactive material [radioisotopes] to show the flow of blood and oxygen in the lungs)
  • Pulmonary angiography (provides images of the pulmonary blood vessels)

In pulmonary angiography, a flexible tube (catheter) is passed through a blood vessel in the upper thigh (groin) and into the lungs. Contrast dye is injected through the catheter and x-rays are taken to show blood flow in the lungs. If a pulmonary embolism is detected, medications can be delivered through the catheter to dissolve the blood clot or it may be removed through the catheter.

An echocardiogram (cardiac echo), electrocardiogram (ECG or EKG), and a chest x-ray may be performed to rule out other conditions. Echocardiogram is an ultrasound examination of the heart. It is used to diagnose conditions such as aortic stenosis, atrial fibrillation, and congestive heart failure (CHF). An EKG measures electrical activity in the heart and can be used to diagnose heart attack, atrial fibrillation, and CHF.

Blood tests, such as the D-dimer test, can be used to help diagnose pulmonary embolism. This test measures a substance in the blood that is produced when blood clots break up. Other types of blood tests include measures of arterial blood gas and tests to look for genetic blood clotting disorders.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 05 Nov 2007

Last Modified: 30 Jul 2015