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Tests and diagnosis
By Mayo Clinic staffPulmonary embolism can be difficult to diagnose, especially in people who have underlying heart or lung disease. For that reason, your doctor may order a series of tests to help find the cause of your symptoms.
Chest X-ray
This noninvasive test shows images of your heart and lungs on film. Although X-rays can't diagnose pulmonary embolism and may even appear normal when pulmonary embolism exists, they can rule out conditions that mimic the disease.
Lung scan
This test, called a ventilation-perfusion scan (V/Q scan), uses small amounts of radioactive material to study airflow (ventilation) and blood flow (perfusion) in your lungs.
For the first part of the test, you inhale a small amount of radioactive material while a camera that's able to detect radioactive substances takes pictures of the movement of air in your lungs. Then a small amount of radioactive material is injected into a vein in your arm, and pictures are taken of blood flow in the blood vessels of your lungs. Comparing the results of the two studies helps provide a more accurate diagnosis of pulmonary embolism than does either study alone.
Spiral (helical) computerized tomography (CT) scan
Regular CT scans take X-rays from many different angles and then combine them to form images showing two-dimensional "slices" of your internal structures. In a spiral or helical CT scan, the scanner rotates around your body in a spiral — like the stripe on a candy cane — to create three-dimensional images. This type of CT can detect abnormalities with much greater precision, and it's also much faster than are conventional CT scans.
Pulmonary angiogram
This test provides a clear picture of the blood flow in the arteries of your lungs. It's the most accurate way to diagnose pulmonary embolism, but because it requires a high degree of skill to administer and carries potentially serious risks, it's usually performed when other tests fail to provide a definitive diagnosis. It also has the advantage of being able to measure the pressure in the right side of your heart. It would be unusual to have normal readings in the presence of pulmonary embolism.
In a pulmonary angiogram, a flexible tube (catheter) is inserted into a large vein — usually in your groin — and threaded through your heart into the pulmonary arteries. A special dye is then injected into the catheter, and X-rays are taken as the dye travels along the arteries in your lungs.
A risk of this procedure is a temporary change in your heart rhythm. In addition, the dye may cause kidney damage in people with decreased kidney function.
D-dimer blood test
Having high levels of the clot-dissolving substance D dimer in your blood may suggest an increased likelihood of blood clots, although D-dimer levels may be elevated by other factors, including recent surgery.
Ultrasound
A noninvasive "sonar" test known as duplex venous ultrasonography (sometimes called duplex scan or compression ultrasonography) uses high-frequency sound waves to check for blood clots in your thigh veins. In this test, your doctor uses a wand-shaped device called a transducer to direct the sound waves to the veins being tested. These waves are then reflected back to the transducer and translated into a moving image by a computer. An echocardiogram of the heart can estimate the blood pressure in the right side of the heart.
Magnetic resonance imaging (MRI)
MRI scans use radio waves and a powerful magnetic field to produce detailed images of internal structures. Because MRI is expensive, it's usually reserved for pregnant women and people whose kidneys may be harmed by dyes used in other tests.
- Pulmonary embolism. National Heart, Lung, and Blood Institute. http://www.nhlbi.nih.gov/health/dci/Diseases/pe/pe_what.html. Accessed June 26, 2009.
- Thompson BT, et al. Overview of acute pulmonary embolism. http://www.uptodate.com/home/index.html. Accessed June 26, 2009.
- Kline JA, et al. Pulmonary embolism and deep venous thrombosis. In: Marx JA, et al. Rosen's Emergency Medicine: Concepts and Clinical Practices. 6th ed. Philadelphia, Pa.: Mosby Elsevier; 2006. http://www.mdconsult.com/das/book/body/146574529-3/0/1365/250.html#4-u1.0-B0-323-02845-4..50092-5--cesec18_4265. Accessed June 29, 2009.
- Bauer KA, et al. Overview of causes of venous thrombosis. http://www.uptodate.com/home/index.html. Accessed June 26, 2009.
- Deep vein thrombosis. American Academy of Orthopaedic Surgeons. http://orthoinfo.aaos.org/topic.cfm?topic=A00219. Accessed June 29, 2009.
- Tapson VF. Pulmonary embolism. In: Goldman L. Cecil Medicine. 23rd ed. Philadelphia, Pa.: Saunders Elsevier; 2007. http://www.mdconsult.com/das/book/body/146574529-5/0/1492/393.html#4-u1.0-B978-1-4160-2805-5..50104-X--cesec7_4150. Accessed June 29, 2009.
- Pulmonary hypertension. National Heart, Lung, and Blood Institute. http://www.nhlbi.nih.gov/health/dci/Diseases/pah/pah_what.html. Accessed June 29, 2009.
- Ferri FF. Pulmonary embolism. In: Ferri FF. Ferri's Clinical Advisor 2009. Philadelphia, Pa.: Mosby Elsevier; 2009. http://www.mdconsult.com/das/book/body/146779547-3/0/1701/492.html#4-u1.0-B978-0-323-04134-8..50019-7--subchapter69_10424. Accessed June 30, 2009.
- General nuclear medicine. Radiological Society of North America. http://www.radiologyinfo.org/en/info.cfm?PG=gennuclear. Accessed June 30, 2009.
- Catheter angiography. Radiological Society of North America. http://www.radiologyinfo.org/en/info.cfm?PG=Angiocath. Accessed June 30, 2009.
- Lip GY, et al. Patient information: Deep vein thrombosis (DVT). http://www.uptodate.com/home/index.html. Accessed June 30, 2009.
- Deep vein thrombosis. National Heart, Lung, and Blood Institute. http://www.nhlbi.nih.gov/health/dci/Diseases/Dvt/DVT_All.html. Accessed June 30, 2009.
- Rosenow EC (expert opinion). Mayo Clinic, Rochester, Minn. July 5, 2009.
