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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 will likely order a series of tests to help find the cause of your symptoms, including:
- 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. First, you inhale a small amount of radioactive material while a special camera designed to detect radioactive substances records air movement in your lungs. Then a small amount of radioactive material is injected into a vein in your arm. Images taken after the injection show whether you have a normal or diminished flow of blood to your lungs. This test is less reliable if you're a smoker.
- Spiral (helical) computerized tomography (CT) scan. Regular CT scans take X-rays from many different angles and then combine them to form images showing 2-D "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 3-D images. This type of CT can detect abnormalities with much greater precision, and it's also much faster than are conventional CT scans. For a possible pulmonary embolism, often an intravenous injection of contrast material is given and the spiral CT is done immediately.
- Pulmonary angiogram. During this test, a flexible tube (catheter) is inserted into a large vein — usually in your groin — and threaded through your heart's right atrium and ventricle and then into the pulmonary arteries. A special dye is injected into the catheter, and X-rays are taken as the dye travels along the arteries in your lungs. Pulmonary angiogiography also can measure the pressure in the right side of your heart. It would be unusual to have normal readings in the presence of pulmonary embolism. This test requires a high degree of skill to administer and carries potentially serious risks, so it's usually performed when other tests fail to provide a definitive diagnosis.
- 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, to minimize radiation exposure to the developing baby, and people whose kidneys may be harmed by contrast dyes used in CT and pulmonary angiogram.
References
- Pulmonary embolism. National Heart, Lung, and Blood Institute. http://www.nhlbi.nih.gov/health/dci/Diseases/pe/pe_all.html. Accessed Aug. 3, 2011.
- Thompson BT, et al. Overview of acute pulmonary embolism. http://www.uptodate.com/home/index.html. Accessed Aug. 3, 2011.
- Kline JA, et al. Pulmonary embolism and deep vein thrombosis. In: Marx JA, et al. Rosen's Emergency Medicine: Concepts and Clinical Practice. 7th ed. Philadelphia, Pa.: Mosby Elsevier; 2010. http://www.mdconsult.com/books/about.do?about=true&eid=4-u1.0-B978-0-323-05472-0..X0001-1--TOP&isbn=978-0-323-05472-0&uniqId=230100505-57. Accessed Aug. 3, 2011.
- Bauer KA, et al. Overview of the causes of venous thrombosis. http://www.uptodate.com/home/index.html. Accessed Aug. 3, 2011.
- Deep vein thrombosis. American Academy of Orthopaedic Surgeons. http://orthoinfo.aaos.org/topic.cfm?topic=A00219. Accessed Aug. 3, 2011.
- Weitz JI. Pulmonary embolism. In: Goldman L, et al. Goldman's Cecil Medicine. 24th ed. Philadelphia, Pa.: Saunders Elsevier; 2011. http://www.mdconsult.com/das/book/body/191371208-2/0/1492/0.html#. Accessed Aug. 3, 2011.
- Rosenow EC (expert opinion). Mayo Clinic, Rochester, Minn. Aug. 21, 2011.
- Troncales FD, et al. Pulmonary embolism. In: Ferri FF. Ferri's Clinical Advisor 2012: 5 Books in 1. Philadelphia, Pa.: Mosby Elsevier; 2012. http://www.mdconsult.com/books/linkTo?type=bookPage&isbn=978-0-323-05611-3&eid=4-u1.0-B978-0-323-05611-3..00025-2--sc0355. Accessed Aug. 16, 2011.
- General nuclear medicine. Radiological Society of North America. http://www.radiologyinfo.org/en/info.cfm?PG=gennuclear. Accessed Aug. 16, 2011.
- Catheter angiography. Radiological Society of North America. http://www.radiologyinfo.org/en/info.cfm?PG=Angiocath. Accessed Aug. 16, 2011.
- Lip GY, et al. Patient information: Deep vein thrombosis (DVT). http://www.uptodate.com/home/index.html. Accessed Aug. 16, 2011.
- Deep vein thrombosis. National Heart, Lung, and Blood Institute. http://www.nhlbi.nih.gov/health/dci/Diseases/Dvt/DVT_All.html. Accessed Aug. 16, 2011.
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