Pulmonary Embolism (cont.)
How is pulmonary embolism diagnosed?
Doctors who treat patients in the emergency room are often the ones to
diagnose pulmonary embolism (PE) with the help of a radiologist (a doctor who
deals with x rays and other similar tests).
Medical History and Physical Exam
To diagnose pulmonary embolism, the doctor will ask about your medical
history and perform a physical exam to:
- Identify your risk factors for deep vein thrombosis (DVT) and pulmonary
- See how likely it is that you could have pulmonary embolism
- Rule out other possible causes for your symptoms
During the physical exam, the doctor will check your legs for signs of DVT.
He or she also will check your blood pressure and your heart and lungs.
There are many different tests that help the doctor determine whether you
have pulmonary embolism. The doctor's decision about which tests to use and in
which order depends on how you feel when you get to the hospital, your risk
factors for pulmonary embolism, available testing options, and other conditions you may have.
You may have one of the following imaging tests:
- Ultrasound. Doctors use this test to look for blood clots in your
legs. Ultrasound uses high-frequency sound waves to check the flow of blood
in your veins. A gel is put on the skin of your leg. A hand-held device
called a transducer is placed on the leg and moved back and forth over the
affected area. The transducer gives off ultrasound waves and detects their
echoes after they bounce off the vein walls and blood cells. A computer then
turns the echoes of the ultrasound waves into a picture on a computer
screen, where your doctor can see the blood flow in your leg. If blood clots
are found in the deep veins of your legs, you will begin treatment. DVT and
pulmonary embolism are both treated with the same medicines.
- Spiral CT scan or CT angiogram. Doctors use this test to look for
blood clots in your lungs and in your legs. Dye is injected into a vein in
your arm to make the blood vessels in your lungs and legs more visible on
the x-ray image. While you lie on a table, an x-ray tube rotates around you,
taking pictures from different angles. This test allows doctors to detect
pulmonary embolism in most patients. The test only takes a few minutes.
Results are available shortly after the scan is completed.
- Ventilation-perfusion lung scan (VQ scan). Doctors use this test
to detect pulmonary embolism. The VQ scan uses a radioactive material to
show how well oxygen and blood are flowing to all areas of the lungs.
- Pulmonary angiography is another test used to diagnose pulmonary
embolism. It's not available at all hospitals, and a trained specialist must
perform the test. A flexible tube called a catheter is threaded through the
groin (upper thigh) or arm to the blood vessels in the lungs. Dye is
injected into the blood vessels through the catheter. X-ray pictures are
taken to show the blood flow through the blood vessels in the lungs. If a
clot is discovered, the doctor may use the catheter to extract it or deliver
medicine to dissolve it.
Certain blood tests may help the doctor find out whether you're likely to
have pulmonary embolism.
- A D-dimer test measures a substance in the blood that's released
when a clot breaks up. High levels of the substance mean there may be a
clot. If your test is normal and you have few risk factors, pulmonary
embolism isn't likely. Other blood tests check for inherited disorders that
cause clots and measure the amount of oxygen and carbon dioxide in your
blood (arterial blood gas). A clot in a blood vessel in your lung may lower
the level of oxygen in your blood. To rule out other possible causes of your
symptoms, the doctor may use one or more of the following tests.
- Echocardiogram uses sound waves to check heart function and to
detect blood clots inside the heart. EKG (electrocardiogram) measures the
rate and regularity of your heartbeat.
- Chest x ray provides a picture of the lungs, heart, large
arteries, ribs, and diaphragm.
- Magnetic resonance imaging (MRI) uses radio waves and magnetic
fields to make pictures of organs and structures inside the body. In many
cases, an MRI can provide information that can't be seen on an x ray.