Checking for a blood clot in your leg (deep venous thrombosis) can help your doctor decide if you are at high risk
for having a pulmonary embolism. After a medical history and physical
examination are done to establish your risk level (pretest probability) for
deep leg vein thrombosis, an
ultrasound is usually done. Your pretest probability
and initial ultrasound results will help your doctor determine the most
appropriate follow-up tests to see whether you have a pulmonary embolism.
For more information, see the topic
scan results are sometimes investigated further using pulmonary angiography or
computed tomography scanning technique called CT
pulmonary angiography, or CTPA. Pulmonary angiography is an
X-ray test that uses
contrast material injected into the bloodstream to
evaluate the blood flow through the arteries leading to the lungs (pulmonary
arteries). Many medical centers or doctors now use CTPA as their first choice
for evaluating a pulmonary embolus rather than a lung scan because CT has
become more available. For more information, see the
Angiogram of the Lung and
CT Scan of the Body.
Lung scan results for
people who have a long-term (chronic) lung disease, such as
emphysema or chronic obstructive pulmonary disease
(COPD), may be hard to interpret. For this reason, other tests, such as CT
angiogram, may be done.
The results of a combined (ventilation and perfusion) lung scan,
often called a V/Q scan, may be hard to interpret. These results should be
interpreted along with a person's symptoms and the results of other tests, such
as a physical examination, lab tests, and a chest X-ray.
Other Works Consulted
Fischbach FT, Dunning MB III, eds. (2009).
Manual of Laboratory and Diagnostic Tests, 8th ed.
Philadelphia: Lippincott Williams and Wilkins.
Pagana KD, Pagana TJ (2010). Mosby?s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.