lung and airway disorders
Pulmonary Embolism (PE)
Diagnosis of Pulmonary Embolism
CT angiography, ultrasonography of the legs, lung perfusion scan, or a combination Doctors suspect pulmonary embolism based on the person’s symptoms and risk factors, such as recent surgery, a prolonged period of bed rest, or a tendency to form blood clots. A large pulmonary embolism may be relatively easy for doctors to diagnose, especially when the person has obvious conditions that could cause pulmonary embolism, such as signs of a blood clot in a leg. However, in many cases, symptoms are minimal or are confused with symptoms of other disorders such as Overview of Pneumonia , or Some routine tests can provide clues that a pulmonary embolism has occurred. However, these tests cannot diagnose with certainty whether a pulmonary embolism is truly present. X-Rays of the Chest None Electrocardiography None Thelevel of oxygenin the blood is measured with a sensor that is attached to a fingertip (pulse oximetry). Because pulmonary embolism blocks pulmonary arteries, the level of oxygen in the blood may be low. Sometimes doctors also take a sample of blood from an artery and measure the level of oxygen and other gases in it. Doctors first judge how likely pulmonary embolism seems to be, based on information such as the person's risk for pulmonary embolism, the severity of their symptoms, and the results of early tests (such as the chest x-ray and level of oxygen in the blood). Importantly, a pulmonary embolism is considered unlikely if risk factors are completely absent. If pulmonary embolism seems unlikely, ablood testthat measures a substance called D‑dimer is typically done. This test may be the only test needed if pulmonary embolism seem unlikely. If the D-dimer level is normal, then the probability that a pulmonary embolus has occurred is extremely low. Although a low level of D-dimer in people at low risk means that pulmonary embolism is unlikely, a high level does not necessarily mean that pulmonary embolism is likely. Other disorders, such as infection or injury, can cause the D-dimer level to be high so additional testing is needed to confirm the diagnosis. If pulmonary embolism seems more likely or if the result of the D-dimer test is abnormal, other testing is done, usually one or more of the following: Magnetic Resonance Imaging (MRI) of the Heart None Lung ventilation perfusion scan Ultrasonography of the legs CT angiographyis a type of CT scan. It is fast, noninvasive, and fairly accurate, particularly for large clots. In this test, contrast material is injected into a vein. The contrast material travels to the lungs via the pulmonary arteries, and a CT scanner generates images of blood in the arteries to determine if a pulmonary embolism is blocking blood flow. CT angiography is the imaging test most often used to diagnose pulmonary embolism. The size of the heart may also indicate how much the heart is being strained. Radionuclide Scanning None For alung perfusion scan,a tiny amount of radioactive substance is injected into a vein and travels through the pulmonary arteries to the lungs, where it outlines the blood supply of the lung. Completely normal perfusion results rule out a pulmonary embolism. Abnormal scan results support the possibility of pulmonary embolism but may also indicate the possibility of other disorders. Doctors sometimes use a lung perfusion scan if a person has a kidney problem that prevents the use of CT angiography because the contrast material used for the CT might further damage the kidneys. In alung ventilation scan, the person inhales a harmless gas containing a trace amount of radioactive material, which is distributed throughout the small air sacs of the lungs (alveoli). The areas where carbon dioxide is being released and oxygen is taken up can then be seen on a scanner. By comparing the ventilation scan to the pattern of blood supply shown on the perfusion scan, doctors can usually determine whether a person has had a pulmonary embolism. Ultrasonography of the legsis noninvasive and can identify clots in the legs, which are the usual sources of pulmonary embolism. The absence of clots in the veins of the leg does not rule out pulmonary embolism. However, if ultrasonography reveals blood clots, and the person has little difficulty breathing and no decrease in their blood pressure or increase in their heart rate, people are occasionally treated as they would be for pulmonary embolism without any further testing, because the treatment for both conditions is often the same. Other variations None Echocardiography and Other Ultrasound Procedures None In people who have no apparent risk factors for blood clots or recurring clots, doctors may also measure proteins in the blood to determine whether a clotting disorder is the cause. 