What radiological finding confirms a pulmonary embolism?

• A. Filling defects in pulmonary arteries on CT pulmonary angiography
• B. Enlarged right ventricle on echocardiography
• C. Increased opacity in lung fields on X-ray
• D. Dilated pulmonary veins on MRI

Answer: (A)

The presence of filling defects in pulmonary arteries on CT pulmonary angiography is a definitive finding that confirms a pulmonary embolism. CT pulmonary angiography is the gold standard imaging modality for diagnosing pulmonary embolism because it allows for direct visualization of the pulmonary vasculature. When a pulmonary embolus is present, it causes a blockage in the blood flow of the affected pulmonary artery, which appears as a filling defect (i.e., a dark area where the contrast cannot flow due to the obstruction). This direct correlation between the observed filling defects and the presence of emboli makes it a highly reliable method for diagnosis.

In contrast, while other imaging modalities like echocardiography can show signs that may be associated with right heart strain due to a pulmonary embolism, they do not provide direct confirmation of the embolus itself. Similarly, increased opacity in lung fields on X-ray may be suggestive of various conditions, including pneumonia or other lung diseases, but it is not specific to pulmonary embolism. Dilated pulmonary veins on MRI could indicate other cardiac or pulmonary conditions, but again, they do not confirm the presence of a pulmonary embolism directly.