A patient with hip surgery presents with tachycardia, tachypnea, and hypoxia. What is the best test to diagnose suspected pulmonary embolism?

A patient with hip surgery presents with tachycardia, tachypnea, and hypoxia. What is the best test to diagnose suspected pulmonary embolism?

• A. Chest X-ray
• B. D-dimer assay
• C. CT pulmonary angiography
• D. Ventilation-perfusion scan

Answer: (C)

In suspected pulmonary embolism, especially in a postoperative patient with high risk, CT pulmonary angiography is the most informative test. It uses IV contrast to directly visualize the pulmonary arteries and reveal filling defects from an embolus, providing rapid and definitive confirmation (or ruling out) of PE. Chest X-ray cannot diagnose PE and is mainly used to exclude other causes of symptoms. D-dimer is highly sensitive but not specific, so it’s not the best choice when pretest probability is high, as many postoperative patients will have elevated D-dimer for other reasons. A ventilation-perfusion scan is a useful alternative if CT is not feasible (for example, due to contrast allergy or renal impairment) or if CT results are inconclusive, but CT angiography generally offers higher diagnostic accuracy and speed in this setting.

In suspected pulmonary embolism, especially in a postoperative patient with high risk, CT pulmonary angiography is the most informative test. It uses IV contrast to directly visualize the pulmonary arteries and reveal filling defects from an embolus, providing rapid and definitive confirmation (or ruling out) of PE. Chest X-ray cannot diagnose PE and is mainly used to exclude other causes of symptoms. D-dimer is highly sensitive but not specific, so it’s not the best choice when pretest probability is high, as many postoperative patients will have elevated D-dimer for other reasons. A ventilation-perfusion scan is a useful alternative if CT is not feasible (for example, due to contrast allergy or renal impairment) or if CT results are inconclusive, but CT angiography generally offers higher diagnostic accuracy and speed in this setting.