On CT angiography, a filling defect in the pulmonary artery indicates which diagnosis?

On CT angiography, a filling defect in the pulmonary artery indicates which diagnosis?

• A. Pulmonary embolism
• B. Pneumothorax
• C. Pulmonary edema
• D. Lung abscess

Answer: (A)

A filling defect in a contrast-filled pulmonary artery on CT angiography reflects intraluminal obstruction of blood flow in the pulmonary circulation, most commonly caused by a thrombus lodging in the artery—pulmonary embolism. The contrast should outline the vessel lumen; when a clot occupies part of that lumen, it appears as a defect where the artery would normally fill with contrast. This finding is specific to an embolic occlusion rather than issues that affect the lung tissue or pleural space. For example, pneumothorax shows air in the pleural space with lung collapse, not a blockage within the pulmonary artery; pulmonary edema presents with diffuse interstitial or alveolar fluid changes; a lung abscess appears as a cavitary lesion with an air-fluid level in the lung parenchyma, not a intraluminal arterial defect.

A filling defect in a contrast-filled pulmonary artery on CT angiography reflects intraluminal obstruction of blood flow in the pulmonary circulation, most commonly caused by a thrombus lodging in the artery—pulmonary embolism. The contrast should outline the vessel lumen; when a clot occupies part of that lumen, it appears as a defect where the artery would normally fill with contrast. This finding is specific to an embolic occlusion rather than issues that affect the lung tissue or pleural space. For example, pneumothorax shows air in the pleural space with lung collapse, not a blockage within the pulmonary artery; pulmonary edema presents with diffuse interstitial or alveolar fluid changes; a lung abscess appears as a cavitary lesion with an air-fluid level in the lung parenchyma, not a intraluminal arterial defect.