On a CT pulmonary angiogram, a patient with acute dyspnea shows a large, saddle-shaped filling defect straddling the bifurcation of the main pulmonary artery into both right and left pulmonary arteries. What is the term for this finding?

• A Saddle embolus ✓
• B Polo mint sign
• C Railway track sign
• D Westermark sign

Explanation

C saddle embolus is a large thrombus that straddles the bifurcation of the main pulmonary artery. The polo mint sign refers to a clot surrounded by contrast on a transverse view. The railway track sign describes contrast surrounding a central clot on a longitudinal view. Westermark sign is a plain X-ray finding of regional oligemia distal to a pulmonary embolus.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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