Explanation Westermark sign is due to focus of oligemia in pu | NEET PG/NEXT (MCQs)

Explanation

Westermark sign is due to focus of oligemia in pulmonary embolism. The sign develops due to following reasons:

• Dilation of pulmonary arteries proximal to the embolus
• Collapse of distal vasculature creating the appearance of a sharp cut off on chest X-ray

The chest X-ray is normal in the majority of Pulmonary Embolism cases, the Westermark sign is seen in 2% of patients.