Westermark Sign
Westermark sign refers to dilation of the pulmonary artery proximal to an embolism with collapse of distal vessels (oligemia, reduced blood volume), sometimes with a sharp cutoff. Other closely related signs are the Fleischner sign which refers to a prominent central artery and Chang’s sign which refers to a dilatation and abrupt change in the calibre of the right descending pulmonary artery. <a class="external" href="http://www.eurorad.org/eurorad/case.php?id=7735" rel="nofollow" target="_blank">[Kirwadi A, and Bickle IC. Plain Film Signs in Pulmonary Embolism (with CT correlate)]</a>
Case 1
This 55 year old female was admitted to ICU with a large pulmonary embolism. She was intubated in ICU.
This is a curved path CTPA section mapping the left descending pulmonary artery. There is extensive clot within the left descending pulmonary artery and abrupt change in calibre (arrowed)
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Discussion
A classic plain film case of Westermark sign is not often seen. This case demonstrates prominence of the central pulmonary arteries and abrupt cut-off of the left descending pulmonary artery, but the best evidence of oligemia is in the right midzone (plain film and CT evidence).