Westermark Sign

Introduction

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.

The supine portable chest image demonstrates ET tube and NGT. There is evidence of abnormal prominence of the central pulmonary arteries with abrupt cut-off of the left pulmonary artery suggesting a Westermark sign. There is evidence of oligemia in the right midzone.

Abrupt change in calibre of the enlarged left descending pulmonary artery (arrowed)

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).