Westermark sign

In chest radiography, the Westermark Sign, is a sign that represents a focus of oligemia (vasoconstriction) seen distal to a pulmonary embolus (PE).^[1] While the chest x-ray is abnormal in the majority of PE cases, the Westermark sign is seen in only 2% of patients.^[2]

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The sign results from a combination of:

1. the dilation of the pulmonary arteries proximal to the embolus and
2. the collapse of the distal vasculature creating the appearance of a sharp cut off on chest radiography.

Sensitivity and specificity

The Westermark sign, like Hampton's hump (a wedge shaped, pleural based consolidation associated with pulmonary infarction), has a low sensitivity (11%) and high specificity (92%) for the diagnosis of pulmonary embolus.^[3]

References

1. ^ Ray J (2003). "Westermark sign and suspected pulmonary embolism.". Can J Cardiol 19 (3): 317; author reply 317. PMID 12680403.
2. ^ Worsley D, Alavi A, Aronchick J, Chen J, Greenspan R, Ravin C (1993). "Chest radiographic findings in patients with acute pulmonary embolism: observations from the PIOPED Study.". Radiology 189 (1): 133-6. PMID 8372182.
3. ^ Gurney J. CT: Diagnosis of Pulmonary Embolism. chestx-ray.com. Available at: http://www.chestx-ray.com/Lectures/PulmEmbLecture/PulmEmbolus.pdf. Accessed on: November 13, 2006.