- 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). [cite journal | author = Ray J | title = Westermark sign and suspected pulmonary embolism. | journal = Can J Cardiol | volume = 19 | issue = 3 | pages = 317; author reply 317 | year = 2003 | pmid = 12680403] While the chest x-ray is abnormal in the majority of PE cases, the Westermark sign is seen in only 2% of patients. [cite journal | author = Worsley D, Alavi A, Aronchick J, Chen J, Greenspan R, Ravin C | title = Chest radiographic findings in patients with acute pulmonary embolism: observations from the PIOPED Study. | journal = Radiology | volume = 189 | issue = 1 | pages = 133–6 | year = 1993 | pmid = 8372182]The sign results from a combination of:
# the dilation of thepulmonary arteries proximal to the embolus and
# the collapse of the distal vasculature creating the appearance of a sharp cut off on chest radiography.ensitivity and specificity
The Westermark sign, like
Hampton's hump (a wedge shaped, pleural based consolidation associated with pulmonaryinfarction ), has a low sensitivity (11%) and highspecificity (92%) for the diagnosis of pulmonary embolus. [Gurney J. CT: Diagnosis of Pulmonary Embolism. chestx-ray.com. Available at: [http://www.chestx-ray.com/Lectures/PulmEmbLecture/PulmEmbolus.pdf http://www.chestx-ray.com/Lectures/PulmEmbLecture/PulmEmbolus.pdf] . Accessed on: November 13, 2006.]References
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