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In chest radiography, the Westermark sign is a sign that represents a focus of oligemia (leading to collapse of vessel) seen distal to a pulmonary embolism (PE). While the chest x-ray is normal in the majority of PE cases,〔Introduction to Chest Radiography. http://www.med-ed.virginia.edu/courses/rad/cxr/index.html〕 the Westermark sign is seen in 2% of patients. The sign results from a combination of: # the dilation of the pulmonary arteries proximal to the embolus and # 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 embolism.〔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.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Westermark sign」の詳細全文を読む スポンサード リンク
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