Westermark sign

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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).[1] While the chest x-ray is normal in the majority of PE cases,[2] the Westermark sign is seen in 2% of patients.[3]

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[edit]

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.[4]


  1. ^ Ray J (2003). "Westermark sign and suspected pulmonary embolism.". Can J Cardiol 19 (3): 317; author reply 317. PMID 12680403. 
  2. ^ Introduction to Chest Radiography. http://www.med-ed.virginia.edu/courses/rad/cxr/index.html
  3. ^ 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. doi:10.1148/radiology.189.1.8372182. PMID 8372182. 
  4. ^ 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.