Westermark sign

Westermark sign
Differential diagnosishypovolemia

In chest radiography, the Westermark sign is a sign that represents a focus of oligemia (hypovolemia) (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]

Essentially, this is a plain X-ray version of a filling defect as seen on computed tomography pulmonary arteriogram.

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.
  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.