Westermark sign
Encyclopedia
In chest radiography
, the Westermark Sign, is a sign that represents a focus of oligemia (vasoconstriction
) seen distal to a pulmonary embolus
(PE). While the chest x-ray is normal in the majority of PE cases, the Westermark sign is seen in 2% of patients.
The sign results from a combination of:
infarction
), has a low sensitivity (11%) and high specificity
(92%) for the diagnosis of pulmonary embolus.
Chest X-ray
In medicine, a chest radiograph, commonly called a chest X-ray , is a projection radiograph of the chest used to diagnose conditions affecting the chest, its contents, and nearby structures...
, the Westermark Sign, is a sign that represents a focus of oligemia (vasoconstriction
Vasoconstriction
Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, small arterioles and veins. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in...
) seen distal to a pulmonary embolus
Pulmonary embolism
Pulmonary embolism is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream . Usually this is due to embolism of a thrombus from the deep veins in the legs, a process termed venous thromboembolism...
(PE). While the chest x-ray is normal in the majority of PE cases, 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 pulmonaryLung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
infarction
Infarction
In medicine, infarction refers to tissue death that is caused by a local lack of oxygen due to obstruction of the tissue's blood supply. The resulting lesion is referred to as an infarct.-Causes:...
), has a low sensitivity (11%) and high specificity
Specificity
Specificity may refer to:* Being specific * Specificity , the proportion of negatives in a binary classification test which are correctly identified...
(92%) for the diagnosis of pulmonary embolus.