Westermark sign is an area of oligemia distal to a large vessel that is occluded by pulmonary embolus.
Focal area of increased translucency due to oligaemia, which occurs due to impaired vascularisation of the lung due to primary mechanical obstruction or reflex vasoconstriction
14% sensitivity, 92% specificity, 38% PPV, 76% NPV PIOPED 1993
1938 – Nils Westermark described a subset of patients diagnosed with pulmonary embolism developed pulmonary infarction. These patients had ‘anemic’ or oligemic peripheral regions of lung parenchyma distal to an occlusive arterial embolus .
In embolism of the pulmonary artery without infarction we get ischaemia of the branches of the pulmonary artery on the peripheral side of the embolus. On the radiogram this ischaemia appears as a clarified area with diminished vascular design corresponding to the extent of the embolised artery. The vascularisation is however maintained in the central parts of the lung. The vascularisation takes however a rapid end to pass over into the above mentioned area of non-vascularisation.Westermark 1938
Case 2: 1938
Case 2. Examination carried out on day before death after taken ill with pulmonary embolism. Decided anaemia of the entire right lung, particularly well marked in its upper lobe and in left upper lobe. The vascular design seems to end abruptly in the central parts of the lung.
- Nils Westermark (1892 – 1980) [Westermark sign 1938]
- Aubrey Otis Hampton (1900 – 1955) [Hampton hump 1940]
- Felix George Fleischner (1893 – 1969) [Fleischner sign 1959]
- C. H. Joseph Chang (1929 – 2017) [Chang sign 1965]
- Antonio Palla (1950 – ) [Palla sign 1983]
- Relative oligemia
- Westermark N. On the roentgen diagnosis of lung embolism: brief review of the incidence, pathology and clinical symptoms of lung embolism. Acta Radiologica 1938; 19(4) :357-372.
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