Chest radiograph signs of Pulmonary Embolism

Classic chest radiograph signs of pulmonary emboli include –

	Signs of Pulmonary Embolism	Findings on X-Ray
1	‘Westermark sign’	Regional oligaemia
2	‘Palla sign’	Right descending pulmonary artery enlargement
3	‘Fleishner sign’	Central pulmonary artery enlargement
4	‘knuckle sign’	Abrupt pulmonary artery tapering

Westermark sign – regional oligaemia

Westermark sign is a sign that represents a focus of oligemia

1. Dilation of the pulmonary arteries proximal to the embolus
2. Collapse of the distal vasculature creating the appearance of a sharp cut off on chest radiography.
3. Low sensitivity (11%) and high specificity (92%) for the diagnosis of pulmonary embolism

Palla sign – right descending pulmonary artery enlargement

Palla sign describes an enlarged right descending pulmonary artery which suggestive of an occlusion of a lobar or segmental pulmonary artery, or widespread occlusion of small arteries.

Fleischner sign – central pulmonary artery enlargement

Fleischner sign refers to a prominent central pulmonary artery that can be commonly caused either by pulmonary hypertension or by distension of the vessel by a large pulmonary embolus

Knuckle sign – abrupt pulmonary artery tapering

knuckle sign refers to the abrupt tapering or cutoff of a pulmonary artery secondary to a pulmonary embolus