The chest X ray in pulmonary embolism: Westermark sign, Hampton's Hump and Palla's sign. What's the difference?

Pulmonary embolism (PE), with the incidence of about 60 per 100000 annually, can be a life-threatening disease if it is not treated promptly. It has been estimated that some 10％ of PE patients die within the first hour of the event. Untreated PE has a mortality of about 30％. PE is a condition that is treatable if suspected and diagnosed early. The chest radiograph is still the first investigation that is ordered in patients presenting with cardiorespiratory symptoms or symptoms suggestive of PE. The CXR is also helpful in identifying or excluding other conditions or diagnoses. Thus, knowing and understanding some of the more specific CXR signs can be useful. We suggest that physicians to be aware of and utilize CXR findings such as Palla's sign, Westermark sign and Hamptons hump to help with the diagnosis of PE and to exclude other conditions that can mimic venous thrombo-embolism. Even if these signs are not common, their presence, even in an unsuspected patient without a high pretest probability of PE, should prompt further investigations such as a D-dimer test, lung scintigraphy or computed tomography pulmonary angiography as required.