Westermark’s and Palla’s Signs in Acute Pulmonary Embolism
A 58-year-old asthmatic man was referred to the Medical Assessment Unit with exertional breathlessness, left shoulder pain, and recurrent syncope. Six weeks before admission, he had sustained a fracture of his right third metatarsal and had been in a right below-knee plaster cast, which had been removed a few days earlier. He had been seen on 2 occasions in the preceding 10 days by his general practitioner and the local emergency department, and he had been started on treatment for angina and antibiotics for a lower–respiratory tract infection. On arrival, his oxygen saturations were 88% on air. A chest x-ray showed an elevated left hemidiaphragm and an area of focal oligemia (Westermark’s sign1) in the right lung (Figure 1, area between white arrowheads), with a prominent right descending pulmonary artery (Palla’s sign2; Figure 1, black arrow). The patient was started on low-molecular-weight heparin. Ventilation–perfusion lung scintigraphy revealed bilateral large mismatched ventilation–perfusion defects, one of which corresponded to the radiographic area of focal oligemia (Figure 2, white arrowhead).
Westermark’s and Palla’s signs in combination are rare3 but, when seen, can help confirm diagnosis of pulmonary embolism.