Radiographic features of pulmonary embolism: Westermark and Palla signs

Classic chest radiograph signs of pulmonary emboli include regional oligaemia (‘Westermark sign’), right descending pulmonary artery enlargement (‘Palla sign’), central pulmonary artery enlargement (‘Fleishner sign’) and abrupt pulmonary artery tapering (‘knuckle sign’).1 We present a case highlighting the importance of recognising these unusual radiological signs in patients presenting with haemodynamically unstable pulmonary emboli (box 1). Box 1 ### CXR appearance of Westermark and Palla signs Westermark sign: regional pulmonary oligaemia Palla sign: enlargement of the descending pulmonary artery A 78-year-old lady presented to the emergency department with collapse and pleuritic chest pain. On examination, the patient was in respiratory distress and haemodynamic …