Subtle chest x-ray signs of pulmonary thromboembolism: the Palla's and Westermark's signs

Palla's sign,1 dilated right descending pulmonary artery >16 mm, and the Westermark's sign,2 focal oligaemia, are useful chest x-ray signs of pulmonary thromboembolism (PTE) even though their sensitivity and specificity are less. Here, we present a case in which PTE was suspected based on these chest x-ray signs. A 35-year-old male with fever, right thigh pain, breathlessness and cough was considered to have community-acquired pneumonia, and received intravenous antibiotics for 2 days before presenting to us. The ECG (figure 1) showed sinus tachycardia, incomplete right bundle branch block, right ventricular (RV) strain and the characteristic S1Q3T3 pattern. Reviewing the initial chest x-ray (figure 2) done at the primary care setting revealed the subtle but characteristic Palla's sign (RDPA 17 mm) and the Westermark's sign. Echocardiogram (figure 3) showed dilated right atrium, RV and the pulmonary arteries (PA), along with RV dysfunction (see online supplementary video S1). Doppler interrogation showed tricuspid regurgitation with a pulmonary artery systolic pressure (PASP) of 56 mm Hg. Contrast-enhanced CT of the PA (figure 4) confirmed massive pulmonary thromboembolism, and he was given intravenous streptokinase. The patient made a significant symptomatic recovery that was associated with an improvement in RV function and reduction in PASP.