Palla's sign is a clinical sign in which an enlarged right descending pulmonary artery is seen on the chest x-ray in patients with pulmonary embolism. It is of low sensitivity, and its specificity is not known. It exhibits as a "sausage" appearance on X-ray. Lee DS, Vo H, Franco A, Keshavamurthy J, Rotem E. "Palla and Westermark Signs". J Thorac Imaging. 2017;32(4):7. at Journal of Thoracic Imaging It is named after italian radiologist Antonio Palla. In 1983, he published his observations that close to 25% of patients with pulmonary embolism had a chest x-ray sign of enlarged right descending pulmonary artery.
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