Palla sign

Palla sign describes right descending pulmonary artery enlargement on chest x-ray, with the characteristic ‘sausage-shaped’ appearance as a potential sign of pulmonary embolism.

Palla sign 1983 Fig 2 PE sausage
Palla sign
  • Left image: Chest radiograph of a patient with pulmonary embolisim, demonstrating a ‘sausage’ appearance of the right descending pulmonary artery.
  • Right image: Enlarged right descending pulmonary artery with dense clear-cut borders (white arrows). The lowest arrow points to an abrupt ending of the vessel, and the branches for the middle and lower lobes appear distorted and lumped (black arrows).


1983 – Palla reviewed 374 consecutive chest x-rays of patients admitted to ICU with suspicion/confirmed pulmonary embolus. The measured diameters of the descending pulmonary arteries at the superior venous angle and 1cm distal had significant diminution in size compared to the recovery chest x-ray.

From the practical point of view, the enlargement of descending pulmonary artery may be useful to raise the suspicion of pulmonary embolism. As documented here, the descending pulmonary artery was wider in patients with confirmed pulmonary embolism than in those without confirmation.The typical ‘ ‘sausage’ ‘ appearance of the descending pulmonary artery, easily recognizable without any measurement,was present in about one-fourth of the patients with confirmed pulmonary embolism and it was never observed in patients in whom the original clinical suspicion of pulmonary embolism was rejected subsequently.

Palla 1983
  • A: CXR of patient with PE with ‘sausage’ appearance of right descending pulmonary artery (solid arrows). Lowest solid arrow points to cut-off ending; branches for middle and lower lobes are hardly visible (open arrows).
  • B: 30 days later. Right descending pulmonary artery appears smaller and less dense than in previous film, with cylindrical appearance (solid arrows). Branches for middle and lower lobes appear more regular and clearly visible (open arrows).

Associated Persons

Alternative names


Palla used the baseline measurements from Chang’s 1962 review without reference to Chang’s 1965 paper, which described right descending pulmonary artery dilatation as a sign of pulmonary infarction secondary to pulmonary embolus (later known as Chang sign).



the names behind the name

Doctor in Australia. Keen interest in internal medicine, medical education, and medical history.

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