Chang sign

Chang sign on chest x-ray describes a dilated left or right descending pulmonary artery with an abrupt change in calibre, with an amputated appearance. This sign is most commonly associated with with pulmonary infarction and pulmonary hypertension following pulmonary embolism


1962 – Chang published an extensive review of 1,085 consecutive chest X-rays to determine the average diameter of the left and right descending pulmonary artery on a PA chest x-ray. He determined the upper limit of normal for the right descending as 16mm in males, and 15mm in females; and for the left descending <17mm as normal. Measurements were made at the widest point of the artery, usually at the level of the 8th/9th rib.

1965 – Chang published findings of 23 consecutive patients with pulmonary infarcts diagnosed at the Man Memorial Hospital between 1959 and 1962. He noted dilatation of a descending pulmonary artery occurred in all 23 cases of pulmonary infarction. Dilation ranged from 17-22mm on the right (19 cases) and 17-26mm on the left (4 cases)

The most constant roentgen signs of pulmonary embolism in our patients were dilatation of the descending pulmonary artery, parenchymal densities and pleural fluid. The earliest consistent sign was widening of a previously normal descending pulmonary artery. This sign usually appeared within 24 hours of the onset of chest pain and shows its maximal measurements within two to three days. Dilatation of the descending pulmonary artery persisted for a period of one to two weeks and usually returned to normal in three to four weeks. The elevation of diaphragm which was described by Fleischner (1962) was seen in 18 (78%) of our series.

Chang 1965
Chang sign case 1 1965
Chang Sign: Case 1 of 23: A 29 year old female post D&C for incomplete miscarriage
  • a) Preoperative CXR. Right descending pulmonary artery 12 mm.
  • b) Pulmonary infarction. Homogeneous density in right lower lobe. Dilated right descending pulmonary artery measuring 17 mm suggesting acute pulmonary hypertension
  • c) Five days later. Right pleural effusion and persistent densities in the right lower lobe. Right descending pulmonary artery 17 mm
  • d) Two months later. Decreased right pleural fluid and resolving pulmonary infarcts with linear scars. Right descending pulmonary artery again 12 mm.

Associated Persons

Alternative names
  • Chang’s sign
  • Palla sign



the names behind the name

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

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