Chang sign explained

Chang sign is a radiologic sign for detecting pulmonary embolism in X-ray films. It refers to the dilatation and abrupt change in calibre of a previously normal descending pulmonary artery on a chest X-ray film.^[1] Chang sign usually appears within 24 hours of the onset of chest pain due to pulmonary embolism,^[2] and the maximal dilatation of the descending pulmonary artery often occurs in two to three days after the onset of pain.^[3]

Chang sign is absent in case of co-existing pneumonia or other conditions causing central opacities, where the descending pulmonary artery cannot be visualised in the X-ray image.^[3]

Notes and References

1. Mossbock . R . [Experience with corrective operations for dysgnathia in cleft lip, palate and jaw]. . Osterreichische Zeitschrift fur Stomatologie . December 1980 . 77 . 12 . 466–9 . 6938914.
2. Saliba . Thomas . Tack . Denis . Central Pulmonary Embolism Detected on a Chest X-Ray: A Case Report . Journal of the Belgian Society of Radiology . 15 February 2023 . 107 . 1 . 11 . 10.5334/jbsr.3052 . free . 9936914 .
3. (Joseph) Change . C.H. . Davis . W. Clayton . A roentgen sign of pulmonary infarction . Clinical Radiology . January 1965 . 16 . 2 . 141–147 . 10.1016/S0009-9260(65)80007-1.