An AP chest radiograph showing atelectasis of the right lower lobe. Note that the collapsing lobe has moved centrally and inferiorly towards the lower dorsal spine, where it is seen as a triangular opacity partially silhouetting the right hemidiaphragm and associated with a subtle air bronchogram. The minor fissure shows inferior displacement. Right–lower-lobe atelectasis can be differentiated from right–middle-lobe atelectasis by the persistence of the right heart border as in this case