Figure 58A: Anteroposterior (AP) supine chest film with patient on backboard shows abnormal lucency in the deep left costophrenic angle (arrow) with sharp demarcation of the left hemidiaphragm. No definite visceral pleural edge is appreciated. Coronal reformatted CT shows air in the pleural space in the left costophrenic angle (arrow), and also in the medial pleural space along the heart border.