Pneumothorax

An abnormal chest x-ray shows the presence of an air pocket (arrows) in the pleural sac surrounding one lung, which has collapsed. This finding is typical of a severe pneumothorax. A normal chest x-ray is shown on the right for comparison; the heart (H), lungs (L), vertebrae (v), and collarbone (C) can be seen.

(Left: AP Fishman, Fishman's Pulmonary Diseases and Disorders, 3 ed, 1998, McGraw-Hill, Fig. 91-5; right: MY Chen, Basic Radiology, 1996, McGraw-Hill, Fig. 4-1b; with permission.)