The chest x-ray shows emphysematous changes. There is an emphysematous bulla in the left upper lobe.

Emphysematous bulla, if large can be mistaken for a pneumothorax.

1. Compare old chest x-rays if available.
2. In a sick patient, decubitus view with left side up will help.
3. CT chest if the patient is able to lie flat.

Features of emphysema on chest x-ray – hyperinflation, hyperlucency, vascular attenuation, flattened hemidiaphragms, increased retrosternal airspace.

Reference: Brant and Helms’ Fundamentals of Diagnostic Radiology 5th Edition.