Pneumothorax and Atelectasis Appearing as a Non-Specific Opacity on a Supine Infant's Chest X-Ray.

Thoracic postoperative complications are difficult to diagnose on supine chest X-rays, with pneumothoraxes accompanied by underlying atelectasis presenting as non-specific opacities due to the superposition of the two entities having opposed radiographic characteristics, with one causing lucency and the other opacity.