Subcutaneous emphysema, refers to gas in the subcutaneous tissues

Clinically it is felt as crepitus

In the trauma situation, its presence indicates possible serious injuries that do require urgent management.

RADIOGRAPHY

CHEST X-RAY

There are often striated lucencies in the soft tissues that may outline muscle fibers. It can outline the pectoralis major, giving rise to the ginkgo leaf sign. Often there are displaced rib fractures indicating a cause of the gas.

CT

Subcutaneous emphysema is visible on CT scans, with pockets of gas seen as extremely dark low attenuation areas in the subcutaneous space.

USG

Well defined comet tail artefacts can be seen