Traumatic Pneumatocele

CT shows two pneumatoceles near the pleural surface with fluid (Traumatic pneumatocele Type I)

A laceration is defined as an abnormal intraparenchymal collection of air resulting from traumatic disruption of the lung architecture.

Types of laceration:

• Type 1 is an air-filled cavity with or without an air-fluid level, resulting from sudden compression of a pliable chest wall wherein the air-containing lung ruptures.
• Type 2 is an air-containing cavity in a paravertebral location, resulting from severe compression of the more pliable lower chest wall and sudden shifting of the lower lobe across the vertebral body causing a shearing type of injury.
• Type 3 is a small peripheral cavity or peripheral linear radiolucency that is always close to the chest wall where a rib has been fractured, resulting from a fractured rib that has punctured the lung.
• Type 4 is a result of previously formed, firm pleuropulmonary adhesions causing the lung to tear when the overlying chest wall is violently moved inward or fractures, diagnosed only at surgery or autopsy.

The intraparenchymal collections of air described are also termed pneumatoceles. When traumatic cavities fill with blood, a hematoma forms. Radiographically, traumatic pneumatoceles and hematomas are not usually seen until a few hours or even several days after trauma, initially obscured by surrounding contusion. The size, shape,thickness of the wall, and number of pneumatoceles varies widely from patient to patient.

Unlike a simple contusion, which resolves fairly quickly and completely, a laceration generally takes weeks to months to resolve and may result in residual scarring.

Occasionally, pneumatoceles can become secondarily infected, resembling formation of a hematoma.

References

• Collins J and Primack SL. CT of nonpenetrating chest trauma. Applied Radiology. 2001 Feb;30(2):11-21.
• Rolando Reyna. Traumatic Pneumatocele. mypacs.net