Pulmonary laceration

Pulmonary lacerations result from frank laceration of lung parenchyma secondary to trauma. There is almost always concurrent contusion.

Epidemiology

Contusions and lacerations follow blunt or penetrating chest trauma, and are almost always seen with other chest (and abdominal) injuries. While pulmonary laceration can affect anyone, children are considered more susceptible due to chest wall greater pliability in that age group ⁴.

Pathology

Due to the elastic recoil of the lung, spheres of torn lung parenchyma form and can fill with blood (termed a haematocele), air (pneumatoceles) or both blood and air. If gas-filled, they tend to fill with blood or fluid over time (days to weeks) and can take months to resolve.

Classification

In 1988, Wagner et al. divided pulmonary lacerations into 4 subtypes based on CT findings and mechanism of injury ⁶:

• type I- compression rupture: most most common type of laceration that usually occurs as a 2-8 cm lesion in the central lung

• type II - compression shear: occurs after sudden compression of the lower chest when the lung suffers from a shear injury to the spine; the the lung is compressed by lateral compression, against the thoracic spine leading to a paravertebral tubular lesionin lower part of the lung.

• type III - direct puncture / rib penetration: occur occur with a penetrating fractured rib; these lesions are commonly multiple

• type IV - adhesion tears: occurs occurs in sudden injuries of the chest wall where prior pleuropulmonary adhesions have been created

Radiographic features

Plain radiograph

The pattern can be similar to contusion but can also have added rib fractures and pneumothoraces. Gaseous lucencies may be seen in or adjacent to the areas of consolidation.

CT

Regions of pulmonary contusion with added blebs (pneumatoceles) with gas-fluid levels.

Due to normal pulmonary elastic recoil, lung tissues surrounding a laceration often pull back from the laceration itself. This results in the laceration manifesting at CT as a round or oval cavity, instead of having the linear appearance typically seen in other solid organs.

Severe laceration has gross disruption of lung parenchymal architecture.

Differential diagnosis

Consider

• cavitation associated with post contusion pneumonia: can develop days after the initial trauma whereas lacerations are seen at the initial time of imaging.

See also

• pulmonary contusion

• traumatic pneumatocoele