Pulmonary contusion and laceration can be caused by direct impact injury or blast injury at the coup site or contrecoup site. Pulmonary contusion is common, and laceration is more severe than contusion. Severe patients may have bronchial fracture and diaphragmatic rupture.
Clinical presentation and pathology
Mild pulmonary contusion is mostly asymptomatic, while severe pulmonary contusion may present with cough and hemoptysis. Pulmonary laceration is common in the lower lung, often accompanied by rib fracture, and the main clinical manifestations are thoracodynia, cough, and hemoptysis.
The main pathological changes of pulmonary contusion are fluid or blood exudation in the pulmonary interstitium or parenchyma, mainly in the periphery of the lung, usually occur within 4 - 6 hours after trauma, and can subside in 3 - 4 days. After the lung parenchyma is torn, the peripheral lung tissue develops elastic retraction; If air enters, an air-filled cyst is formed; if blood enters, an air-fluid cyst is formed; if it is filled with blood, a pulmonary hematoma is formed. Pulmonary hematoma resolves slowly, often lasts for several weeks to months or even longer, and residual irregular linear lesions may remain.
Imaging manifestations
X-ray
Pulmonary contusion is manifested by unclear edges of lung markings; patchy, slightly dense opacities inconsistent with the range of lung segments or lobes, with hazy edges, can be seen. The air-containing cyst formed after pulmonary laceration shows thin-walled annular lucency, with or without air-fluid level. Pulmonary hematoma shows subrounded dense opacity.
CT
Mild pulmonary contusion is manifested by ground-glass opacity with hazy edges, often with peripheral non-segmental distribution, mostly near rib fracture and chest wall hematoma. Peripheral air-containing cystic cavity or cystic cavity with air-fluid level is more common. Cystic cavity with air-fluid level beside the spine at the base of the lung is pulmonary laceration caused by the compression of lung tissue to the spine. Peripheral small air-containing cystic cavities or linear lucencies are often accompanied by rib fracture. Pulmonary laceration after pleural adhesion is not easy to show. Pulmonary hematoma shows subrounded, homogeneous, hyperdense opacity, and the edges may be hazy due to the presence of pulmonary contusion.
Figure 1 Pulmonary laceration
a. Plain CT lung window and b. plain CT mediastinal window show patchy ground-glass opacities in the right lung, multiple small cystic cavities with air-fluid level (↗), and mild pneumothorax and pleural adhesion and thickening in the right pleural cavity.
Diagnosis and differential diagnosis
Pulmonary contusion is often part of complex chest injury at the coup site or contrecoup site of the trauma, and shows irregular, hazy, dense opacity with hazy edges. On the basis of the history of trauma, it can often be diagnosed. Sometimes, it needs to be differentiated from infectious lesions. The rapid regression of pulmonary contusion is helpful for differentiation.
Pulmonary laceration is more common in patients with severe blunt chest injuries, often in the lower lungs, with typical imaging manifestations, and diagnosis is not difficult. The manifestations of intrapulmonary hematoma in remission may resemble those of tumor; on the basis of the history of chest trauma and imaging findings, it is generally not difficult to differentiate.