Recognizing the Imaging Findings of Trauma

Chapter 17 Recognizing the Imaging Findings of Trauma

Trauma is the leading cause of death, hospitalization, and disability in Americans from the age of 1 year through age 45. The major imaging findings of most organ system’s trauma will be discussed as a group in this chapter. Table 17-1 summarizes some of the traumatic injuries that are discussed in other chapters.

Trauma-related injuries are divided into the two major mechanisms which produce them.

• Blunt trauma is usually the result of motor vehicle accidents and is the more common of the two.

• Penetrating trauma is usually the result of accidental or criminal stabbings and gunshot wounds.

TABLE 17-1 OTHER MANIFESTATIONS OF TRAUMA

Injury	Discussed in
Pleural effusion/hemothorax	Chapter 6
Aspiration	Chapter 7
Pneumothorax, pneumomediastinum and pneumopericardium	Chapter 8
Fractures and dislocations	Chapter 22
Head trauma	Chapter 25

Chest Trauma

Chest injuries in trauma patients are very common and are responsible for one out of four trauma-related deaths. The overwhelming majority of chest trauma is the result of motor vehicle accidents.

Rib Fractures

The severity of underlying visceral injury is usually more important than the rib fractures themselves, but their presence might provide clues to unsuspected pathology.

Fractures of the first three ribs are relatively uncommon and, if they occur following blunt trauma, indicate a sufficient amount of force to produce other internal injuries (Fig. 17-1).

Fractures of ribs 4-9 are common and important if they are displaced (pneumothorax) or if there are two fractures in each of three or more contiguous ribs (flail chest).

• Flail chest is almost always accompanied by a pulmonary contusion (see below). Because of the severity of the injuries with which it is usually associated, a flail chest has a significant mortality (Fig. 17-2).

Fractures of ribs 10-12 may indicate the presence of underlying trauma to the liver (right side) or the spleen (left side), especially if they are displaced.

In cases of minor trauma, it is not unusual for rib fractures to be undetectable on the initial examination but to become visible in several weeks after callus begins to form.

Figure 17-1 Rib fractures.

Rib fractures are important primarily for the complications they might produce or the unsuspected pathology they might herald. Fractures of the first three ribs (solid white arrows) are relatively uncommon; following blunt trauma, their presence is a clue that the force to the chest may have been sufficient to produce other internal injuries. Don’t mistake the normal costovertebral junction (solid black arrow) for a fracture.

Figure 17-2 Flail chest.

There are two or more fractures (dotted white arrow demonstrates second fracture in rib 4) present in more than three contiguous ribs (solid white arrows). The airspace disease in the left lung is an underlying pulmonary contusion, which almost always accompanies a flail chest.

Pulmonary Contusions

Pulmonary contusions are the most frequent complications of blunt chest trauma. They represent hemorrhage into the lung, usually at the point of impact.

Recognizing a pulmonary contusion

• The history of trauma is of paramount importance as contusions present as airspace disease that is indistinguishable from other airspace diseases like pneumonia or aspiration.

• Contusions tend to be peripherally placed and frequently occur at the point of maximum impact. Air bronchograms are usually not present because blood fills the bronchi as well as the airspaces (Fig. 17-3).

Classically, they appear within 6 hours after the trauma and, because blood in the airspaces tends to be reabsorbed quickly, disappear within 72 hours, frequently sooner.

Airspace disease that lingers more than 72 hours should raise suspicions of another process such as aspiration pneumonia or a pulmonary laceration.

Figure 17-3 Pulmonary contusions, chest radiograph and CT.

A, Pulmonary contusions tend to be peripherally placed most frequently at the point of maximum impact (dotted white arrow). Air bronchograms are usually not present because blood fills the bronchi as well as the airspaces. B, A second patient, who was in an unrestrained passenger in an automobile accident, also has a large contusion (solid white arrow) associated with multiple rib fractures (solid black arrows).

Pulmonary Lacerations (Hematoma or Traumatic Pneumatocele)

Pulmonary hematomas result from a laceration of the lung parenchyma and, as such, may accompany more severe blunt trauma or penetrating chest trauma.

A pulmonary laceration is also called a traumatic pneumatocele or hematoma.

They are sometimes masked by the airspace disease from a surrounding pulmonary contusion, at least for the first few days until the contusion resolves.

Unlike pulmonary contusions that clear rapidly, pulmonary lacerations, especially if they are blood filled, may take weeks or months to completely clear.

Figure 17-4 Pulmonary lacerations, conventional radiograph, and CT.

Lacerations are sometimes masked, at least for the first few days, by the airspace disease in a surrounding pulmonary contusion. A, If they are completely filled with blood, they will appear as an ovoid mass (dotted white arrow). B, If they are partially filled with blood and partially filled with air, they may contain a visible air-fluid level (solid black arrow). Unlike the neighboring pulmonary contusion (solid white arrow), pulmonary lacerations, especially if they are blood filled, may take weeks or months to completely clear. The top of the left hemidiaphragm (D) is seen in this image.

Aortic Trauma

Trauma to the aorta is most frequently the result of deceleration injuries in motor vehicle accidents. Although the survival rates are improving, most patients with rupture of the thoracic aorta die before reaching the hospital and, of those who survive an aortic injury, the likelihood of death increases the longer the abnormality remains untreated. Only those with incomplete tears in which the adventitial lining prevents exsanguination (producing a pseudoaneurysm) survive to be imaged.

The most common site of injury is the aortic isthmus, which is the portion of the aorta just distal to the origin of the left subclavian artery. Seat-belt injuries may involve the abdominal aorta, but such injuries are far less common than the deceleration injuries to the thoracic aorta.

Only emergency surgery will prevent approximately 50% of patients with blunt aortic injuries from dying within the first 24 hours if left untreated.

Recognizing aortic trauma

• Findings seen on conventional radiographs of the chest are the same as those discussed under Aortic Dissection in Chapter 9. A completely normal chest radiograph has a relatively high negative predictive value for aortic injury, but an abnormal chest x-ray has a relatively low positive predictive value

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Tags: Learning Radiology Recognizing the Basics

Mar 2, 2016 | Posted by admin in GENERAL RADIOLOGY | Comments Off

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