Approach Considerations
Upright chest radiography is the ideal primary diagnostic study in the evaluation of hemothorax. Additional imaging studies, such as ultrasonography and computed tomography (CT), may sometimes be required for identification and quantification of a hemothorax noted on a plain chest radiograph.
In some cases of nontraumatic hemothorax, especially those resulting from metastatic pleural implants, patients may present with the finding of a new pleural effusion of unknown etiology, and hemothorax may not be identified until the initial diagnostic needle aspiration is performed.
Laboratory Studies
Measurement of the hematocrit of pleural fluid is virtually never needed in a patient with a traumatic hemothorax, but may be indicated for the analysis of a bloody effusion from a nontraumatic cause. In such cases, a pleural effusion with a hematocrit value more than 50% of that of the circulating hematocrit is considered a hemothorax.
Chest Radiography
Plain radiography of the upright chest may be adequate to establish diagnosis by showing blunting at the costophrenic angle or an air-fluid interface if a hemopneumothorax is present. (See the image below.) If the patient cannot be positioned upright, a supine chest radiograph may reveal apical capping of fluid surrounding the superior pole of the lung. A lateral extrapulmonary density may suggest fluid in the pleural space.
In the normal unscarred pleural space, a hemothorax is noted as a meniscus of fluid blunting the costophrenic angle or diaphragmatic surface and tracking up the pleural margins of the chest wall when viewed on the upright chest x-ray film. This is essentially the same chest radiographic appearance found with any pleural effusion.
In cases in which pleural scarring or symphysis is present, the collection may not be free to occupy the most dependent position within the thorax, but will fill whatever free pleural space is available. This situation may not create the classic appearance of a fluid layer on a chest radiograph.
In the acute trauma setting, the portable supine chest radiograph may be the first and only view available from which to make definitive decisions regarding therapy. The presence and size of a hemothorax is much more difficult to evaluate on supine films. Although as much as 400-500 mL of blood is required to obliterate the costophrenic angle on an upright chest radiograph, as much as 1000 mL of blood may be missed when viewing a portable supine chest x-ray film. Only a general haziness of the affected hemithorax may be noted.
In blunt trauma cases, hemothorax is frequently associated with other chest injuries visible on the chest radiograph, such as rib fractures (see the image below), pneumothorax, or a widening of the superior mediastinum.
Ultrasonography
Trauma ultrasonography is used at some trauma centers in the initial evaluation of patients for hemothorax. Even with the use of chest radiography and helical CT, some injuries can remain undetected. In particular, patients with penetrating chest injuries may harbor serious cardiac injury and a pericardial effusion that may be clinically difficult to determine. Bedside echocardiography can provide immediate, accurate information regarding the pericardium and the need for immediate surgery. It can also improve patient outcome. [33]
One drawback of ultrasonography for the identification of traumatic hemothorax is that associated injuries readily seen on chest radiographs in the trauma patient, such as bony injuries, widened mediastinum, and pneumothorax, are not readily identifiable on chest ultrasonograms. Ultrasonography more likely plays a complementary role in specific cases where the chest x-ray findings of hemothorax are equivocal.
Computed Tomography
Thoracic CT (see the image below) has a definite role to play in evaluation of hemothorax, particularly if plain radiography results are ambiguous or initial therapy is inadequate. [34, 35] CT is a highly accurate diagnostic study for pleural fluid or blood and is particularly helpful in localizing loculated collections of blood.
In the trauma setting, CT does not play a primary role in the diagnosis of hemothorax but is complementary to chest radiography. Because many victims of blunt trauma do undergo evaluation with chest CT, abdominal CT, or both, hemothorax not evident on initial chest radiographs might be identified and treated.
Currently, CT is of greatest value later in the course of management of the chest trauma patient, in particular for localization and quantification of any retained collections of clot within the pleural space.
Although multidetector CT allows for the accurate diagnosis of most traumatic injuries, in pediatric patients it should be used in selected cases only. Routine use would result in an unacceptably high radiation exposure to a large number of patients without proven clinical benefit. [36]
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Left hemothorax in patient with rib fractures.
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Upright posteroanterior chest radiograph of patient with right hemothorax.
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Contrast-enhanced CT scan of patient with right hemothorax.
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Insertion of chest tube. Video courtesy of Therese Canares, MD, and Jonathan Valente, MD, Rhode Island Hospital, Brown University.
