Role of Pleural Fluid Attenuation Value Measurement on Computed Tomography as a Diagnostic Tool for Hemothorax in Traumatic Patients

Hemothorax is defined as blood accumulation in the pleural space. It is a consequence of blunt trauma in 90% of cases. Hemothorax due to blunt trauma mechanisms e.g traffic accidents,sport accidents and falls are among the commonest injuries of the chest. It is manifested in 30-50% of chest trauma cases. In such cases, bleeding might be caused by damage to pulmonary parenchyma or intercostal arteries associated with or without rib fractures and other chest wall tissue injuries including parietal pleura or other thoracic structures. Although other pleural effusion types may also manifest such as chylothorax in case of chest trauma, however fluid detected in pleural space is usually considered blood unless proven not to be. Despite the clinical and radiological findings provide important data about the content of pleural cavity, however tube thoracostomy and diagnostic thoracocentesis are still required to relieve pressure and characterize the fluid. Tube thoracostomy is an invasive procedure which can lead to immediate procedural injuries, infections and pain which can contribute to respiratory failure in patients with chest wall injury. Although needle thoracocentesis is less invasive than tube thoracostomy, however it carries small but definitive risks such as pneumothorax, bleeding and chest wall hematoma. Since hemothorax is a potentially life threatening, it must be diagnosed quickly and accurately and all these unnecessary complications should be avoided. Chest computed tomography [CT] has been accepted as the gold standard imaging study for evaluating chest trauma and usually performed in patients with grossly severe chest trauma, as it helps to detect even small hemothorax.

CT can also allow for more advanced characterization of pleural fluid and distinguish hemothorax from any other types of effusion by means of scaling Hounsfield units as in literature, any attenuation value for pleural fluid between 35 and 70 HU is considered typically blood, so it can be considered as an important non-invasive diagnostic tool for diagnosis of hemothorax in traumatic patients.