A hemothorax, a collection of blood in the pleural space, is relatively common in blunt or penetrating thoracic trauma and is an acute indication for pleural drainage.
Trauma patients are commonly initially evaluated with a supine chest x-ray. In traditional upright films, pleural blood layers inferiorly, obscuring the costophrenic angle laterally and/or the hemidiaphragm more medially. The top CXR shows a left hemothorax. Most studies agree that it takes somewhere between 200-500mL of fluid to blunt a hemidiaphragm.
In contrast, supine films may conceal sizeable hemothoraces. In supine films (bottom CXR), blood layers posteriorly, which causes generalized haziness of the affected hemithorax. Often the ipsilateral costophrenic angle and hemidiaphragm edges are preserved. In fact, up to 1 liter of pleural blood may go undetected on plain films.
With CT as the gold standard, bedside ultrasonoraphy by emergency physicians has been shown to be comparable in sensitivity to an initial supine chest x ray. This may expedite diagnosis.
References Ma OJ, Mateer JR. Trauma ultrasound examination versus chest radiography in the detection of hemothorax. Ann Emerg Med. March 1997;29:312-316.
This "EM Lightbox" case was authored by guest blogger, Dr. Eric Silman.