Minor chest trauma can cause hemothorax when the bloods ability to clot is diminished as result either of anticoagulant medications or when there are bleeding disorders such as hemophilia. Iatrogenic
Iatrogenic hemothorax can occur as a complication of heart and lung surgery, for example the rupture of lung arteries caused by the placement of catheters, thoracotomy, thoracostomy, or thoracentesis. The most common iatrogenic causes include subclavian venous catheterizations and chest tube placements, with an occurrence rate of around 1% Sometimes, a Swan-Ganz catheter causes rupture of the pulmonary artery, causing a massive hemothorax. It can also be caused by other procedures like pleural, lung, or transbronchial biopsies, CPR, Nuss procedure, or endoscopic treatment of esophageal varices. Iatrogenic hemothorax is more common in people who have chronic kidney disease in the intensive care unit. Nontraumatic
Less frequently, hemothoraces may occur spontaneously. Nontraumatic hemothoraces most frequently occur as a complication of some forms of cancer if the tumour invades the pleural space. Cancers responsible for hemothoraces include angiosarcomas, schwannomas, mesothelioma, thymomas, germ cell tumours, and lung cancer. Significant hemothoraces can occur with spontaneous rupture of small vessels when the bloods ability to clot is diminished as result of anticoagulant medications. In cases caused by anticoagulant therapy, the hemothorax becomes noticeable 4–7 days after anticoagulant therapy is started. In cases of hemothorax complicating pulmonary embolism treatment, the hemothorax is usually on the side of the original embolism.
However, CT is less used as a primary means of diagnosis within the trauma setting, as these scans require a critically ill person to be transported to a scanner, are slower, and require the subject to remain supine.Magnetic resonance imaging (MRI) can be used to differentiate between a hemothorax and other forms of pleural effusion, and can suggest how long the hemothorax has been present for. Fresh blood can be seen as a fluid with low T1 but high T2 signals, while blood that has been present for more than a few hours displays both low T1 and T2 signals. MRI is used infrequently in the trauma setting due to the prolonged time required to perform an MRI, and the deterioration in image quality that occurs with motion. Thoracentesis
Although imaging techniques can demonstrate that fluid is present within the pleural space, it may be unclear what this fluid represents. To establish the nature of the fluid, a sample can be removed by inserting a needle into the pleural cavity in a procedure known as a thoracentesis or pleural tap. In this context, the most important assessment of the pleural fluid is the percentage by volume that is taken up by red blood cells (the hematocrit) A hemothorax is defined as having a hematocrit of at least 50% of that found in the affected persons blood, although the hematocrit of a chronic hemothorax may be between 25 and 50% if additional fluid has been secreted by the pleura.