Hemothorax

A hemothorax (derived from hemo- + thorax , plural hemothoraces) is an accumulation of blood within the pleural cavity. The symptoms of a hemothorax include chest pain and difficulty breathing, while the clinical signs include reduced breath sounds on the affected side and a rapid heart rate. Hemothoraces are usually caused by an injury but may occur spontaneously: due to cancer invading the pleural cavity, as a result of a blood clotting disorder, as an unusual manifestation of endometriosis, in response to a collapsed lung, or rarely in association with other conditions. Hemothoraces are usually diagnosed using a chest X-ray, but can be identified using other forms of imaging including ultrasound, a CT scan, or an MRI scan. They can be differentiated from other forms of fluid within the pleural cavity by analysing a sample of the fluid, and are defined as having a hematocrit of greater than 50% that of the person's blood. Hemothoraces may be treated by draining the blood using a chest tube, but may require surgery if the bleeding continues. If treated, the prognosis is usually good. Complications of a hemothorax include infection within the pleural cavity and the formation of scar tissue. The symptoms of a hemothorax depend on the quantity of blood that has been lost into the pleural cavity. A small hemothorax usually causes little in the way of symptoms, while larger hemothoraces commonly cause breathlessness and chest pain, and occasionally lightheadedness. Other symptoms may occur in association with a hemothorax depending on the underlying cause. The clinical signs of a hemothorax include reduced or absent breath sounds and reduced movement of the chest wall on the affected side. When the affected side is tapped or percussed, a dull sound may be heard in contrast to the usual resonant note. Large hemothoraces that interfere with the ability to transfer oxygen may cause a blue tinge to the lips (cyanosis). In these cases the body may try to compensate for the loss of blood, leading to a rapid heart rate (tachycardia), and pale, cool, clammy skin. A hemothorax is often caused by an injury, either blunt trauma or wounds that penetrate the chest, and these cases are referred to traumatic hemothoraces. Even relatively minor chest injuries can lead to significant hemothoraces. Injuries often cause the rupture of small blood vessels such as those found between the ribs. However, if larger blood vessels such as the aorta are damaged, the blood loss can be massive. Hemothorax can also occur as a complication of heart and lung surgery, for example the rupture of lung arteries caused by the placement of catheters. Less frequently, hemothoraces may occur spontaneously. A hemothorax can complicate some forms of cancer if the tumour invades the pleural space. Tumours responsible for hemothoraces include angiosarcomas, schwannomas, mesothelioma, and lung cancer. Hemothoraces are more likely to occur in response to very minor trauma when blood is less able to form clots, either as result of medications such as anticoagulants, or because of bleeding disorders such as haemophilia. Rarely, hemothoraces can arise due to endometriosis, a condition in which tissue that normally covers the inside of the uterus forms in unusual locations. Endometrial tissue that implants on the pleural surface can bleed in response to the hormonal changes of the menstrual cycle, causing what is known as a catamenial hemothorax as part of the thoracic endometriosis syndrome. It represents 14% of cases of thoracic endometriosis syndrome. Those with an abnormal accumulation of air within the pleural space (a pneumothorax) can bleed into the cavity, which occurs in about 5% of cases of spontaneous pneumothorax. The resulting combination of air and blood within the pleural space is known as a hemopneumothorax.