Endometriotic 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 thoracic endometriosis along with catamenial pneumothorax, catamenial hemoptysis, and lung nodules of endometriosis. Catamenial hemothorax represents 14% of cases of thoracic endometriosis syndrome while catamenial pneumothorax is seen in 73%, catamenial hemoptysis in 7%, and pulmonary nodules in 6%. Mechanism
When a hemothorax occurs, blood enters the pleural cavity. The blood loss from the circulation has several effects. Firstly, as blood builds up within the pleural cavity, it begins to interfere with the normal movement of the lungs, preventing one or both lungs from fully expanding and thereby interfering with the normal transfer of oxygen and carbon dioxide to and from the blood. Secondly, blood that has been lost into the pleural cavity can no longer be circulated. Hemothoraces can lead to significant blood loss – each half of the thorax can hold more than 1500 milliliters of blood, representing more than 25% of an average adults total blood volume. The body may struggle to cope with this blood loss, and tries to compensate by maintaining blood pressure by forcing the heart to pump harder and faster, and by squeezing or constricting small blood vessels in the arms and legs. These compensatory mechanisms can be recognised by a rapid resting heart rate and cool fingers and toes.If the blood within the pleural cavity is not removed, it will eventually clot.
This clot tends to stick the parietal and visceral pleura together and has the potential to lead to scarring within the pleura, which if extensive leads to the condition known as a fibrothorax. Following the initial loss of blood, a small hemothorax may irritate the pleura, causing additional fluid to seep out, leading to a bloodstained pleural effusion. Furthermore, as enzymes in the pleural fluid begin to break down the clot, the protein concentration of the pleural fluid increases. As a result, the osmotic pressure of the pleural cavity increases, causing fluid to leak into the pleural cavity from the surrounding tissues. Diagnosis
Hemothoraces are most commonly detected using a chest X-ray, although ultrasound is sometimes used in an emergency setting. It can be suspected in any person with any form of chest trauma. However, plain X-rays may miss smaller hemothoraces while other imaging modalities such as computed tomography (CT), or magnetic resonance imaging may be more sensitive. In cases where the nature of an effusion is in doubt, a sample of fluid can be aspirated and analysed in a procedure called thoracentesis. Physical examination is used initially. Auscultation has been reported to have an accuracy of nearly 100% in diagnosing hemopneumothorax. Chest X-ray
A chest X-ray is the most common technique used to diagnosis a hemothorax. X-rays should ideally be taken in an upright position (an erect chest X-ray), but may be performed with the person lying on their back (supine) if an erect chest X-ray is not feasible.