<unk> es 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<unk> es 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<unk> . 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. On an erect chest X-ray, a<unk>  is suggested by blunting of the costophrenic angle or partial or complete opacification of the affected half of the thorax. On a supine film the blood tends to layer in the pleural space, but can be appreciated as a haziness of one half of the thorax relative to the other. A small<unk>  may be missed on a chest X-ray as several hundred milliliters of blood can be hidden by the diaphragm and abdominal viscera on an erect film. Supine X-rays are even less sensitive and as much as one liter of blood can be missed on a supine film. Other methods Ultrasonography may be used to detect<unk>  and other pleural effusions. This technique is of particular use in the critical care and trauma settings as it provides rapid, reliable results at the bedside. Ultrasound is more sensitive than chest x-ray in detecting<unk> . Ultrasound can cause issues in people who are morbidly obese or have subcutaneous emphysema. When CT is unavailable in the current setting or the person cannot be moved to the scan, ultrasound is used. Computed tomography (CT or CAT) scans may be useful for diagnosing retained<unk>  as this form of imaging can detect much smaller amounts of fluid than a plain chest X-ray. 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<unk>  and other forms of pleural effusion, and can suggest how long the<unk>  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. File:UOTW 38 - Ultrasound of the Week 4.Ultrasound scan of the chest showing a left-sided<unk>  File:CT scan showing<unk>  caused by warfarin use.CT scan of the chest showing a<unk>  caused by warfarin use File:Chest MRI showing<unk>  in a 16 day old infant (cropped).Chest MRI showing a<unk>  in a 16-day-old infant Thoracentesis alt=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<unk>  is defined as having a hematocrit of at least 50% of that found in the affected person's blood, although the hematocrit of a chronic<unk>  may be between 25 and 50% if additional fluid has been secreted by the pleura. Pleural fluid can dilute<unk> es in as low as 3–4 days. The red blood cells in the effusion spontaneously break down. Distinguishing the pleural fluid from blood by colour is impossible when the hematocrit value is over 5%. For these reasons, even if there is a hematocrit value under 50%, further investigations can be done in order to figure out if there is a source of bleeding. Hematocrit can be roughly calculated by dividing the red blood cell count of the pleural fluid by 100,000. Thoracentesis is the test most commonly used to diagnose a<unk>  in animals.<unk>  can itself be a rare complication of thoracentesis if the intercostal artery is punctured.
Hemothorax
Pneumothorax
Urinothorax
Traumatic cardiac arrest
Chylothorax
Pulmonary hematoma
Hydropneumothorax
Hemopneumothorax