Pleural biopsy is done to determine the cause of an exudative pleural effusion Pleural Effusion Pleural effusions are accumulations of fluid within the pleural space. They have multiple causes and usually are classified as transudates or exudates. Detection is by physical examination and... read more 
when thoracentesis How To Do Thoracentesis Thoracentesis is needle aspiration of fluid from a pleural effusion. Thoracentesis may be done for diagnosis and/or therapy. Diagnostic thoracentesis Indicated for almost all patients who have... read more 
is not diagnostic.
The yield of closed pleural biopsy is about twice as high for tuberculosis than it is for pleural cancers. Improved laboratory techniques, newer diagnostic tests for pleural fluid (eg, adenosine deaminase levels, interferon-gamma, polymerase chain reaction studies for suspected tuberculosis), and more widespread availability of thoracoscopy have made pleural biopsy less necessary and therefore uncommonly done.
Percutaneous pleural biopsy should be done only by a pulmonologist or surgeon trained in the procedure and should be done only in patients who are cooperative and have no coagulation abnormalities. Technique is essentially the same as that for thoracentesis How To Do Thoracentesis Thoracentesis is needle aspiration of fluid from a pleural effusion. Thoracentesis may be done for diagnosis and/or therapy. Diagnostic thoracentesis Indicated for almost all patients who have... read more and can be done at the bedside; no specific additional patient preparation is necessary. At least 3 specimens obtained from one skin location, with 3, 6, and 9 o’clock positioning of the needle-cutting chamber, are needed for histology and culture.
Chest x-ray Chest x-ray Chest imaging includes use of plain x-rays, computed tomography (CT) scanning, magnetic resonance imaging (MRI), nuclear scanning, including positron emission tomography (PET) scanning, and... read more should be done after biopsy because of increased risk of complications, which are the same as those for thoracentesis but with higher incidence of pneumothorax Pneumothorax Pneumothorax is air in the pleural space causing partial or complete lung collapse. Pneumothorax can occur spontaneously or result from trauma or medical procedures. Diagnosis is based on clinical... read more 
and hemothorax Hemothorax Hemothorax is accumulation of blood in the pleural space. (See also Overview of Thoracic Trauma.) The usual cause of hemothorax is laceration of the lung, intercostal vessel, or an internal... read more 
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