<P> Massive pleural effusion, later proven to be hemothorax in a South Indian male . </P> <P> Once a pleural effusion is diagnosed, its cause must be determined . Pleural fluid is drawn out of the pleural space in a process called thoracentesis, and it should be done in almost all patients who have pleural fluid that is at least 10 mm in thickness on CT, ultrasonography, or lateral decubitus X-ray and that is new or of uncertain etiology . In general, the only patients who do not require thoracentesis are those who have heart failure with symmetric pleural effusions and no chest pain or fever; in these patients, diuresis can be tried, and thoracentesis is avoided unless effusions persist for more than 3 days . In a thoracentesis, a needle is inserted through the back of the chest wall in the sixth, seventh, or eighth intercostal space on the midaxillary line, into the pleural space . The use of ultrasound to guide the procedure is now standard of care as it increases accuracy and decreases complications . After removal, the fluid may then be evaluated for: </P> <Ol> <Li> Chemical composition including protein, lactate dehydrogenase (LDH), albumin, amylase, pH, and glucose </Li> <Li> Gram stain and culture to identify possible bacterial infections </Li> <Li> White and red blood cell counts and differential white blood cell counts </Li> <Li> Cytopathology to identify cancer cells, but may also identify some infective organisms </Li> <Li> Other tests as suggested by the clinical situation--lipids, fungal culture, viral culture, tuberculosis cultures, lupus cell prep, specific immunoglobulins </Li> </Ol> <Li> Chemical composition including protein, lactate dehydrogenase (LDH), albumin, amylase, pH, and glucose </Li>

Difference between pneumothorax and pleural effusion on x ray