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Pleural Effusions

A pleural effusion is an abnormal collection of fluid in the pleural space (the area between the surface lining of the lung and the inside of the chest wall). Normally, only several drops of fluid are present in the pleural space; this small amount of fluid cannot be seen on chest radiographs (x-rays). There are several causes of excessive pleural fluid accumulation within the pleural space. These include: 1) increased pressure in the pulmonary blood vessel system as seen in congestive heart failure, 2) increase in the "leakiness" of small blood vessels in the pleural tissues, 3) decrease in the patient's blood protein levels, or 4) obstruction of the lymph fluid drainage system.

Pleural fluid accumulation can be without symptoms or can cause a wide range of symptoms such as shortness of breath or chest pain. A physician may suspect the presence of a pleural effusion by hearing diminished breath sounds with the stethoscope or by feeling dullness when gently tapping the chest on the affected side. The chest x-ray shows a fluid collection around the lung. A lateral decubitus film (done with the patient lying on their side) may be done to confirm the presence of fluid.

Pleural fluid may be transudative (thin fluid with a low protein count) or exudative (thick fluid with a high protein count). Transudative fluid collections are the result of generalized medical conditions such as congestive heart failure, liver disease, low protein state, collapsed lung or kidney disease. Exudative fluid collections are the result of local pleural space processes such as infections, pulmonary embolism, connective tissue diseases, or cancer.

Pleural fluid may be sampled by thoracentesis (pleural tap). Often the cause of the pleural effusion is suggested by the patient's history and presentation and results of pleural fluid testing. If the causes of pleural effusion remain undiagnosed, two additional procedures can be done to better determine the cause of the fluid collection - a closed pleural biopsy or a thoracoscopic pleural biopsy. A closed pleural biopsy is similar to a thoracentesis, except a larger needle is used which can biopsy the outer layer of pleural tissue. A thoracoscopic pleural biopsy involves inserting a small scope through the skin and tissues into the pleural space to both view the pleura and biopsy the tissue.

The treatment of pleural effusion depends, to a large degree, on the cause of the pleural effusion. Treatment of pleural effusions caused by congestive heart failure usually involves a therapeutic thoracentesis as well as the administration of diuretics and other medications to improve the heart function. Pleural effusions associated with a nearby pneumonia are treated with thoracentesis and antibiotics. If the pleural fluid is directly infected (empyema), drainage of the fluid by a larger chest tube inserted into the pleural space may be necessary in addition to antibiotic treatment. Treatment of a cancer-related (malignant) pleural fluid collection may involve pleurodesis (drainage of the fluid by a chest tube, followed by instilling of a chemical into the pleural space to prevent re-accumulation) or may be aimed at treating the underlying cancer.

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