The pleura is a thin membrane that lines the surface of the lungs and the inside of the chest wall outside the lungs. In pleural effusions, fluid accumulates in the space between the layers of pleura. Normally, only teaspoons of watery fluid are present in the pleural space, allowing the lungs to move smoothly within the chest cavity during breathing.
Numerous medical conditions can cause pleural effusions. Some of the more common causes are:
Congestive heart failure
Liver disease (cirrhosis)
End-stage renal disease
Lupus and other autoimmune conditions
Standard posteroanterior and lateral chest radiography remains the most important technique for the initial diagnosis of pleural effusion. Free pleural fluid flows to the most dependent part of the pleural space. In the
upright position, this is the subpulmonic region, and accumulation of fluid causes apparent elevation of the hemithorax, lateral displacement of the dome of the diaphragm, and blunting of the costophrenic angle.
However, at least 250 mL of fluid must accumulate before it becomes visible in a posteroanterior radiograph.
Transudative effusions are usually managed by treating the underlying medical disorder. However, whether transudates or exudates, large, refractory pleural effusions causing severe respiratory symptoms, even if the cause is understood and disease-specific treatment is available, can be drained to provide relief.
The management of exudative effusions depends on the underlying etiology of the effusion. Pneumonia, malignancy, or TB causes most diagnosed exudative pleural effusions, with the remainder typically deemed idiopathic. Complicated parapneumonic effusions and empyemas should be drained to prevent development of fibrosing pleuritis. Malignant effusions are usually drained to palliate symptoms and may require pleurodesis to prevent recurrence.
Although small, freely flowing parapneumonic effusions can be drained by therapeutic thoracentesis, most larger effusions and complicated parapneumonic effusions or empyemas require drainage by tube thoracostomy.
Traditionally, large-bore chest tubes (20-36F) have been used to drain thick pleural fluid and to break up loculations in empyemas. However, such tubes are not always well tolerated by patients and are difficult to direct correctly into the pleural space. However, small-bore tubes (7-14F) inserted at the bedside or under radiographic guidance have been shown to provide adequate drainage, even when empyema is present. These tubes cause less discomfort and are more likely to be placed successfully within a pocket of pleural fluid. Using 20-cm water suction and flushing the tube with normal saline every 6-8 hours may prevent occlusion of small-bore catheters.
Treatment for pleural effusions may often simply mean treating the medical condition causing the pleural effusion. Examples include giving antibiotics for pneumonia, or diuretics for congestive heart failure.
Large, infected, or inflamed pleural effusions often require drainage to improve symptoms and prevent complications. Various procedures may be used to treat pleural effusions, including:
Thoracentesis (described above) can remove large amounts of fluid, effectively treating many pleural effusions.
Tube thoracotomy (chest tube): A small incision is made in the chest wall, and a plastic tube is inserted into the pleural space. Chest tubes are attached to suction and are often kept in place for several days.
Pleurodesis: An irritating substance (such as talc or doxycycline) is injected through a chest tube, into the pleural space. The substance inflames the pleura and chest wall, which then bind tightly to each other as they heal. Pleurodesis can prevent pleural effusions from recurring, in many cases.
Pleural drain: For pleural effusions that repeatedly recur, a long-term catheter can be inserted through the skin into the pleural space. A person with a pleural catheter can drain the pleural effusion periodically at home.
Pleural decortication: Surgeons can operate inside the pleural space, removing potentially dangerous inflammation and unhealthy tissue. Decortication may be performed using small incisions (thoracoscopy) or a large one (thoracotomy).