Pleural Effusion (Fluid in the Pleural Space)

A pleural effusion is a buildup of fluid in the pleural space, the area between the layers of tissue that line the lungs and chest wall. It may also be called effusion or pulmonary effusion. The fluid in a pleural effusion can be categorized as transudate or exudate.

• Transudate is usually composed of plasma ultrafiltrates due to an imbalance in vascular hydrostatic and oncotic forces in the chest (heart failure, cirrhosis).
• Exudate is typically produced by inflammatory conditions (lung infection, lung cancer). Exudative pleural effusions are often more serious and difficult to treat.

What causes pleural effusion?

There are many causes of pleural effusions.

Some major causes include:

• Congestive heart failure
• Kidney failure
• Infection
• Malignancy
• Pulmonary embolism
• Hypoalbuminemia
• Cirrhosis
• Lung cancer
• Trauma

A pleural effusion develops when fluid seeps into the pleural space, the thin area between the visceral and pleural membranes in the chest cavity. This space normally contains a small amount of fluid to facilitate smooth lung movement. However, under pressure, malignant cells and infectious agents can enter the pleural cavity, causing abnormal amounts of fluid and other compounds to accumulate (see diagnosis section).

What are the risk factors for pleural effusion?

Pleural effusions are caused by the underlying medical problems mentioned above, making the presence of any of these medical problems a risk factor for developing pleural effusions. However, not all individuals with these medical problems will develop pleural effusions.

Congestive heart failure is the most common cause of transudative pleural effusions, while infection (pneumonia) and malignancy are the most common causes of exudative pleural effusions.

What are the symptoms of pleural effusion?

Common symptoms of pleural effusion may include:

• Chest pain
• Difficulty breathing
• Painful breathing (pleurisy)
• Cough (dry or productive)

Deep breathing usually increases the pain.

Symptoms such as fever, chills, and loss of appetite often accompany pleural effusions caused by infectious agents.

What procedures and tests diagnose pleural effusions?

A patient’s history and physical exam may indicate a presumptive diagnosis of pleural effusion. For example, a patient with a history of congestive heart failure or cirrhosis experiencing symptoms such as cough, difficulty breathing, and pleuritic chest pain may have a pleural effusion. Findings from the physical exam, such as dullness to percussion of the lung area, decreased vibration, and asymmetrical chest expansion, may also suggest the presence of a pleural effusion. Other physical exam findings detected with a stethoscope may include reduced or inaudible breath sounds on the affected side, egophony, and a friction rub.

Chest X-rays can detect pleural effusions, which appear as whitish areas at the lung base and can occur unilaterally or bilaterally. When a person lies on their side, most pleural effusions will move and layer along that side of the chest cavity. This movement can be seen on a chest X-ray taken with the person lying on their side (a lateral decubitus X-ray).

Other imaging tests, such as CT scans, may be ordered to further identify the possible cause and extent of the pleural effusion.

Diagnosing the cause(s) of a pleural effusion often begins with determining whether the fluid is transudate or exudate. This is important because the results of this fluid analysis may provide a diagnosis and determine the course of treatment. Thoracentesis, a procedure to remove the fluid from the pleural space, followed by laboratory analysis of the fluid, can differentiate between transudate and exudate. Results from the fluid analysis are compared to certain blood tests. Additional testing of the pleural fluid may include a cell count, cytology, and cultures. Criteria are then used to differentiate exudate from transudate.

Exudative effusions have the following characteristics:

• Pleural fluid LDH > 0.45 of the upper limits of normal blood values
• Pleural fluid protein level > 2.9g/dL
• Pleural fluid cholesterol level > 45mg/dL

Other healthcare professionals may use different criteria to determine the presence of exudate, such as the ratio of pleural fluid to serum protein levels > 0.5, LDH ratio > 0.6, and LDH ratio > 2/3 the upper limits of normal. Other pleural fluid analysis test results (cytology or amylase, for example) may also reveal the source of the effusion.

What is the treatment for pleural effusion?

Small transudative effusions may require no treatment, while larger ones and most exudative pleural effusions require treatment. The initial treatment of choice is drainage of the pleural fluid through thoracentesis, where a chest tube is inserted into the effusion and the fluid is drained. This procedure may be both diagnostic and therapeutic. The need for repeated thoracentesis varies from patient to patient depending on the underlying cause, the amount of effusion fluid, the type of effusion, and if there is a recurrence of the pleural effusion.

Some pleural effusions, mainly exudative ones, may require surgery to break up adhesions or pleurodesis, a procedure that seals the pleural space to prevent the reaccumulation of pleural effusions, by inserting irritant substances or medications into the pleural space to promote scarring of the visceral and pleural surfaces.

The use of medications for pleural effusions depends on the underlying cause. Antibiotics are used for infectious causes, while diuretics such as furosemide (Lasix) may be used to help reduce the size of the pleural effusion.

What are the complications of pleural effusion?

Potential complications of pleural effusion include:

• Lung scarring
• Pneumothorax (lung collapse) as a complication of thoracentesis
• Empyema (pus collection within the pleural space)
• Sepsis (blood infection) leading to death

Can you prevent a pleural effusion?

In some cases, the development of pleural effusions may be prevented by early treatment of the underlying causes mentioned above. However, in certain cases, the development of pleural effusions may not be preventable.

Pleurodesis, a procedure that seals the pleural space, may help prevent the recurrence of some pleural effusions.

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