Section 4. Lung and Airway Disorders

Chapter 52. Pleural Disorders

Topics: Introduction | Pleurisy | Pleural Effusion | Pneumothorax

Pleural Effusion

Pleural effusion is the abnormal accumulation of fluid in the pleural space.

Normally, only a thin layer of fluid separates the two layers of the pleura. An excessive amount of fluid may accumulate for many reasons, including heart failure, cirrhosis, pneumonia, and cancer. Depending on the cause, the fluid may be either rich in protein (exudate) or watery (transudate). Doctors use this distinction to help determine the cause.

Blood in the pleural space (hemothorax) usually results from a chest injury. Rarely, a blood vessel ruptures into the pleural space when no injury has occurred, or a bulging area in the aorta (aortic aneurysm) leaks blood into the pleural space. Because blood in the pleural space does not clot fully, it is usually easy for a doctor to remove using a large-bore needle or a chest tube.

Pus in the pleural space (empyema) can accumulate when pneumonia or a lung abscess spreads into the space. A wide range of bacteria as well as certain fungi and mycobacteria (especially the mycobacterium that causes tuberculosis) are the most common organisms causing pleural effusion. Empyema may also complicate an infection from chest wounds, chest surgery, rupture of the esophagus, or an abscess in the abdomen.

Milky fluid in the pleural space (chylothorax) is caused by an injury to the main lymphatic duct in the chest (thoracic duct) or by a blockage of the duct by a tumor.

High-cholesterol fluid in the pleural space results from a long-standing pleural effusion caused by a condition such as tuberculosis or rheumatoid arthritis.

See the sidebar Common Causes of Pleural Effusion.

Symptoms and Diagnosis

The most common symptoms, regardless of the type of fluid in the pleural space or its cause, are shortness of breath and chest pain. However, many people with pleural effusion have no symptoms at all.

A chest x-ray, which shows fluid in the pleural space, is usually the first step in making the diagnosis. Computed tomography (CT) more clearly shows the lung and the fluid and may show evidence of pneumonia, a lung abscess, or a tumor. An ultrasound may help a doctor determine the position of a small accumulation of fluid.

A specimen of the fluid is almost always removed for examination using a needle, a procedure called thoracentesis (see Section 4, Chapter 39). The appearance of the fluid may help a doctor determine its cause. Certain laboratory tests evaluate the chemical composition of the fluid and determine the presence of bacteria, including the bacteria that cause tuberculosis. The fluid specimen is also examined for the number and types of cells and for the presence of cancerous cells.

If these tests cannot identify the cause of the pleural effusion, a biopsy of the pleura may be needed (see Section 4, Chapter 39), which can detect cancer and tuberculosis. Using a biopsy needle, a doctor removes a sample of the outer layer of the pleura for analysis. If the specimen is too small for an accurate diagnosis, a tissue sample must be taken through a small incision in the chest wall, a procedure called an open pleural biopsy. Sometimes, a sample is obtained using a thoracoscope (a viewing tube that allows a doctor to examine the pleural space and obtain samples (see Section 4, Chapter 39)).

Occasionally, bronchoscopy (a direct visual examination of the airways through a viewing tube) helps the doctor find the cause of the fluid. In about 20% of people with pleural effusion, the cause is not obvious after initial testing, and in some people a cause is never found, even after extensive testing.

Treatment

Small pleural effusions may require treatment of only the underlying cause. Larger pleural effusions, especially those that cause shortness of breath, may require drainage of the fluid. Usually, drainage dramatically relieves shortness of breath. Often, fluid can be drained using thoracentesis. An area of skin between two lower ribs is anesthetized, then a small needle is inserted and gently pushed deeper until it reaches the fluid. A thin plastic catheter is often guided over the needle into the fluid to lessen the chance of puncturing the lung and causing a pneumothorax. Although thoracentesis is usually performed for diagnostic purposes, a doctor can safely remove as much as 1.5 liters of fluid at a time using this procedure.

When larger amounts of fluid must be removed, a tube (chest tube) may be inserted through the chest wall. After numbing the area by injecting a local anesthetic, a doctor inserts a plastic tube into the chest between two ribs. Then the doctor connects the tube to a water-sealed drainage system that prevents air from leaking into the pleural space. A chest x-ray is taken to check the tube's position. Drainage can be blocked if the chest tube is incorrectly positioned or becomes kinked. If the fluid is very thick or full of clots, it may not flow out.

An accumulation of pus from an infection (empyema) requires intravenous antibiotics and drainage of the fluid. Tuberculosis or fungal infections such as coccidioidomycosis require prolonged treatment with antibiotics or antifungal drugs. If the pus is very thick or if it has formed within fibrous compartments, drainage is more difficult. Sometimes drugs called fibrinolytics are instilled into the pleura space to help drainage, which may avoid the need for surgery. If surgery is needed, it can be performed by a procedure called video-assisted thorascopic debridement or by thoracotomy. During surgery, a thick peel of fibrous material is removed from the lung surface to allow the lung to expand normally.

Fluid accumulation caused by tumors of the pleura may be difficult to treat because fluid tends to reaccumulate rapidly. Draining the fluid and giving antitumor drugs sometimes prevents further fluid accumulation. But if fluid continues to accumulate, sealing the pleural space (pleurodesis) may be helpful. All fluid is drained through a tube, which is then used to administer a pleural irritant, such as a doxycycline solution or a talc mixture, into the space. The irritant seals the two layers of pleura together, so that no room remains for additional fluid to accumulate.

If blood has entered the pleural space, usually drainage through a tube is all that is needed--as long as the bleeding has stopped. Drugs that help break up blood clots, such as streptokinase and urokinase, are occasionally administered through the drainage tube if a substantial portion of the clot remains in the pleural space. Caution should be taken because these drugs can trigger rebleeding. If the bleeding continues or if the accumulation of fluid cannot be removed adequately with a tube, surgery may be needed.

Treatment of chylothorax focuses on repairing the damage to the lymphatic duct. Such treatment may consist of surgery, chemotherapy, or radiation treatment for a cancer that is blocking lymph flow.