Pus in the pleural space (empyema) can accumulate when pneumonia or a lung abscess spreads into the space. Empyema may also complicate an infection from chest wounds, chest surgery, rupture of the esophagus, or an abscess in the abdomen.

Lymphatic (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.

Fluid in the pleural space that contains excessive amounts of cholesterol results from a long-standing pleural effusion caused by a condition such as tuberculosis or rheumatoid arthritis.

Symptoms

Many people with pleural effusion have no symptoms at all. The most common symptoms, regardless of the type of fluid in the pleural space or its cause, are shortness of breath and chest pain. Chest pain is usually of a type called pleuritic pain. It may be felt only when the person breathes deeply or coughs, or it may be felt continuously but may be worsened by deep breathing and coughing. The pain is usually felt in the chest wall right over the site of the inflammation. However, the pain may be felt also or only in the upper abdominal region or neck and shoulder as referred pain. Pleuritic pain is also called pleurisy. Pleurisy can be caused by disorders other than pleural effusion.

Pleuritic chest pain due to a pleural effusion may disappear as fluid accumulates. Large amounts of fluid can cause difficulty in expanding one or both lungs when breathing, causing shortness of breath.

Diagnosis

A chest x-ray, which shows fluid in the pleural space, is usually the first step in making the diagnosis. However, small amounts of fluid may not be visible on a chest x-ray. Computed tomography (CT) more clearly shows the lung and the fluid and may show evidence of pneumonia, a pulmonary embolus, a lung abscess, or a tumor. An ultrasound examination may help doctors 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. The appearance of the fluid may help doctors 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, other tests may be done. Sometimes a sample is obtained using a thoracoscope (a viewing tube that allows doctors to examine the pleural space and obtain tissue samples of the covering of the chest wall or the lung). This procedure is called thoracoscopy and can detect cancer and tuberculosis. If thoracoscopy is unavailable, a needle biopsy of the pleura may be done. Occasionally, bronchoscopy (a direct visual examination of the airways through a viewing tube) helps doctors 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 not require treatment, although the underlying disorder must be treated. 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 done for diagnostic purposes, doctors can safely remove as much as about 1½ quarts (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, doctors insert a plastic tube into the chest between two ribs. Then doctors connect 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.

Effusions Caused by Pneumonia: An accumulation of fluid from pneumonia requires intravenous antibiotics and sampling of the fluid. If the fluid is pus or if the fluid has certain characteristics, the fluid needs to be drained, usually with a chest tube. If the fluid has formed within scars (fibrous compartments) in the pleural space, drainage is more difficult. Sometimes drugs called thrombolytics (fibrinolytics) are instilled into the pleural space to help drainage, which may avoid the need for surgery. If surgery is needed, it can be done by using a procedure called video-assisted thoracoscopic debridement or by thoracotomy. During surgery, any thick peels of fibrous material over the lung surface are removed to allow the lung to expand normally.

Effusions Caused by Cancers: Fluid accumulation caused by cancers of the pleura may be difficult to treat because fluid often reaccumulates rapidly. Draining the fluid and giving antitumor drugs sometimes prevents further fluid accumulation. A small tube can be left in the chest so that the fluid can be drained periodically into vacuum bottles. But if fluid continues to accumulate, sealing the pleural space (pleurodesis) may be helpful. For pleurodesis all fluid is drained through a tube, which is then used to administer a pleural irritant, such as a doxycycline solution, bleomycin, 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. Pleurodesis can also be done using thoracoscopy.

Chylothorax: Treatment of chylothorax focuses on eliminating the leakage from the lymphatic duct. Such treatment may consist of surgery, chemotherapy, or radiation treatment for a cancer that is blocking lymph flow.

Last full review/revision February 2008 by Richard W. Light, MD