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). Family
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 family 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.

Symptoms & 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 family 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. The appearance of the fluid may
help a family 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, which can detect cancer and tuberculosis. Using
a biopsy needle, a family 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 family doctor to examine
the pleural space and obtain samples.
Occasionally, bronchoscopy (a direct visual examination of the airways
through a viewing tube) helps the family 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.

Common Causes of Pleural Effusion
Abscess under the diaphragm
Cirrhosis
Coccidioidomycosis and other fungal infections
Drugs such as hydralazine, procainamide, isoniazid, phenytoin,
chlorpromazine, nitrofurantoin, bromocriptine, dantrolene, procarbazine
Heart failure
Heart surgery
Improper placement of feeding tubes or intravenous catheters
Injury to the chest
Low protein levels in the blood
Pancreatitis
Pneumonia
Pulmonary embolus
Rheumatoid arthritis
Systemic lupus erythematosus
Tuberculosis
Tumors

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 family 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 family doctor inserts a plastic tube into the chest between
two ribs. Then the family 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. [AAFP]