Pleural fluid analysis

Pleural fluid analysis is a test that examines a sample of fluid that has been collected in the pleural space. This is the space between the lining of the outside of the lungs (pleura) and the wall of the chest. When fluid collects in the pleural space, the condition is called pleural effusion.

How the Test is Performed

A procedure called thoracentesis is used to get a sample of pleural fluid. The health care provider examines the sample to look for:

• Cancerous (malignant) cells
• Other types of cells (for example blood cells)
• Levels of glucose, protein and other chemicals
• Bacteria, fungi, viruses, and other germs that can cause infections
• Inflammation

How to Prepare for the Test

No special preparation is needed before the test. A chest x-ray will be performed before and after the test.

DO NOT cough, breathe deeply, or move during the test to avoid injury to the lung.

Tell your provider if you take medicines to thin the blood.

How the Test will Feel

For thoracentesis, you sit on the edge of a chair or bed with your head and arms resting on a table. The provider cleans the skin around the insertion site. Numbing medicine (anesthetic) is injected into the skin.

A needle is placed through the skin and muscles of the chest wall into the pleural space. As fluid drains into a collection bottle, you may cough a bit. This is because your lung re-expands to fill the space where fluid had been. This sensation lasts for a few hours after the test.

During the test, tell your provider if you have sharp chest pain or shortness of breath.

The provider may use ultrasound to get a better view of the fluid in your chest.

Why the Test is Performed

The test is performed to determine the cause of a pleural effusion. It is also done to relieve the shortness of breath that a large pleural effusion can cause.

Normal Results

Normally the pleural cavity contains less than 20 milliliters (4 teaspoons) of clear, yellowish (serous) fluid.

What Abnormal Results Mean

Abnormal results may indicate possible causes of pleural effusion, such as:

• Cancer
• Cirrhosis
• Heart failure
• Infection
• Severe malnutrition
• Trauma
• Abnormal connections between the pleural space and other organs (for example, the esophagus)

If the provider suspects an infection, a culture of the fluid is done to check for bacteria.

The test may also be performed for hemothorax . This is a collection of blood in the pleura.

Risks

Risks of thoracentesis are:

• Collapsed lung ( pneumothorax )
• Excessive loss of blood
• Fluid re-accumulation
• Infection
• Pulmonary edema
• Respiratory distress

Serious complications are uncommon.

Pleural fluid culture

Culture – pleural fluid

Pleural fluid culture is a test that examines a sample of fluid that has collected in the pleural space to see if you have an infection or understand the cause of buildup of fluid in this space. The pleural space is the area between the lining of the outside of the lungs (pleura) and the wall of the chest. When fluid collects in the pleural space, the condition is called pleural effusion .

How the Test is Performed

A procedure called thoracentesis is used to get a sample of pleural fluid. The sample is sent to a laboratory and examined under a microscope for signs of infection. The sample is also placed in a special dish (culture). It is then watched to see if bacteria or any other germs grow.

How to Prepare for the Test

No special preparation is needed before the test. A chest x-ray will be performed before and after the test.

DO NOT cough, breathe deeply, or move during the test to avoid injury to the lung.

How the Test will Feel

For thoracentesis, you sit on the edge of a chair or bed with your head and arms resting on a table. The health care provider cleans the skin around the insertion site. Numbing medicine (anesthetic) is injected into the skin.

A needle is placed through the skin and muscles of the chest wall into the pleural space. As fluid drains into a collection bottle, you may cough a bit. This is because your lung re-expands to fill the space where fluid had been. This sensation lasts for a few hours after the test.

During the test, tell your provider if you have sharp chest pain or shortness of breath.

Why the Test is Performed

Your provider may order this test if you have signs of a certain infection or if a chest x-ray or CT scan of the chest shows you have too much fluid in the space around the lungs.

Normal Results

A normal result means no bacteria or fungi were seen in the test sample.

A normal value is no growth of any bacteria. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

Abnormal results may indicate:

• Empyema (collection of pus in the pleural space)
• Lung abscess (collection of pus in a lung)
• Pneumonia
• Tuberculosis

Risks

Risks of thoracentesis are:

• Collapsed lung ( pneumothorax )
• Excessive loss of blood
• Fluid re-accumulation
• Infection
• Pulmonary edema
• Respiratory distress
• Serious complications are uncommon

Cytology exam of pleural fluid

Pleural fluid cytology; Lung cancer – pleural fluid

A cytology exam of pleural fluid is a laboratory test to detect cancer cells and certain other cells in the area that surrounds the lungs. This area is called the pleural space. Cytology means the study of cells.

How the Test is Performed

A sample of fluid from the pleural space is needed. The sample is taken using a procedure called thoracentesis .

The procedure is done in the following way:

• You sit on a bed or on the edge of a chair or bed. Your head and arms rest on a table.
• A small area of skin on your back is cleaned. Numbing medicine (local anesthetic) is injected in this area.
• The doctor inserts a needle through the skin and muscles of the chest wall into the pleural space.
• Fluid is collected.
• The needle is removed. A bandage is placed on the skin.

The fluid sample is sent to a laboratory. There, it is examined under the microscope to determine what the cells look like and whether they are abnormal.

How to Prepare for the Test

No special preparation is needed before the test. A chest x-ray will likely be done before and after the test.

DO NOT cough, breathe deeply, or move during the test to avoid injury to the lung.

How the Test will Feel

You will feel stinging when the local anesthetic is injected. You may feel pain or pressure when the needle is inserted into the pleural space.

Tell your health care provider if you feel short of breath or have chest pain.

Why the Test is Performed

A cytology exam is used to look for cancer and precancerous cells. It may also be done for other conditions, such as identifying systemic lupus erythematosus cells.

Your doctor may order this test if you have signs of fluid buildup in the pleural space. This condition is called pleural effusion . The test may also be done if you have signs of lung cancer.

Normal Results

Normal cells are seen.

What Abnormal Results Mean

In an abnormal test, there are cancerous (malignant) cells. This may mean there is a cancerous tumor . This test most often detects:

• Breast cancer
• Lymphoma
• Lung cancer
• Ovarian cancer
• Stomach cancer

Risks

Risks are related to thoracentesis and may include:

• Bleeding
• Infection
• Collapse of the lung ( pneumothorax )
• Difficulty breathing

Pleural fluid Gram stain

Gram stain of pleural fluid

The pleural fluid Gram stain is a test to diagnose bacterial infections in the lungs.

How the Test is Performed

Normally the lungs fill a person’s chest with air. If fluid builds up in the space outside the lungs but inside the chest, it can cause many problems. Removing the fluid can relieve a person’s breathing problems and help explain how the fluid built up there.

A sample of the fluid can be removed for testing. This process is called thoracentesis . One test that can be done on the pleural fluid involves placing the fluid onto a microscope slide and mixing it with a violet stain (called a Gram stain). A laboratory specialist uses a microscope to look for bacteria on the slide.

If bacteria are present, the color, number, and structure of the cells are used to identify the type of bacteria. This test will be done if there is concern that a person has an infection involving the lung or the space outside the lung but inside the chest (pleural space).

Why the Test is Performed

The test is performed when the health care provider suspects an infection of the pleural space, or when a chest x-ray reveals an abnormal collection of pleural fluid.

Normal Results

Normally, no bacteria are seen in the pleural fluid.

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

You may have a bacterial infection of the lining of the lungs (pleura).

Pleural needle biopsy

Closed pleural biopsy; Needle biopsy of the pleura

Pleural biopsy is a procedure to remove a sample of the tissue lining, the lungs, and the inside of the chest wall to check for disease or infection.

How the Test is Performed

This test may be done in the hospital. It may also be done at a clinic or doctor’s office.

The procedure involves the following:

• During the procedure, you are sitting up.
• Your health care provider cleanses the skin at the biopsy site.
• Numbing drug (anesthetic) is injected through the skin and into the lining of the lungs and chest wall (pleural membrane).
• A larger, hollow needle is then placed gently through the skin into the chest cavity. Sometimes, the provider uses ultrasound or CT imaging to guide the needle.
• A smaller cutting needle inside the hollow one is used to collect tissue samples. During this part of the procedure, you are asked to sing, hum, or say “eee.” This helps prevent air from getting into the chest cavity, which can cause the lung to collapse ( pneumothorax ). Usually, 3 or more biopsy samples are taken.
• When the test finished, a bandage is placed over the biopsy site.

In some cases, pleural biopsy is done using a fiberoptic scope. The scope allows the doctor to view the area of the pleura from which the biopsies are taken.

How to Prepare for the Test

You will have blood tests before the biopsy. You will likely have a chest x-ray .

How the Test will Feel

When the local anesthetic is injected, you may feel a brief prick (like when an intravenous line is placed) and a burning sensation. When the biopsy needle is inserted, you may feel pressure. As the needle is being removed, you may feel tugging.

Why the Test is Performed

Pleural biopsy is usually done to find the cause of a collection of fluid around the lung ( pleural effusion ) or other abnormality of the pleural membrane. Pleural biopsy can diagnose tuberculosis , cancer, and other diseases.

If this type of pleural biopsy is not enough to make a diagnosis, you may need a surgical biopsy of the pleura .

Normal Results

Pleural tissues appear normal, without signs of inflammation, infection, or cancer.

What Abnormal Results Mean

Abnormal results may reveal cancer (including primary lung cancer , malignant mesothelioma , and metastatic pleural tumor ), tuberculosis, other infections, or collagen vascular disease.

Risks

There is a slight chance of the needle puncturing the wall of the lung, which can partially collapse the lung. This usually gets better on its own. Sometimes, a chest tube is needed to drain the air and expand the lung.

There is also a chance of excessive blood loss.

Considerations

If a closed pleural biopsy is not enough to make a diagnosis, you may need a surgical biopsy of the pleura.