Your lungs are protected by two membranes, called the pleurae. The visceral pleura covers the lungs, and the parietal pleura lines the inside of your rib cage. A small amount of space between the two pleurae and lubricating fluid at their contact points allows the lungs to expand.
The pleurae are important for proper functioning of your lungs, and a pleural fluid culture is a test used to see if this fluid contains any bacteria, viruses, or fungi.
This test is usually performed if a chest X-ray shows that you have fluid in the space between the pleurae, a condition called pleural effusion. It’s also done if you show symptoms of certain infections, such as pneumonia, or to see if there’s air in the pleural space (e.g., a pneumothorax).
There are a number of reasons why you might have a buildup of fluid in your pleural space, also called the pleural cavity. This test is performed to see if an infection is the cause of the buildup.
There are some risks associated with having a pleural fluid culture, including:
- excessive bleeding while the sample is being taken
- reaccumulation of the fluid in the lung
- infection at the puncture site where the sample is taken
- pneumothorax, or air in the chest
- respiratory distress, or breathing difficulties
The risk of experiencing negative side effects from a pleural fluid culture is low for most people, but not for everyone. The following is a list of factors that put people at higher risk of having negative side effects:
- having a bleeding disorder
- experiencing heart failure
- having an enlarged heart
- having recently undergone lung surgery
- being on blood thinners
Your doctor will determine if you are eligible for the culture. As always, talk to your doctor about any concerns you have.
No special preparation is necessary. Tell your doctor about any allergies you have, especially if you are allergic to latex or any cleaning agent.
Your doctor will give you a chest X-ray if you haven’t had one already. Then, a sample of pleural fluid is extracted to test for infection. This sample is obtained through a procedure called thoracentesis.
For thoracentesis, you will have to sit down and lean forward, with your head and arms resting on a table, while your doctor takes the sample. Your doctor will numb a small patch of skin on your back and insert a needle until it reaches the pleural space. To avoid injuring your lung, it’s important not to move, cough, or breathe deeply while the fluid is being extracted.
Fluid is drawn out through the needle and stored in a tube. Your doctor may want to take another chest X-ray at the end of the procedure.
The pleural fluid is then sent to a lab for testing, where it is put on slides and stained with dyes for examination under a microscope. The examination will look for bacteria, viruses, or fungi that signal infection.
When the lab testing is complete, your doctor will notify you of the results.
What is a normal result for a pleural fluid culture?
A normal result is a sample that contains no bacteria, viruses, or fungi.
What is an abnormal result for a pleural fluid culture?
Abnormal results show the presence of bacteria, viruses, or fungi in the sample of your pleural fluid. This may mean that you have an infection in the pleural space, such as pneumonia or tuberculosis.
If left untreated, an infection in your pleural space can lead to serious complications, such as:
- pleurisy, an inflammation of the pleura
- empyema, a collection of pus between the pleura
- a lung abscess
You will need medical care and possibly hospitalization to treat pleurisy, which may compromise your ability to breathe. If you have another condition, your doctor may perform more tests and will treat you accordingly.
Pleural disorders can be serious if left untreated. For most people, the low risk of negative side effects and the potential to detect and diagnose a pleural disorder or infection makes a pleural fluid culture a valuable and beneficial procedure. The sooner an infection is detected, the better. Be sure to tell your doctor about any recent surgeries or preexisting conditions you have and any medications you’re taking before having a pleural fluid culture.