Pleural Fluid Analysis

A pleural fluid analysis is a group of tests that examine a sample of abnormal fluid that builds up in the space between your lungs and chest wall. This space is called the pleural space. The pleura is a thin tissue that covers the outside of your lungs and lines the inside wall of your chest.

Normally, a small amount of fluid, called pleural fluid, fills the space between the two layers of pleural tissue. This fluid keeps the pleura moist and helps the layers of tissue glide smoothly over each other as you breathe. If too much fluid builds up in your pleural space, it's called a pleural effusion.

Many different types of conditions can cause pleural effusion. The fluid buildup doesn't always cause symptoms, but if it presses on your lungs, you may have trouble breathing, even if your lungs are healthy. A pleural fluid analysis can help find the cause of a pleural effusion.

Treating the cause may help keep the fluid from building up in the future. The fluid buildup you have now usually needs treatment, too. Without treatment, it may lead to a collapsed lung and other serious health problems.

Why this test is done

You may need this test if you have symptoms of pleural effusion and an imaging test, such as an MRI scan or chest x-ray, shows that you have fluid buildup around your lungs.

The symptoms of pleural effusion depend on the cause and the amount of fluid. They may include:

• Chest pain that doesn't have another explanation
• Dry cough that doesn't bring up mucus
• Trouble breathing
• Fatigue

If the cause of your pleural effusion is known, you may not need a pleural fluid analysis even if you have symptoms.

Pleural effusions don't always cause symptoms, so sometimes a pleural effusion is found on a chest imaging test that's done for another reason. If this happens, a pleural fluid test is often done, even though you don't have symptoms.

How to prepare

In general, a thoracentesis doesn't require special preparations. Your provider will let you know if there's anything you need to do or avoid doing. For example, you may need to stop taking certain medicines before your test.

But never stop taking any prescription medicines without talking with your provider first. or a blood test.

Other names for this test

pleural fluid aspiration, diagnostic thoracentesis, pleural fluid tap, pleural fluid culture, pleural fluid cytology, pleural effusion testing, LDH body fluid