Patient education: Fluid culture (The Basics)

What is a fluid culture? — 

This is a lab test to check a sample of fluid for bacteria and other germs. The sample can come from different places.

Examples of fluids that might be sent for a culture include:

●Fluid from inside a joint ("synovial fluid")

●A buildup of fluid in the abdomen ("ascites")

●Fluid from a rash or blister

●Fluid from around the heart ("pericardial fluid") or lungs ("pleural fluid")

●Fluid from inside the lung ("bronchial fluid")

●Fluid from around the spine and brain ("cerebrospinal fluid")

For a fluid culture, a doctor or nurse uses a small needle with a syringe to obtain a fluid sample. Sometimes, they use an imaging test to help guide where to take fluid from. These create pictures of the inside of the body.

They send the sample to the lab for testing. In the lab, they add a special substance that causes germs to grow. If there are germs in the fluid, these will show up within a few days. In some cases, the fluid is also sent for other tests.

Why might I get a fluid culture? — 

Your doctor might order a fluid culture:

●If an imaging test suggests you might have infected fluid

●If an exam suggests you might have an infection. You might have symptoms, like pain, swelling, or warmth around the infected area. If the infection is in your heart or lungs, you might have chest pain, breathing problems, cough, or fever.

●To help decide what antibiotics or other medicines to prescribe – A culture can show what kind of germs are causing an infection. This is important for deciding how to treat it.

●To check if antibiotics are working

What do my results mean? — 

Your doctor or nurse will tell you when to expect your results, and will contact you with the results. Or if you use an online "patient portal," you might get an alert there when your results are ready.

●If your fluid culture is "positive," it usually means you do have bacteria or other germs in the fluid. Your doctor or nurse will talk to you about what to do next and whether you need treatment. If you have a bacterial infection, your doctor will prescribe antibiotics to treat it.

●If your fluid culture is "negative," it usually means you do not have bacteria or other germs in the fluid. If you still have symptoms, your doctor might do other tests to try to figure out the cause.

More on this topic

Patient education: Bacterial wound culture (The Basics)
Patient education: Viral culture (The Basics)
Patient education: What you should know about antibiotics (The Basics)