Test Overview

Blood and urine are often tested to find the cause of health problems. But other body fluids also can be tested. Most of these fluids help organs and joints—and the membranes around them—move smoothly. Sometimes a health problem can cause too much fluid to build up in part of the body. The fluid can be tested to look for the reason for the buildup.

Some of the most common body fluids that are tested are:

• Peritoneal fluid in the space (peritoneum) between membranes that line the belly.
• Pericardial fluid in the sac (pericardium) that surrounds the heart.
• Pleural fluid in the space between the membranes that separate the chest and the lungs.
• Synovial fluid in joints such as knees, shoulders, and hips.
• Fluid from the genital area, such as semen or cervical mucus.

How It Is Done

Body fluid tests are done by taking some fluid from the body. In most cases, a needle is used to take out some fluid.

Genital tests are done by taking a swab or sample of fluid. For example, a doctor collects cervical mucus from the vagina or cervix in a way similar to a Pap smear. Then tests can be done on the mucus.

Results

Tests on body fluids can be done to look for signs of infection or inflammation. For example, Gram stain and culture and sensitivity tests can find the type of bacteria that is causing an infection. The tests also can show what kind of medicine can best treat the infection.

Tests of body fluids also can be done to look for cancer or another disease.

• Peritoneal fluid can be tested for bacteria and white and red blood cells, protein, and glucose. Results can show the cause of fluid buildup. Possible causes include an infection, heart failure, cirrhosis, and kidney disease.
• Pericardial fluid may be tested to find out why the fluid is building up around the heart. Reasons can include infection, chest trauma, heart failure, and kidney problems.
• Pleural fluid can be tested for infection from pneumonia, tuberculosis (TB), fungus, or other things. Tests also could show signs of lung cancer.
• Synovial fluid may show crystals that are a sign of gout. A cell count test of the fluid can show if there is an increase in certain types of white blood cells. That could be a sign of an infection or rheumatoid arthritis. Glucose levels in the fluid also can help a doctor diagnose osteoarthritis or rheumatoid arthritis.
• Fluid from the genital area can be tested for bacteria and other germs.