Pericardial Fluid Analysis
When a doctor suspects that someone has a condition associated with inflammation of the pericardium and/or fluid accumulation around the heart
Pericardial fluid is a liquid that acts as a lubricant for the movement of the heart. It is found in small quantities between the two layers of the pericardium. Pericardial fluid is produced by mesothelial cells in the membranes and reduces friction as the heart pumps blood.
A variety of conditions and diseases can cause inflammation of the pericardium (pericarditis) and/or excessive accumulation of pericardial fluid (pericardial effusion). Pericardial fluid analysis is a group of tests used to help find the cause of the problem. There are two main reasons why fluid may collect in the pericardial space:
- Fluid may accumulate because of an imbalance between the pressure within blood vessels—which drives fluid out of blood vessels—and the amount of protein in blood—which keeps fluid in blood vessels. The fluid that accumulates in this case is called a transudate. Transudates are most often caused by cirrhosis of the liver or congestive heart failure.
- Fluid accumulation may be caused by injury or inflammation of the peritoneum, in which case the fluid is called an exudate. This type of fluid may be the result of conditions such as infection, cancer (metastatic cancer, lymphoma, mesothelioma), rheumatoid disease, or systemic lupus erythematosus.
It is important to distinguish between the two types of fluid because it helps diagnose the disease or condition. Doctors use an initial set of tests (cell count, protein or albumin and appearance of the fluid) to distinguish between transudates and exudates. Once the sort of fluid has been identified, additional tests may be done to help pinpoint the disease or condition causing pericarditis and/or pericardial effusion.
How is the sample collected for testing?
A sample of fluid is collected from the pericardial sac by a doctor with a syringe and needle using a procedure called a pericardiocentesis.
Is any test preparation needed to ensure the quality of the sample?
No special preparation is usually needed.
How is it used?
Pericardial fluid analysis is used to help diagnose the cause of inflammation of the pericardium (pericarditis) and/or fluid accumulation around the heart (pericardial effusion). An initial set of tests (protein or albumin, cell count and appearance) is used to differentiate between the two types of fluid that may be produced (transudate and exudate). Additional tests on the fluid itself may be used to help distinguish possible conditions causing an exudate:
- Infectious diseases - caused by viruses, bacteria, or fungi. Infections may originate in the pericardium or spread there from other places in the body. For example, pericarditis may follow a respiratory infection.
- Bleeding - bleeding disorders and/or trauma can lead to blood in the pericardial fluid.
- Inflammatory conditions - pericarditis may follow a heart attack, radiation treatment, or be part of autoimmune disorders such as rheumatoid arthritis and systemic lupus erythematosus.
- Cancer - such as mesothelioma in the pericardium or metastatic cancer that has spread to it.
When is it requested?
Pericardial fluid analysis may be requested when a doctor suspects that a patient has a condition or disease that is causing pericarditis and/or pericardial effusion. It may be used when a patient has some combination of the following signs and symptoms:
- Chest pain, sharp or sometimes dull, that may be relieved by bending forward
- Difficulty breathing
- Changes in heart rhythm
- Enlarged heart size on chest X-ray
- Abnormal pericardial appearance on echocardiogram
What does the test result mean?
- Physical characteristics—fluid appears clear
- Protein or albumin level—decreased
- Cell count—few cells are counted
- Physical characteristics—fluid may appear cloudy
- Protein or albumin level—higher than normal
- Cell count—increased
Exudates can be caused by a variety of conditions and diseases and usually require further testing to aid diagnosis. Exudates may be caused by, for example, infections, trauma, various cancers, or pancreatitis. The following is a list of additional tests that the doctor may order depending on the suspected cause:
Physical characteristics – the normal appearance of a sample of pericardial fluid is straw coloured and clear. Abnormal results may give clues to the conditions or diseases present:
- Milky appearance—may point to lymphatic system involvement
- Reddish pericardial fluid may indicate the presence of blood
- Cloudy thick pericardial fluid may indicate the presence of microorganisms and/or white blood cells
Chemical tests –in addition to protein or albumin, a glucose test may be performed. Glucose in pericardial fluid samples is typically about the same as blood glucose levels. It may be lower with infection.
Microscopic examination – Normal pericardial fluid has small numbers of white blood cells (WBCs) but no red blood cells (RBCs) or microorganisms. Laboratories may examine drops of the pericardial fluid and/or use a special centrifuge (cytocentrifuge) to concentrate the fluid’s cells at the bottom of a test tube. Samples are placed on a slide, treated with special stain, and an evaluation of the different kinds of cells present is performed.
- Total cell counts—quantity of WBCs and RBCs in the sample. Increased WBCs may be seen with infections and other causes of pericarditis.
- WBC differential—determination of percentages of different types of WBCs. An increased number of neutrophils may be seen with bacterial infections.
- Cytology – a cytocentrifuged sample is treated with a special stain and examined under a microscope for abnormal cells. This may be done when a mesothelioma or metastatic cancer is suspected. The presence of certain abnormal cells, such as tumour cells or immature blood cells, can indicate what type of cancer is involved.
Infectious disease tests – routine tests may be performed to look for microorganisms if infection is suspected:
- Gram stain - for direct observation of bacteria or fungi under a microscope. There should be no organisms present in pericardial fluid.
- Bacterial culture and susceptibility testing - used to detect any microorganisms, which will grow in the culture. If bacteria are present, susceptibility testing can be performed to guide antimicrobial therapy. If there are no microorganisms present, it does not rule out an infection; they may be present in small numbers or their growth may be inhibited because of prior antibiotic therapy.
Is there anything else I should know?
Increased amounts of pericardial fluid also can restrict the movement of the heart. Cardiac tamponade is when pericardial fluid builds up to the point that pressure on the heart prevents it from filling normally. Rapid fluid build-up can be a medical emergency, causing heart failure and death. When fluid accumulates slowly, the pericardial sac stretches and symptoms gradually worsen.
A blood glucose, protein, or albumin may be ordered to compare concentrations with those in the pericardial fluid.
What is pericardiocentesis and how is it performed?
Pericardiocentesis is the removal of pericardial fluid from the pericardial sac with a needle and syringe. An intravenous (IV) line may be started and the person may be given medications prior to the sample collection. The patient is positioned lying down. A local anaesthetic is applied, then the doctor inserts the needle into the space between the ribs (fifth to sixth intercostals space) on the left side of the chest and into the pericardial sac and removes a fluid sample. An ultrasound scan may be used to help guide the needle.
Are there other reasons to do a pericardiocentesis?
Yes. Sometimes it will be performed to drain excess pericardial fluid – to relieve pressure on the heart and/or to aid in the treatment of an infection. Sometimes a catheter drain is left in place for a period of time to remove larger amounts of fluid and to drain recurrent fluid accumulations. Sometimes medications will be introduced into the space during the pericardiocentesis.
On This Site
Tests: Pleural fluid analysis, Peritoneal fluid analysis, Gram stain, Susceptibility testing, Protein, Albumin, Glucose, AFB smear and culture
Conditions: Liver disease, Kidney disease, Bleeding disorders, Autoimmune disorders, Congestive Heart Failure, Systemic Lupus Erythematosus, Tuberculosis
Elsewhere On The Web
BBC Health: Pericarditis
National Heart Lung and Blood Institute: What is Pericarditis?
MedlinePlus Medical Encyclopedia: Pericarditis
American Heart Association: Pericardium and Pericarditis