Pericardial Fluid Gram Stain – Indications, Procedures, Results

Last updated: February 8, 2026 Medically reviewed by: RxHarun Orthopedic Specialist Doctor Reading time: 2 min read

Gram stain of pericardial fluid

Pericardial fluid Gram stain is a method of staining a sample of fluid taken from the sac surrounding the heart to diagnose a bacterial infection. The Gram stain method is one of the most commonly used techniques for the rapid diagnosis of bacterial infections.

How the Test is Performed

A sample of fluid will be taken from the sac surrounding the heart. Before this is done, some people may have a cardiac monitor to check for heart disturbances. Patches called electrodes are put on the chest, similar to during an electrocardiogram ( ECG ). You will have a chest x-ray or ultrasound before the test.

The skin of the chest is cleaned with antibacterial soap. A trained physician, often a cardiologist, inserts a small needle into the chest between the ribs and into the thin sac that surrounds the heart (the pericardium). A small amount of fluid is taken out.

You may have an ECG and chest x-ray after the procedure. Sometimes the pericardial fluid is taken during open heart surgery.

A drop of the pericardial fluid is placed in a very thin layer on a microscope slide. This is called a smear. A series of special stains are applied to the sample. This is called a Gram stain. A laboratory specialist looks at the stained slide under the microscope, checking for bacteria.

The color, size, and shape of the cells help identify the bacteria.

How to Prepare for the Test

You will be asked not to eat or drink anything for several hours before the test. A chest x-ray or ultrasound may be done before the test to identify the area of fluid collection.

How the Test Will Feel

You will feel pressure and some pain as the needle is inserted into the chest and when the fluid is removed. Your doctor should be able to give you pain medicine so that the procedure does not hurt very much.

Why the Test is Performed

Your doctor may order this test if you have signs of a heart infection or a pericardial effusion (fluid buildup) with an unknown cause.

Normal Results

A normal result means no bacteria are seen in the stained fluid sample.

What Abnormal Results Mean

If bacteria are present, you may have an infection of the pericardium or heart. Blood tests and bacterial culture can help identify the specific organism causing the infection.

Risks

Complications are rare but may include:

Heart or lung puncture
Infection

Frequently Asked Questions

Is this article a replacement for a doctor?

No. It is educational content only. Patients should consult a qualified clinician for diagnosis and treatment.

When should I seek urgent care?

Seek urgent care for severe symptoms, rapidly worsening condition, breathing difficulty, severe pain, neurological changes, or any emergency warning sign.

References

Add references, clinical guidelines, textbooks, journal articles, or trusted medical sources here. You can edit this area later with a custom field named _rx_references.

Written by Dr. Harun Ar Rashid, MD - Arthritis, Bones, Joints Pain, Trauma, and Internal Medicine Specialist

Dr. Md. Harun Ar Rashid, MPH, MD, PhD, is a highly respected medical specialist celebrated for his exceptional clinical expertise and unwavering commitment to patient care. With advanced qualifications including MPH, MD, and PhD, he integrates cutting-edge research with a compassionate approach to medicine, ensuring that every patient receives personalized and effective treatment. His extensive training and hands-on experience enable him to diagnose complex conditions accurately and develop innovative treatment strategies tailored to individual needs. In addition to his clinical practice, Dr. Harun Ar Rashid is dedicated to medical education and research, writing and inventory creative thinking, innovative idea, critical care managementing make in his community to outreach, often participating in initiatives that promote health awareness and advance medical knowledge. His career is a testament to the high standards represented by his credentials, and he continues to contribute significantly to his field, driving improvements in both patient outcomes and healthcare practices. Born and educated in Bangladesh, Dr. Rashid earned his BPT from the University of Dhaka before pursuing postgraduate training internationally. He completed his MD in Internal Medicine at King’s College London, where he developed a special interest in inflammatory arthritis and metabolic bone disease. He then undertook a PhD in Orthopedic Science at the University of Oxford, conducting pioneering research on cytokine signaling pathways in rheumatoid arthritis. Following his doctoral studies, Dr. Rashid returned to clinical work with a fellowship in interventional pain management at the Rx University School of Medicine, refining his skills in image-guided joint injections and minimally invasive pain-relief techniques.