Other Body Fluids: Pleural, Pericardial, and Peritoneal Spaces


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Subject: Other Body Fluids: Pleural, Pericardial, and Peritoneal Spaces

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  • Under normal conditions, a very small amount of fluid (up to 50 mL) is present. This facilitates movement of membranes against each other. Abnormal fluid accumulation is called a serous effusion. In the presence of effusions, fluid can be aspirated from the affected cavity, either for diagnosis or for relief of pressure, commonly both. Finding substantial amounts of fluid always reflects a pathologic process.


  • Pleural fluid

    • Appearance

      • Cloudiness: neutrophils present, indicating infection

      • Milkiness: chylous effusion

      • Bloody: traumatic tap, malignancy, pneumonia, trauma, status postmyocardial infarction, or pulmonary infarction

    • Cell counts and differentials

      • WBC count >1 × 109/L with lymphocytes >50%: TB, cancer, lymphoma, CLL

      • WBC count >1 × 1010/L with approximately 80% neutrophils: effusions associated with bacterial pneumonia

      • WBC with eosinophilia: postpneumothorax, trauma, hypersensitivity reactions, CHF, fungal and parasitic infections, SLE, Hodgkin lymphoma

  • Pericardial fluid

    • Appearance

      • Bloody: pericarditis, status postmyocardial infarction, TB, RA, SLE, carcinoma, aspiration of blood from the cardiac cavity

    • Cell counts and differential

      • WBC count 1 × 109/L with increased lymphocytes: pericardial tuberculosis

      • WBC count 1 × 109/L with increased neutrophils: bacterial or viral pericarditis

  • Peritoneal fluid

    • Appearance

      • Cloudy or turbid: appendicitis, pancreatitis, intestinal volvulus, ruptured bowel, sepsis

      • Bile-stained: perforated duodenal ulcer, perforated intestine, gallbladder disease or perforation, acute pancreatitis

      • Milky: chylous effusion

      • Bloody: traumatic tap, intra-abdominal injury

    • Cell counts and differential on lavage fluid

      • RBC count >1 × 1011/L: intra-abdominal injury

      • WBC count 0.5 × 109/L: possible peritonitis

    • Cell counts and differential on undiluted ascitic fluid

      • WBC count 0.3 × 109/L: bacterial peritonitis if >50% neutrophils, cirrhosis of the liver if <25% neutrophils

      • Increased lymphocytes: tuberculous peritonitis

      • Increased eosinophils: CHF, hypereosinophilic syndrome, eosinophilic gastroenteritis, chronic peritoneal dialysis, abdominal lymphoma, ruptured hydatid cyst, vasculitis


  • All cell counts should be performed promptly to prevent cell deterioration; distorted or degenerated cells should not be counted.

  • Specimens with large clots cannot be processed.