AUBF Serous

• The three serous cavities of the body are the Pleural cavity, Pericardial cavity, and Peritoneal cavity.
• These cavities are lined with two membranes: the Parietal (outer) membrane which lines the cavity wall, and the Visceral (inner) membrane which covers the organ within a cavity.
• Serous fluid is an ultrafiltrate of plasma.
• The formation of serous fluid is controlled by four factors: the permeability of the capillaries in the parietal membrane, hydrostatic pressure in these capillaries, oncotic pressure produced by the presence of plasma protein within the capillaries, and the absorption of fluid by the lymphatic system.
• Effusion is the accumulation of fluid between the membranes and is indicative of a pathologic process.
• Effusion can be caused by increased capillary hydrostatic pressure (CHF), decreased oncotic pressure (hypoproteinemia), increased capillary permeability (inflammation and infection), or lymphatic obstruction (tumors).
• Types of effusion include exudates, which are produced by conditions that directly involve the membranes of the cavity such as inflammation, malignancy, and infection, and transudates, which are produced by conditions that do not involve the membranes of the cavity such as increased capillary hydrostatic pressure (CHF).
• Accumulation of fluid in the peritoneal cavity is called ascites and the fluid is commonly called ascitic fluid.
• Leukocytes in pseudochylous are mixed cells, while predominant in chylous are lymphocytes.
• TAG levels in pericardial fluid are >110 mg/dL.
• The differential cell count is the most clinically significant hematology test performed on serous fluids.
• Peritoneal lavage is commonly done to detect abdominal injuries or intra-abdominal bleeding in blunt trauma cases where RBC counts are greater than 100,000/mL.
• Cholesterol crystals are absent in pericardial fluid.
• The same cells are also found on pericardial and peritoneal fluids.
• Neutrophils make up 1 – 2% of the cells in pericardial fluid.
• Lymphocytes make up 18 – 30% of the cells in pericardial fluid.
• The significance of pericardial fluid testing is determined by its appearance, which can be normal, transudate, blood-streaked, grossly-bloody, or milky.
• Increased neutrophils in pericardial fluid can be indicative of bacterial endocarditis.
• Macrophages make up 64 – 80% of the cells in pericardial fluid.
• Cirrhosis of the liver is a clinical significance of peritoneal fluid.
• Bacterial infections (Peritonitis) is a clinical significance of peritoneal fluid.
• Cells of medical importance in pericardial fluid are malignant cells.
• Sudan III staining is strongly positive in chylous fluid.
• Bloody pleural fluid could be a result of Hemothorax, Hemorrhagic effusion, or other causes.
• Transudate fluid serum LD ratio is less than 0.6, while exudate fluid serum LD ratio is greater than 0.6.
• Types of effusion are mainly differentiated using protein and LDH.
• Specimen collection for transudates involves needle aspiration on the respective cavities: Pleural – Thoracentesis, Pericardial – Pericardiocentesis, Peritoneal – Paracentesis.
• Specimens for pH must be maintained anaerobically on ice to prevent cellular metabolism.
• Specimen collection for transudates involves EDTA for cell and differential count, Heparin or SPS for microbiology and cytologic analysis, Plain tube or heparin for Chemistry and Serological tests.
• Hemothorax distribution of blood is uneven, while in Hemorrhagic effusion, hematocrit in pleural fluid is less than whole blood hematocrit.
• Leukocytes in pleural fluid can be predicted.
• Pleural fluid appearance and disease appearance can be different, for example, clear, pale yellow can be normal, while turbid, white can indicate microbial infection.
• Chemical tests on the fluid are compared with plasma concentrations.
• Gross examination, chemistry, microbiology, and serologic tests are part of the analysis for serous fluid analysis.
• Transudate fluid serum protein ratio is less than 0.5, while exudate fluid serum protein ratio is greater than 0.5.
• Transudates are produced from systemic disorders related to absorption and filtration of fluid and include conditions such as Congestive Heart Failure, Nephrotic Syndrome, Cirrhosis.
• Transudate appearance is clear, while exudate appearance is cloudy/bloody.
• Exudate bilirubin ratio is greater than 0.6, while transudate bilirubin ratio is less than 0.6.
• Rivalta’s/Serosamucin Clot Test uses Acetic Acid as a reagent and a positive result indicates heavy precipitation.
• Exudate WBC count is greater than 1000/uL, while transudate WBC count is less than 1000/uL.