Serous Fluid (Textbook) Flashcards
Serous Fluid Formation
Like synovial fluids, serous fluids are formed as ultrafiltrates of plasma; no additional material is contributed by the mesothelial cells that line the membranes.
Hydrostatic and Oncotic Pressures
Production and reabsorption of ultrafiltrate are subject to hydrostatic pressure and colloidal pressure (oncotic pressure) from the capillaries that serve the cavities and the capillary permeability.
Oncotic pressure from serum proteins is the same in the capillaries on both sides of the membrane, so hydrostatic pressure in the parietal and visceral capillaries causes fluid to enter between the membranes. Filtration of the plasma causes increased oncotic pressure in the capillaries that allows reabsorption of fluid back into the capillaries.
Effusion in Serous Fluids
Disruption of the mechanisms of serous fluid formation and reabsorption causes an increase in fluid between the membranes.
Primary causes: increased hydrostatic pressure (congestive heart failure), decreased oncotic pressure (hypoproteinemia), increased capillary permeability (inflammation and infection), and lymphatic obstruction (tumors)
Three kinds of Aspiration Procedures
- Thoracentesis (pleural)
- Pericardiocentesis (pericardial)
- Paracentesis (peritoneal)
Serous Fluid Anticoagulants
- EDTA: cell counts/differential
- Heparinized or sodium polyanethol sulfonate (SPS): microbiology and cytology.
Transudates in Serous Fluid
Form because of a systemic disorder that disrupts the balance in the regulation of fluid filtration and reabsorption
- Congestive heart failure: changes in hydrostatic pressure
- Nephrotic syndrome: hypoproteinemia
Usually it is unnecessary to test transudate fluids.
Exudates in Serous Fluid
Produced by conditions that directly involve the membranes of the particular cavity:
- Infections
- Malignancies
Differentiating Transudates from Exudates
Most reliable differentiation is usually obtained by determining the fluid:blood ratios for protein and lactic dehydrogenase.
Exudative Testing
Examined for microbiologic and cytologic
abnormalities
RBC/WBC counts are not routinely performed, however differentials are because cell type ratios can give and idea of what is causing the exudate:
- Neutrophils are increased in effusions resulting from pancreatitis and pulmonary infarction
- Elevated lymphocyte counts are seen in tuberculosis, viral infections, malignancy, and autoimmune disorders (RA and SLE)
Differentiating Pleural Effusions
Either transudative or exudative, differentiated by pleural fluid cholesterol level, pleural fluid:serum cholesterol ratio and the pleural fluid:serum total bilirubin ratio.
A pleural fluid cholesterol >60 mg/dL, a pleural fluid:serum cholesterol ratio >0.3, or a fluid:serum total bilirubin ratio of >0.6 provides reliable information that the fluid is an exudate.
Determining Source of Blood in Pleural Samples
If the fluid hematocrit is more than 50% of the whole blood hematocrit, the effusion comes from a (hemothorax) injury.
A lower hematocrit indicates a chronic membrane
disease because the effusion contains both blood and increased pleural fluid
Cholesterol Testing in Pleural Fluids
- Chylous material: Thoracic Duct leakage, high concentration of triglycerides
- Pseudochylous material: Chonic Inflammatory conditions, higher concentration of cholesterol.
Pleural Fluid Differential
In addition to Neutrophil and Lymphocyte counts,
Mesothelial cells: noticeable lack of associated with tuberculosis, from exudate covering the pleural membranes, and an increase in the presence of pleural fluid plasma cells.
Pleural Fluid Chemical Tests
Glucose: Decreased glucose in tuberculosis, rheumatoid inflammation, and purulent infections (Lactate will also be elevated).
pH: 0.30 degrees lower than the blood pH is considered significant, value as low as 6.0 indicates an esophageal rupture that is allowing the influx of
gastric fluid.
Adenosine deaminase (ADA): Levels higher than 40 U/L indicate tuberculosis or malignancy.
Amylase: Elevated levels associated with pancreatitis, often elevated first in the pleural fluid.
Triglyceride levels may be included to confirm a chylous effusion.
Pleural Fluid Serelogical Tests
Differentiates effusions of immunologic origin from noninflammatory processes:
- Antinuclear antibody (ANA)
- Rheumatoid factor (RF)
Or tumor markers:
- Carcinoembryonic antigen (CEA)
- CA 125 (metastatic uterine cancer)
- CA 15.3
- CA 549 (breast cancer)
- CYFRA 21-1 (lung cancer)
Pericardial Effusions
Exudates: Primarily the result of changes in the membrane permeability due to infection (pericarditis), malignancy, and trauma
Transudates: Metabolic disorders such as uremia, hypothyroidism, and autoimmune disorders
Tamponade
An effusion is suspected when cardiac compression occurs, caused by fluid surrounding the heart.
Pericardial Effusion Appearance
- Malignant effusions are frequently blood streaked.
- Grossly bloody effusions are associated with accidental cardiac puncture and misuse of anticoagulant medications.
- Milky fluids representing chylous and pseudochylous effusions may also be present.
Differentiating Pericardial Fluid Effusions
The fluid:serum protein and lactic dehydrogenase (LD) ratios.
A count of >1000 WBCs/µL with a high percentage of neutrophils can indicate bacterial endocarditis.
During differentials, the malignant cells most frequently encountered are the result of metastatic lung or breast carcinoma a
Pericardial Fluid Special Testing
Fluid tumor marker levels correlate well with cytologic studies.
Acid-fast staining/adenosine deaminase due to tubercular effusions are increasing as a result of AIDS.
Peritoneal Fluid
Fluid between the peritoneal membranes is called ascites, or ascites fluid
Peritoneal Transudates and Exudates
Transudates: hepatic disorders (cirrhosis)
Exudates: Bacterial infections (peritonitis) (a result of intestinal perforation/ruptured appendix) and malignancy
Peritoneal Lavage
Sensitive test to detect intra-abdominal bleeding in blunt trauma cases, and results of the RBC count can be used along with radiographic procedures to aid in determining the need for surgery.
Peritoneal Cell Counts/Differentials
Requested on fluid from peritoneal dialysis to detect infection, and eosinophil counts to detect allergic reactions to the equipment or introduction of air into the peritoneal cavity.
An absolute neutrophil count >250 cells/µL
or >50% of the total WBC count indicates infection.
Lymphocytes are the predominant cell in tuberculosis.
Serum-ascites Albumin Gradient (SAAG)
Recommended over the fluid:serum total protein and LD ratios to detect transudates of hepatic origin.
Fluid and serum albumin levels are measured concurrently, and the fluid albumin level is subtracted from the serum albumin level.
A difference (gradient) of >1.1 is a transudate effusion of hepatic origin, and lower gradients are associated with exudative effusions
Peritoneal Fluid Appearance
- Green or dark-brown: presence of bile, which can be confirmed using standard chemical tests for bilirubin.
- Blood-streaked: after trauma, and with tuberculosis, intestinal disorders, and malignancy.
- Chylous or pseudochylous: material may be present with trauma or lymphatic vessels blockage.
Peritoneal Fluid Malignancy Cellular Findings
Most frequently of gastrointestinal, prostate, or ovarian origin, and include cells with mucin-filled vacuoles
Psammoma bodies: containing concentric striations of collagen-like material, seen in benign conditions and ovarian/thyroid malignancies
Normal cells present in ascitic fluid include leukocytes, abundant mesothelial cells, and macrophages, including lipophages
Peritoneal Fluid Chemical Tests
Primarily of glucose, amylase, and alkaline phosphatase determinations.
If a ruptured bladder or accidental puncture during paracentesis is of concern, blood urea nitrogen and creatinine are requested.
When leakage of bile into the peritoneum is suspected following trauma or surgery, bilirubin is measured - bile has mostly conjugated bilirubin; so total bilirubin is used.
Pancreatitis or damage to the pancreas is suspected, amylase or lipase can be measured
Peritoneal Fluid Serology
Tumor markers:
- CEA
- CA 125
Positive CA 125 antigen with a negative CEA suggests the source is from the ovaries, fallopian tubes, or endometrium.
