Table of Contents
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Pleural fluid aspiration is covered here!
Types of pleural effusion
- Serous fluid (hydrothorax)
- May be transudate or exudate
- Causes below
- Blood (haemothorax)
- Exudate
- Caused by trauma, malignancy, PE with infarct
- Chyle (chylothorax)
- May be transudate or exudate
- Leakage from thoracic duct caused by lymphoma or thoracic surgical trauma
- Pus (empyema/ pyothorax)
- Exudate with pH <7.2
- Secondary to pneumonia/ abscess
Appearances
- Straw: serous effusion (clear = transudate; cloudy = exudate)
- Blood stained: trauma, malignancy, PE with infarct
- Frank blood: trauma, malignancy (esp. mesothelioma)
- Pus: empyema
- Food particles: oesophageal rupture
Transudate vs exudates

Tests
- Cells
- Cell count (normally <1×109/L) + differential: lymphocytosis occurs in tuberculosis and malignancy; neutrophilia in parapneumonic effusion, PE and pancreatitis; eosinophilia in drug reaction, asbestos, parasite infection, Churg-Strauss
- MC&S: identify infective agents
- Cytology: identify malignant causes
- Tests for transudate vs exudates (see table above)
- Protein
- LDH
- pH (normally Ì´ 7.6): if pH <7.2, empyema is likely and requires a chest drain to be inserted
- Other tests to consider
- Glucose (normally similar to serum levels): low in MEAT: Malignancy, Empyema, Arthritis (rheumatoid), TB
- Amylase (normally similar to serum levels): raised in pancreatitis
- Ziehl-Neelsen stain: positive in tuberculosis
- Haematocrit: if bloody effusion haematocrit is <1%, it is insignificant
- Triglycerides (normal <50mg/dl), cholesterol & chylomicrons: chylomicrons present and triglycerides raised (>110mg/dl) in chylothorax; cholesterol is used to differentiate a pseudocyclothorax (>200mg/dl)
- Rheumatoid factor & complement: raised in rheumatic causes