Makindo Medical Notes

Related Subjects: |Assessing Breathlessness

The appearance of the meniscus is a visual illusion due to the shape of the chest thorax with more fluid seen laterally. There is no real meniscus. Diagnostic tap with 20 ml syringe with a 21 G needle to obtain 20 mL of fluid. This should be sent to the laboratory for Protein/LDH, Cell count, Culture, including TB, Large volume really needed to be spun down for cytology for malignant cells. In cases of massive pleural effusion, rapidly draining large volumes can cause re-expansion pulmonary oedema. Drain slowly and monitor carefully.

About

• Pleural effusion is the accumulation of fluid within the pleural space, leading to impaired lung function and breathlessness.
• The presence of fluid suggests underlying lung or pleural pathology, such as infection, malignancy, or systemic disease.

Types

• Pleural Effusion: Fluid within the pleural space.
• Pneumothorax: Air within the pleural space.
• Empyema: Pus within the pleural space, often following infection.
• Haemothorax: Blood in the pleural space, typically due to trauma or malignancy.
• Chylothorax: Lymphatic fluid (chyle) in the pleural space, often from thoracic duct injury or malignancy.

Aetiology

• Fluid accumulation can result from multiple mechanisms including inflammation, malignancy, altered permeability, and changes in osmotic pressure.
• Effusions are classified based on protein content using Light's criteria into high-protein exudates and low-protein transudates, aiding in identifying the cause.

Clinical (needs > 500 mL to be clinically detectable)

• Progressive breathlessness.
• Pleuritic chest pain, especially with inflammatory causes.
• Reduced chest wall movement on the affected side.
• Stony dullness to percussion over the fluid.
• Mediastinal shift or tracheal deviation away from a large effusion.
• Decreased vocal resonance and absent breath sounds over the fluid area.
• Bronchial breath sounds may be heard above the effusion.

Light's Criteria: Fluid is exudate if one of the following is present

• Effusion protein/serum protein ratio > 0.5.
• Effusion LDH/serum LDH ratio > 0.6.
• Effusion LDH > two-thirds the upper limit of normal serum LDH.

Classical Findings

• Cancer: Serous exudate, sometimes bloody. Malignant cells may be detected in pleural fluid cytology or biopsy.
• Heart Failure: Serous transudate, straw-coloured. May respond to fluid restriction and diuretics. Elevated BNP levels suggest heart failure.
• Tuberculosis: Clear or amber fluid with lymphocytosis, exudative. Elevated adenosine deaminase (ADA) levels can support diagnosis.
• Pulmonary Embolism: Fluid can be clear or blood-stained, exudate or transudate. Diagnosed by imaging (e.g., CTPA).
• Rheumatoid Disease: Often turbid fluid, high lymphocytes. Positive rheumatoid factor, low glucose, and sometimes cholesterol crystals.
• SLE: Serous, lymphocytic fluid. Positive antinuclear antibodies (ANA) or anti-DNA.
• Pancreatitis: Serous or bloody fluid with elevated amylase.
• Chylothorax: Milky fluid from obstruction of the thoracic duct, containing chylomicrons.

Causes Using Light's Criteria

• Exudates: Increased protein or LDH.
  • Bacterial pneumonia, TB, lung abscess, fungal infections.
  • Malignancy: carcinoma, lymphoma, mesothelioma.
  • Rheumatic diseases: rheumatoid arthritis, lupus, Churg-Strauss.
  • Pancreatitis, oesophageal perforation.
  • Radiation or asbestosis-related lung injury.
• Transudates: Lower protein content.
  • Heart failure, nephrotic syndrome, liver cirrhosis.
  • Hypoalbuminemia, peritoneal dialysis.
  • Urinothorax due to obstructive uropathy.
  • CSF leaks into pleural space.

Therapeutic Tap

• Indicated in large effusions causing significant breathlessness or when the cause is unclear. Avoid in heart failure-related effusions unless resistant to diuretics.
• Thoracentesis can relieve symptoms and provide fluid for analysis.
• Drainage should be performed with a small-bore (10-14 F) intercostal drain, placed under ultrasound guidance when possible.
• Drain slowly, clamping intermittently to avoid re-expansion pulmonary oedema.
• Empyema requires antibiotics and sometimes more aggressive drainage with a larger drain and intrapleural fibrinolytics.

References

• BTS Pleural Disease Guidelines
• BMJ Best Practice: Pleural Effusion