Pleural effusion, or hydrothorax, is the accumulation of serous fluid in the pleural cavity, which can be unilateral or bilateral and is clinically detectable when approximately 0.5 liters is present. It can be classified as transudate or exudate based on protein content, with transudates (<30g/l) typically resulting from systemic conditions like cardiac or liver failure, while exudates (>30g/l) arise from inflammatory or neoplastic processes. Clinical features include chest pain, cough, and difficulty in breathing, with specific physical examination signs indicating the presence of pleural effusion.

1. Pleural effusion
(hydrothorax)

2. Introduction
• Definition – it is accumulation of serous fluid in the plural
cavity
• It can be unilateral or bilateral
• It is detected clinically when approximately 0.5 L is present
• It first appears on the costophrenic angles
• Normal pleural fluid has a protein concentration of 0.4 g/dL

3. Classification
• Transudate – caused by either increased hydrostatic pressure or decreased osmotic
pressure. The protein content is <30g/l
• Cardiac failure,
• liver failure
• renal failure
• Nephrotic syndrome
• Malnutrition
• Exudate fluid – are caused by inflammatory or neoplastic process. The protein content >30
g/L.
• Pneumonia
• TB
• Malignancy
• Connective tissue diseases – SLE, Rheumatoid arthritis
• Meigs’ syndrome (ovarian tumour plus pleural effusion)

4. Differences between exudate and transudate
• Light’s criteria
• Suspect Exudate when
 Pleural fluid protein : serum protein ratio > 0.5
 Pleural fluid LDH : serum LDH ratio > 0.6
 Pleural fluid LDH > two-thirds of the upper limit of normal serum
LDH
• LDH = lactate dehydrogenase)

5. Clinical features
• Chest pain – on inspiration and coughing
• Pleural rub
• Difficult in breathing
• Cough
• Extrapulmonary signs suggestive of cause –
• Night sweats, fever, hemoptysis, and weight loss should suggest TB

6. Physical examination
• Reduced chest movement
• Asymmetrical chest expansion
• Stony dullness
• Tracheal deviation
• Reduced or absent breath sound

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