Pleural Effusion

Question 1

What is a pleural effusion?

Answer 1

Fluid in the pleural cavity

Transudate:
= fluid protein <25g/L, often bilateral
- Pulmonary oedema (e.g. heart failure), cirrhosis, nephrotic syndrome, hypothyroidism intestinal malabsorption

Exudate:
= fluid protein >35g/L, unilateral or bilateral
- Pneumonia, malignancy, PE, vasculitides, rheumatoid
- If purulent and pH <7.2 = empyema = infection

"The I's and the fails":
Exudate = i's 
- Infection (pneumonia)
- Infarction (PE)
- Infiltrative malignancy 
Transudate = fails 
- Heart failure 
- Renal failure (incl. nephrotic synd.)
- Liver failure 
- GI failure (malabsorption)
- Thyroid failure (hypothyroidism)

Similarly:

• Anything that causes cell death in the lungs is a potential exudative cause of pleural effusion
• This is because when the cells die, intracellular protein leaks out, resulting in higher protein levels in the pleural fluid

Question 2

How do you assess the cause of a pleural effusion?

Answer 2

Light’s Criteria:

• Useful to differentiate when protein 25-35g/L and so cause more unsure
• Pleural protein:serum protein >0.5
• Pleural LDH:serum LDH >0.6
• OR pleural LDH >2/3rds upper limit of normal serum value

If one of these criteria are met - points towards an exudative cause of pleural effusion

Question 3

How do pleural effusions present?

Answer 3

Asymptomatic
Gradual onset breathlessness +/- pleuritic chest pain

Stony dullness on percussion, reduced air entry, tachypnoea

Other stigmata of underlying disease

Question 4

How do pleural effusions present on CXR?

Answer 4

Featureless, homogeneous white area at base leading to loss of costophrenic/costocardiac angles +/- meniscus (upper surface sloping up to the chest wall)

Question 5

How do you manage a pleural effusion?

Answer 5

Oxygen - depending on saturations and resp rate etc

Investigate the cause

If large:

• Pleural aspiration/drain (what colour?) + send for: MC+S, cytology and biochemistry (LDH, protein, pH)
• Do not drain too quickly (>1.5L/24hr) as can cause rebound pulmonary oedema which is often very difficult to treat