Pleural effusion

Question 1

List the causes of a pleural effusion?

Answer 1

Exudative: local disease

• > inflammation -> increased permeability of pleural BVs
• infection: pneumonia, TB
• malignancy: primary pleural ca (mesothelioma), bronchogenic lung ca, lung mets
• vascular: PE
• local trauma
• inflammatory: SLE (induces PE), RA (induces pleuritis), Goodpastures disease

Transudative: systemic disease

• > increased hydrostatic or decreased oncotic pressure -> fluid overload
• CHF (increased hydrostatic)
• cirrhosis (hypoalbuminaemia, decreased oncotic)
• malnutrition (hypoalb)
• renal failure (low urine output, increased hydrostatic pressure)
• nephrotic syndrome (hypoalb) . - drug induced (sodium valproate)

Question 2

What investigations would you do?

Answer 2

Diagnostic:
- CXR PA and lateral
- pleural US 
- thorcentesis (Lights criteria using protein and LDH) 
- Exudate: raised RBC (localised), WCC (lymphocytes if malignant, neutrophils pneumonia), cytology, culture, pH, glucose (low in infection and malignancy), amylase
Bedside:
- ABG
Lab
- FBC
- CRP
- sputum MCS
- acid fast bacili (TB)
- blood cultures
- EUC
- LFTs
- CMP
Imaging:
- Chest CT
- PET
- CTPA
- Echo

Question 3

Describe the lymphatic drainage of the pleura?

Answer 3

Parietal pleura: along intercostal spaces

• ventral: parasternal LNs (along thoracic a) -> bronchomediastinal trunks
• dorsally: internal intercostal LNs -> thoracic duct -> subclavian LNs
• visceral pleura: bronchial LNs -> tacheobronchial LNs -> L and R bronchomediastinal trunk -> subclaivian vein

Question 4

How do you differentiate between types of pleural effusion?

Answer 4

Light’s criteria: allows for classification of cause of pleural effusion (local/exudate or systemic/transudate)
Exudate:
- pleural protein : serum protein ratio >0.5
- OR pleural LDH : serum LDH ratio >0.6
- OR pleural LDH > 2/3rds upper limit for normal serum

Question 5

How would you manage a pleural effusion?

Answer 5

If haemodynamic compromise -> chest drain

Treat underlying cause:
Systemic (transudate)
- CCF: diuretics, physio, therapeutic thoracentesis, O2
- liver failure or malnutrition (hypoalb): Alb
- renal failure: dialysis

Local (exudate):

• infective: IV ABx, therapeutic thoracentesis, physio, O2
• empyema: chest drain, or thorascopy to remove adhesions
• malignant: therapeutic thoracentesis, physio, O2, pleurodesis