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Common Pleural Effusion exam questions for medical finals, OSCEs and MRCP PACES

 

Question 1.

How do you define a transudate and exudate in pleural effusions?

  • Transudate
    • Protein <30 g/l
  • Exudate
    • Protein >30 g/l
  • Light’s criteria
    • More sensitive for diagnosis of exudative effusions and helpful if fluid protein between 25-35 g/l. Positive if one of these is true:
      • Pleural:serum protein ratio; >0.5 = exudate
      • Pleural:serum LDH ratio; >0.6 = exudate
      • Pleural LDH >2/3 the upper limit of normal serum LDH

 

Question 2.

What are the causes of transudative pleural effusions?

  • Failures
    • Left ventricular failure
    • Liver failure (cirrhotic liver disease)
    • Nephrotic syndrome and hypoalbuminaemia
  • Pulmonary
    • Pulmonary embolism (can be transudates or exudates)
    • Atelectasis
    • Malignancy (5% are transudate)
  • Cardiac
    • Constrictive pericarditis
  • Other
    • Hypothyroidism
    • Meig’s syndrome (ovarian tumours producing right-sided effusion)

 

Question 3.

What are the causes of exudative pleural effusions?

  • Infection
    • Parapneumonic
    • TB
    • Empyema
  • Malignancy
  • Rheumatological
    • Rheumatoid arthritis
    • Connective tissue disease (RA, SLE)
  • Pulmonary embolism (can be transudates or exudates)
  • Rare causes
    • Post-MI, pancreatitis, meothelioma, sarcoidosis, asbestosis
    • Drug induced (methotrexate, amiodarone, bromocriptine, phenytoin, nitrofurantoin)
    • Radiotherapy
    • Yellow-nail syndrome, familial Mediterranean fever
    •  Lymphangioleiomyomatosis
      • Pneumothoraces and cylothoraces in middle-aged women.

 

Question 4.

What should you send pleural fluid for after aspiration?

  • Note colour
  • Biochemestry: protein, LDH, glucose, pH
  • To get a reliable and quick pH take a sample in an ABG syringe – can run this on blood gas machines
  • Cytology (at least 20ml sample)
  • MCS and AFB
  • Other if indicated: amylase, cholesterol, RF and ANA