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
- 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 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