Pleural effusions in PACES

There is decreased chest expansion.
The trachea is deviated away from the effusion.
The percussion note is stoney dull.
Vocal resonance and breath sounds are reduced.

Recap of MRCP Parts 1 and 2 notes on pleural effusion here

Differential diagnosis of a dull lung base includes:
  • consolidation - but you'd expect increased vocal resonance and possibly bronchial breathing
  • collapse - there would be decreased breath sounds but the trachea would be deviated towards
  • raised hemidiaphragm
  • pleural thickening - but you'd expect normal vocal resonance

Look for signs that would help determine the cause:
  • Transudate causes
    • congestive cardiac failure - raised JVP, oedema
    • chronic renal failure - arterio-venous fistula
    • nephrotic syndrome - periorbital oedema
    • hepatic failure - signs of chronic liver disease such as spider naevi, gynaecomastia
    • yellow nail syndrome - yellow nails
    • hypothyroidism - weight gain, dry skin
  • Exudate causes
    • cancer - clubbing, lymphadenopathy, cachexia
    • connective tissue diseases - signs of SLE/RA
    • PE - signs of DVT
    • TB/pneumonia - less likely to be seen in PACEs

What investigations would you perform?
  • a CXR - although around 200mls of fluid is needed for radiological change to occur
  • Pleurocentesis, sending pleural fluid for protein, LDH, cytology and cell count, gram stain and microbiology, and possibly for pH, glucose, triglycerides and amylase depending on the suspected underlying pathology.  Must send matching blood sample for protein and LDH.
  • Possibly a pleural biopsy
  • CT chest/bronchoscopy depending on likely cause.

How can you determine an exudate from a transudate?
  • broadly speaking, an exudate tends to be a fluid containing >3g/dl of protein whilst a transudate contains less than 3g/dl of protein
  • a more accurate method is using Lights criteria, which states a fluid is an exudate if either pleural fluid protein to blood protein is >0.5 or pleural fluid LDH to blood LDH is >0.6 or pleural fluid LDH >2/3s upper limit normal range of lab blood LDH.

How would you manage a pleural effusion?
  • management would depend on the symptoms produced and the likely aetiology
  • symptomatic effusions should be drained, either by a therapeutic pleural aspiration or a chest drain.  Care should be taken not to drain too rapidly due to risk of pulmonary oedema as the lungs re-expand; many physicians use 1.5L at a time as a guide.
  • asymptomatic effusions which are not suspected to be empyema may be observed
  • recurrent pleural effusions may require pleurodesis or surgical pleurectomy.

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