Pleural effusion and empyema — branching viva

Opening

Examiner: A 4-year-old admitted with a right lower lobe pneumonia is still febrile after three days of intravenous antibiotics and now has pleuritic chest pain and stony dullness at the right base. What is going on and what do you do? ^[1]

Candidate: A pneumonia that fails to improve after two to three days of appropriate antibiotics has a complication until proven otherwise, and the commonest is a parapneumonic effusion, possibly an empyema. The new pleuritic pain, stony dullness and reduced breath sounds fit fluid at the base. I would reassess her septic state and oxygenation, continue intravenous antibiotics, give analgesia, and arrange an urgent chest ultrasound to confirm and stage the collection. ^{[1] [2]}

Branch 1 — imaging and staging

Examiner: Why an ultrasound rather than a chest X-ray or a CT? ^[1]

Candidate: The chest radiograph will show an opacity but cannot reliably tell simple fluid from loculated pus, and it can overcall consolidation as effusion. Ultrasound confirms the fluid, estimates its size, shows whether it is anechoic and free-flowing or septated and loculated, and marks a safe drainage site — exactly the information that guides whether and how to drain. CT is not routine; I would reserve it for atypical or non-resolving disease or a suspected underlying lesion. ^{[1] [2]}

Examiner (probe): If I aspirate fluid, what tests do I send and what does a low pH mean? ^[4]

Candidate: I would send Gram stain, culture and pneumococcal PCR, and on non-purulent fluid measure pH, glucose and LDH and apply Light's criteria. A low pH, below about 7.2, with a low glucose and a high LDH marks a complicated parapneumonic effusion — the fibrinopurulent stage — which will not settle on antibiotics alone and needs drainage. Frank pus is diagnostic of empyema and needs no biochemistry. ^{[4] [1]}