Pleural effusion and empyema — formative SAQs

SAQ 1 (10 marks)

A 4-year-old girl was admitted three days ago with a right lower lobe pneumonia and started on intravenous antibiotics. She has continued to spike fevers to 39.5 °C, is lethargic and off her food, and now complains of a sharp right-sided chest pain worse on coughing. On examination she is tachypnoeic with stony dullness and reduced breath sounds at the right base. [1] [2]

1. What complication do you suspect, and what is your first-line investigation and why? (3) [1]
2. Outline your initial management, including antibiotics. (4) [1] [2]
3. If the ultrasound shows a large, loculated collection, describe your drainage options. (3) [3]

Model answer — SAQ 1

(1) Complication and investigation (3). I suspect a parapneumonic effusion, and possibly an empyema, because her pneumonia is failing to improve after appropriate antibiotics — persistent fever, new pleuritic chest pain and the physical signs of fluid (stony dullness and reduced breath sounds at the base). My first-line investigation is a chest ultrasound, because it confirms the opacity is fluid, estimates its size, shows whether it is simple (anechoic) or complicated (septated and loculated), and marks a safe drainage site — information a plain chest radiograph cannot provide. [1]

(2) Initial management (4). Continue and, if needed, broaden intravenous antibiotics to cover the likely organisms — Streptococcus pneumoniae, Staphylococcus aureus and group A streptococcus — per the local guideline, adding MRSA cover where it is prevalent, and narrow to culture and pneumococcal PCR results when available. Give oxygen for any hypoxia, provide regular analgesia so she can breathe and cough, and ensure hydration. Assess her septic state and observations closely, and arrange the ultrasound urgently to stage the effusion. A small, free-flowing simple effusion in a stable child may settle on antibiotics alone, but a complicated collection will need drainage. [1] [2]

(3) Drainage options (3). For a large loculated collection or empyema, the two effective options are a chest drain with intrapleural fibrinolytics (for example urokinase instilled via the drain to break down the fibrin septations) and primary video-assisted thoracoscopic surgery (VATS) to break down loculations directly. Randomised evidence shows the two are clinically equivalent, with fibrinolytics less invasive and cheaper, so I would insert an ultrasound-guided chest drain and give intrapleural fibrinolytics first-line, reserving VATS (and decortication for an organised peel) for failure to improve. [3]

SAQ 2 (10 marks)

A 3-year-old boy has a moderate right pleural effusion complicating pneumonia. A diagnostic aspiration returns cloudy fluid. The laboratory reports pleural fluid pH 7.1, glucose 1.5 mmol/L and a high LDH; the Gram stain is negative. His mother is anxious about the long-term effects on his lungs. [1] [4]

1. Interpret the pleural fluid results and classify the effusion. (4) [4]
2. Why is the Gram stain negative, and how would you improve the microbiological yield? (3) [5]
3. What would you tell the mother about the long-term outlook? (3) [2]

Model answer — SAQ 2

(1) Interpretation (4). The cloudy fluid with a low pH (7.1), a low glucose (1.5 mmol/L) and a high LDH indicates a complicated parapneumonic effusion. By Light's criteria this is an exudate, consistent with pleural infection rather than a transudate from heart failure or hypoalbuminaemia. The low pH and low glucose reflect the metabolic activity of bacteria and neutrophils in the fibrinopurulent stage, and they mark a collection that will not settle on antibiotics alone and needs drainage. [4]

(2) Negative Gram stain and improving yield (3). Pleural fluid cultures and Gram stains are frequently negative in childhood empyema, largely because antibiotics have usually been given before the fluid is sampled and because some causative organisms are fastidious. To improve the yield I would send fluid for pneumococcal (and broader bacterial) PCR, which detects organisms that will not grow, alongside culture; I would also ensure blood cultures were taken and interpret the results in the light of the local epidemiology (pneumococcus, S. aureus, group A streptococcus). [5]

(3) Long-term outlook (3). I would reassure her that, although the illness can be long and the treatment intensive — a chest drain and possibly surgery — the prognosis for children with empyema is excellent: the great majority recover completely, and follow-up studies show that long-term lung function and chest imaging return to normal in most children. I would explain that we will review him with a chest radiograph after a few weeks to confirm the effusion has resolved, and that a full recovery is the expected outcome. [2]