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Pleural effusion — ABIM Board MCQ

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ModeratePulmonary/Critical CarePleural effusionABIM Board

A 60-year-old man is hospitalized with fever and community-acquired pneumonia. Appropriate intravenous antibiotics are started. Chest ultrasonography shows a moderate pleural effusion. Thoracentesis yields cloudy but nonpurulent fluid with a pH of 7.12, glucose of 32 mg/dL, lactate dehydrogenase of 1200 U/L, and neutrophil predominance. Pleural fluid Gram stain and culture are pending. Which of the following is the most appropriate next step in management?

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Correct answer: B — Insert an image-guided chest tube for pleural drainage

The correct answer is B. This patient has a complicated parapneumonic effusion. The decisive feature is the pleural fluid pH of 7.12; a pH below 7.20 indicates pleural infection requiring prompt drainage, even if the fluid is not frankly purulent and Gram stain and culture are still pending. The low glucose and high LDH provide additional support. Antibiotics alone or observation after thoracentesis is appropriate only for an uncomplicated, free-flowing parapneumonic effusion with pH above 7.20. Diuretics treat transudative effusions due to volume overload, which is inconsistent with this inflammatory fluid profile. Pleural fluid amylase is useful when pancreatic disease or esophageal rupture is suspected but should not delay drainage here. Follow-up radiography alone would permit progression to loculated infection or empyema.

Reference: Zhou L, et al. Local management of pleural infection: a narrative review. Eur J Med Res. 2026;31(1):181. https://pubmed.ncbi.nlm.nih.gov/41484935/