Parapneumonic effusion

Background

Definition

• Pleural effusion secondary to bacterial pneumonia
• Complicated (i.e. infected and needs drainage) if:
  • Frankly purulent drainage
  • Positive Gram stain or culture
  • Pleural fluid pH <7.2
  • Possibly also:
    • >50% of the hemithorax
    • Loculated
    • LDH > 1000
    • WBC > 25
    • Glucose < 3.4

Stages

• Stage 1: not infected but exudative, generally echo-free on pleural ultrasound, free flowing, and with minimal to no enhancement on CT scan
• Stage 2: generally fibropurulent, likely infected, usually loculated with echogenic fluid, debris, and septations, and associated with pleural enhancement
• Stage 3: organized empyemas with significantly thickened, scarred pleural membranes

Risk Classification

Risk	Anatomy	Microbiology	Chemistry
Very low	free-flowing effusion <1cm on lateral decubitus	AND Gram stain and culture unknown	AND pH unknown
Low	free-flowing effusion 1cm ot 1/2 hemithorax	AND Gram stain and culture negative	AND pH ≥7.2
Moderate	free-flowing effusion ≥1/2 hemithorax, or loculated effusion, or thickened parietal pleura	OR Gram stain or culture positive	OR pH <7.2
High		pus

Differential Diagnosis

• Pleural effusion from other causes

Investigations

• Chest x-ray with PA, lateral, and lateral decubitus
  • Check to free-flowing or loculated effusion
  • If base of meniscus on the lateral is > 5cm or on the lateral decubitus is > 1cm, need to perform diagnostic thoracentesis
• Diagnostic thoracentesis, sent for pH, protein, cell count and differential, and Gram stain and culture

Management

• Can add metronidazole for anaerobic coverage (unless confirmed pneumococcal infection)
• Drainage, if complicated (see Definition, above)
  • Ideally chest tube
  • If not chest tube, then pigtail catheter, but this often needs upsizing to chest tube
• Can add intrathoracic tPA and DNAse, but unclear benefit

Further Reading

• Light RW. Parapneumonic effusions and empyema. Proc Am Thorac Soc 2005;3:75-80.
• Colice GL et al. Medical and surgical treatment of parapneumonic effusions: an evidence-based guideline. Chest 2000;118(4):1158-71.
• Davies HE et al. Management of pleural infection in adults: British Thoracic Society Pleural Disease Guideline 2010. Thorax 2010;65 Suppl 2:ii41-53.