Pleural Infections

Microbiology

Diagnosis

  • Pleural effusion in the setting of a pneumonia

  • Spectrum of pleural processes from uncomplicated (sterile) parapneumonic effusion to empyema (infected)

  • Parapneumonic effusion are exudative, identified by the presence of any one of the following (Light's criteria):

    • Pleural fluid protein/serum protein >0.5
    • Pleural fluid LDH/serum LDH >0.6
    • Pleural fluid LDH >2/3 upper limited of normal for serum LDH

  • CXR in particular lateral decubitus films showing more than 1cm of fluid

  • Ultrasound Chest is more accurate for quantifying volume than CXR, can also detect septations and guide pleural drainage

  • CT Chest should be done in all cases of suspected empyema, and non-resolving pneumonia despite adequate antibiotic therapy

  • Pneumonia with resolving symptoms and persistent/progressive pleural effusion

  • Pleural effusion is free-flowing >25mm in depth on lateral decubitus films or CT

  • Pleural effusion is loculated on CT

  • Pleural effusion is associated with thickened parietal pleura on contrast-enhanced CT

  • Blood cultures in all patients suspected of having a pleural infection

  • Serum LDH and total protein concurrently with pleural fluid sampling

  • Pleural fluid ALWAYS send: cell count & differential, bacterial culture, LDH, total protein, pH, glucose, cytology

    • As directed by history/presentation: AFB and mycobacterial culture, fungal culture

Differential diagnosis for pleural acidosis and/or low glucose includes malignancy, TB, rheumatoid pleurisy, and lupus

Management