Aspiration as a Cause of Pleural Effusion

Pathophysiology and Clinical Presentation

Aspiration can lead to pleural effusion through several mechanisms, including aspiration pneumonia and chemical pneumonitis, which can cause infection and inflammatory damage to lung tissue that can extend to the pleural space 1
Parapneumonic effusions associated with aspiration pneumonia are usually unilateral 2
The pleural fluid may show low pH (<7.2), high LDH (>1000 IU/l), and positive Gram stain or culture, particularly anaerobic organisms, in cases of aspiration pneumonia with pleural involvement 1

Simple parapneumonic effusions usually resolve with antibiotics alone, while complicated parapneumonic effusions require chest tube drainage 1
Diagnostic thoracentesis should be performed when a significant pleural effusion is present, and pleural fluid should be sent for Gram stain and bacterial culture, biochemistry, and cytology to rule out malignancy 4, 3, 1, 5

Ultrasound is recommended to locate pleural fluid and guide aspiration, and CT scanning may help differentiate pleural empyema from a parenchymal lung abscess in difficult cases 1, 2
Anaerobic cultures should always be obtained when aspiration is suspected, and prior antibiotic therapy may have sterilized the pleural fluid in patients with suspected aspiration but negative cultures 1, 2