A parapneumonic effusion is a type of pleural effusion (accumulation of fluid in the pleural cavity) that arises as a result of a pneumonia, lung abscess, or bronchiectasis.

Uncomplicated effusions generally respond well to appropriate antibiotic treatment.

The criteria for a complicated parapneumonic effusion include Gram stain–positive or culture-positive pleural fluid, pleural fluid pH <7.20, and pleural fluid LDH that is greater than three times the upper limit of normal of serum LDH.

[2] Diagnostic techniques available include plain film chest x-ray, computed tomography (CT), and ultrasound.

Treatment of empyemas includes antibiotics, complete pleural fluid drainage, and reexpansion of the lung.