Parapneumonic Pleural Effusions and Empyema Thoracis

A parapneumonic effusion refers to the accumulation of exudative pleural fluid associated with an ipsilateral lung infection, mainly pneumonia. Parapneumonic effusions are mainly associated with bacterial infections. Parapneumonic pleural effusions are classified into: Uncomplicated parapneumonic effusions, which are exudative,  neutrophilic effusion. Gram stain and culture are negative, glucose level greater than 60 mg/dl, pH above 7.20. Complicated parapneumonic effusions, resulting from a bacterial introduction into the pleura. In this type of parapneumonic effusion, there is a decreased glucose level, pleural fluid is below 7.20. Cultures of fluid from complicated parapneumonic effusions are negative and rapid bacterial clearance from the pleural space, or low bacterial count may explain this. The fluid termed as complicated because it necessitates drainage for resolution. Empyema thoracis in which there is frank pus in the pleural space, or there is evidence of bacterial infection of the pleural fluid by Gram stain or a positive culture. Pleural effusions are common in patients who develop pneumonia. At least 40-60% of patients with bacterial pneumonia will develop a pleural effusion of varying severity. Today, these parapneumonic effusions are not common because of prompt antibiotic therapy. However, in some patients the parapneumonic effusion becomes fibrinous and later develops an infection, resulting in an empyema.