Pneumococcal Pleural Empyema in Children. A parapneumonic process is defined as a pleural effusion associated with pneumonia, lung abscess or bronchiectasis. Not all parapneumonic processes are empyemas. The pleural space is actually a potential space created by the visceral and parietal pleura. It normally contains a scant amount of fluid which facilitates movement of the lung with the diaphragm and chest wall.
Several mechanisms contribute to the development of an effusion.
Pleural fluid can accumulate when alterations in hydrostatic and oncotic pressure accompany cardiac, renal, hepatic or metabolic disease, or when there are changes in pleural fluid permeability secondary to inflammation, infection, toxin, malignancy or trauma. A pleural effusion provides a rich culture medium in which white blood cell defenses can be impaired and an empyema may flourish. During the first or exudative phase, pus accumulates. This is followed by fibrin deposition and loculation of pleural fluid known as the fibrinopurulent phase. However, empyema is a rare complication of pneumonia.