PathoPhysIology of ParaPneumonIc effusIon

of large amount of pleural fluid with many polymorphonuclear leukocytes, bacteria and cellular debris. The pleural fluid becomes clottable due to leakage of plasma proteins and loss of fibrinolytic activity in pleural space resulting in the formation of thick layer of fibrin over parietal and visceral pleura. The migration of fibroblasts into pleural space leads to collagen deposition and along with dense layer of fibrin leads to formation of loculations. The pleural fluid at this stage is invariably turbid with pH<7.20, glucose level of <40mg/dl and LDH level of >1000 U/L. Most of the patients at this stage need pleural space drainage along with appropriate antibiotics to resolve the pleural sepsis. In case of delayed pleural space drainage and inappropriate antibiotics, the stage of empyema ensues over a period of two to several weeks. The empyema is either in the form of single loculus with thick inelastic pleural peel or it is multiloculated. The management of empyema is always by chest tube drainage with or without fibrinolytics or by surgical drainage. classIfIcatIon of ParaPneumonIc effusIon: Though Light has classified parapneumonic effusion into seven categories,4 yet the more practical and easy to follow classification5 is as follows: 1. Uncomplicated (Simple) Parapneumonic Effusion : This corresponds to exudative stage and pleural fluid is freeflowing, clear, sterile with pH>7.20, glucose>60mg/dl and LDH<1000 IU/L. It resolves with antibiotics alone. 2. Complicated Parapneumonic Effusion : This corresponds to late fibrinopurulent stage. The pleural fluid is usually clear or turbid but nonpurulent, usually has fibrin strands with or without loculations. The pH is <7.20, glucose<40mg% and LDH>1000 IU/L. 3. Empyema : Frank pus with single or multiple loculations.