Editing Empyema (section)

== '''Natural history''' ==

* Progressive process - takes about 4-6 weeks in total

=== Stage I: exudative phase ===

** Fluid associated with an infection, which can easily ''become'' infected and lead to the following stages of empyema
** Signs:
*** Free-floating, serous fluid
*** pH > 7.2, LDH < 1000 U/L, glucose > 60
*** Often no organisms seen/growth on culture, although neutrophils generally high
** Parapneumonic effusion which is clear and free-floating in the pleural space
** Pleural fluid is normally sterile and the pH and glucose levels are normal
** 10F to 14Fm, imaging-guided where possible, is adequate to drain most effusions
** ACCP indications for insertion of chest drain (as opposed to thoracentesis)
*** Large or loculated effusion
*** Positive cultures
*** pH < 7.2 (means infection 92% accuracy)
*** Pus

=== Stage II: fibrinopurulent phase ===

** Signs
*** Multiloculated effusion, with septa
*** Cloudy or purulent effusion
*** Bacterial colonisation
*** WCC > 500, pH < 7.2, LDH > 1000 U/L, glucose <6
*** Failure of antibiotics and drainage alone
*** Persistent sepsis
*** Variable presentation though
** The effusion is complicated by loculations (caused by fibrin deposition, activation of the coagulation cascade, and downregulation of the fibrinolytic pathway)
** 40% treatment failure for chest tube alone; 15% for chest drain and fibrinolytics; 10% for thoracotomy; none for VATS debridement
*** Large, loculated, frankly purulent effusions with positive cultures are less likely to resolve with chest drainage alone
*** VATS has significantly shorter length of stay

=== Stage III: chronic organising phase ===

** Signs:
*** Frank pus or no fluid at all
*** WCC >15,000, pH <7, LDH >1000U/L, glucose <5
*** Pleural cortex
*** Fibrothorax
** Pleural fluid is turned into frank pus by fibroblast chemotaxis
** Pleural thickening encases the lung causing restriction, decreased ventilation and perfusion-ventilation mismatch which can lead to a fibrothorax
** Final stage - not fully reversible even after eradication of the infection
** Chest drain and antibiotics can remove fluid and control infection, but respiratory impairment requires surgical removal of the peel to restore physiology
** Can be hard to differentiate from stage II using imaging