Editing Empyema

''Infection of the pleural space''

== '''Risk factors''' ==

* Young or elderly
* Intrinsic lung disease (COPD)
* Diabetes or other immunosuppression
* Alcohol
* IVDU

== '''Aetiology''' ==

=== Primary (complication of lung infection) ===

** Parapneumonic
*** Parapneumonic effusions occur in patients with concurrent LRTI or pneumonia
*** Normally an exudate
*** Accompanies and often worsens the pneumonia

=== Secondary (extrinsic) ===

** Trauma
** Thoracic surgery
*** Bronchopleural fistula predisposes to empyema
*** Management requires evaluation of the underlying cause, drainage of the infection, and obliteration of the residual pleural space
** Haematologic spread
** Rupture of a pulmonary or mediastinal abscess
** Oesophageal perforation

== '''Pathophysiology''' ==

* Commonly an exudate
* Occurs after a reactive pleural effusion as a consequence of lung infection (increased vascular permeability, inflammatory cytokines, chemotaxis of neutrophils)
* Microbiology
** Different flora to pneumonia due to difference in oxygen and pH levels between lung and pleura
** Staph aureus most common
** Community-acquired infections are usually gram-positive - strep milleri or strep pneumoniae
** Hospital infections are most staph or gram negative bacteria
** Historically associated with streptococcal or pneumococcal pneumonia

== '''Symptoms''' ==

* Constitutional symptoms - malaise, fever, loss of appetite
* Cough and dyspnoea
* Chest pain

== '''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

== '''Workup''' ==

* Aspiration
** Gold standard for diagnosis is culture of organism
* CXR
* CT
** Not as good for imaging septations as USS
* USS
** Can detect loculations reliably
** Four different patterns - homogenous anechoic (mainly transudative), complex non-septated with internal echogenic foci, complex septated (fibrinopurulent phase empyema), and homogenously echogenic (blood or frank pus)
* PET
** Not useful

== '''Management''' ==

* To follow
* Removal of infected fluid and debridement of pleural space
** Uncomplicated infections can be drained by ultrasound-guided insertion of a pleural drain (pigtail catheter)
** Loculated effusions may require more than one catheter
** Chest tubes may assist in drainage of turbid effusions
** Fibrinolytic agents can be effective - tPA and Dnase may improve drainage of the pleural space and reduce the need for surgical drainage
** Macroscopic pus should be treated aggressively with fibrinolysis and surgery
** VATS decortication - stage II disease, <2 weeks since admission
** Thoracotomy with debridement or formal decortication - for later stage empyema with persistent dyspnoea, loculations or continued sepsis. Also preferred in gram negative empyema. Necessary whenever adequate decortication cannot be accomplished thoracoscopically.
* Supportive care
** PT
** Nutritional support
** Thromboembolic prophylaxis
* Systemic treatment of the underlying cause of infection
* Full re-expansion of the lung
* Chronic empyema can be treated with drainage, gauze packing, or skin flap (Eloesser flap) with eventual muscle transposition and skin closure. Lung resection of pleuropneumonectomy is rarely required.

== '''Complications''' ==

* Lung fibrosis
* Contraction of the hemithorax (fibrothorax)
* Necrosis
* Spontaneous drainage of pus through the chest wall (empyema necessitatis) or into the bronchial tree (bronchopleural fistula)
* Pericarditis
* Mediastinitis
* Osteomyelitis
* Metastatic spread of infection

[[Category:Thoracics]]