Defined as a pleural effusion with positive Gram stain or gross pus.
Also known as pyothorax or purulent pleuritis.
Refers to an accumulation of pus in the pleural cavity that can develop when bacteria invade the pleural space.
It is usually seen associated with pneumonia.
There are three stages to an empyema: exudative, fibrinopurulent, and organized.
The exudative phase reflects increasing pleural fluid with or without the presence of pus.
The fibrinopurulent phase occurs when fibrous septa form localized pus pockets.
The organizing stage occurs when there is scarring of the pleura membranes with inability of the lung to expand.
Simple pleural effusions occur in up to 40% of cases of bacterial pneumonias, and usually are small and resolve with antibiotic therapy.
The incidence of pleural empyema and the prevalence of specific causative microorganisms depends on whether the infection is community acquired vs. hospital acquired pneumonia, the age of the patient and the host’s immune status.
Risk factors for the development of emphysema include: alcoholism, drug use, HIV infection, neoplasm and pulmonary disease.
Found in about 0.7% of patients needing hospitalization for a community acquired pneumonia.
In a UK study of 430 adult patients with community acquired pleural empyema found negative pleural-fluid cultures in 54% of patients,
In the above study pleural cultures revealed Streptococcus milleri group in 16%, Staphylococcus aureus in 12%, Streptococcus pneumoniae in 8%, other Streptococci in 7% and anaerobic bacteria in 8%.
The risk of empyema in children is comparable to adults, and is calculated to be around 1.5% in children hospitalized for community acquired pneumonia.
The types of causative organisms does differ greatly from that in adults: with negative cultures in 27% of patients, Streptococcus pneumoniae in 51%, Streptococcus pyogenes in 9% and Staphylococcus aureus in 8%.
While the use of pneumococcal vaccination has dramatically decreased the incidence of pneumonia it has not decreased the incidence of emphysema which is rising in children and adults.
Typical presenting symptoms include cough, chest pain, shortness of breath and fever.
Most cases present in the setting of a pneumonia.
Up to one third of patients do not have clinical signs of pneumonia, and as many as 25% of cases is associated with trauma, the includes surgery.
Initial evaluation for suspected empyema is the chest X-ray.
Chest X-Ray cannot differentiate an empyema from uninfected parapneumonic effusion.
Ultrasound of the chest can confirm the presence of a pleural fluid collection and can estimate the size of the effusion.
Ultrasound of the chest can differentiate between free and loculated pleural fluid and guide thoracocentesis.
In evaluating an empyema Chest CT and MRI do not provide additional information, and in most cases and should not be performed routinely.
The most significant criteria for empyema are pleural effusion with presence of pus, a positive Gram stain or culture of pleural fluid, or a pleural fluid pH under 7.2 with normal peripheral blood pH.
It is suggested to perform diagnostic pleural fluid aspiration in patients with pleural effusion in association with sepsis or pneumonic illness.
Micro-organisms responsible for development of empyema is not necessarily the same as the organism causing the pneumonia, especially in adults.
The sensitivity of pleural fluid culture is generally low, partly due to prior administration of antibiotics.
The pleural culture yield can be increased if pleural fluid is injected into blood culture bottles, aerobic and anaerobic, immediately after aspiration.
Testing for specific pathogens using polymerase chain reaction or antigen detection, especially for Streptococcus pneumoniae, Streptococcus pyogenes and Staphylococcus aureus can increase bacterial infection confirmation.
Pneumococcal antigen detection in pleural fluid can provide rapid diagnosis of pneumococcal empyema.
Treatment is the placement of a draining chest tube..
Chest tube drainage shortens the time for resolution of the infection and hospitalization time.
Pleural fluid pH of <7.2 is the most significant indicator to predict the need for chest tube drainage in patients with non-purulent, culture negative fluid.
Indications for drainage include poor clinical progress during treatment with antibiotics, and for loculated pleural collections.
Approximately 15 to 40 percent of patients require surgical drainage of the infected pleural space because of inadequate drainage and can be done by open thoracic drainage or Video-assisted thoracoscopic surgery (VATS).
All patients with empyema should be hospitalized and treated with antibiotics.
Antibiotic therapy is chosen based on Gram stain and culture, or on local epidemiologic data.
If aspiration is suspected anaerobic antibiotic coverage must be included.
Antibiotic agents with good pleural and empyema include: penicillins, ceftriaxone, metronidazole, clindamycin, vancomycin, gentamycin and ciprofloxacin.
Aminoglycosides have poor penetration into the pleural space.
No consensus on duration of intravenous and oral therapy exists, but should be continued for weeks based on clinical, biochemical and radiological response.
Patients require follow-up with a repeat chest X-ray and inflammatory biochemistry analysis within 4 weeks following hospital discharge.
Chest radiograph returns to normal by 6 months.
Complications are rare but include bronchopleural fistula formation, recurrent empyema and pleural thickening.
Pleural thickening can lead to impaired lung function.
Approximately 15% of adult patients with empyema die within 1 year of the event, due to comorbid conditions.
Mortality in children is less than 3%.
No clinical, radiological or pleural fluid characteristics accurately determine prognosis.