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Thoracic empyema

Thoracic empyema or pleural empyema refers to accumulation of pus in the pleural cavity. The most common bacteria involved are streptococci and staphylococci. Mycobacteria are a rare cause.

Development of thoracic empyema is a cause of treatment failure for pneumonia, and it should be considered in those cases where patients don’t get better on antibiotic treatment.

Etiology

Thoracic empyema can be primary (idiopathic) or secondary to:

When secondary to pneumonia it’s sometimes called a parapneumonic effusion.

Clinical features

The clinical features of thoracic empyema are similar to those of pneumonia, with fever, cough, pleuritic chest pain, dyspnoea, sputum, etc. Physical examination may reveal findings of pleural fluid, like dullness on percussion, decreased breathing sounds, and decreased fremitus.

Thoracic empyema develops in stages, from a simple effusion to empyema to chronic organisation of the fluid.

Diagnosis and evaluation

All cases with suspected pneumonia should undergo routine chest radiography to confirm the diagnosis with the presence of consolidations. A pleural effusion (which is not know to be an empyema at this point) will be visible on the x-ray. From there, ultrasound or CT may be used to assess the pleural fluid further and to guide thoracocentesis. Only thoracocentesis and analysis of the fluid can prove that the fluid is an empyema. The fluid should be cultured for bacteria. Biochemical analysis can prove that the fluid is an empyema and not another form of effusion. The following findings of the fluid confirms that it is an empyema:

  • The fluid is purulent
  • pH < 7.20
  • Elevated leukocyte count
  • Decreased glucose level
  • Elevated LDH level

Treatment

The infection will not improve unless there is source control, which in this case means drainage of the fluid. Treatment involves drainage and antibiotics. Drain may be one-time (thoracocentesis) or continuous with a tube thoracostomy.