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:

Pneumonia (most common)
Infected haemothorax or hydrothorax
Ruptured lung abscess
Thoracic surgery

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.

I have no idea what they mean by infective thoracic disorders, but Lee assumed it to include lung abscess. This was not covered by lecture, but we’ll discuss a bit about lung abscess at least.

Lung abscess

Lung abscess is a rare disorder, most frequently seen as a complication following aspiration.

Etiology

Aspiration
Pneumonia
Septic emboli (endocarditis)

Aspiration is the most common cause of lung abscess, accounting for 80% of cases. Abscesses are typically polymicrobial, having similar flora as the oral cavity.

Clinical features

Symptoms are similar as for pneumonia, with cough, sputum, dyspnoea, chest pain, and fever. However, symptoms typically progress over a longer period of time, like weeks or months.

Diagnosis and evaluation

X-ray or CT can show the abscess with a thick wall and inner air-fluid level. It must be differentiated from other diseases which can form cavitations, like tuberculosis. Sputum and blood cultures should be obtained to guide therapy.

Aspiration of the abscess is usually not necessary unless there is treatment failure. If performed, the fluid should be cultured.

Treatment

The main treatment is antibiotics. Drainage is performed if patients don’t improve on antibiotics. It can be performed percutaneously or transbronchially.