Empyema

What is Empyema?

The lung is lined by two thin membranes of pleura (inner visceral and outer parietal), which allows the lung to expand and shrink with each breath with minimal friction.An empyema represents a collection of pus in the pleural space. This is the potential space between the two layers (parietal and visceral) of pleura.

Statistics on Empyema?

It is difficult to calculate the incidence of empyema, but it most commonly occurs as a complication in pneumonia due to Staphylococcus aureus.

Risk Factors for Empyema

A number of conditions are risk factors for the development of an empyema. Unresolved pneumonia, usually due to S. aureus (and particularly a lung abscess) can lead to infection that spreads to the pleural space (space between the lining of the chest cavity and the lung). Other conditions such as bronchiectasis, airway-obstructing cancer, thoracic surgery, penetrating wounds, and secondary spread from a distant focus (particularly a subphrenic abscess) are all possible mechanisms of disease development. Occasionally an empyema may arise as primary pathology (especially if due to Mycobacteria or Nocardia infection).

Progression of Empyema

The natural course depends on the exact cause of the empyema. Possible complications include a bronchopleural fistula (which is a permanent communication between a bronchus and the pleural space) - allowing for air to enter the pleural space as well as the pus - leading to a pyopneumothorax (air or pus in the plural cavity).

How is Empyema Diagnosed?

A full blood count will demonstrate a lhigh white cell count with raised platelets, CRP and ESR.

The chest x-ray will show a pleural effusion or a pleural mass. Loculations may be visible on the x-ray.

Sputum and blood cultures are usually done to look for the causative organism.

Prognosis of Empyema

Usually empyema does not result in permanent pulmonary damage.

How is Empyema Treated?

The basis of treatment is to drain the pus out with a chest drain. This should preferably be inserted underneath radiological guidance. If the effusion is organised and loculated then agents can be injected to break down the adhesions and allow free drainage (e.g. streptokinase or urokinase). Appropriate antibiotics should also be given. Antibiotics should continue for at lease 2 weeks after the empyema is drained.Surgery may be required if there are thick adhesions present that do not respond to fibrinolytic agents.

Empyema References

[1] Cotran RS, Kumar V, Collins T. Robbins Pathological Basis of Disease Sixth Ed. WB Saunders Company 1999. p737[2] Kumar P, Clark M. Clinical Medicine. Fourth Ed. WB Saunders, 1998. pp815-186[3] Talley NJ, O'Connor S. Clinical examination. Third Ed. MacClennan & Petty, 1996.