Pyothorax in Dogs

Pyothorax is an infection of the chest cavity generally caused by bacteria, although less commonly it may be due to other organisms, such as viruses or fungi. The infection causes fluid to accumulate in the chest cavity – the space between the lungs and the body wall – which causes difficulty breathing. This is a serious condition and is often fatal if not treated promptly and aggressively.

The route by which the thoracic cavity becomes infected is often not apparent and there are numerous ways that infection can occur in the chest cavity.

Causes

Spread of infection from the blood stream

Migration of foreign objects, such as plant material or thorns, through the chest cavity or lungs

Penetrating wounds, particularly bite wounds

Extension of infection from the vertebrae

Extension from pneumonia

Lung tumors or abscesses that rupture

Lung or chest wall trauma

Perforation of the esophagus

Complication of surgery

There is usually a fairly long gap between the incident that caused the infection and the development of clinical signs. When the infection is caused by an animal bite, the wound has often healed and the owner has forgotten about it by the time that the pet becomes ill.

Pyothorax is particularly common in hunting dogs where the infection is related to the entrance of a foreign body, such as a piece of plant material, into the chest cavity through the body wall. Alternately, the plant material may be inhaled and migrate through the lung.

What to Watch For

Difficulty breathing

Fever

Lethargy/listlessness

Decreased appetite

Cyanosis (gums appear blue)

In some cases, despite aggressive treatment, pyothorax can be fatal.