What is a pyothorax?
Pyothorax is the presence of inflammatory fluid or pus within the chest cavity, which is the area between the lungs and the inner walls of the ribs.
What causes pyothorax?
Pyothorax is usually caused by a bacterial infection in the chest cavity. In most cases, pus is present in both sides of the chest, but sometimes, only one side is affected.
The source of the infection is rarely found, with an underlying cause identified in only 2-22% of cases. Possible causes include:
- Penetrating wounds to the chest wall, such as a bite wound
- Wounds to internal structures, such as the esophagus or trachea (windpipe), especially following ingestion or inhalation of a foreign object
- A migrating foreign body, such as a grass seed, that entered the body elsewhere (the most commonly identified cause in dogs)
- Spread of an infection from the lungs
- Secondary to cancer
What are the clinical signs of pyothorax?
Rapid, shallow, open-mouthed breathing that may be painful, depression, lethargy, decreased appetite, and other signs of general illness are seen in most dogs with pyothorax. Affected dogs usually have a high temperature contributing to some clinical signs. Rapid, open-mouthed breathing, or breathlessness, is caused by fluid in the chest that prevents the lungs from expanding normally. The severity of these signs is highly variable, and dogs may suddenly die without any previous signs of illness.
How is pyothorax diagnosed?
Clinical examination by a veterinarian, particularly listening to the chest with a stethoscope, may indicate fluid within the chest. In mildly affected cases, chest radiographs (X-rays) will be performed to detect the presence and location of the fluid. Ultrasound examination of the chest cavity may also be recommended. Additional supporting diagnostics include a complete blood count (CBC), a biochemical panel, and a urinalysis.
In severe cases, it may be necessary to drain the fluid out of the chest immediately (thoracocentesis or chest tap) before taking radiographs. Your dog may require sedation for the procedure. In many cases, the pus from both sides of the chest can be drained from one side, although it may be necessary to drain both sides in some dogs. Sometimes, the fluid is in pockets, and multiple drainage procedures will be needed. Your veterinarian will send the fluid samples to a laboratory for evaluation and bacterial culture and sensitivity testing so that the correct antibiotic can be administered.
How is pyothorax treated?
Draining the infected fluid is essential in treating this condition and may be needed multiple times during the initial treatment period. In most cases, a flexible catheter will be inserted into the chest to remove the fluid. The tube may also be used to flush the chest cavity with fluids (lavage).
In some cases, a chest drain may be inserted surgically, allowing drainage of the chest and administration of antibiotics into the chest cavity. The drain may be left in place for several days to allow these procedures to be repeated. Surgery may also be required to identify and remove necrotic (dead) tissue or foreign material from the chest cavity.
"Draining the infected fluid is essential in treating this condition"
In some cases, a chest drain may be inserted surgically, allowing drainage of the chest and administration of antibiotics into the chest cavity. The drain may be left in place for several days to allow these procedures to be repeated.
Treatment with oral antibiotics is essential and may be prescribed for several weeks. In very sick dogs, supportive treatment with intravenous fluids may also be needed in the initial stages.
What is the prognosis for a dog with pyothorax?
This depends on the cause of the disease. In cases where no underlying disease is found, and the dog survives the critical initial stage, the outlook is good. Unfortunately, some dogs die in the early stages of their disease. An overall survival rate of 83% has been reported.