What is a pyothorax?
Pyothorax is the presence of inflammatory fluid or pus in 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 on both sides of the chest, but sometimes only one side is affected. The source of the infection is rarely found. An underlying cause is identified in only 2% to 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 after ingesting or inhaling a foreign object
- A migrating foreign body, such as a grass seed that entered the body elsewhere (the most common cause of pyothorax in dogs)
- Spread of an infection from the lungs
- Spred of infection through the bloodstream
- Secondary to cancer
What are the clinical signs of pyothorax?
Signs of pyothorax in dogs include:
- Rapid, shallow, open-mouthed breathing that may be painful (caused by fluid in the chest that prevents the lungs from expanding normally)
- Depression, lethargy
- Decreased appetite, other signs of general illness
- Fever and signs related to fever
The severity of these signs is highly variable, and dogs may suddenly die without any previous signs of illness.
How is pyothorax diagnosed?
Your veterinarian will examine your dog and listen to their chest with a stethoscope, which may indicate fluid in the chest. In mild 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 tests may include a complete blood count (CBC), a biochemical panel, and a urinalysis.
In severe cases, it may be necessary to drain the fluid from the chest immediately before taking radiographs, in a procedure called a thoracocentesis or chest tap. Your dog may need to be sedated for this procedure. In many cases, the pus from both sides of the chest can be drained from one side, although it is sometimes necessary to drain both sides. Occasionally, the fluid occurs in pockets, and multiple drainage procedures are necessary. Your veterinarian will send fluid samples to a laboratory for evaluation so 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 so these procedures can be repeated. Surgery may also be required to identify and remove necrotic (dead) tissue or foreign material from the chest cavity.
Oral antibiotics are essential for treatment 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?
The prognosis 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, although survival tends to be lower in dogs that become septic before or during treatment.
