By Dr. Becker
Pyothorax is an infection in the chest cavity that is usually caused by bacteria, but occasionally is caused by a virus or fungus. Pyothorax is a fairly common form of respiratory distress in both dogs and cats, but it’s a quite serious disorder and can be fatal if not treated promptly and aggressively.
Pus in the Chest Cavity
“Pyo” (which means pus) and “thorax” (another word for the chest cavity) describes an accumulation of pus in the chest cavity between the lungs and the chest wall caused by an infection.
Pus is the body’s natural immune response to a bacterial invasion, and is made up of white blood cells, or neutrophils, and dead cells. The gunk gathers at the site of infection. The white blood cells die off as they fight infection, creating an accumulation of the thick, white-yellowish fluid we all know as pus.
Pus in the chest cavity doesn’t form abscesses like pus in other parts of the body. Instead of creating a wall of tissue around itself to slow down the spread of bacteria, pus in the chest forms into sacs that cling to the pleura, the lining around the lungs. This results in scarring and severely impaired lung function.
Causes of a Pyothorax Infection
A bacterial infection that settles in a dog or cat’s chest cavity generally enters from the lungs or esophagus.
Many pets get pyothorax from a bite wound that pierces the chest, but there are several other potential causes of the infection, including an inhaled foreign body, spread of a lung infection like pneumonia, spread of an infection from the bloodstream, a migration of a foreign body like plant material or a plant seed from the esophagus, spread of infection from the vertebra to the lungs, lung tumors, or ruptured abscesses of the lungs.
Trauma to the lung or chest wall, perforation of the esophagus, lung torsion (a twisted lung lobe), a parasitic infection, and sometimes cancer can also be root causes of pyothorax.
Symptoms and Diagnosis
Symptoms of pyothorax include coughing, fatigue, fever, and loss of appetite. Many pets lose weight. There’s obvious chest discomfort. Changes in breathing and a bluish tinge to the gums are commonly noted. Pets with the infection usually experience extreme fatigue after exercise and a very slow recovery rate.
Since cats are often less expressive than dogs, especially when they’re ill, often the first obvious symptom in a kitty with a pyothorax infection is a sudden episode of respiratory distress, shock, or sometimes even collapse.
There’s typically a fairly lengthy gap between the trigger for the infection and the appearance of the symptoms. In fact, when the infection is the result of a bite wound, often the injury has healed and is long forgotten by the time the dog or cat becomes ill.
Diagnostic tests to determine what’s causing your pet’s symptoms will include a blood test, chest X-ray, possibly an ultrasound, and often a chest tap, which means your vet will remove the fluid from the chest to help your pet breathe easier and also so that the fluid can be analyzed. This test can be done without sedation, but some animals do need to be sedated. In fact, some pets require general anesthesia for this procedure.
The fluid removed from the chest will be analyzed through cytology (which means looking at the cells microscopically), and a culture sensitivity test will be completed. This test determines what type of bacteria is present and what medication is most effective to treat it.
Treatment of Pyothorax
In very ill pets that have considerable breathing difficulty, some of the fluid in the chest cavity will be removed immediately to ease respiration, and IV fluids will be started. Antibiotic treatment is also usually started at this time, as well as supplemental oxygen if required.
Once a definitive diagnosis of pyothorax has been made, a chest tube is often placed to help remove the fluid as it builds up, and to treat the infection. Sometimes we also use this tool to wash or lavage the chest cavity.
A technique called coupage may also be performed. This procedure helps aid in dislodging debris from the chest cavity. The patient will also need some light exercise every few hours to help promote breathing and speed healing.
Sometimes surgery is required to remove a foreign body that has been determined to be the cause of the infection, to treat abscesses in the lungs, or to address stiffening of the lining of the chest cavity. Surgery may also be needed to correct a twisted lung lobe or to remove a tumor in the thoracic cavity. Typically, long-term antibiotic therapy (four to six weeks) is required to resolve a pyothorax infection.
Preventing a Pyothorax Infection
Since most cases of pyothorax are the result of bite wounds, not allowing your pet to fight with other animals is a good way to reduce the risk of infection. Also, don’t feed cooked bones of any kind, or any other brittle food for that matter, that could become splintered or stuck in the esophagus as your pet swallows.
As always, I recommend you keep your pet’s immune system in excellent shape, and address any new symptoms as soon as possible to prevent secondary infections and other disorders from popping up.