Serious Cause of Respiratory Distress, Do You Keep This No. 1 Trigger at Bay?

pyothorax in cats

Story at-a-glance -

  • Pyothorax is a serious infection in the chest cavity that is fairly common in both dogs and cats
  • The most common cause of pyothorax is a bite wound to the chest, but there are a number of other potential causes, including an inhaled foreign body such as plant material or a plant seed
  • Symptoms of pyothorax include coughing, fatigue, fever, loss of appetite, weight loss, chest discomfort and changes in breathing
  • Treatment of pyothorax is determined by the cause and severity of the infection; long-term antimicrobial therapy is usually needed to resolve the infection

By Dr. Karen Shaw Becker

Pyothorax is a fairly common form of respiratory distress in both dogs and cats as a result of an infection in the chest cavity. The infection is typically caused by bacteria, though a virus or fungus can also be the culprit. It's important to understand that pyothorax is a serious disease that can be fatal if not treated promptly and aggressively.

'Pyothorax' = 'Pus in the Chest Cavity'

Pyo- (which means pus) and thorax (the scientific word for chest cavity) describes an accumulation of pus in the chest cavity between the lungs and the chest wall caused by an infection.

Pus is actually the body's natural immune response to a bacterial invasion. It's composed of white blood cells, or neutrophils, and dead cells that gather at the site of infection. The white blood cells die off as they fight the infection, creating an accumulation of the thick, white-yellowish fluid we refer to 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, which is the lining around the lungs. The result is 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 the body through the lungs or esophagus. Many pets develop pyothorax from a bite wound that pierces the chest, but there are several other potential causes of the infection, including:

Inhaled foreign body

Ruptured abscesses of the lungs

Spread of a lung infection like pneumonia

Trauma to the lung or chest wall

Spread of an infection from the bloodstream

Perforation of the esophagus

Migration of a foreign body (e.g., plant material or a plant seed) from the esophagus

Lung torsion (a twisted lung lobe)

Spread of infection from the vertebra to the lungs

Parasitic infection

Lung tumors


Symptoms of a Pyothorax Infection

Symptoms of pyothorax include:

  • Coughing
  • Fatigue
  • Fever
  • Loss of appetite
  • Weight loss

Pets also experience obvious chest discomfort, and changes in breathing and a bluish tinge to the gums are commonly reported. Dogs and cats with the infection usually experience extreme fatigue after exercise, as well as a very slow recovery rate. Since cats are typically 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 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.

Diagnosing Pyothorax

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.

In a chest tap, the veterinarian removes fluid from the chest to help your pet breathe more easily. Some of the fluid is also sent off for analysis. The procedure can be done without sedation in some cases, but many 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 (looking at the cells through a microscope), and a culture and sensitivity test will be completed to determine what type of bacteria is present and what medication will be most effective to treat it.

Treatment Options

In very ill pets with considerable breathing difficulty, at either the veterinary clinic or emergency animal hospital, some of the fluid in the chest cavity will be removed immediately to ease respiration, and intravenous (IV) fluids will be started. Antimicrobial treatment is also usually instituted at this time, as well as supplemental oxygen.

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. The tube can also be used to wash or lavage the chest cavity. A technique called coupage may also be performed to help dislodge debris from the chest cavity. Patients also need some light exercise every few hours to help promote breathing and speed healing.

Sometimes surgery is required to remove a foreign body identified as 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 antimicrobial therapy (four to six weeks) is required to resolve a pyothorax infection.

The very best way to treat pyothorax, in my opinion, is with nebulization therapy. This form of respiratory therapy allows delivery of medications directly to infected lungs by creating aerosolized solutions of medication the patient breathes in. This "direct access" of medication to the site of infection is substantially more effective than oral medications, and can be combined with IV medications to synergistically address aggressive infections.

Preventing a Pyothorax Infection in Your Own Pet

Since most cases of pyothorax are the result of bite wounds, keeping your pet safe from animal bites 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.