Pyothorax in Dogs


Overview of Canine Pyothorax

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 in dogs 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 of Pyothorax in Dogs

  • 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

    Signs of pyothorax in dogs include: 

  • Difficulty breathing
  • Fever
  • Lethargy/listlessness
  • Decreased appetite
  • Cyanosis (gums appear blue)

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

  • Diagnosis of Pyothorax in Dogs

    Diagnostic tests are needed to determine why your dog is having difficulty breathing and to determine if there is an underlying cause. If your pet is diagnosed with pyothorax, he will require veterinary care. Your veterinarian’s efforts will be directed at three things:

  • Making your pet more comfortable by removing as much of the fluid from the chest cavity as possible
  • Performing tests to determine whether there is an identifiable cause for the pyothorax
  • Treating the infection so that it does not recur

    Diagnostic tests that your veterinarian may wish to perform include:

  • Blood work. Animals with pyothorax often have an increased number of white cells in their blood stream.
  • Chest radiograph. Chest radiographs or X-rays are done to confirm the presence of fluid in the chest cavity and to help determine how much fluid is present.
  • Chest tap. A chest tap (needle thoracentesis) is done to remove some fluid to allow your pet to breathe easier and also to obtain some fluid for analysis.

    Most animals tolerate chest taps and the procedure can be done without any sedation, but occasionally your veterinarian may need to give your pet some sedation or even general anesthesia in order to remove the fluid.

  • Fluid analysis. The fluid is typically opaque or turbid looking and may be somewhat smelly. It can range from amber to red or white in color and may appear bloody.
  • Cytology. Your veterinarian will examine the fluid under a microscope to determine what type of cells are present and whether bacteria can be seen.
  • Culture and sensitivity. Your veterinarian will likely culture the fluid to determine which bacteria are present. Often they will test various antibiotics to see which ones are most effective against the invading bacteria.

    Treatment of Pyothorax in Dogs

  • If your dog is very ill and having difficulty breathing, your veterinarian will initially remove some of the fluid to allow him to breathe more easily and will likely place your pet on intravenous (IV) fluids. They will also initiate antibiotic treatment.
  • Once it has been determined that your dog has pyothorax, your veterinarian may wish to place a chest tube to facilitate removal of the fluid and to help treat the infection. The chest tube can be used to lavage (wash) the chest cavity. This is done by placing sterile fluid into the chest cavity through the tube and then removing the fluid.
  • If a cause for the infection is found, your dog may require surgery.
  • Long-term antibiotic therapy is an important part of treating pyothorax. Initially, antibiotics may be given intravenously, but you will need to continue oral antibiotics for 4 to 8 weeks.
  • Home Care and Prevention

    Administer all medications that your veterinarian prescribes until they are gone. Observe your pet closely for evidence of difficulty breathing. If he becomes lethargic or stops eating, contact your veterinarian immediately.

    Do not allow your pet to fight with other animals. If you notice a wound on the chest wall, have your veterinarian examine it. Take note of any wounds so that if your pet develops a problem later you can point it out to your veterinarian.

    Do not feed your pet bones or other hard objects that might become lodged in the esophagus and cause perforation.

    There is very little else that you can do to prevent your animal from developing pyothorax, but being alert to the signs will allow the condition to be diagnosed earlier and may allow treatment to be more effective.


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