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Pus in the Chest Cavity of Dogs

Pyothorax in Dogs

Pyothorax in dogs occurs when an infection leads to the accumulation of pus within the chest (pleural) cavity. Pus, composed of white blood cells (neutrophils) and dead cells, represents the body’s natural immune response to infection. Over time, the white blood cells perish, leaving behind the characteristic thick, whitish-yellow fluid of pus.

Unlike an abscess, pus within the chest cavity doesn’t form an enclosed tissue wall to contain bacteria. Instead, it forms sacs that line the pleura, resulting in scarring of the cavity and severe impairment of lung function.

Bacterial infections that settle in the chest cavity can originate from the lungs or esophagus. Dogs typically acquire such infections by inhaling foreign objects like grass awns (the bristles on grass tips) or through chest-penetrating wounds. Hunting dogs and sporting breeds are particularly prone to developing these infections.

This medical condition described can affect both dogs and cats.

Symptoms and Types

  • Coughing
  • Fatigue
  • Low-grade fever
  • Chest pain or discomfort
  • Loss of appetite (anorexia)
  • Weight loss (which may be the sole indicator)
  • Increased or decreased breathing rate
  • Collapsing after exercise with slow energy recovery
  • Recent history of fights or puncture wounds


Pyothorax is commonly caused by infections from bacteria such as:

  • Bacteroides
  • Peptostreptococcus
  • Fusobacterium
  • Corynebacterium
  • Escherichia coli
  • Pasteurella
  • Streptococcus

Other contributing factors may include bacterial and fungal infections, often originating from agents present in the soil, such as actinomycosis and nocardiosis.


To diagnose pyothorax in your dog, your veterinarian will require a comprehensive history of your pet’s health, including any symptoms and potential preceding incidents such as fights or chest injuries.

A thorough physical examination will be conducted, focusing on your dog’s chest for signs of inflammation of cellular tissue (cellulitis) or scarring. A complete blood profile, including a chemical blood profile, complete blood count, and electrolyte panel, will be performed. Additionally, a urinalysis and a sample of fluid from the chest cavity will be sent to the laboratory for cytologic evaluation and gram staining to enhance bacterial visibility.

Samples of the fluid in the pleural cavity will be sent for aerobic and anaerobic bacterial cultures, as well as for serological testing to detect fungal agents. If the parasite S. lupi is suspected, an esophagoscopy can be performed for examination of the esophagus.

X-ray and ultrasound imaging will be utilized to visualize the interior of the dog’s chest cavity, revealing fluid accumulation, lung consolidation, lung collapse, and/or masses.


For dogs diagnosed with pyothorax, hospitalization in the intensive care unit is essential for treatment. The recovery process may span several days to weeks until the infection is completely eradicated. Drainage of the chest cavity using a tube is imperative for resolution; without it, the condition cannot be effectively treated. The chest cavity will be regularly flushed (via the chest tube) every six to eight hours using warm, sterile saline solution.

To aid in removing debris from the chest cavity, a technique called coupage may be employed. Coupage involves gently slapping the chest wall, with care taken not to harm the animal. If there’s no improvement in your dog’s condition, a bacterial culture will be repeated.

Encouraging light exercise, such as 10-minute intervals every six to eight hours, can promote breathing and expedite recovery. Surgical intervention becomes necessary in cases involving abscesses in the lungs, stiffening of the chest cavity lining, lung-lobe twisting, extensive pustule clumping, or mediastinal involvement.

Surgery is also indicated for the removal of foreign bodies if they are identifiable through imaging techniques like X-ray, ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI). Following a thoracotomy, your pet will receive pain medication and antibiotics to prevent incision-related infections. The choice of antibiotics may be adjusted based on the results of culture and sensitivity tests.

Living and Management

After discharge from the hospital, your veterinarian will schedule monthly follow-up appointments for your pet, which will include complete blood counts and X-rays to monitor its progress. While some lung damage may persist in the chest cavity due to previous pus formations, fluid accumulation should be absent.

Antibiotic treatment should be continued for at least a month after the infection clears or until blood work results normalize and there is no evidence of fluid re-accumulation on the dog’s X-ray. Typically, this antibiotic regimen lasts between 3 to 12 months, though it may extend longer in some cases.

With consistent antibiotic therapy and adequate drainage of the chest cavity, the prognosis ranges from fair to excellent. Your dog’s exercise level can gradually return to normal over a period of two to four months.

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