Pus in the Chest Cavity of Cats

By PetMD Editorial on Jan. 19, 2009

Pyothorax in Cats

Pyothorax occurs when pus, the body's natural immune response to an invasion of bacteria, accumulates in the chest (pleural) cavity. Made up of white blood cells (neutrophils) and dead cells, pus gathers at the site of an infection. Eventually, the white blood cells die, leaving the thick whitish-yellow fluid that is characteristic of pus.

Pus that accumulates in the chest cavity, however, differs from an abscess, in that it does not create an enclosed wall of tissue to inhibit the bacteria from spreading. Instead, the pus forms into sacs that line the pleura, eventually scarring the cavity and severely impairing lung function.

A bacterial infection that settles in the cat's chest cavity can enter from the lungs or esophagus. Cats generally get these types of infections from bite wounds, but they can also get them from inhaling foreign bodies, or from the spread of a lung infection, such as pneumonia, into the chest cavity.

The condition described in this medical article can affect both dogs and cats. If you would like to learn how pyrothorax affects dogs, please visit this page in the PetMD health library.

Symptoms and Types

Cats with pyothorax commonly display such symptoms as shock and sudden respiratory distress; they may also collapse.


The most common causes for pyrothorax include infections with the bacteria:

  • Pasteurella Multocida
  • Bacteroides
  • Peptostreptococcus
  • Fusobacterium

Other causes include:

  • Cancer
  • Parasitic infestation (e.g., Spirocerca lupi)
  • Lung torsion (twisting of a lung lobe)
  • The presence of foreign objects within the chest cavity
  • Rupture of inflamed, granulated tumor in the esophagus


You will need to give a thorough history of your cat's health to the veterinarian, as well as its symptoms and possible incidents that might have preceded this condition, such as any fight wounds or chest injuries your pet might have sustained.

Your veterinarian will perform a thorough physical exam, checking your cat’s chest for inflammation of cellular tissue (cellulites) or scarring. A complete blood profile will be conducted, including a chemical blood profile, a complete blood count, electrolyte panel. In addition, a urinalysis sample of fluid from the chest cavity will be sent to the laboratory for cytologic (microscopic) evaluation and gram staining -- a procedure that makes bacteria more visible by causing it to stand out from the other cells.

A sample of the fluid in the pleural cavity will be sent for aerobic and anaerobic bacterial cultures (bacteria that need oxygen, and bacteria that does not, respectively), and for serological testing to detect the presence of a fungal agent. If the parasite S. lupi is suspected, an examination of the esophagus (esophagoscopy) can be done.

Your veterinarian can also use X-ray and ultrasound imaging to examine the interior of the cat's chest cavity. These images will show fluid in the chest cavity, possible lung hardening (consolidation), lung collapse, and/or masses.


Cats with this condition should be hospitalized in the intensive care unit for treatment. It may take several days to weeks to fully eradicate the infection. Drainage of the chest cavity through a tube is critical; otherwise, the condition cannot be resolved. The chest cavity will be rinsed out (through the chest tube) every six to eight hours with warm, sterile saline.

Coupage -- a technique that involves rapidly slapping the chest wall, but not with enough force to injure the animal -- may help remove debris from the chest cavity. A bacterial culture will be repeated if your cat's condition does not improve.

The infected cat should be encouraged to lightly exercise -- 10 minutes every six to eight hours -- to promote breathing and speed up the recovery process. If there are abscesses in the lungs, stiffening of the lining of the chest cavity, lung-lobe twisting, extensive clumping of pustules, or if the mediastinum is involved, surgery will be indicated.

Surgery will also be necessary for removing a foreign body if your veterinarian can find it on X-ray, ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI).

If your veterinarian chooses to perform a thoracotomy, your pet will be treated with pain medication following the procedure, and antibiotics to prevent infection from the incision. The type of antibiotics may be changed depending on the results of the culture and sensitivity tests.

Living and Management

Your veterinarian will schedule monthly follow-up appointments for your pet after it is discharged from the hospital, including complete blood counts and X-rays to follow its progress. While there may be some lung damage remaining in the chest cavity, resulting from the pus formations, fluid should be absent.

An antibiotic regimen should be continued for at least a month after the infection has cleared, or when the blood work results are normal or there is no evidence of fluid re-accumulation on the cat's X-ray. This antibiotic treatment regimen is generally between 3 to 12 months, although it may take longer.

The prognosis is fair to excellent with continuous antibiotic therapy and sufficient drainage of the chest cavity. Your cat’s exercise level can gradually be returned to normal over a period of two to four months.

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