Pyothorax in Cats
Dr. Theresa Welch Fossum
Determine that fluid is present in the chest cavity
Diagnostic tests will be performed to:
Verify that the fluid is infected
Determine if there is an underlying disease, such as abscess, lung tumor or foreign body, that might have caused the infection.
To determine is fluid is present
Your veterinarian will take a complete medical history and will perform a thorough physical examination.
Careful auscultation of the chest (using a stethoscope) will help determine whether the heart and lung sounds are normal. When fluid is present, the heart sounds may be muffled. Additionally, lung sounds may be difficult to hear in certain parts of the chest if fluid is present.
Thoracic radiographs (chest X-rays) will be taken to identify fluid in the chest and determine how much is present and where it is located. The radiographs will also be evaluated to determine whether other causes of difficult breathing such as pneumonia, asthma or tumor or fluid formation (lung lobe torsion) might be present.
To confirm that the fluid is infected
Fluid removed from the chest by needle thoracentesis (chest tap) is analyzed for physical characteristics (color, clarity), the type and number of cells, amount of protein and the presence of bacteria or other infective organisms.
Most infected fluids contain bacteria that are present within cells that have phagocytized (eaten) them as well as bacteria that are present outside of cells. The type of bacteria, whether they are round or oblong and how they stain, will be used to help identify the type of infection that is present.
Fluid will be submitted for a culture, during which the bacteria type is determined by growing it on certain medias, and for sensitivity in which different antibiotics are tested on the bacteria to see which ones are most effective in killing them.
To determine if there is an underlying disease
After removing the fluid, your veterinarian may wish to repeat the radiographs to see if there is evidence of a tumor or abscess in the lung tissue or to look for the presence of a foreign body or diskospondylitis. The chest cavity will be checked to identify any evidence of a bone or other material in the esophagus that might have caused a perforation. The lungs will also be inspected to determine whether they are able to inflate normally once the fluid is removed.
An echocardiogram may be performed if there is any concern of heart dysfunction.
Routine blood work (complete blood count and serum biochemical panel) will often be done to help assess organ function and overall health of your pet.
Your veterinarian may recommend other tests to help further identify potential diseases that may have caused the pyothorax or to identify concurrent diseases that might be present.
Treatment of pyothorax may require medical management alone or in combination with surgery, depending on the underlying cause.
The initial concern in treating your cat is to improve his ability to breathe. Your veterinarian will generally remove the fluid in your pet's chest cavity using a needle. Occasionally, sedation or anesthesia are required but a chest tap can often be performed with the animal awake. Depending on the degree of difficulty that your animal is experiencing when breathing, oxygen therapy may be required.
Further treatment will depend on whether or not an underlying disease was identified. If an underlying lesion is found, your veterinarian will need to treat it and the infection.
Medical management of pyothorax usually involves placing the animal on fluids to correct dehydration and other blood abnormalities and initiating antibiotics. Generally, broad-spectrum antibiotics, which are those effective against a wide variety of bacteria, are initiated until the results of the culture and sensitivity are obtained. Antibiotic therapy is generally continued for a total of 6 to 8 weeks.
Many times antibiotic therapy alone is not enough to rid the chest of the infection completely. In such animals, chest tubes are often inserted so that fluid can be placed into the chest via the tube and then removed. This helps to wash the bacteria and clots out of the chest cavity and may decrease the likelihood of the infection recurring. This procedure of thoracic lavage is generally done two to three times a day for 5 to 7 days or until there is clinical improvement.
If an underlying cause for the infection is identified, such as a lung tumor, abscess or a foreign body, then surgery is necessary. The foreign body or mass must be removed in order to clear the infection. Additionally, if there is no response to the medical management, surgery is often recommended despite a definitive mass or lesion not being readily identified on the radiographs.
Several surgical approaches can be used for pyothorax depending on the lesion that has been identified. An incision may be made between the ribs if a lung mass has been identified, or the sternum may be opened so that both sides of the chest cavity can be evaluated. Many times it is not possible to find the foreign body that caused the infection, despite evidence that one was present previously.
The surgeon will remove as much of the infected tissues as possible and will submit it for histologic examination (under a microscope) and for culture.
Often a chest tube will be placed to allow lavage of the chest cavity to be continued after surgery.