Abscesses in Cats

My cat was diagnosed with an abscess. What exactly is an abscess?

An abscess is a “pocket of pus” located somewhere in the body. Abscesses are typically described by where they are in the body. For instance, a tooth root abscess occurs at the tip of a tooth root, and a subcutaneous abscess occurs under the skin.

Typically, an abscess appears suddenly as a painful swelling that may be either firm to the touch or compressible like a water balloon. If the abscess is located inside a body cavity or deep tissue, you may not notice any swelling.

The abscess may be large or small, will often cause redness if it is under the skin, and may cause local tissue destruction. Some abscesses will rupture, discharging a foul-smelling thick liquid.

A cat with an abscess will often have a fever, even if the abscess has ruptured and drained to the outside of the body. If the abscess is located inside the body (e.g., in the liver), fever would be expected, and there may be the additional complication of a widespread internal infection or bacteria in the bloodstream if the abscess has ruptured internally. Affected cats will often be lethargic or withdrawn, dehydrated, and have a poor appetite.

What causes abscesses?

There are many potential causes of abscesses in cats. One of the most common causes is a bite from another animal. The bite introduces bacteria into the wound, which becomes infected and, depending on the bacteria involved and how deep the bite is, an abscess can result. Penetrating injuries from inanimate objects like sticks and grass seeds can also lead to abscesses, as can having had a previous infection in the site.

Certain bacterial species are often involved in abscess formation, including:

• pus-forming bacteria like Staphylococcus, Escherichia coli, certain Streptococcus species, Pseudomonas, Mycoplasma, Pasteurella, Corynebacterium, Actinomyces, Nocardia, and Bartonella
• bacteria that can only live and grow in the absence of oxygen, in deeper or internal abscesses, including Bacteroides, Clostridium, and Fusobacterium.

Multiple bacterial species can be present within the same abscess.

Are there any particular risk factors for abscess development?

Certain tissues and organs are more commonly affected by abscesses.

• Damage to a tooth or severe periodontal disease may result in a tooth root abscess.
• A bite wound can result in an abscess under the skin, so cats that fight or go outside are at higher risk.
• An inhaled foreign object, or severe pneumonia, may cause a lung abscess. Cats with severe or chronic upper respiratory infections or asthma can be more prone to these lung infections.
• An inner ear infection, severe sinus infection, or infection deep in the mouth can result in a brain abscess.
• Blood borne infection can cause a liver abscess.
• Chronic gastrointestinal disease or pancreatitis can cause pancreatic abscesses.
• Impacted anal glands may lead to anal gland abscesses.
• Cancerous tumours are also prone to secondary infection and abscesses due to lack of blood supply.

Cats with compromised immune systems, such as those affected by feline immunodeficiency virus (FIV) or feline leukemia virus (FeLV), can be more susceptible to abscess formation, as their body does not properly fight off infection. Immunosuppressive medications can also compromise the immune system, as can conditions such as diabetes mellitus and Cushing’s disease.

How are abscesses treated?

Abscess treatment depends on the location and the severity of the infection. Most abscesses are treated on an outpatient basis, rather than in the hospital. The key is to remove the pocket of pus, either surgically or by draining and flushing. If a foreign object caused the abscess, it is critical that it is fully removed or the abscess will return. If a tooth root abscess is present, the diseased tooth must be surgically removed.

Appropriate antibiotic therapy is a critical component of the successful treatment of abscesses, no matter the location. The antibiotic will be chosen based on the bacteria involved. The length of treatment will depend on both the bacteria and the location of the abscess. Often, your veterinarian will recommend that a sample of the pus be sent to a referral laboratory to be cultured so that the bacteria involved can be identified and an appropriate antibiotic can be chosen.

It is important to give the antibiotics for the entire time they are prescribed. It is also important to ensure adequate pain relief during treatment of an abscess. Your veterinarian may prescribe appropriate pain medication to be given alongside the antibiotic. Your veterinarian may also talk with you about adequate nutrition and hydration to ensure proper healing, which may involve a temporary dietary modification.

Finally, it will be important to restrict activity during recovery to allow the tissue involved to heal properly. If surgery was involved to remove the abscess, keeping the cat quiet and contained is mandatory. 

Is there any follow-up for my cat that I should be aware of?

While your cat is healing from an abscess, it is important to monitor for any increased draining from the abscess site (if the abscess is superficial), or any evidence that the cat is not improving (if the abscess is internal). Avoiding a future recurrence depends on where the abscess occurred and what tissues are involved. For instance, in the case of repeated anal sac abscesses, surgical removal of the gland may be recommended. In the case of a prostate abscess, neutering may prevent a recurrence. For bite wound abscesses, avoid fighting or play-fighting situations that may cause a recurrence.

Delayed or inadequate treatment may lead to chronically draining tracts in the tissue or even to organ system compromise, so it is important to follow all treatment instructions from your veterinarian. Adequate draining or removal of the abscess, followed by appropriate follow-up care and delivery of antibiotics, pain medication, and nutrition, should result in a complete recovery.