Abscesses in Dogs

What is an abscess?

The simple description of an abscess is a “pocket of pus” located somewhere in the body. Abscesses are usually described by where they are located anatomically; 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 (if it is not located inside a body cavity or deep within tissue) that may be firm to the touch or compressible like a water balloon. 

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 rupture and drain foul-smelling material (pus).

A dog with an abscess often has 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 is expected, and if the abscess has ruptured internally, there may also be the additional complication of a distributed internal infection — that is, bacteria in the bloodstream.

What causes abscesses?

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

Certain bacterial species are often responsible for abscesses, including:

• Pus-forming bacteria like Staphylococcus, Escherichia coli, certain Streptococcus species, Pseudomonas, Mycoplasma, Pasteurella multocida, Corynebacterium, Actinomyces, Nocardia, and Bartonella
• Bacteria that can only live and grow in the absence of oxygen, including Bacteroides, Clostridium, and Fusobacterium

Are there any risk factors for abscess development?

Certain tissues and organs are more common sites of abscesses.

• A generalized blood-borne infection may result in a liver abscess.
• Damage to a tooth may result in a tooth root abscess.
• A sexually intact male dog may develop an infection in the prostate gland and a subsequent abscess.
• A bite wound can result in an abscess under the skin.
• An inhaled foreign object or severe pneumonia may cause a lung abscess.
• An inner ear infection, severe sinus infection, or infection deep in the mouth can result in a brain abscess.
• Impacted or infected anal sacs may develop abscesses.

How are abscesses treated?

Treatment depends on the location of the abscess 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 to remove it or the abscess will return. Antibiotic therapy is a critical component of successful abscess treatment. The antibiotic will be chosen based on the bacteria involved, and the length of treatment will depend upon both the bacteria and the location. 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 will prescribe appropriate pain medication to be given with the antibiotic.

Your veterinarian may talk with you about maintaining adequate nutrition to ensure good healing; this may involve a temporary dietary change. Finally, it will be important to restrict activity during recovery to allow the tissue to heal properly. If the abscess was surgically removed, then it is mandatory to keep the dog quiet and contained.

Is there any follow-up for my dog?

If the abscess is superficial, it is important to monitor the abscess site for any increased draining. If the abscess was internal, monitor for any evidence your dog is not improving. Avoiding a 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, prevent fighting.

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 treatment instructions precisely. Your dog should have a complete recovery provided there is adequate draining or removal of the abscess followed by appropriate follow-up care and delivery of antibiotics, pain medication, and nutrition.