Abscesses in Dogs

My dog seemed fine, and then I found a swelling on his side that felt warm to the touch and seemed to get bigger overnight. He was diagnosed with an abscess, and I am not sure I understand just what that means.

The simple description of an abscess is a “pocket of pus” located somewhere in the body.  Abscesses are typically described anatomically by where they are located – 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 either firm to the touch, or fluctuant 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 will rupture and drain foul-smelling material.

A dog with an abscess will often have a fever, even if the abscess has ruptured and drained to the outside of the body. Should the abscess be located inside the body – in the liver, for instance – fever would be expected, and there may be the additional complication of a disseminated internal infection – that is, bacteria in the bloodstream – if the abscess has ruptured internally.

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 injury introduces bacteria into the wound, the wound becomes infected, and depending on the bacteria involved and how deep the bite is, an abscess can develop. 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, and these include:

• Pus-forming bacteria like Staphylococcus, Escherichia coli, certain Streptococcus speccies, 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 particular risk factors for abscess development?

There are certain tissues and organs that are fairly commonly sites abscesses. For example, anal sacs that become impacted or infected may develop an abscess. 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 and subsequent abscess in the prostate gland.  A bite wound can result in an abscess under the skin. An inhaled foreign object or a severe pneumonia may case a lung abscess. Finally, an inner ear infection, severe sinus infection, or infection deep in the mouth can result in a brain abscess.

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 ensure that it be removed or the abscess will return.

Antibiotic therapy is a critical component of successful treatment of abscesses. 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 an appropriate pain medication to be given alongside 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 keeping the dog quiet and contained is absolutely mandatory.

Is there any follow-up for my dog that I should be thinking about?

During 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 dog is not improving (if the abscess was more internal). Avoiding a recurrence in the future 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 to the letter.  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!