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Fact Sheet
Abscesses in Dogs and
Cats
 An
abscess is a localized, encapsulated, accumulation of solid
or liquid material. This material represents tissue breakdown
products. The material inside an abscess (pus) is generally
cloudy and white to off-white to yellowish in color. It is
composed primarily of serum, blood, liquefied tissue debris
and degenerated or toxic neutrophils (a type of white blood
cell) with lesser numbers of other types of white blood cells
such as macrophages and lymphocytes.
Abscesses occur when microorganisms,
or foreign objects, or both, gain entrance into body tissues.
The resultant tissue reaction causes an accumulation of purulent
exudates in the tissue, with components as described above.
At this early point, the affected area is best described as
a cellulitis. If the cellulitis is not quickly resolved, or
if the accumulating debris is not promptly discharged to an
external body surface, then the body will attempt to wall
off the affected area by forming a capsule of fibrin around
it. Fibrin is gluey, web-like type of protein that also serves
as a main component of scabs. Once the fibrin capsule is complete,
the cellulitis is said to have become an abscess.
Progressive increases in the pressure
within the abscess cavity can lead in time to rupture of the
abscess. However, prolonged delay in evacuation of the contents
of the abscess cavity can result in a thicker, tougher, more
rigid abscess wall composed of fibrous connective tissue.
In this case, healing will eventually require the filling
of the cavity by scar tissue. Unfortunately, this does not
always result in total elimination of the inciting elements
of the abscess; chronic or intermittent discharge of exudates
from a draining sinus tract is a potential squela.
Among dogs and cats, abscesses can occur
almost anywhere, but they are most common on the skin, within
the anal glands, prostate gland, or mammary glands, and behind
the eyeball.
Signs and Symptoms
Clinical signs of an abscess will vary
depending on the location of the abscess and the organ system(s)
affected. In general, however, all abscesses cause some degree
of pain, swelling, redness, heat, and loss of function.
A painful, angry, open wound with material
draining out may be visible if the abscess is superficial
and has ruptured to an external body surface. Sometimes fever,
loss of appetite, and/or painfulness in a particular area
are the only signs.
Often there is some prior history of
trauma, fighting, or infection in the affected area. Tissue
destruction may be minor or substantial. Even body organs
not directly involved in the abscess can be hampered and compromised
due to pressure from an adjacent abscess mass.
Diagnosis
Abscesses are usually diagnosed presumptively
by physical examination and observation. Often microscopic
examination of the abscess contents is necessary in order
to confirm that the structure is an abscess and not a similarly
appearing tumor, cyst, or granuloma.
Blood testing will usually show abnormalities
in the white blood cell counts.
Treatment
Treatment of abscesses centers around
identifying and removing the original cause(s), beginning
antibiotic therapy, and establishing adequate drainage, if
possible. Large abscess and those associated with large amounts
of dead tissue may require surgery.
The prognosis for abscesses is generally
good, but some abscesses may become complicated by sepsis
(blood-borne infection), or chronic, draining tracts. Furthermore,
abscesses which rupture internally may lead to peritonitis
or pleuritis. In these cases, the prognosis is worse.
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