Abscessation
An abscess is a localized collection of purulent exudate contained within a cavity.
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.
PATHOPHYSIOLOGY
Bacteria are often inoculated under the skin via a puncture wound; the wound surface then seals.
When bacteria and/or foreign objects persist in the tissue, purulent exudate forms and collects.
Accumulation of purulent exudates—if not quickly resorbed or discharged to an external surface, stimulates the formation of a fibrous capsule; may eventually lead to abscess rupture.
Prolonged delay of evacuation—formation of a fibrous abscess wall; to heal, the cavity must be filled with granulation tissue from which the causative agent may not be totally eliminated; may lead to chronic or intermittent discharge of exudate from a draining sinus tract.
SYSTEMS AFFECTED
Skin/Exocrine—percutaneous (cats > dogs); anal sac (dogs > cats)
Reproductive—prostate gland (dogs > cats); mammary gland
Ophthalmic—periorbital tissues
Hepatobiliary—liver parenchyma
Gastrointestinal—pancreas (dogs > cats)
Predominant Sex
Mammary glands (female); prostate gland (male)
SIGNS
General Comments
Determined by organ system and/or tissue affected.
Associated with a combination of inflammation (pain, swelling, redness, heat, and loss of function), tissue destruction, and/or organ system dysfunction caused by the accumulation of exudates.
Historical Findings
Often presented for nonspecific signs such as lethargy and anorexia.
History of traumatic insult or previous infection.
A rapidly appearing painful swelling with or without discharge, if the affected area is visible.
Physical Examination Findings
Determined by the organ system or tissue affected.
Classic signs of inflammation (heat, pain, swelling, and loss of function) are associated with a specific anatomic location of the abscess.
Inflammation and discharge from a fistulous tract may be visible if the abscess is superficial and has ruptured to an external surface.
A variably sized, painful mass of fluctuant to firm consistency attached to surrounding tissues may be palpable.
Fever if the abscess is not ruptured and draining.
Sepsis occasionally, especially if the abscess ruptures internally.
CAUSES
Foreign objects.
Pyogenic bacteria—Staphylococcus spp.; Escherichia coli; β-hemolytic Streptococcus spp.; Pseudomonas; Mycoplasma and Mycoplasma-like organisms (l-forms); Pasteurella multocida; Corynebacterium; Actinomyces spp.; Nocardia; Bartonella.
Obligate anaerobes—Bacteroides spp.; Clostridium spp.; Peptostreptococcus; Fusobacterium.
RISK FACTORS
Anal sac—impaction; anal sacculitis.
Brain—otitis interna sinusitis oral infection.
Liver—omphalophlebitis sepsis.
Lung—foreign object aspiration bacterial pneumonia.
Mammary gland—mastitis.
Periorbital—dental disease; chewing of wood or other plant material.
Percutaneous—fighting, trauma, or surgery.
Prostate gland—bacterial prostatitis.
Immunosuppression—FeLV/FIV infection, immunosuppressive chemotherapy, acquired or inherited immune system dysfunctions, underlying predisposing disease (e.g., diabetes mellitus, chronic renal failure, hyperadrenocorticism).
DIAGNOSIS
DIFFERENTIAL DIAGNOSIS
Mass Lesions
Cyst—less or only transiently painful; slower growing.
Fibrous scar tissue—firm; non-painful.
Granuloma—less painful; slower growing; generally firmer without a fluctuant center.
Hematoma/seroma—variable pain (depends on the cause); non-encapsulated; rapid initial growth but slow increase once full size is attained; unattached to surrounding tissues; fluctuant and fluid filled initially but more firm with the organization.
Neoplasia—variable growth; consistent; painful.
Draining Tracts
Mycobacterial disease
Mycetoma—botryomycosis, actinomycotic mycetoma, eumycotic mycetoma
Neoplasia
Phaeohyphomycosis
Sporotrichosis
Systemic fungal infection—blastomycosis, coccidioidomycosis, cryptococcosis, histoplasmosis, trichosporosis
CBC/BIOCHEMISTRY/URINALYSIS
CBC—normal or neutrophilia with or without regenerative left shift. Neutropenia and degenerative left shift if sepsis present.
Urinalysis and serum chemistry profile—depends on the system affected.
Prostatic—pyuria.
Liver and/or pancreatic—high liver enzymes and/or total bilirubin.
Pancreatic (dogs)—high amylase/lipase.
Diabetes mellitus—persistent hyperglycemia and glucosuria.
OTHER LABORATORY TESTS
FeLV and FIV—for cats with recurrent or slow-healing abscesses.
CSF evaluation—increase in cellularity and protein expected with brain abscess.
Adrenal function— evaluate for hyperadrenocorticism.
IMAGING
Radiography—soft-tissue density mass in the affected area; may reveal the foreign body.
Ultrasonography—determine if the mass is fluid-filled or solid; determine organ system affected; reveal the flocculent-appearing fluid characteristic of pus; may reveal the foreign object.
Echocardiography—helpful for diagnosis of a pericardial abscess.
CT or MRI—helpful for diagnosis of brain abscess.
DIAGNOSTIC PROCEDURES
Aspiration
Reveals a red, white, yellow, or green liquid.
Protein content > 2.5–3.0 g/dL.
Nucleated cell count—3,000–100,000 (or more) cells/μL; primarily degenerative neutrophils with lesser numbers of macrophages and lymphocytes.
Pyogenic bacteria—may be seen in cells and free within the fluid.
If the causative agent is not readily identified with a Romanowsky-type stain, specimens should be stained with an acid-fast stain to detect mycobacteria or Nocardia and PAS stain to detect fungus.
Biopsy
Sample should contain both normal and abnormal tissue in the same specimen.
Impression smears—stained and examined.
Tissue—submit for histopathologic examination and culture.
Contact the diagnostic laboratory for specific instructions.
Culture
Affected tissue and/or exudate—aerobic and anaerobic bacteria and fungus.
Blood and/or urine—isolate bacterium responsible for possible sepsis.
Bacterial sensitivity.
PATHOLOGIC FINDINGS
Pus-containing mass lesion accompanied by inflammation.
Palpable—variably firm or fluctuant mass.
Ruptured—may see pus draining directly from the mass or an adjoining tract.
Exudate—large numbers of neutrophils in various stages of degeneration; other inflammatory cells; necrotic tissue.
Surrounding tissue—congested; fibrin; a large number of neutrophils; variable number of lymphocytes; plasma cells; macrophages.
Causative agent is variably detectable.
TREATMENT
APPROPRIATE HEALTH CARE
Depends on the location of the abscess and treatment required.
Outpatient—bite-induced abscesses.
Inpatient—sepsis; extensive surgical procedures; treatment requiring extended hospitalization.
Establish and maintain adequate drainage.
Surgical removal of the nidus of infection or foreign object(s) if necessary.
Institution of appropriate antimicrobial therapy.
NURSING CARE
Depends on the location of the abscess.
Apply hot packs to the inflamed areas as needed.
Use protective bandaging and/or Elizabethan collars as needed.
Accumulated exudate—drain abscess; maintain drainage by medical and/or surgical means.
Sepsis or peritonitis—aggressive fluid therapy and support.
ACTIVITY
Restrict until the abscess has resolved and adequate healing of tissues has taken place.
DIET
Sufficient nutritional intake to promote a positive nitrogen balance.
Depends on the location of the abscess and treatment required.
CLIENT EDUCATION
Discuss the need to correct or prevent risk factors.
Discuss the need for adequate drainage and continuation of antimicrobial therapy for an adequate period of time.
SURGICAL CONSIDERATIONS
Appropriate debridement and drainage— may need to leave the wound open to an external surface; may need to place surgical drains.
Early drainage—to prevent further tissue damage and formation of abscess wall.
Remove any foreign objects(s), necrotic tissue, or nidus of infection.
Visit your veterinarian as early recognition, diagnosis, and treatment are essential.