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Basics ⬇

Basics

Definition

An abscess is a localized collection of purulent exudate contained within a cavity.

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 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)

Genetics

N/A

Incidence/Prevalence

N/A

Geographic Distribution

N/A

Signalment

Species

Cat and dog

Breed Predilections

N/A

Mean Age and Range

N/A

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 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 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 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 abscess is not ruptured and draining.
  • Sepsis occasionally, especially if abscess ruptures internally.

Causes

  • Foreign objects.
  • Pyogenic bacteria-Staphylococcus spp.; Escherichia coli; -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 ⬆ ⬇

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 fluctuant center.
  • Hematoma/seroma-variable pain (depends on 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 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 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 affected area; may reveal foreign body.
  • Ultrasonography-determine if mass is fluid filled or solid; determine organ system affected; reveal flocculent-appearing fluid characteristic of pus; may reveal foreign object.
  • Echocardiography-helpful for diagnosis of 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; large number of neutrophils; variable number of lymphocytes; plasma cells; macrophages.
  • Causative agent variably detectable.

Treatment ⬆ ⬇

Treatment

Appropriate Health Care

  • Depends on location of 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 nidus of infection or foreign object(s) if necessary.
  • Institution of appropriate antimicrobial therapy.

Nursing Care

  • Depends on location of abscess.
  • Apply hot packs to inflamed area 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 location of abscess and treatment required.

Client Education

  • Discuss need to correct or prevent risk factors.
  • Discuss 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.

Medications ⬆ ⬇

Medications

Drug(s) Of Choice

  • Antimicrobial drugs-effective against the infectious agent; gain access to site of infection.
  • Broad-spectrum agent-bactericidal and with both aerobic and anaerobic activity; until results of culture and sensitivity are known. Dogs and cats: amoxicillin (11–22 mg/kg PO q8–12h); amoxicillin/clavulanic acid (12.5–25 mg/kg PO q12h); clindamycin (5 mg/kg PO q12h); and trimethoprim/sulfadiazine (15 mg/kg PO IM q12h). Cats with Mycoplasma and l-forms: doxycycline (5 mg/kg PO q12h).
  • Aggressive antimicrobial therapy-sepsis or peritonitis.

Contraindications

N/A

Precautions

N/A

Possible Interactions

N/A

Alternative Drug(s)

N/A

Follow-Up ⬆ ⬇

Follow-Up

Patient Monitoring

Monitor for progressive decrease in drainage, resolution of inflammation, and improvement of clinical signs.

Prevention/Avoidance

  • Percutaneous abscesses-prevent fighting.
  • Anal sac abscesses-prevent impaction; consider anal saculectomy for recurrent cases.
  • Prostatic abscesses-castration possibly helpful.
  • Mastitis-prevent lactation (spaying).
  • Periorbital abscesses-do not allow chewing on foreign object(s).

Possible Complications

  • Sepsis.
  • Peritonitis/pleuritis if intra-abdominal or intrathoracic abscess ruptures.
  • Compromise of organ function.
  • Delayed evacuation may lead to chronically draining fistulous tracts.

Expected Course and Prognosis

Depends on organ system involved and amount of tissue destruction.

Miscellaneous ⬆

Miscellaneous

Associated Conditions

  • FeLV or FIV infection
  • Immunosuppression

Age-Related Factors

N/A

Zoonotic Potential

  • Minimal for pyogenic bacteria.
  • Mycobacteria and systemic fungal infections carry some potential.

Pregnancy/Fertility/Breeding

Teratogenic agents-avoid use in pregnant animals.

Abbreviations

  • CSF = cerebrospinal fluid
  • CT = computed tomography
  • FeLV = feline leukemia virus
  • FIV = feline immunodeficiency virus
  • MRI = magnetic resonance imaging
  • PAS = periodic acid-Schiff

Suggested Reading

Birchard SJ, Sherding RG, eds., Saunders Manual of Small Animal Practice. Philadelphia: Saunders, 1994.

DeBoer DJ. Nonhealing cutaneous wounds. In: August JR, ed., Consultations in Feline Internal Medicine. Philadelphia: Saunders, 1991, pp. 101–106.

McCaw D. Lumps, bumps, masses, and lymphadenopathy. In: Ettinger SJ, Feldman EC, eds., Textbook of Veterinary Internal Medicine, 4th ed. Philadelphia: Saunders, 1995, pp. 219–222.

Author Adam J. Birkenheuer

Consulting Editor Stephen C. Barr

Acknowledgment The author and editors acknowledge the prior contributions of Johnny D. Hoskins.

Client Education Handout Available Online