Pyothorax is an umbrella term for any disease which presents with free-forming pus or multiple abscesses in the thoracic cavity.
This is a relatively infrequent presentation in dogs and commonly associated with a secondary bacterial infection.
- Penetrating chest trauma or bite wounds
- Inhaled small plant parts or migrating foreign body such as grass awn
- Necrotic pulmonary mass due to neoplasia - e.g. lymphoma
Regardless of cause, secondary infections invariably ensue and in dogs, purulent pleural effusion is usually composed of a mixture of obligate anaerobic and facultative bacteria, including:
- - Escherichia coli
- - Nocardia spp
- - Fusobacterium spp
- - Bacteroides spp
- - Actinomyces viscosus
- - Streptococcus spp
- - Staphylococcus spp
- - Clostridium spp
- - Rhodococcus equi
- - Klebsiella spp
- - Peptostreptococcus spp
- - Mycoplasma spp
- - Porphyromonas spp
- - Prevotella spp
- - Pasteurella spp
- - Propionibacterium spp
- - Pseudomonas spp
Affected dogs are usually febrile, dyspneic and lethargic. Auscultation usually reveals muffled heart sounds and moist rales over dorsal lung fields.
Diagnosis is usually determined by thoracocentesis, but radiographic findings are usually confirmatory of a suspicion, based on presenting clinical signs. Immediate bacterial/fungal cultures are required, but treatment should be commenced immediately due to the often prolonged time for culture or PCR assay determination. Thoracoscopy may assist both diagnosis and treatment.
Treatment usually requires pleural lavage via thoracostomy-tube drainage and heparin treatment or thoracostomy followed by aggressive antimicrobial agents.
Invasive (surgical) versus noninvasive treatment of pyothorax in dogs leads to a better long-term outcome in most canine patients, underlying the importance of pleural lavage as a critical part of eliminating bacteria within the pleural space. Recurrent pyothorax often leads to a poorer prognosis.
Aggressive antimicrobial therapy is indicated in most cases.
|Drug||Dosage in dogs|
|Amikacin||5–10 mg/kg IV, IM, or SC q8–12h|
|Amoxycillin/clavulanate||22 mg/kg PO q8–12h|
|Ampicillin||20–40 mg/kg IV, IM, SC, or PO q6–8h|
|Cefazolin||15–25 mg/kg IV, IM, or SC q4–8h|
|Cephalexin||25–60 mg/kg PO q8h|
|Chloramphenicol||50 mg/kg IV, IM, SC, or PO q6–8h|
|Clindamycin||5–11 mg/kg IV, IM, SC, or PO q8h|
|Enrofloxacin||5–20 mg/kg IV, IM, SC, or PO q24h|
|Erythromycin||10–20 mg/kg PO q8h|
|Gentamicin||6 mg/kg IV, IM, or SC q24h|
|Metronidazole||10–15 mg/kg IV or PO q12h|
|Penicillin G||20,000–100,000 U/kg IV, IM, SC, or PO q4–8h|
|Rifampin||10–20 mg/kg IV, IM, or PO q12–24h|
|Tetracycline||20–50 mg/kg PO q8–12h|
|Trimethoprim–sulfamethoxazole||30–60 mg/kg IV or PO q12h|
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