Pyothorax was rare and had favorable outcomes in cats: clinical findings from 31 cases in a Swiss private practice (2018-2021).

Objective: To retrospectively describe the prevalence, clinical features, and outcomes of feline pyothorax over 3 years in a Swiss private practice.

Animals: 31 cats with pyothorax.

Clinical presentation: Cats with purulent pleural effusion and either bacterial growth from culture or intracellular bacteria on microscopic examination were identified from medical records (2018 to 2021). Data collected included signalment, clinical signs, treatment, hospitalization, and outcomes.

Results: Pyothorax was confirmed in 31 of 4,847 (0.64%) cats. Most were European shorthairs (15 of 31 cats) or Maine Coon Cats (12 of 31 cats); 17 were male. Median age was 36 months (range, 7 to 144 months), and median body weight was 4.3 kg (range, 2.8-7.5 kg). Most lived in multicat households (16 of 31 cats) and had an outdoor lifestyle (18 of 31 cats). Common owner-reported concerns included lethargy (26 of 31 cats), inappetence (23 of 31 cats), and weight loss (5 of 31 cats). At admission, tachypnea (23 of 31 cats), dyspnea (21 of 31 cats), fever (16 of 31 cats), and periodontal disease (7 of 31 cats) were frequently observed. Mixed anaerobic bacteria were identified in 19 of 31 cats. All cats received antibiotics and pleural lavage via thoracic drains; 16% (5 of 31 cats) underwent thoracotomy. Hospitalization was for a median of 7 days (range, 1 to 13 days). Survival rates were 77% (24 of 31 cats) at discharge (4 deaths, 3 euthanasia for financial constraints) and 68% (21 of 31 cats) at 3 months (1 death, 2 euthanasia due to clinical deterioration). Nonsurvivors had less pleural effusion volume drained by thoracocentesis at admission (9.6 mL/kg [range, 2.0 to 25.6 mL/kg]) compared to survivors (23.0 mL/kg [range, 1.5 to 48.8 mL/kg]).

Clinical relevance: Pyothorax was uncommon. Nonspecific signs may delay recognition, though survival was generally favorable. Lower pleural effusion volumes drained in nonsurvivors warrant further study to clarify any causal or clinical prognostic implications.