CT Reveals Key Indicators for Survival in Feline Pyothorax Cases

CT features and short-term outcome in cats presenting with pyothorax

Ines Lopes Rei, Emilie Paran, Helen Wilson, Mariette Pilot, Alison Catherine Major

Background

Feline pyothorax, characterized by purulent pleural effusion, is a life-threatening condition requiring complex management. Despite clinical experience, the optimal treatment approach remains debated, and the diagnostic utility of CT imaging in affected cats is under-explored. Prior studies have described CT features in dogs with pyothorax, but no such comprehensive data existed for feline cases, highlighting the need for species-specific diagnostic characterization and outcome evaluation.

Methods

This retrospective, descriptive study evaluated CT findings and short-term outcomes in 41 cats diagnosed with pyothorax and presented to a referral hospital between 2012 and 2023. Diagnosis was confirmed via cytology or positive culture of pleural fluid. CT scans were reviewed blindly by two board-certified radiologists and a radiology resident, assessing predefined features such as pleural changes, pneumonia, lymphadenomegaly, and foreign body suspicion. Clinical data, treatments (medical vs. surgical), and outcomes (survival to discharge and hospitalization length) were analyzed.

Results

All 41 cats had pleural effusion, mostly bilateral (88%). Common CT findings included pleural thickening (85%), pannus formation (81%), and thoracic lymphadenomegaly (85%). Pneumonia was suspected in 49% of cases, while pulmonary abscesses were seen in 22%. Foreign bodies were suspected in 12%, with histological confirmation in two surgical cases. Pneumothorax occurred in 73% of cats, often associated with pre-CT interventions. Treatment was evenly split between medical (20) and surgical (21, including one converted case). Survival to discharge was high (88%), with no significant difference between treatment groups. Median hospital stay was 7 days.

Limitations

The retrospective nature and lack of standardized treatment protocols may limit the generalizability of findings. Timing of CT scans varied, and not all imaging findings were histopathologically confirmed. The study also lacked long-term follow-up and could not assess recurrence or survival beyond discharge. CT reviewer interpretations were subjective, and clinical decision-making context was not fully captured.

Conclusions

CT imaging in feline pyothorax reveals consistent thoracic abnormalities, including pleural effusion, thickening, pannus, and lymphadenomegaly. Pneumonia and abscessation are frequent findings, though foreign bodies are uncommon and may be missed by imaging alone. Despite variable presentation, both medical and surgical treatments are associated with favorable short-term outcomes. These findings support the use of CT as a valuable diagnostic tool in feline pyothorax and underscore the need for further studies linking imaging features with long-term prognosis and treatment decision-making.

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