Introduction

Parapneumonic effusion is defined as free fluid in the pleural space in association with a simultaneous diagnosis of bacterial pneumonia. The incidence of parapneumonic effusion in human patients is reported to be 40–60%. Parapneumonic effusion has been described in dogs with pneumonia, but its incidence has not been reported. The aim of this study was to assess the incidence of parapneumonic effusion in dogs with a clinical diagnosis of pneumonia in a veterinary university clinic. The second objective was to assess the frequency of thoracocentesis and thoracic drain placement in these patients. A final objective was to evaluate the outcome of dogs with and without parapneumonic effusion.

Methods

Medical records were searched for dogs with a clinical diagnosis of bacterial pneumonia from 2017 to 2021. Clinical diagnosis was suspected on a combination of thoracic radiographs compatible with bacterial bronchopneumonia and increased serum C-reactive protein (CRP) levels. Moreover, a positive bronchoalveolar lavage culture or positive clinical evolution and decreased CRP levels in response to antibiotic therapy were required to confirm the clinical diagnosis of bacterial pneumonia. Patients diagnosed with inflammatory non-septic pneumonia, parasitic pneumonia, or neoplastic disease, were excluded.

Results

One hundred and thirty dogs were included. The incidence of parapneumonic effusion was 33,8% (44/130). In only 4 dogs (3%) a thoracocentesis was performed. Two of these dogs displayed regional effusion and thoracocentesis was performed to characterize the effusion. In the two other dogs, thoracic drains were placed after thoracocentesis due to unilateral or bilateral severe effusion. Regarding outcome, overall mortality rate was 22.3% (29/130). In dogs with parapneumonic effusion, mortality was 18.1% (8/44). One dog undergoing thoracocentesis was euthanized for financial reasons, while the 3 others survived.

Conclusion

In this single-center retrospective observational study, the incidence of parapneumonic effusion in dogs with a clinical diagnosis of pneumonia was 33,8%. Although parapneumonic effusion appeared to be rather common, it rarely required thoracocentesis or thoracic drain placement. Moreover, outcomes of dogs with or without parapneumonic effusion appeared to be similar.

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