Bicavitary septic effusion associated with staphylococcal cholecystitis in a dog.

Objective: To describe a case of concurrent septic pyothorax, peritonitis, and cholecystitis due to Staphylococcus pseudintermedius in a dog.

Case summary: A 10-year-old neutered male, medium-sized, mixed-breed dog presented with an acute abdomen. Initial investigations found the presence of a septic pyothorax, septic peritonitis, and bacterial cholecystitis. Exploratory celiotomy did not identify the source of infection, and no macroscopic communication between pleural and peritoneal space was detected. An abdominal Jackson-Pratt drain and bilateral small-bore thoracostomy tubes were placed for further management, with the dog receiving antimicrobial therapy and intensive supportive care. Subsequently, microbiological cultures confirmed scant growth of S. pseudintermedius in bile, pleural, and peritoneal fluid. The dog was discharged after 1 week of hospitalization. Antimicrobial therapy was discontinued 4 weeks after discharge due to an improvement of clinical signs and normalization of C-reactive protein concentration. A diagnosis of hyperadrenocorticism was made 6 weeks after discharge, and appropriate therapy was initiated.

New or unique information provided: Septic peritonitis and septic pyothorax are both common life-threatening conditions in veterinary medicine. To the authors' knowledge, this is the first report describing septic bicavitary effusion associated with a biliary staphylococcal infection in a dog. The exact mechanism by which the infection spread remains unclear, but hematogenous or lymphatic routes are considered the most probable. However, the presence of microscopic diaphragmatic defects and an anicteric gallbladder rupture cannot completely be excluded. The concurrent hyperadrenocorticism may have also contributed to an immunocompromised state, predisposing the dog to the development of infection.