Sepsis and elevated creatinine predict poor outcomes in uncomplicated canine pyometra, and empirically prescribed antibiotics do not match bacterial susceptibility or improve survival.

OBJECTIVE: To identify variables associated with prolonged hospitalization or nonsurvival in the surgical management of pyometra in dogs and to report uterine bacterial susceptibility in comparison with empirically prescribed antibiotics. METHODS: Retrospective study of dogs that underwent ovariohysterectomy for management of pyometra at 8 tertiary referral centers between December 1, 2008, and December 31, 2023. Data collected included signalment, preoperative/operative data, antibiotic utilization, and clinical follow-up. RESULTS: 625 dogs met inclusion criteria. Forty dogs (6.4%) experienced major short-term complications, and 604 dogs (96.6%) survived to discharge. Elevated preoperative creatinine concentration and sepsis increased the risk of nonsurvival. Survival to discharge did not differ between nonseptic dogs that received pre- or intraoperative antibiotics and those that did not. Sepsis, elevated creatinine, and interaction between elevated creatinine and altered mentation increased hospitalization duration. At least 1 inappropriate outpatient antibiotic was prescribed in 34.4% (116 of 337) of cases; most dogs that received inappropriate antibiotics were empirically prescribed amoxicillin-clavulanic acid (102 of 116 [87.9%]). CONCLUSIONS: Surgical management of pyometra in the tertiary referral setting had a good prognosis regardless of prescribed antibiotic bacterial susceptibility. Elevated creatinine and/or sepsis increased risk of mortality and prolonged hospitalization. The use of pre- and intraoperative antibiotics in nonseptic dogs was not associated with outcome. CLINICAL RELEVANCE: There was no clear clinical benefit of antibiotic use in the surgical management of pyometra in nonseptic dogs. If empiric antibiotics are indicated, the bacterial susceptibility profile of this patient population suggests a high likelihood of resistance to amoxicillin-clavulanic acid.