Journal watch13 January 2026
Author(s): A. Ylhäinen, M. Rantala, K. Thomson, T. Grönthal, J. Junnila, O. Laitinen-Vapaavuori and S. Mölsä
Published in: The Veterinary Journal
Date: September 2025
DOI: https://doi.org/10.1016/j.tvjl.2025.106449
Type of access: Open access (click for full article)
Our summary
Ylhäinen, A. et al. (2025) Placebo is non-inferior to postoperative antimicrobial treatment in uncomplicated canine pyometra – A double-blinded randomized controlled trial. The Veterinary Journal.
The aim of this randomised, double-blinded, placebo-controlled trial was to investigate whether postoperative antimicrobial therapy is necessary to prevent surgical site infections (SSIs) and urinary tract infections (UTIs) in dogs undergoing surgery for uncomplicated pyometra.
The study was performed at the Veterinary Teaching Hospital of the University of Helsinki. All dogs presenting to the hospital between June 2019 and October 2023 with a clinical diagnosis of pyometra and requiring surgical treatment were assessed for eligibility. Exclusion criteria included complicated pyometra, underlying disease or concurrent medications which would increase infection risk, body weight under 3 kg or over 94 kg, and known sensitivity to sulphonamides. After the criteria were applied, 153 dogs were eligible for the trial, which were then randomly assigned to the placebo group (76) or the active control group (77).
The study protocol, based on Finnish guidelines and surveillance data, included a single dose of intravenous sulfadoxine-trimethoprim (SXT) administered to all dogs prior to incision. After surgery, dogs received either peroral placebo or active control (SXT) twice daily for 5 days.
Preoperative patient history was collected from owners via a standardised questionnaire form and recorded alongside physical, ultrasonographic, and laboratory findings from the initial visit. Intraoperative details such as surgical technique were documented using standardised forms, and urine and uterine specimens were collected. Following surgery, owners were instructed to monitor their dogs for signs of SSIs, UTIs, or potential drug-related adverse events. A follow-up visit was scheduled 12 days post-surgery, where the dogs were assessed for signs of SSI or suture reaction, and culture specimens were collected for patients with suspected SSI or UTI. An interview was conducted with the owners 30 days post-surgery, with any reported signs of ongoing infection leading to another follow-up appointment and assessment by a veterinarian.
Results indicated no signs of inferiority between the placebo treatment and the active control (SXT) treatment. Among the eight dogs with confirmed SSIs within 30 days, two were in the placebo group and six in the active control group. Of the urine specimens collected at the 12-day follow-up from the 43 dogs with documented perioperative bacteriuria, 16 samples yielded bacterial growth (14 placebo, two active control), but only two dogs exhibited clinical signs of UTI, both dogs in the active control group. Postoperative signs of illness were reported in 51 dogs, with similar rates in both groups (24 placebo, 27 active control).
A limitation of this study is the reliance on owner compliance for drug administration which, despite monitoring via owner questionnaires and tablet counts, cannot be fully verified. Other limitations include the choice of antibiotic treatment, as SXT is not commonly used as a perioperative antimicrobial in dogs in the UK.
Take home
This study suggests that no longer prescribing postoperative antibiotic therapy following uncomplicated canine pyometra would not affect clinical outcomes. This conclusion is useful for clinicians looking to limit antimicrobial usage in their practice.
The following may also be of interest
Journal watch: Postoperative complications and antibiotic use in dogs with pyometra: a retrospective review of 140 cases (2019). [RCVS Knowledge] [Online] Available from: https://www.rcvsknowledge.org/resource/postoperative-complications-and-antibiotic-use-in-dogs-with-pyometra-a-retrospective-review-of-140-cases-2019/ [Accessed 13 January 2026]
Allerton, F. et al. (2025) European Network for Optimization of Veterinary Antimicrobial Therapy (ENOVAT) 2025 guidelines for surgical antimicrobial prophylaxis in dogs and cats. Journal of Small Animal Practice. https://doi.org/10.1111/jsap.70072
Evidence collection: Responsible use of antibiotics in veterinary practice. [RCVS Knowledge] [Online] Available from: https://www.rcvsknowledge.org/resource/responsible-use-of-antibiotics-in-veterinary-practice/ [Accessed 13 January 2026]
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