Evaluation of post-operative complications after mastectomy performed without perioperative antimicrobial prophylaxis in dogs

BACKGROUND: Mastectomy is the most common procedure for treatment of mammary tumours. Dogs undergoing mastectomy have a risk of developing surgical site infections (SSI) and other postoperative complications. However, potential risk factors associated with such complications have been sparsely investigated. Thus, the objective of this retrospective study was to determine the incidence of, and identify risk factors for, SSI and non-SSI postoperative complications after mastectomy performed without perioperative antimicrobial prophylaxis in privately owned otherwise clinically healthy dogs. RESULTS: Medical records were reviewed retrospectively for 135 client-owned female dogs, 10–35 kg in weight and three to 10 years of age, which had undergone mastectomy due to mammary tumours at three referral animal hospitals in Sweden over a 3-year period. Twelve (8.9%) dogs developed SSI, and 21 dogs (17.1%) dogs suffered a non-SSI postoperative complication. The incidence of SSI and all complications (SSI and non-SSI) were higher in dogs that had two to three (SSI: P = 0.036 and all complications: P = 0.0039) and four to five (SSI and all complications: P = 0.038) mammary glands excised, compared to dogs that had one mammary gland excised. The incidence of SSI was 1.7% (n = 1/60) in dogs that had one gland removed. The incidence of non-SSI postoperative complications was higher in dogs with a higher body weight (P = 0.02). CONCLUSIONS: The incidence of SSI was lower than or similar to previously reported incidences of SSI in dog populations that have undergone tumour excisional surgery, despite the fact that dogs in the present study had not received perioperative antibiotics. Dogs that had two or more glands excised had an increased risk of developing SSI and non-SSI complications compared to dogs that had one gland excised. Furthermore, higher BW was associated with an increased risk of non-SSI complications. Results from the study indicate that routine use of perioperative antibiotics in tumour excisional surgery can be questioned, at least in single gland mastectomy in otherwise clinically healthy dogs.