Factors influencing complications following mastectomy procedures in dogs with mammary gland tumors: 140 cases (2009-2015).

OBJECTIVE

To evaluate complication rates for various types of mastectomy procedures, identify factors associated with an increased risk of complications, and determine the consequences of such complications.

ANIMALS

140 female dogs that underwent 154 separate mastectomy procedures to treat mammary gland tumors.

PROCEDURES

Medical records of dogs in the Penn Vet Shelter Canine Mammary Tumor Program from July 2009 to March 2015 were reviewed. Data regarding signalment, tumor characteristics (ie, number and size, benign or malignant, and bilateral or unilateral), mastectomy type, anesthesia time, concurrent ovariohysterectomy or ovariectomy, surgeons' qualifications, antimicrobial administration after surgery, postoperative placement of surgical drains, and complications (seroma, abscess, dehiscence, or infection) were collected. Complications that required hospitalization were recorded. Fisher exact tests were used to evaluate associations between variables of interest and complications. Multivariable analysis was used to identify factors independently associated with an increased risk of complications.

RESULTS

Complication rate following all mastectomy procedures was 16.9% (26/154); of these, 9 (34.6%) required hospitalization. High body weight, undergoing bilateral mastectomy, and postoperative antimicrobial administration were associated with significantly increased odds of complications. The odds of complications associated with postoperative antimicrobial administration, however, varied according to mastectomy type; dogs undergoing chain mastectomy that did not receive antimicrobials postoperatively had the highest odds of developing complications. Dogs undergoing concurrent ovariohysterectomy or ovariectomy had significantly decreased odds of complications.

CONCLUSIONS AND CLINICAL RELEVANCE

Previously spayed dogs with a large body size that underwent the most extensive mastectomy procedures had increased odds of having postoperative complications.