Radical surgical excision of extensive perianal melanomas on standing horses: Twenty cases.

Objective: To report a radical surgical technique for perianal melanomas involving the anal margin in standing horses.

Study design: Observational retrospective study.

Sample population: Twenty client-owned horses presented for surgical excision of extensive (≥4 cm) perianal melanomas.

Methods: Demographic data, surgical technique, intraoperative, immediate- and late-postoperative complications were reviewed.

Results: All horses (median age 15, Q1-Q3 12 to 17.3 years) were operated under standing sedation and epidural anesthesia. Median hospitalization period was 6.5 days (Q1-Q3 5 to 8.3 days). The anal margin was fully resected in 14 cases. A deep perirectal dissection was performed in 16 cases. Eight cases required additional local anesthetics. One case bled profusely during and after the procedure. One case became recumbent during the procedure, showed intense postoperative pain, and was eventually euthanized 6 weeks later because of ataxia. During hospitalization, one horse displayed colic signs and 10 others required manual evacuation of the rectum because of decreased fecal output. Complications after hospital discharge included mild colic signs (n = 4), partial wound dehiscence (n = 1) and hypergranulation of the wound (n = 2). All other cases healed without complications in 6 to 12 weeks. Median follow-up period was 11.8 months (Q1-Q3 6.3 to 27.2 months). Six horses developed new melanomas with only one in the perianal region.

Conclusion: This technique of surgical excision of extensive perianal melanomas was efficiently performed on standing horses with minimal local recurrence. This procedure led to high client satisfaction. Early postoperative pain was commonly encountered. Owners should be warned of the potentially large surgical wound that will be created.

Clinical significance: This technique allowed for removal of large perianal melanomas with limited recurrence during the long term follow up and may improve the quality of life of affected horses.