Modified Closed Anal Sacculectomy for Adenocarcinoma

In the Literature

Davey EL, Prpich CY. Outcomes of dogs with apocrine gland anal sac adenocarcinoma treated via modified closed anal sacculectomy (2015-2022). Vet Surg. 2024;53(6):973-979. doi:10.1111/vsu.14084

The Research …

Apocrine gland anal sac adenocarcinoma (AGASACA) is a locally aggressive and metastatic tumor, with the most common metastatic site being the iliosacral lymphocenter.^1,2 Primary treatment includes anal sacculectomy and extirpation of metastatic lymph nodes.¹ Open and closed techniques for anal sacculectomy have been described. A closed technique is recommended for AGASACA because it allows removal of the anal sac without penetration of the lumen; however, the anal sac duct is not fully excised, and the portion of the duct left in situ may contribute to local recurrence.^1,3,4

This retrospective study reviewed records of 47 dogs with AGASACA that underwent anal sacculectomy via a modified closed technique. The goal of surgery was to marginally excise all anal sac tissue en bloc, including the sac and associated tumor, duct, and ductal orifice. Outcomes, including postoperative complications and local tumor recurrence rates, were evaluated.

Postoperative complications were noted in 31.9% of dogs. The most common complication was incisional dehiscence (23.4%). Other complications included surgical site infection (14.9%), transient fecal incontinence (2.1%), and diarrhea (2.1%). Forty-five dogs were available for follow-up ≥150 days after surgery. One dog (2.2%) developed local recurrence of AGASACA at 90 days. At the conclusion of the study, 42.6% of the original 47 dogs were alive. Mean survival time of confirmed deceased patients (excluding 2 dogs euthanized in the immediate postoperative period) was 521 days (range, 156-1,409 days), and median survival time was 388 days.

… The Takeaways

Key pearls to put into practice:

• Rectal examinations should be performed during routine veterinary visits, as early detection and surgical excision of anal sac masses may contribute to improved prognosis in dogs with AGASACA, regardless of surgical technique. Dogs with smaller anal sac tumors (<2.5 cm) have lower rates of metastasis, and dogs with confirmed metastatic disease have shorter disease-free intervals and decreased survival times.^4-6

• A closed or modified closed anal sacculectomy should be performed in dogs with AGASACA, with technique selection based on surgeon preference. Although complete excision of the anal sac and associated duct is a potential advantage of the modified closed technique, completeness of surgical excision has not been associated with disease-free interval or survival time, and no significant differences in local recurrence rates were found between modified closed and closed anal sacculectomy.^2,4

• A theoretical concern associated with the modified closed technique is increased risk for postoperative complications, including surgical site infection, dehiscence, and/or fecal incontinence due to close proximity of the incision and anus and increased dissection of the external anal sphincter; however, no significant differences in complication rates were noted between modified closed and closed anal sacculectomy.⁴ If a modified closed technique is used, dissection of the external anal sphincter should be minimized, and reapposition of the muscle should be ensured at the time of closure.