Endoscopic mucosal resection and snare polypectomy for treatment of a colorectal polypoid adenoma in a dog.

Case Description: An 11-year-old castrated male mixed-breed dog was examined for a 3-month history of hematochezia and tenesmus. Abdominal ultrasonography and rectal examination prior to referral had revealed a colorectal polyp, diagnosed as a benign colorectal polypoid adenoma after histologic examination of tissue samples. The patient was referred for treatment.

Clinical Findings: A 2-cm-diameter sessile polypoid mass was located approximately 6 cm orad to the anus in the right dorsolateral region of the descending colon just caudal to the pubis. There was no evidence of metastasis on thoracic radiography or abdominal ultrasonography. Results of a CBC and serum biochemical analysis were within reference limits.

Treatment And Outcome: Endoscopic mucosal resection (EMR) and snare electrocautery were used to resect the mass and a definitive histopathologic diagnosis of a sessile colorectal polypoid adenoma was made. A 9.9-mm gastroduodenoscope was used during colonoscopy to inspect the mass. To aid in EMR, a 25-gauge endoscopic injection needle was used to infuse sterile saline (0.9% NaCl) solution under the base of the polyp, into the submucosa to elevate the mucosa from the muscularis layer beneath the polyp prior to polypectomy. This was necessary because of the sessile, rather than pedunculated, base of the mass. The entire polyp was successfully removed with endoscopic guidance. The clinical signs of hematochezia and tenesmus resolved immediately, and serial rectal examinations were performed over the following 36 months with no palpable evidence of recurrence.

Clinical Relevance: The patient described in the present report underwent successful colonic EMR and snare polypectomy with no known evidence of mass recurrence during the following 36 months, suggesting that this minimally invasive procedure may be a valuable treatment option for sessile polyps. The advantage of this technique was that elevation of the mucosa via injection of saline solution improved visibility of the polyp and helped to separate the polyp base from the deeper submucosal colorectal tissue, making complete resection possible.