Transendoscopic Electrosurgery for Partial Removal of a Gastric Adenomatous Polyp in a Horse

A 9-year-old Hanoverian gelding used for hunter jumper and dressage disciplines was presented to the Colorado State University Veterinary Teaching Hospital’s Equine Medicine Service for suspected gastric ulceration. The owner reported that the horse had become more reluctant to work and had soft stool when traveling and competing over the past year. According to the owner, the horse also seemed lethargic, paced the fence line, and displayed unsocial behavior toward other horses. Physical examination was within normal limits. Gastroscopy identified a 10 9 5 9 4 cm, lobulated mass in the antrum just orad to the pylorus; no gastric ulcers were seen (Fig 1). Histologic examination of 2.5 mm diameter gastric mass biopsy specimens collected with endoscopic biopsy forceps disclosed multifocal lymophoplasmacytic gastritis with mild fibroplasia. Plasma biochemistry results included a slightly increased total bilirubin concentration of 2.9 mg/dL (reference interval, 0.4–1.8 mg/dL) and icterus 5.0 mg/L (reference interval, 1.0–3.0 mg/dL; determined by spectrophotometry) attributed to the horse being fasted, but were otherwise normal. A CBC disclosed leukopenia with a decreased nucleated cell count of 3.1 9 10/lL (reference range, 5.5–10.5 9 10/ lL), neutropenia 1.5 9 10 cells/lL (reference range, 3.0–7.0 9 10/lL), and a mildly decreased hematocrit (30%; reference range, 31–47%). Abdominal palpation per rectum and transcutaneous abdominal ultrasound examinations were within normal limits. Peritoneal fluid analysis was normal. Biopsy samples of the rectal mucosa showed mild, diffuse eosinophilic lymphoplasmacytic proctitis. The owner reported a negative fecal egg count 3 weeks before presentation. Based on the concern for further growth of the gastric mass and risk of subsequent pyloric obstruction, transendoscopic debulking was suggested. Concurrently, this procedure would allow evaluation of a larger biopsy sample, because transendoscopic biopsies of the equine gastric mucosa often yield specimens too small to adequately evaluate. The debulking procedure was performed under standing sedation using an initial dose of detomidine (14 lg/kg IV) followed by 2 additional doses of detomidine (7 lg/kg IV) and butorphanol (7 lg/kg IV) administered during the procedure. A 3 m endoscope was passed into the stomach through which an insulated polypectomy snare was passed. When the mass was visible at the level of the pylorus, the snare was looped around the base of the mass (Fig 2A). A surgical energy platform combined with patient return electrode was used to deliver monopolar electrocautery through the snare in blended cut mode at 50 W at intervals of 5–10 seconds until the mass was separated from the underlying base. The residual base then was monitored for any evidence of hemorrhage (Fig 2B), after which the mass was retrieved for histopathology with 3.5 m endoscopic grasping forceps. In this fashion, 40% of the mass was removed in multiple sections. There were challenges with loop performance at the 3 m length making minor adjustments of position difficult. We elected therefore to reevaluate the resection site the next day and remove more tissue if needed. Histopathology of 2 sections of the mass indicated an adenomatous polyp with focal surface ulceration and mild, suppurative and lymphoplasmacytic inflammation (Fig 3). The mass was well defined and unencapsulated and composed of well-differentiated, hyperplastic gastric glands lined by a single layer of tall columnar cells with small, round, basally located nuclei separated by moderate amounts of fibrovascular stroma. The differentiation of gastric adenomatous polyp from adenoma was based on the low mitotic activity, minimal cellular atypia, and glandular structures lined by only a single layer of welldifferentiated epithelial cells. The horse was given flunixin meglumine (0.9 mg/kg IV) once and sucralfate (29 mg/kg PO) q8h after the procedure. The next day, an additional 30% of the mass was resected transendoscopically using the same technique. Twenty-four hours after the initial resection, the surface of the resection site had an edematous appearance with a thin layer of yellowish fibrin covering the defect. After this second procedure, the horse again was given 1 dose of flunixin From the Department of Clinical Sciences, (Marley, Repenning, Hackett, Nout-Lomas); and the Department of Microbiology, Immunology and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO (Frank). This work was performed at the James L. Voss Veterinary Teaching Hospital at Colorado State University. None of the information presented here has been reported elsewhere. Corresponding author: Y.S. Nout-Lomas, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, 300W. Drake Road, Fort Collins, CO 80523; e-mail: Yvette.NoutLomas@colostate.edu. Submitted March 28, 2016; Revised April 19, 2016; Accepted May 4, 2016. Copyright © 2016 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. DOI: 10.1111/jvim.13979 Case Report