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

• Autores: Kristin A. Coleman
• Localización: JAVMA: Journal of the American Veterinary Medical Association, ISSN-e 0003-1488, Vol. 244, Nº. 12, 2014, págs. 1435-1440
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • 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.

    A 28.1-kg (61.8-lb) 11-year-old castrated male German Shepherd Dog mix was examined because of a 3-month history of hematochezia and tenesmus. Pertinent history included treatment for Giardia and hookworms 3 months prior, a subcutaneous mast cell tumor removed from the head 2 months prior, and multiple lipoma removals over the previous 6 years. The patient was prescribed a gastrointestinal diet,a but no improvement was noted. One month after initial evaluation, abdominal ultrasonography and rectal examination were performed at the referring facility. At that time, a polypoid mass was palpated approximately 6 cm cranial to the anus within the pelvic canal. A portion of the mass was digitally removed, and histologic evaluation of the sample identified the lesion as a benign colorectal polypoid adenoma. At this time, the dog was referred to the Interventional Radiology and Interventional Endoscopy Service at the Animal Medical Center for further diagnostic testing and endoscopic polypectomy. The dog was not being administered any medications and was eating a combination of a canned and dry prescription gastrointestinal dieta with boiled white rice.

    On examination, the dog was in good body condition (body condition score, 5/9) and had multiple subcutaneous freely mobile masses that were previously diagnosed as lipomas on the basis of fine-needle aspirates. On rectal examination, the dog had a polypoid mass approximately 6 cm orad to the anus in the right dorsolateral region of the descending colon just caudal to the pubis.

    The dog was admitted to the hospital for colonoscopy and possible polypectomy. Thoracic radiographs showed a mild diffuse bronchointerstitial lung pattern consistent with normal age-related variant with no evidence of pulmonary metastatic disease. Abdominal ultrasonography was performed, and results were considered normal, with sublumbar lymph nodes appearing normal. The colonic mass was not visualized. Fecal examination for parasites and Giardia was performed and was also negative. A CBC and serum biochemical profile were performed, and all results were within reference limits.

    Serial warm water and lubrication enemas (800 to 1,000 mL/enema) were administered every 4 hours for 18 hours to allow for colonic mucosal cleansing. Following placement of an IV catheter, the dog was started on fluid therapy (3 mL/kg/h [1.36 mL/lb/h]) for 24 hours prior to anesthesia.

    The dog was premedicated with IM administration of hydromorphone (0.1 mg/kg [0.045 mg/lb], IM) and midazolam (0.25 mg/kg [0.11 mg/lb], IM), and general anesthesia was induced with propofol (3 mg/kg [1.36 mg/lb], IV). The patient was intubated, and anesthesia was maintained with isoflurane in oxygen. The dog was then positioned in left lateral recumbency. Cefoxitin (30 mg/kg [13.6 mg/lb], IV) was administered at the beginning of the procedure and was repeated every 2 hours (20 mg/kg [9 mg/lb], IV).

    A colonoscopy was performed with a 9.9-mm gastroduodenoscope.b A polypoid mass was found (Figure 1) located in the right dorsolateral region of the distal colon, as previously palpated. The mass was approximately 2 cm in diameter. Prior to polypectomy, biopsy samples were obtained endoscopically from the proximal ascending, transverse, and descending colon with a 2.8-mm endoscopic cup biopsy instrumentc during a colonoscopy examination from the ileocolic junction to the level of the rectum. No other masses were seen throughout the colon, and the visual endoscopic appearance of the colon was considered normal. Next, a 6-mm gastroduodenoscoped was inserted to the level of the polypoid mass. By use of a 2.0-mm endoscopic polypectomy devicee with a 2-cm loop, the mass was manipulated to better assess the base. Because of the broad-based, sessile nature, the snare was removed, and a 25-gauge endoscopic injection needlef was inserted through the working channel of the endoscope to aid in EMR. The needle device was primed with bacteriostatic sterile saline (0.9% NaCl) solution to remove all the air in the syringe and device. The needle was inserted under the base of the polyp into the submucosal tissue, and approximately 0.25 mL of saline solution was injected into the submucosa, creating a large enough pocket of fluid to separate the mucosa from the deeper tissue layers of the colon. This allowed the mass to become more pedunculated so that it could be resected more carefully at the base, avoiding the muscularis layer (Figures 1 and 2). The needle was then removed, and the snare device was placed around the polyp to the base of the mass, including the saline solution bleb in the submucosa. This assisted in achieving an appropriate depth of resection with EMR, while protecting the deeper tissues from thermal burn and perforation. The snare device was attached to the electrocautery unit.g With the electrocautery foot pedal, a power of 15 W was used to remove the mass at the base in the monopolar blend mode (ie, a combination of both coagulation and cutting). Caudal traction was placed on the mass with the polypectomy snare device to prevent it from touching the wall of the colon orad to the mass, which was not easily seen during the polypectomy. Snare electrocautery removed the polyp from its base, including the entire mucosa and a portion of submucosa, and the polyp was retrieved from the colonic lumen with the same snare device. Once the mass was removed, it was submitted for histologic evaluation. Colonoscopy was then repeated, confirming that there was no evidence of colonic wall perforation. With use of a 50% mixture of contrast mediumh and saline solution, a colonogram was then performed by means of fluoroscopic guidance, further confirming no extravasation or perforation. The mixture was then suctioned from the colon, and the dog recovered uneventfully from anesthesia. The total procedure time for colonic polyp resection was 30 minutes. Because of the presumptive diagnosis of chronic inflammation contributing to the formation of a colonic polyp, the dog was prescribed metronidazole (13 mg/kg [6 mg/lb], PO, q 12 h) and additional dietary fiber. The dog was discharged 4 hours after the procedure.

    View larger version(49K) Figure 1— Endoscopic images of a colonic polyp obtained during colonoscopy in an 11-year-old castrated male mixed-breed dog with hematochezia and tenesmus. Abdominal ultrasonography and rectal examination prior to referral revealed a colorectal polyp, diagnosed as a benign colorectal polypoid adenoma after histologic examination of tissue samples. A—A polypoid mass in the distal descending colon with a broad base. The mass is approximately 2 cm in diameter. An endoscopic injection needle is passed inside a safety sheath through the working channel of the endoscope prior to EMR. B—The endoscopic needle inserted under the colonic mucosa during infusion of saline (0.9% NaCl) solution created a pocket of fluid separating the mucosa from the other layers of the colon. C—After saline solution infusion, the polyp is shown to be more pedunculated. D—The snare device is placed around the base of the polyp. Via electrocautery, the mass is removed at the base. E—A nonbleeding, intact area of the colonic wall (black arrow) from which the polyp was removed is seen, and the polypoid mass is free within the lumen (black asterisk) prior to retrieval.

    View larger version(90K) Figure 2— Schematic drawing of the EMR procedure showing a sessile mass that is lifted with fluid (eg, saline solution or sterile water) at the base prior to polypectomy. (Adapted from Morris ML, Tucker RD, Baron TH, et al. Electrosurgery in gastrointestinal endoscopy: principles to practice. Am J Gastroenterol 2009;104:1563–1574. Reprinted with permission.) Histologic evaluation of the mass revealed a colonic polypoid adenoma (no features of dysplasia to suggest carcinoma) isolated to the mucosal layer and no evidence of invasion of the underlying submucosa, confirming that a full resection was accomplished. The proximal and distal colonic mucosal biopsy specimens were normal colonic mucosa.

    The hematochezia and tenesmus resolved immediately after the polypectomy. Repeated colonoscopy was recommended at 6- to 12-month intervals to assess for additional or recurrent polyp formation or transformation of the site to invasive colorectal adenocarcinoma, but this was declined. For the following 36 months, serial rectal exams were performed at 3, 6, 13, 24, 30, and 36 months by the referring veterinarian, and the dog had no clinical signs or evidence of polyp recurrence. The dog was ultimately euthanized 37 months later for metastatic hemangiosarcoma.