Endoscopic Polypectomy Using Endocautery in Three Dogs and One Cat
Endoscopic polypectomy has long been employed in humans with either gastric or colonic polyps. Despite the frequency of use in humans, reports in veterinary medicine remain scarce. The medical records of three dogs and one cat were reviewed. Two animals that were presented with hematochezia underwent colonoscopic polypectomy and were clinically normal 22 months and 6 months postpolypectomy. One animal that was presented with chronic vomiting underwent gastric polypectomy and was clinically normal 21 months postpolypectomy. One animal with an incidentally discovered gastric polyp underwent polypectomy without complication. Endoscopic polypectomy may be a viable alternative to surgery in veterinary patients with gastric or colonic polyps.
Introduction
Both endoscopic gastric and colonic polypectomy have been performed in humans for over 35 years, with colonoscopic and gastric polypectomy first reported in 19721 and 1973,2,3 respectively. The technique has since progressed to utilization of forceps or snares to remove polyps.4,5 Forceps are typically reserved for the removal of small polyps (≤6 mm maximum width), with the vast majority of large polyps (>6 mm maximum width) being removed with snares.4 Colonoscopic polypectomy has since been shown to be highly valuable in the prevention of colorectal carcinoma6,7 and has been described as the most effective visceral cancer prevention tool in clinical medicine.8
To date, few reports in the veterinary literature document the use of endoscopic snares and polypectomy. Use of a polypectomy snare to obtain superior biopsy specimens of the gastric antrum in horses has been reported.9 Two reports describe transanal endoscopic treatment of benign rectal tumors in dogs.10,11 These reports demonstrate the use of an electrode-cutting loop and ball-end electrode to cytoreduce rectal tumors, with cure achieved in five of 13 dogs and palliation achieved in three of 13 dogs.10,11 Electrosurgery has been reported in a small fraction of dogs with colorectal adenocarcinoma, but the procedure and instruments used were not described.12 We are unaware of any veterinary studies reporting gastroscopic or colonoscopic polypectomy using snares.
The purpose of this case series is to report the use of endoscopic polypectomy as a novel method to diagnose and treat gastrointestinal (GI) polyps in dogs and cats. Three dogs (one with a gastric polyp and two with colorectal polyps) and one cat (with a gastric polyp) were treated with this procedure at the University of Wisconsin-Madison Veterinary Medical Teaching Hospital (VMTH); we report herein the clinical presentations, treatment protocols, and outcomes.
Materials and Methods
Endoscopic polypectomy was performed on three dogs and one cat referred to the VMTH between May 2007 and October 2008. Gastroduodenoscopy or colonoscopy was performed when clinical signs or imaging findings suggested disease involving the respective region of the GI tract. When a polypoid mass was found, a clinical decision was made as to whether the mass was amenable to endoscopic polypectomy. This determination was based on the location, size, and presentation of the mass. Polypectomy was only performed on pedunculated masses and was not attempted for sessile masses. Consent for polypectomy was obtained from the owner after discussion of the procedure, including risks and complications.
The animal was shaved along the medial aspect of the thigh, and an adhesive cautery pada was placed. Endoscopic polypectomy was performed in all cases via direct visualization of the polyp and placement of an electrosurgical snareb either around the entire polyp (with tightening of the snare around the stalk) or around sections of the polyp (allowing for gradual reduction in polyp mass until a snare could encircle the stalk). A monopolar electrosurgical unitc was used to deliver electrocautery through the snare. Current was applied in a blended fashion, which included both a cutting and a coagulation waveform. Current was applied in intervals of 5 to 10 seconds or until the mass was separated from the underlying mucosa. The residual stalk was then monitored for a minimum of 60 seconds for any evidence of hemorrhage, after which the mass was retrieved for histopathology. Representative mucosal biopsies also were obtained from affected GI tract in all cases. Due to the novelty of the procedure, all animals were monitored in the hospital for 24 hours before discharge.
Results
Case No. 1
A 9.5-year-old, neutered male Labrador retriever crossbreed dog was presented to the referring veterinarian for hematochezia noted consistently at the conclusion of defecation. No tenesmus or change in stool consistency was noted, and no other abnormalities were reported by the owner. A fecal examination performed by the referring veterinarian showed coccidia oocysts and hookworm ova, and treatment with sulfadimethoxine and fenbendazole was instituted. Signs were reported to improve, but hematochezia was still noted during 30% to 50% of the dog’s bowel movements. Digital rectal examination performed 4 months after initial presentation revealed a mass approximately 5 cm orad to the anus.
The dog was referred for colonoscopy approximately 7 months after clinical signs were first noted. The only problem reported at presentation was persistent hematochezia, and physical examination was unremarkable with the exception of the rectal mass. Results of a complete blood count (CBC) showed only eosinopenia (81/μL, reference range 100 to 750/μL). All results of a serum biochemical profile were within reference ranges. Thoracic radiographs revealed no abnormalities.
Colonoscopy was performed and was unremarkable except for a 1.5 × 1 × 1-cm polyp noted 4 to 5 cm cranial to the anus on the dorsal rectal wall. The polyp appeared pedunculated, and the electrosurgical snare was passed over the polyp and tightened around the stalk. Electrocautery was applied with coagulation at 20 watts (W) and cutting at an increasing intensity, beginning at 20 W and concluding at 30 W. No hemorrhage was noted following polyp removal [Figures 1A–1C]. The polyp was successfully separated from the rectal wall, removed digitally, and submitted for histopathology along with representative mucosal biopsies from throughout the colon. The dog was monitored overnight and had multiple episodes of tenesmus with occasional drops of frank blood and soft stool, but he was otherwise stable. The dog was discharged the following morning.
Histopathology revealed a colorectal papillary adenoma, but margins were unable to be fully assessed because of tissue damage secondary to cauterization. The colonic mucosal biopsies were normal. The dog was clinically normal at home within 5 days, with normal stool and no blood evident. A mass was not palpable on rectal examination 15 months postprocedure, and no recurrence of clinical signs was seen 22 months postprocedure.
Case No. 2
A 12-year-old, neutered male domestic shorthair cat was presented to the referring veterinarian with a 6-month history of chronic vomiting and progressive weight loss. Hematemesis was noted intermittently for 4 months prior to presentation, but it resolved when the cat’s diet was switched to a canned food. Initial diagnostics performed by the referring veterinarian included a CBC, serum biochemical profile, and abdominal ultrasound. Results were within normal limits except for a decreased mean corpuscular volume (MCV; 36.1 fL, reference range 37.7 to 50.0 fL) and pyloric antral thickening with a loss of layering and bilaterally irregular renal cortical margins on abdominal ultrasound.
The cat was referred approximately 1 month later for evaluation of suspected gastric neoplasia. The owner reported increased lethargy but no other changes relative to initial presentation. Physical examination was unremarkable, with the cat having a soft and nonpainful abdomen on palpation; however, the cat had lost 0.1 kg since examination 1 month previously. A CBC indicated a low-normal hematocrit (27%, reference range 27% to 45%) and a low MCV (35.0 fL, reference range 39 to 55 fL), and all serum biochemical values were within reference ranges. Abdominal ultrasound showed a 1.5 × 2.7-cm pyloric mass, mildly thickened small intestines at 2.8 mm (normal >2.5 mm),13 and nonspecific renal cortical changes. Thoracic radiographs revealed no evidence of metastatic disease.
Gastroduodenoscopy, performed the following day, revealed a 3 × 1-cm bezoar at the pyloric antrum. Upon its removal, a polypoid structure projecting from the incisura was exposed. The mass appeared to almost completely occlude the gastric outflow tract. The remainder of the stomach appeared grossly normal, while the duodenum showed only mild erythema. Mucosal biopsies of the polypoid structure and gastric and duodenal mucosa were performed. Histopathology of the polypoid structure was consistent with a gastric polyp, while biopsies of the gastric and duodenal mucosa showed mild to moderate lymphoplasmacytic gastritis and moderate lymphoplasmacytic duodenitis, respectively.
The cat was returned approximately 3 weeks later for endoscopic polypectomy. Due to the location and size of the polyp (2 × 1.8 × 1.5 cm), it was removed in five sections using an electrosurgical snare, with cautery applied at intensities ranging from 20 to 30 W coagulation and 20 to 25 W cutting. No hemorrhage was observed endoscopically, and the snare was subsequently used to remove the individual sections from the stomach. Following endocautery, 90% to 95% of the polyp had been removed, but limitations of the endoscope precluded further removal without risking trauma to the adjacent mucosal surface. The cat was monitored overnight after the procedure. Prior to the procedure, packed cell volume (PCV) and total protein (TP) measured 23% and 7.2 g/dL, respectively. The following day, the cat was alert and had an unremarkable physical examination with no appreciable abdominal pain. Prior to discharge, PCV and TP measured 27% and 7.5 g/dL, respectively.
Histopathology of the polyp sections confirmed a hyperplastic polyp. No treatment for the gastritis or duodenitis was instituted until the cat’s clinical response could be evaluated postpolypectomy. Eight days postprocedure, the cat was reported to have had one episode of vomiting with no blood noted, but he was otherwise normal. One month postpolypectomy, the cat’s PCV and TP were 34% and 8.0 g/dL, respectively. The cat gained weight and was reported to be clinically normal with no recurrence of vomiting 21 months postpolypectomy.
Case No. 3
An 11.5-year-old, spayed female Labrador retriever was initially presented to the VMTH for evaluation of increased liver enzymes and possible hyperadrenocorticism. A serum biochemical profile showed a markedly elevated alkaline phosphatase (ALP; 2630 U/L, reference range 13 to 289 U/L) with a normal alanine aminotransferase (131 U/L, reference range 14 to 151 U/L). Abdominal ultrasound revealed a large liver mass in the left lateral lobe. Surgical removal of the left lateral lobe was performed, and histopathology of the mass identified a hepatic adenoma. Serial abdominal ultrasounds were performed in the following months to screen for evidence of recurrence, and 8 months after surgery, a mural or polypoid gastric mass (16.6 × 16.8 mm) was detected. The dog exhibited no clinical signs related to the gastric mass, and the owner elected monitoring rather than intervention. Six months later, abdominal ultrasound showed an increase in the size of the gastric mass to 20.5 × 15.2 mm, and the owner elected to proceed with gastroscopy. A preanesthesia CBC was unremarkable, with all values within reference intervals. A serum biochemical profile was normal except for an elevated ALP (692 U/L).
Gastroduodenoscopy revealed no gross abnormalities except for a 2 × 1.5 × 1-cm, pedunculated, polypoid mass located on the fundic aspect of the incisura, with no obvious occlusion of the gastric outflow tract at the time of endoscopy. The electrosurgical snare was looped over the polyp and tightened around the stalk. The polyp was removed using electrocautery with coagulation increasing from 20 to 30 W and cutting at 20 W. No evidence of hemorrhage was noted postpolypectomy, and the snare was then used to remove the polyp from the gastric lumen [Figures 2A–2C]. The polyp along with mucosal biopsies from the stomach and duodenum were submitted for histopathology. The PCV and TP prior to procedure were 45% and 6.0 g/dL, respectively. The dog was monitored overnight in the hospital, ate well following the procedure, and was discharged the following morning after PCV and TP measured 45% and 6.2 g/dL, respectively.
Histopathology of the gastric mass confirmed a polyp. The gastric biopsies indicated moderate lymphoplasmacytic inflammation and glandular atrophy, while the duodenal biopsies showed only mild lymphoplasmacytic inflammation. Because the dog had no signs of upper GI disease, no further treatment was implemented. Ultrasound performed 1 year following the polypectomy showed a mural thickening (16 mm) in the region where the polyp was previously located, but gastric wall layering appeared intact with thickening restricted ultrasonographically to the mucosal layer. Repeat gastroscopy was recommended but declined.
Case No. 4
A 5.5-year-old, neutered male Labrador retriever was presented to the referring veterinarian with a 1-month history of hematochezia; blood was noted throughout most bowel movements but was more prominent at the conclusion of defecation. Stools were reported to occasionally be soft but generally normal. No other abnormalities related to the GI tract were present. A fecal examination for parasite ova was negative, and an abdominal ultrasound revealed no abnormalities except one mildly enlarged, slightly hypoechoic, mesenteric lymph node. The dog was treated symptomatically but did not respond to treatment with sulfadimethoxine, fenbendazole, metronidazole, sulfasalazine, or prednisone. The dog was referred for colonoscopy.
Signs had been present for approximately 5 months at the time of the dog’s presentation. The owners reported no additional problems except for a recent diagnosis of superficial yeast and bacterial pyoderma. Physical examination was unremarkable except for crusting along the ventrum and inguinal area, consistent with the previous diagnosis of pyoderma. Blood was evident on the examination glove following rectal examination, but no abnormalities were palpable. A CBC, serum biochemical profile, and urinalysis all were within reference ranges. Abdominal radiographs and ultrasound were normal.
Rectal examination performed with the dog anesthetized revealed a mass 6 to 7 cm cranial to the anus. Colonoscopy was performed, and a 2 × 2 × 2-cm mass was visualized as bilobed and pedunculated in appearance. The remainder of the colonoscopy was unremarkable except for erythema and edema observed in the immediate vicinity of the mass. The polyp was encircled by the electrosurgical snare and was removed in two sections using coagulation ranging from 20 to 30 W and cutting at 20 W, with no hemorrhage noted after endocautery. The snare was used to remove the excised sections from the colon. The mass and mucosal biopsies from both the unaffected colon and the region around the mass were submitted for histopathology. The dog was monitored overnight, was noted to have mild tenesmus with soft feces and a few drops of blood in the stool, and was discharged the following morning.
Histopathology of the mucosal biopsies showed minimal change with mild goblet cell hyperplasia but no inflammation. The primary differential for the mass was a colonic polyp; however, this could not be confirmed, as the biopsy sections did not allow full visualization of the submucosa necessary to rule out adenocarcinoma.14 The owners reported a very rapid recovery within days following polypectomy, with resolution of tenesmus and hematochezia. Reevaluation 2 months following the procedure was unremarkable with a normal rectal examination. Six months postpolypectomy, the owners reported that the dog exhibited no signs of tenesmus and no recurrence of hematochezia.
Discussion
Endoscopic polypectomy is commonly utilized in human medicine, with large-scale studies reported in humans for both gastric15 and colonic polypectomy.6,7 However, few reports describe use of this technique in veterinary patients. We report successful endoscopic polypectomy in four cases. Minimal postpolypectomy complications were reported, and long-term follow-up revealed no recurrence of the clinical signs for which three of the animals initially were presented.
Two dogs underwent colonoscopic polypectomy. In both cases, the dogs were presented with histories of hematochezia but no other significant clinical signs. They were otherwise in good health on the basis of owner observation, physical examination, and clinicopathological data. Other than the polyp, colonoscopy was unremarkable in each of the two dogs; however, the entire length of the colon should be examined endoscopically, because multiple colonic masses have been documented in some dogs.12,16 The procedure was well tolerated, and the only problems noted postpolypectomy were small amounts of blood in the stool and mild to moderate tenesmus the day after the procedure. Both dogs were reported to be clinically normal within 5 days of discharge.
Surgical removal of colorectal polyps via bilateral pubic and ischial osteotomy has been reported and provides greater visualization and a larger surgical field; however, animals are not expected to ambulate normally for 2 to 3 days postoperatively.17 In this study, one dog was diagnosed with a colorectal papillary adenoma, and the other was diagnosed with the primary differential of a colonic polyp. Neither dog has shown recurrence of clinical signs 22 months and 6 months postpolypectomy.
One dog and one cat had a gastroscopic polypectomy; however, only the cat was presented with clinical signs referable to upper GI disease, including chronic vomiting, hematemesis, and weight loss. The polyp in the dog was noted incidentally during abdominal ultrasound. The procedure was well tolerated in both of these animals, with no signs of abdominal pain or vomiting noted postpolypectomy. Both animals were clinically stable and eating the following day. Both were diagnosed with gastric polyps, and the cat has shown no clinical signs of recurrence 21 months postpolypectomy. The dog did have a thickened region of the gastric wall on abdominal ultrasound 12 months postpolypectomy, but no clinical signs were evident, and repeat endoscopy was declined by the owner.
The limitations of this study include the small number of cases and the lack of repeat endoscopy in all cases. Our cases were limited partly due to the small number of animals with GI polyps that were presented to the VMTH; this is to be expected, however, because colorectal polyps do not appear to be nearly as common in dogs or cats as they are in humans.6,7,16,18–20 We only performed this procedure on animals with pedunculated polyps, and because of associated risks of perforation and hemorrhage,8 we did not attempt to perform endoscopic polypectomy in animals with sessile polyps. Perforation is a rare complication and results from thermal injury to the intestinal wall during electrocautery, but it is reported in only 0.08% of 277,434 human colonoscopies.21 Hemorrhage can occur immediately or may be delayed (up to 1 week); it is the most common complication in humans undergoing polypectomy.22 Immediate bleeding is more common when using a blended (combination of coagulation and cutting) current.23 All animals in this study had polyps removed using a blended current, but no hemorrhage was noted when the resection site was observed endoscopically for at least 60 seconds. All polyps were easily removed following endocautery by either digital extraction or use of the polypectomy snare.
Histological diagnosis was confirmed in all cases except case no. 4, but cautery application compromised polyp margins in case nos. 1 and 4, preventing biopsy confirmation of complete excision. Cautery damage into the polyp from case no. 4 prevented evaluation of the submucosa, precluding a definitive diagnosis of a colonic polyp.14
In humans, polyps are classified as neoplastic (including adenomas with or without carcinoma in situ) or nonneoplastic (including hyperplastic and inflammatory polyps).24 In humans, repeat colonoscopy is recommended in those who undergo polypectomy, and biopsies of the scar obtained 3 to 6 months postpolypectomy that show dysplasia predict the recurrence of a polyp at the resection site.24–26 Human cases in which a nonneoplastic polyp is diagnosed following polypectomy do not necessarily require subsequent colonoscopy; however, repeat colonoscopy is recommended in all humans with either undetermined or neoplastic polyps.24 Ideally, endoscopy and biopsy would have been repeated in all of the animals in our study; however, this was difficult to justify in animals without recurrent clinical signs.
Conclusion
Endoscopic polypectomy using endocautery is a viable tool for use in companion animals. If availability becomes more widespread, its use could supplant surgery for excision of certain gastric and colorectal polyps, with decreased morbidity associated with endoscopy. Further studies are needed to determine necessary long-term follow-up in veterinary patients and to document proficiency in handling more challenging sessile lesions.
Electrosurgical plate (model 30K152); 3M, St. Paul, MN 55101
Disposable electrosurgical snare (model SD-24OU-25); Olympus, Melville, NY 11747
Electrosurgical unit (model PSD-30); Olympus, Melville, NY 11747
Citation: Journal of the American Animal Hospital Association 46, 3; 10.5326/0460168
Citation: Journal of the American Animal Hospital Association 46, 3; 10.5326/0460168
Figure 1A shows the colorectal polyp visualized endoscopically in case no. 1. Figure 1B shows the polyp with the snare encircling the stalk and application of gentle traction pulling the snare away from the normal mucosa. Figure 1C shows the defect in the mucosa remaining after completion of endocautery.
Figure 2A shows the gastric polyp originating from the incisura in case no. 3. Figure 2B shows the polyp with the snare tightened around the stalk. Figure 2C shows the residual aspect of the stalk following endocautery.
