A 1-year-old 0.62-kg (1.4-lb) spayed female ferret (ferret 1) was referred to the Cummings Veterinary Medical Center at Tufts University for evaluation of a 5-day history of vomiting. The ferret had been examined by the referring veterinarian 3 days previously when radiographs of the thorax and abdomen were obtained, and amoxicillin-clavulanic acid was prescribed to treat gastroenteritis. On initial physical examination, the ferret was alert, responsive, and afebrile; however, it was intermittently retching during handling, and slight pulmonary crackles were evident on caudal thoracic auscultation bilaterally. A CBC revealed hemoconcentration (PCV, 60% [reference range, 34.6% to 55%]; RBC count, 12.2 × 106 cells/μL [reference range, 6.77 × 106 cells/μL to 9.76 × 106 cells/μL]; and hemoglobin concentration, 20.7 g/dL [reference range, 11.9 to 17.4 g/dL]), and relative neutropenia (1.62 × 103 neutrophils/μL; reference range, 3 × 103 neutrophils/μL to 15.2 × 103 neutrophils/μL). Results of serum biochemical analyses were within reference limits. Review of the radiographs obtained by the referring veterinarian revealed a mass-like effect in the cranial portion of the thorax suggestive of esophageal foreign bodies (Figure 1).
Ventrodorsal (A) and lateral (B) radiographic images of the thorax and abdomen of a 1-year-old spayed female ferret (ferret 1) referred for evaluation of a 5-day history of vomiting. The radiographs were obtained by the referring veterinarian 3 days previously. Notice the mass evident in the region of the esophagus cranial to the heart (arrows). The provisional diagnosis was esophageal foreign body (single or multiple).
Citation: Journal of the American Veterinary Medical Association 251, 4; 10.2460/javma.251.4.451
No abnormalities were noted overnight, and the ferret was discharged the day after surgery. The owner was provided with a 10-day supply of the medications prescribed as well as instructions to monitor the ferret for any signs of dysphagia. Initially, the owner was advised to provide soaked kibble, with gradual reintroduction of hard kibble a week after discharge. No complications were reported, and the ferret was apparently doing well 2 years after initial examination.
The ferret was premedicated with oxymorphone (0.1 mg/kg [0.045 mg/lb], IM), midazolam (0.2 mg/kg [0.09 mg/lb], IM), and glycopyrrolate (0.01 mg/kg [0.0045 mg/lb], IM). General anesthesia was induced with ketamine (8 mg/kg [3.6 mg/lb], IV) and midazolam (0.4 mg/kg [0.18 mg/lb], IV). An orotracheal tube was placed, and anesthesia was maintained with delivery of 2% sevoflurane in oxygen. Heart rate, respiratory rate, an ECG, arterial oxygen saturation (measured with pulse oximetry), and end-tidal carbon dioxide concentration (measured with capnography) were monitored for the duration of general anesthesia with a multiparameter monitor.a With the ferret positioned in sternal recumbency, esophagoscopy was performed with a pediatric bronchoscope.b Two foreign bodies were identified and retrieved with endoscopic grasping forceps. Mild adjacent esophageal mucosal hyperemia was noted, but results of the esophageal examination were otherwise unremarkable. The retrieved foreign bodies were circular and rubbery and, on later discussion and examination, determined to be buttons from a remote control device. On completion of the procedure, general anesthesia was discontinued; the ferret recovered without apparent complications and was hospitalized overnight for monitoring. Prescribed treatments included omeprazole (0.7 mg/kg [0.32 mg/lb], PO, q 24 h), sucralfate (100 mg/kg [45 mg/lb], PO, q 8 h), amoxicillin (20 mg/kg [9 mg/lb], PO, q 12 h), and syringe feedingsc (15 mL/kg [7 mL/lb], PO, q 8 h; 2:1 mixture in water).
An approximately 2-year-old 1.26-kg (2.8-lb) castrated male ferret (ferret 2) was referred to the Cummings Veterinary Medical Center at Tufts University because of a 4-day history of vomiting, gagging, anorexia, and straining to defecate. Physical examination revealed wheezes in all lung fields during thoracic auscultation and mild splenomegaly on abdominal palpation. Serum biochemical analysis revealed mild hypophosphatemia (3.6 mg/dL; reference range, 4 to 8.7 mg/dL). Lateral and ventrodorsal radiographs of the thorax and abdomen obtained by the referring veterinarian showed a mild bronchial pattern and a mid-abdominal mass suspected to be enlarged mesenteric lymph nodes. The ferret underwent abdominal ultrasonography with no abnormalities detected. The owner elected medical treatment, and the ferret was discharged with instructions for 2 weeks of syringe feedingc (45 mL/kg/d [20 mL/lb/d]), amoxicillin (20 mg/kg, PO, q 12 h), metronidazole (20 mg/kg, PO, q 12 h), famotidine (0.5 mg/kg [0.23 mg/lb], PO, q 24 h), and sucralfate (80 mg/kg [36 mg/lb], PO, q 12 h) to treat a possible respiratory tract infection, enteritis, or both.
The ferret was reevaluated 2 weeks later, after the owner had noticed worsening signs of gagging and dysphagia. On physical examination, the ferret had lost 40 g (weight, 1.22 kg [2.7 lb]). The patient was sedated with acepromazine (dose unknown), and underwent positive-contrast esophagography with fluoroscopic guidance. Oral boluses of barium sulfate liquid, barium sulfate paste, and barium sulfate–coated kibble were administered to evaluate the oropharyngeal and esophageal phases of motility. No abnormalities were seen when barium liquid was administered; however, administration of both the barium paste and the barium paste–coated kibble revealed a marked circumferential decrease in the esophageal diameter at the level of C3, spanning a quarter of the length of the vertebral body (Figure 2). Orad to the stricture, the paste accumulated but was observed to pass beyond the stricture and into the distal portion of the esophagus, where motility appeared normal after multiple peristaltic movements. Mild aspiration of barium material in the cranioventral aspect of the trachea was also noted.
Fluoroscopic image of a 2-year-old castrated male ferret (ferret 2) that underwent positive-contrast esophagography because of a failure to respond to 2 weeks of medical treatment for gastrointestinal and respiratory signs. Notice the esophageal stricture (black arrow) at the level of C3 (asterisk), distal to the upper esophageal sphincter (white arrow).
Citation: Journal of the American Veterinary Medical Association 251, 4; 10.2460/javma.251.4.451
The ferret was anesthetized for esophagoscopy,b which revealed a 4-mm-diameter piece of soft rubber that was subsequently removed. The adjacent esophageal mucosa was hyperemic, and mild superficial erosions were present. During the same anesthetic episode, endoscopic balloon dilation with a 7-mm-diameter balloon was elected for treatment of the stricture. The balloon was inflated for 2 minutes and the esophagus was observed to remain patent and unobstructed after a single dilation. The ferret tolerated the procedure well, and recovered from anesthesia without any apparent complications. Postoperative treatments included syringe feeding with the patient in an upright position (45 mL/kg/d),c amoxicillin (20 mg/kg, PO, q 12 h) for 10 to 14 days, sucralfate (80 mg/kg, PO, q 6 to 8 hours) for 7 days, and omeprazole (1 mg/kg [0.45 mg/lb], PO, q 24 h until otherwise directed). The ferret was discharged the same day.
During a follow-up examination, including esophagoscopy, 1 week later, a new rubber esophageal foreign body was discovered. This was gently advanced into the stomach and retrieved endoscopically. The site of the previous stricture appeared patent, but the involved mucosa remained hyperemic and eroded. In view of the discovery of a new small foreign body, decreased esophageal motility was suspected. Therefore, metoclopramide (0.5 mg/kg, PO, q 8 h) was added to the treatment regimen in an effort to decrease esophageal sphincter tone, increase gastric emptying rate, and reduce the likelihood of gastroesophageal reflux. The importance of upright feeding of the liquid dietc followed by syringe feeding of water was emphasized to the owner as well as the need to continue the previously prescribed medications.
One week later, the ferret was again evaluated because of regurgitation of water and food. Repeated esophagoscopy indicated recurrence of the prior stricture with almost complete esophageal obstruction. The site of mucosal damage had worsened and was hyperemic with areas of ulceration, and white plaques were evident throughout the cranial two-thirds of the esophagus. On completion of the examination, a 7-mm-diameter balloon was again passed endoscopically and the affected region was dilated for 2 minutes, which completely opened the stricture. An endoscopic brush specimen of mucosa was obtained from the esophagus orad to the site of the stricture and submitted for cytologic examination. Results of this examination revealed minimal inflammation and no evidence of neoplasia. The ferret was discharged, and the owner was instructed to continue administering the previously prescribed treatments. At a follow-up visit 4 months later, the ferret's condition was greatly improved, and the client was advised to continue the omeprazole, metoclopramide, and sucralfate treatments; and maintain syringe feeding of the liquid dietc with the ferret in an upright position. The patient received the prescribed medications for 6 months, after which the owner discontinued administration. Two years later, the ferret reportedly continued to do well, ate a water-soaked kibble diet, and had an excellent quality of life according to the owner.
An approximately 2-year-old 0.8-kg (1.76-lb) castrated male ferret (ferret 3) was referred to the Matthew J. Ryan Veterinary Hospital, University of Pennsylvania, for evaluation of a possible esophageal stricture. The ferret had a recent (2-week) history of surgery for removal of a gastric foreign body, performed by the referring veterinarian. Two days after surgery, the ferret had been reexamined at the referring veterinarian's practice for vomiting or regurgitation. At that time a provisional diagnosis of an esophageal stricture was made on the basis of results of positive contrast radiography (barium sulfate liquid), and the ferret was subsequently referred for further evaluation and treatment. On initial physical examination, the ferret was hypersalivating and had greenish diarrhea. A CBC and serum biochemical analysis indicated lipemia and hemolysis, but results were otherwise within reference limits. Abdominal radiography revealed gas-distended intestinal loops consistent with the presence of a gastrointestinal foreign body or with ileus secondary to gastroenteritis. The differential diagnoses included epizootic catarrhal enteritis (ie, corona-virus infection), and the ferret was initially treated with ampicillin (20 mg/kg, SC, q 8 h), metronidazole (20 mg/kg, PO, q 12 h), ranitidine (3.5 mg/kg [1.6 mg/lb], SC, q 8 h), and sucralfate (25 mg/kg [11 mg/lb], PO, q 8 h).
General anesthesia was induced with ketamine (10 mg/kg [4.5 mg/lb], IM), butorphanol (0.1 mg/kg, IM), and midazolam (0.3 mg/kg [0.14 mg/lb], IM), followed by orotracheal intubation, and was maintained with delivery of isoflurane in oxygen. Liquid-barium fluoroscopic esophagography was performed and confirmed a diagnosis of cranial esophageal stricture. The esophageal diameter was 9 mm immediately orad to the lesion, 5 mm in the stenotic region, and 9 mm aborad to the lesion. The stricture was treated with endoscopic balloon dilation. Prednisone (0.25 mg/kg [0.11 mg/lb], PO, q 12 h) was added to the treatment plan. The ferret was hospitalized for approximately 2 weeks. During the course of postoperative care, the patient initially received crystalloid fluidsd (3 mL/kg/h [1.4 mL/lb/h], IV) until it was able to tolerate small amounts of food without signs of regurgitation. Three days after surgery, the ferret continued to regurgitate or vomit intermittently and have green diarrhea. Therefore, it was again anesthetized with the protocol as described for repeated radiography and barium fluoroscopic esophagography. These examinations revealed foreign bandage material in the esophagus orad to a recurrent esophageal stricture. The foreign material was subsequently retrieved endoscopically.
The following day, the ferret was again anesthetized, and a nitinol-covered self-expanding metallic stente was placed in the esophagus at the site of the stricture and dilated to a diameter of 4 mm under fluoroscopic guidance (Figure 3). After stent placement, the esophagus was evaluated radiographically and endoscopically. On recovery from the procedure, the ferret was noted to be lethargic, with clinical signs of dehydration and vomiting after liquid syringe feeding.f Therefore, fluids were administered SC (17 mL/kg [8 mL/lb], q 8 h) and, subsequently, IV (6 mL/kg/h [2.7 mL/lb/h]). A CBC and serum biochemical analyses revealed leukopenia and mild anemia, which were thought to have been artifactual results secondary to the requirement for placement of an IV catheter and collection of venous blood samples. The ferret received isotonic crystalloid fluids and 6% hetastarch (5 mL/kg [2.3 mL/lb], over 1 h; followed by 0.4 mL/kg/h [0.2 mL/lb/h]). Food and water were withheld for 24 hours.
Fluoroscopic, radiographic, and endoscopic images of the esophagus of an approximately 2-year-old castrated male ferret (ferret 3) referred for evaluation and treatment of a presumptive diagnosis of an esophageal stricture. The ferret had a recent (2 weeks) history of surgery for removal of a gastric foreign body. After confirmation of the diagnosis, the esophageal stricture was initially treated with balloon dilation but recurred; therefore, esophageal stenting was elected. A—Lateral radiographic image showing deployment of a nitinol-covered self-expanding metallic stent that has been deployed at the site of the stricture (dashed line) but has not yet been expanded. The guidewire (black) and endotracheal tube (arrows) are evident. B—Lateral radiographic image of the fully expanded stent. C—Endoscopic image of the stent in the esophagus at the completion of the procedure. D—Endoscopic image of the stent acquired during a recheck examination approximately 6 weeks later. Notice the epithelialization at the stent location.
Citation: Journal of the American Veterinary Medical Association 251, 4; 10.2460/javma.251.4.451
Two days after stent placement, the oral liquid dietf was reintroduced, and the volume fed was gradually increased over the next 5 days. Seven days after stent placement, IV fluid therapy was discontinued and the diet was changed to an alternative highly digestible liquid diet.c The patient was discharged on syringe feedings, with a plan to switch to soaked hard kibble after 4 weeks. Prednisone (initially, 0.25 mg/kg, PO, q 12 h, and then tapered), sucralfate (25 mg/kg, PO, q 8 h), metronidazole (20 mg/kg, PO, q 12 h), amoxicillin-clavulanic acid (12.5 mg/kg [5.7 mg/lb], PO, q 12 h), and ranitidine (3.5 mg/kg, PO, q 12 h) were continued at home. Antimicrobials were prescribed for 14 days. Six weeks after discharge, the patient was reevaluated because of recurrent vomiting. Repeated esophagoscopy showed almost complete epithelialization of the stent (Figure 3) but recurrence of the stricture at the stenting site in the original lesion location. Therefore, the stricture was balloon dilated to a diameter of 10 mm, and triamcinolone (0.09 mg) was topically applied to the affected mucosa. One month later, the ferret was examined again because of coughing and regurgitation. The ferret was fed barium-coated hard kibble, and contrast esophagography with fluoroscopic guidance was performed, which indicated dysphagia. Esophagography was then repeated with barium-coated soft food, and no dysphagia or signs of decreased esophageal motility were noted. A stricture had recurred in the same location previously treated; measurements were not obtained and the owners elected against pursuing further treatment. Three and a half months after that visit, the ferret was examined again and contrast esophagography was performed with barium-coated soft food. Signs of dysphagia were not evident; however, the stricture noted previously was still present. Therefore, the ferret was returned 1 week later for esophagoscopy under general anesthesia. Esophagoscopy revealed that the orad aspect of the stent was completely epithelialized and that the stricture was located mid-stent. Balloon dilation of the stricture to a diameter of 6 mm was performed. Subsequent telephone follow-up with the owners indicated that the patient continued to do well, eating soft food for approximately 2 years before progressing to eating solid food for the remainder of its life. The ferret died suddenly at home 5 years after treatment; the cause of death was apparently unrelated to the history of esophageal disease.
Discussion
Gastroesophageal reflux resulting in postanesthetic esophagitis is one of the most common causes of esophageal stricture in humans and small animal patients.1–4 Common diagnostic modalities used for evaluation of suspected esophageal strictures are contrast radiography (with or without fluoroscopy) and endoscopy. Treatment options include dilation with mechanical dilators or balloon dilators, placement of self-expanding stents, or surgical resection.1–3,5–13 Ferrets are notorious for consuming inappropriate objects. As such, they are highly susceptible to foreign body obstruction of the gastrointestinal tract. If ingested foreign bodies lodge in the esophagus, a ferret may be examined for clinical signs consistent with dysphagia, including regurgitation or vomiting, hypersalivation, signs of pain (eg, tachypnea and tachycardia), pawing at the mouth, and fever as a result of secondary infection. Procedures to treat esophageal foreign bodies have been reported in dogs, cats, and ferrets.5,14
Some of the most common causes of benign esophageal stricture in dogs and cats are esophageal foreign bodies, gastroesophageal reflux secondary to general anesthesia, ingestion of corrosive agents, and thermal irritation.1,2,6 Similarly, in human patients, common causes cited in the literature are gastroesophageal reflux disease, ingestion of a corrosive substance, ablation therapy, and radiation therapy.7 Blackshaw et al15 suggested that the underlying etiologic mechanisms of gastrointestinal reflux in ferrets and humans are similar, such that ferrets may be a valuable species for studying human esophageal disease. One ferret of the present report (ferret 3) had a history of recent general anesthesia for removal of a gastric foreign body, with subsequent reexamination by the referring veterinarian for initial signs of an esophageal stricture. At the time of stricture diagnosis, the differentiation between vomiting and regurgitation was not clear. The presence of these clinical signs in view of the recent anesthetic episode prompted the referring veterinarian to perform positive contrast radiography, which led to the provisional diagnosis of esophageal stricture. Results of a previous study16 suggested that in human patients, gastroesophageal reflux was more likely to occur immediately prior to extubation. In a study1 of 20 dogs and cats with benign esophageal strictures, 13 (65%) had a history of general anesthesia resulting in gastroesophageal reflux. Decreased lower esophageal sphincter tone in dogs has been reported to occur with the administration of certain drugs that are commonly part of a balanced anesthesia protocol, including atropine, isoflurane, acepromazine, and xylazine.1 As such, we suggest that these are factors that may contribute to the purported association between general anesthesia and subsequent development of esophageal stricture.
Another common condition contributing to the development of esophageal strictures is the presence of an esophageal foreign body. Foreign body ingestion resulting in clinical signs of esophageal disease is reportedly more common in ferrets < 2 years old,17 presumably because of the curious nature of these animals. In an older ferret with upper gastrointestinal signs, alternative diagnoses such as gastroesophageal reflux disease secondary to gastritis or general anesthesia may be more likely.17 For one ferret of the present report (ferret 1), an esophageal foreign body was detected with esophagoscopy, and mucosal irritation caused by the foreign body presumably predisposed the patient to development of esophageal stricture. Additionally, ferret 2 had a history suggestive of gastroenteritis 2 weeks prior to the diagnosis of esophageal stricture and an associated esophageal foreign body. Because of the concurrent diagnoses in that patient, it was unclear whether gastroenteritis, the foreign body, or both predisposed the ferret to development of an esophageal stricture. On the basis of published information for dogs,1,2,6 we speculated that both conditions were likely contributors, particularly because the esophageal musculature in both dogs and ferrets is composed of striated muscle throughout the entire thoracic length.
Contrast esophagography is the recommended diagnostic test for confirmation of esophageal lesions suggested by the results of survey radiography.18 However, it is suggested that patients should also undergo esophagoscopy as part of a complete diagnostic evaluation because this is reportedly1,2,12 the most sensitive technique for evaluating the severity of injury to the esophageal mucosa and muscularis in small animal patients.1,2,12 Esophagoscopy also allows for diagnostic evaluation, collection of biopsy specimens for histologic examination, and treatment (eg, foreign body retrieval or balloon dilation) during a single anesthetic episode.2 Nonetheless, esophagoscopy as a sole diagnostic modality is not recommended. If a patient has multiple strictures, a proximal esophageal lesion may preclude complete examination because the decreased esophageal diameter can prevent further passage of the endoscope. Contrast esophagography can be performed with liquid barium sulfate or with barium mixed with canned food or dry kibble to achieve the desired consistency for adequate imaging of the entire length of the esophagus. If fluoroscopy is available, iohexol may also be used.2,3,8,14
Treatment of esophageal strictures by means of mechanical dilation with bougienage or balloon dilation with a catheter have been described for both human and small animal patients. In human patients, both procedures are reported to be equally safe.7 Balloon dilation for treatment of esophageal strictures in small animals was first described in 1987 as an adjunct treatment for stricture, after bougienage or esophageal resection and anastomosis.8 Both veterinary2 and human patients7 may require more than 1 procedure for a successful outcome.
Plastic or metal self-expanding stents have been placed in human and small animal patients for treatment of refractory esophageal strictures.9,11,19 The present report included a description of placement of a nitinol-covered self-expanding metallic stent in ferret 3. We are not aware of previous reports of application of this treatment modality in this species. As for tracheal stenting, esophageal stenting requires fluoroscopic guidance; as such, we suggest that this procedure may be most feasible for treatment of patients in a referral hospital setting. Although we have previously successfully placed intraluminal tracheal stents in dogs with endoscopic guidance,20 we are not aware of any published reports of endoscopic esophageal stent placement, and the feasibility and safety of an endoscopically guided technique in ferrets requires further investigation.
In human patients, refractory esophageal stricture may refer to lesions that fail to remain expanded multiple attempts at mechanical or balloon dilation.10 In the present report, ferret 3 underwent only 1 dilation procedure prior to stent placement, and we speculate that repeated dilation may have resolved the stricture, as was the case for ferret 2. It has been our clinical experience when treating dogs and cats that covered stents are more likely to migrate, resulting in complications, compared with uncovered stents. Although placement of both types of stents is not particularly technically difficult for trained clinicians, because the potential complications can be severe (eg, migration and mucosal hyperplasia),9 use in veterinary patients should not be considered without risk.11 Results of a recent experimental study21 in dogs indicated that placement of iodine 125 seeds at the esophageal stent site reduced the volume of fibroblast proliferation and therefore decreased hyperplasia.
A previous report5 described a foreign body in a ferret that perforated the esophagus and was lodged in the thoracic cavity; in that patient, the diagnosis was made with radiography, endoscopy, and contrast esophagography. The ferret was treated with esophageal repair by means of open thoracotomy.5 Similar to ferret 2 of the present report, the ferret described5 subsequently developed a severe esophageal stricture that required surgical treatment. Mechanical dilation was not elected, reportedly because of the severity of the stricture. To our knowledge, endoscopic retrieval of esophageal foreign bodies in ferrets has not been described previously. In one of the patients of the present report (ferret 2), an esophageal foreign body was endoscopically advanced to the stomach and then successfully retrieved, avoiding the need for gastrotomy.
Ferrets are prone to foreign body ingestion and esophageal strictures may be a complication of treatment for such foreign bodies. Endoscopic retrieval of esophageal, and possibly gastric, foreign bodies may be a less-invasive management option for foreign body ingestion in ferrets, avoiding the need for traditional open surgery. Further investigation of the potential applications of esophageal stents for the treatment of esophageal strictures in ferrets is indicated.
Acknowledgments
Presented in abstract form at the 12th Annual Conference of the Association of Exotic Mammal Veterinarians, Indianapolis, Ind, September 2013.
Footnotes
Passport 2, Mindray, Mahwah, NJ.
60001VL Bronchoscope, Karl Storz Veterinary Endoscopy America Inc, Goleta, Calif.
Carnivore Care, Oxbow Animal Health, Murdock, Neb.
Plasmalyte, Infiniti Medical, Menlo Park, Calif.
Infiniti Medical, Menlo Park, Calif.
TwoCal HN, Abbott Nutrition, Abbott Park, Ill.
Weisse C, Berent A, Kaae J, et al. Preliminary evaluation of esophageal stenting for recurrent benign esophageal strictures in 1 ferret and 2 dogs (abstr), in Proceedings. Vet Endosc Soc Conf 2008;11.
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