Esophageal bougienage refers to dilation of the esophagus with mechanical dilators, also known as rigid dilators, push dilators, or bougies,1,2 and has been commonly used for the treatment of BES in animals and people. The 2 main types of mechanical esophageal dilators currently available include freely passed mercury-filled bougies (eg, Maloney and Hurst dilators) and wire-guided polyvinyl (eg, Savary-Gilliard dilators) or metal olive (eg, Eder-Puestow) bougies.2,3
In 1981, the use of balloon catheters for esophageal dilation in people was described,4 and balloon dilation rapidly gained popularity with gastroenterologists, as it was thought to be safer and more efficacious than bougienage.5,6 Balloon dilators allow radial forces to be applied to an area of esophageal stenosis, whereas mechanical dilators result in progressive proximal-to-distal application of longitudinal and radial forces. Despite this difference, most randomized studies2,3 comparing the use of mechanical and balloon dilators in people have failed to show that balloon dilation was superior. Currently, both mechanical and balloon dilators are commonly used and recommended for the treatment of BES in people.2,7
In 1987, Burk et al8 described excellent outcomes following 1 to 2 episodes of balloon dilation in 6 dogs and cats with BES and concluded that balloon dilation was a superior method of treatment. Since that time, most reports9–17 describing esophageal dilation for treatment of BES in dogs and cats have been limited to use of balloon dilation, although a few reports10,18,19 have described using an endoscope tip as a mechanical dilator. Other reports20–23 refer to the use of esophageal bougienage in dogs with BES, but do not describe the dilators used, the procedure itself, or the outcome in detail. Despite a substantial cost advantage of mechanical dilation, compared with balloon dilation,7 esophageal bougienage appears to be uncommon in dogs and cats at the present time.
Gastroesophageal reflux associated with general anesthesia is reportedly the most common cause of BES in dogs and cats.10,12,14,15 However, any substantial chemical or mechanical injury to the esophageal mucosa has the potential to result in stricture formation. Esophageal strictures can be devastating for pet owners, as they can be costly to treat and associated with a poor prognosis. In previous studies,10,12,14,20 10% to 30% of affected dogs and cats died or were euthanized and 15% to 30% could only be fed liquids long term, despite multiple episodes of esophageal dilation.
The primary purpose of the study reported here was to determine outcome of bougienage for treatment of BES in dogs and cats. Secondarily, we wanted to identify risk factors associated with development of BES.
Materials and Methods
Case selection criteria—The medical records and radiology database of the North Carolina State University Veterinary Teaching Hospital were searched to identify dogs and cats examined between January 1995 and December 2004 in which a diagnosis of BES had been made. Cases were included in the study if the diagnosis of BES had been confirmed by means of esophagoscopy and the stricture had been treated by means of bougienage.
For identification of risk factors associated with development of BES, a reference population was obtained by randomly selecting, for each dog or cat with BES, 3 dogs or 3 cats admitted to the hospital on the same day as the dog or cat with BES. Reference dogs and cats were selected by the use of computer-generated random numbers from a numbered list of all dogs or cats admitted to the small animal hospital on dates corresponding to the initial examination of each dog or cat with BES. Dogs and cats with esophageal disease were excluded from the reference population.
Medical records review—Data retrieved from the medical records of dogs and cats with BES included date of admission, signalment, clinical signs at the time of admission, any history of events that occurred prior to the onset of clinical signs and could have been associated with esophageal injury (eg, general anesthesia, oral administration of drugs, vomiting, and gastrointestinal tract foreign material), physical examination findings, results of esophageal imaging (ie, radiography, fluoroscopy, and endoscopy), dates and details of all bougienage procedures, complications associated with esophageal bougienage, and outcome. Esophagoscopy images were reviewed by a single board-certified internist (SAB) for consistency in interpretation of mucosal abnormalities.
Data retrieved from the medical records of reference dogs and cats included in the study consisted of age, sex, breed, body weight, and any history of events that could have been associated with esophageal injury.
Esophageal bougienage procedure—For all dogs and cats with BES, esophageal bougienage was performed with Savary-Gilliard bougies.a Following endoscopic inspection of the stricture site, diameter of the stricture was estimated by comparison with various-sized bougies, endoscopic forceps, or the tip of a 9.8-mm gastroscope. A guide wire was then advanced down the esophagus past the stricture site, and a well-lubricated bougie was passed over the guide wire until its maximum diameter had passed the stricture site. This bougie was then removed, and a slightly larger bougie was passed over the guide wire and through the stricture site. In general, the initial bougie was selected to be the same size as or up to 2 mm larger than the estimated diameter of the stricture. Subsequent bougies were 1 to 3 mm larger than the previous bougie, and typically, 2 to 4 bougies, depending on the degree of mucosal trauma and friction encountered, were passed during each esophageal bougienage session. To avoid excessive mucosal injury, the largest bougie selected was usually ≤ 6 mm larger than the initial estimated diameter of the stricture. Bougies were typically passed blindly over the guide wire, but when possible, passage was monitored endoscopically. The esophageal mucosa was inspected following passage of each bougie, and the session was discontinued if excessive mucosal bleeding or tearing was seen. Additional esophageal bougienage sessions were recommended by the primary clinician in charge of each case as needed; additional bougienage sessions were usually recommended if the estimated diameter of the stricture site remained < 10 mm or if clinical signs persisted or recurred.
Outcome—Information on long-term outcome was obtained through a telephone questionnaire administered to owners. Owners were asked to provide information on frequency of regurgitation, consistency of food tolerated, cause of death (if known), whether they considered treatment to have been successful, and how satisfied they were with the outcome. When available, medical records were also obtained from referring veterinarians.
On the basis of information obtained from medical records and telephone questionnaires, dogs and cats with BES were categorized according to potential cause of BES (ie, general anesthesia, oral antimicrobial administration, vomiting, or trichobezoars [cats only]) and outcome following bougienage. Outcome was classified as good if the animal was able to tolerate solid food with regurgitation less than once a week and was classified as poor otherwise (eg, animal regurgitated more than once a week if fed solid or liquid food or was able to tolerate liquid food with regurgitation less than once a week). For purposes of the present study, solid food was defined as kibble, kibble soaked in water, and canned food, and liquid food was defined as any food with a consistency of gruel.
Statistical analysis—Because data for most variables were not normally distributed, the median and 5th and 95th percentiles are reported. Logistic regression was used to identify risk factors potentially associated with BES; odds ratios and 95% confidence intervals were calculated for factors significantly (P ≤ 0.05) associated with BES. Age was categorized as young (< 6 years old for dogs and < 8 years old for cats) or old (≥ 6 years old for dogs and ≥ 8 years old for cats). For dogs, body weight was categorized as small-medium (< 26 kg [58.5 lb]) or large (≥ 26 kg). The χ2 test was used to compare distributions for age, sex, body weight (dogs only), and a history of general anesthesia, vomiting, antimicrobial use (all types combined and E-lactams or enrofloxacin [dogs only]), or gastrointestinal tract trichobezoars (cats only) between animals with BES and animals in the reference population. Because of potential confounding of possible risk factors for BES (eg, a history of general anesthesia, vomiting, and antimicrobial administration), multivariate logistic regression was used to identify risk factors for BES in dogs. However, the small number of cats with BES included in the study precluded development of a multivariate model. Finally, for the dogs, the χ2 test was used to determine whether possible risk factors (eg, a history of general anesthesia, vomiting, or antimicrobial administration) or physical property of the stricture (eg, location, initial stricture diameter, and presence of concurrent esophagitis) were associated with outcome. All analyses were performed with standard software.b Values of P ≤ 0.05 were considered significant.
Results
Twenty dogs and 8 cats with BES met the criteria for inclusion in the study. The reference population consisted of 60 dogs and 24 cats without any evidence of esophageal disease.
Signalment—Of the 20 dogs with BES, 3 were of mixed breeding, with the remaining 17 representing 13 breeds (Boston Terrier, Chow Chow, Labrador Retriever, and Toy Poodle [2 dogs each] and Bulldog, Cocker Spaniel, Golden Retriever, Great Dane, Jack Russell Terrier, Old English Sheepdog, Pomeranian, Shetland Sheepdog, and Shih Tzu [1 dog each]). The 8 cats with BES included 3 domestic shorthairs, 3 domestic longhairs, 1 Manx, and 1 Tonkinese. Notably, fewer cats with BES were domestic shorthairs (3/8 [38%]) and more cats were domestic longhairs (3/8 [38%]) than cats in the reference population (19/24 [79%] and 1/24 [4.2%], respectively). Other substantial differences in breed distribution between animals with BES and animals in the reference populations were not identified. All 3 of the domestic longhair cats with BES had a history of gastrointestinal tract trichobezoars.
Age and body weight did not differ significantly between animals with BES and animals in the reference populations (Table 1). However, dogs with BES were significantly more likely to be female than were dogs in the reference population.
Age, sex distribution, and body weight of dogs and cats with BES (affected) and of dogs and cats in a reference population without evidence of esophageal disease.
| Variable | Dogs | Cats | ||
|---|---|---|---|---|
| Affected (n = 20) | Reference (n = 60) | Affected (n = 8) | Reference (n = 24) | |
| Age (y) | 6.8 (1.0–11.5) | 8.0 (0.5–16) | 4.5 (0.3–15.5) | 8.0 (2.5–17) |
| Sex | ||||
| Male | 5 (25) | 39 (65) | 5 (63) | 14 (58) |
| Female | 15 (75) | 21 (35) | 3 (37) | 10 (42) |
| Weight (kg) | 17.2 (2.0–48.0) | 22.7 (3.2–65.5) | 3.8 (1.7–4.8) | 4.4 (3.2–7.0) |
Data are given as median (5th percentile–95th percentile) or as number (%) of animals. Sex distribution differed significantly (P ≤ 0.05) between affected dogs and dogs in the reference population.
Risk factors for BES—Results of multivariate logistic regression indicated that dogs with BES were more likely to be female, have a recent history of general anesthesia, have received an antimicrobial orally, or have a history of vomiting than were dogs in the reference population (Table 2). Univariate analyses indicated that cats with BES were more likely to have a recent history of general anesthesia, vomiting, or gastrointestinal tract trichobezoars than were cats in the reference population (Table 3).
Results of univariate and multivariate logistic regression analysis of factors potentially associated with development of BES in dogs.
| Variable | Univariate analysis | Multivariate analysis | ||||
|---|---|---|---|---|---|---|
| OR | 95% CI | P value | OR | 95% CI | P value | |
| Age (y) | 1.2 | 0.4–3.3 | 0.79 | NA | NA | NA |
| Sex | 5.6 | 1.8–17.5 | < 0.01 | 46.5 | 2.4–903.5 | 0.01 |
| Weight (kg) | 1.3 | 0.4–3.8 | 0.68 | NA | NA | NA |
| History of: | ||||||
| Recent general anesthesia | 83.3 | 14.9–500 | < 0.01 | 333.3 | 15.2–1,000 | < 0.01 |
| Oral antimicrobial administration | 10.4 | 3.3–33.3 | < 0.01 | 13.0 | 1.1–166.7 | 0.04 |
| Oral administration of a β-lactam | 13.2 | 3.7–47.6 | < 0.01 | NA | NA | NA |
| Oral administration of enrofloxacin | 5.5 | 1.6–21.3 | < 0.01 | NA | NA | NA |
| Vomiting | 6.0 | 1.4–24.4 | 0.01 | 27.0 | 1.1–1,000 | 0.05 |
Analyses were performed with data for 20 dogs with BES and 60 dogs in a reference population without esophageal disease. The odds ratio represents the odds of BES among dogs < 6 years old, compared with the odds among dogs ≥ 6 years old; the odds of BES among female dogs, compared with the odds among male dogs; the odds among dogs weighing < 26 kg, compared with the odds among dogs weighing ≥ 26 kg; or the odds among dogs with a history of the factor of interest, compared with the odds among dogs without any such history.
CI = Confidence interval. NA = Not applicable (factor was not included in multivariate model). OR = Odds ratio.
Results of univariate logistic regression analysis of factors potentially associated with development of BES in cats.
| Variable | OR | 95% CI | P value |
|---|---|---|---|
| Age (y) | 3.6 | 0.6–22.2 | 0.17 |
| Sex | 0.8 | 0.2–4.4 | 0.84 |
| History of: | |||
| Recent general anesthesia | 18.2 | 2.4–149.2 | < 0.01 |
| Oral antimicrobial administration | 0.4 | 0.1–1.9 | 0.23 |
| Vomiting | 6.3 | 1.1–35.7 | 0.04 |
| Gastrointestinal tract trichobezoar | 11.0 | 1.5–83.3 | 0.02 |
Analyses were performed with data for 8 cats with BES and 24 cats in a reference population without esophageal disease. The odds ratio represents the odds of BES among cats < 8 years old, compared with the odds among cats ≥ 8 years old; the odds of BES among female cats, compared with the odds among male cats; or the odds among cats with a history of the factor of interest, compared with the odds among cats without any such history.
See Table 2 for remainder of key.
Clinical signs of BES—Median duration of clinical signs of esophageal disease prior to referral was 24 days (5th percentile, 5 days; 95th percentile, 47 days) for dogs and 19 days (5th percentile, 3 days; 95th percentile, 36 days) for cats. Reported clinical signs and physical examination findings for animals with BES included regurgitation (20 dogs and 8 cats), gagging associated with eating (11 dogs), ptyalism (9 dogs and 1 cat), exaggerated swallowing and lip licking (8 dogs and 6 cats), odynophagia (3 dogs and 2 cats), weight loss (15 dogs), coughing (7 dogs), and decreased appetite (3 dogs and 5 cats).
Causes of esophageal injury—Eighteen (90%) dogs and 5 (63%) cats with BES had undergone general anesthesia for various reasons between 1 and 17 days prior to the onset of clinical signs of esophageal disease. Procedures performed in animals that had undergone general anesthesia included abdominal surgery (8 dogs [including 3 that underwent ovariohysterectomy] and 2 cats), removal of pharyngeal or esophageal trichobezoars (4 cats, including 1 cat that underwent abdominal surgery), skin mass removal (4 dogs), aural surgery (3 dogs), and thoracic surgery, orthopedic surgery, and contrast myelography (1 dog each). Thirteen of the dogs and all 5 cats with a history of having recently undergone general anesthesia had a history of other events that might have caused esophageal injury. Only 6 of the 60 (10%) dogs and 2 of the 24 (8%) cats in the reference populations had a history of undergoing general anesthesia within 30 days prior to admission.
Two dogs and 3 cats with BES did not have any history of having recently undergone general anesthesia. However, all 5 had a history of other events that might have caused esophageal injury, including vomiting and oral enrofloxacin administration in the 2 dogs and oral doxycycline administration in the 3 cats.
Fifteen (75%) dogs and 5 (63%) cats with BES had a history of oral drug administration within 1 to 17 days prior to the onset of clinical signs of esophageal disease. Antimicrobials were administered in 14 dogs and 5 cats, including E-lactam antimicrobials (ie, cephalexin, amoxicillin, and amoxicillin-clavulanic acid) in 11 dogs and 3 cats, enrofloxacin in 7 dogs, doxycycline in 3 cats, clindamycin in 1 dog, and metronidazole in 1 dog. Six dogs and 1 cat received 2 or 3 antimicrobials at the same time. All 15 dogs and 3 of the cats with a history of oral drug administration also had a history of other events that might have caused esophageal injury. Eleven of the 60 (18%) dogs and 9 of the 24 (38%) cats in the reference populations had a history of oral antimicrobial administration within 30 days prior to admission, although none of these cats had received doxycycline.
Six (30%) dogs and 5 (63%) cats with BES had a history of vomiting prior to the onset of clinical signs of esophageal disease. Vomiting was classified as acute (1 to 12 days prior to the onset of regurgitation) in 5 dogs and 2 cats and was classified as chronic (> 3 weeks prior to the onset of regurgitation) in 1 dog and 3 cats. Small pieces of plastic or bone were identified in the vomitus from 3 dogs, whereas trichobezoars were identified in the vomitus from 4 (50%) cats. Three cats with a history of vomiting had had esophageal trichobezoars removed prior to referral for evaluation of regurgitation. Two of these cats had endoscopic evidence of esophagitis at the time of trichobezoar removal. The fourth cat had had a trichobezoar removed from its pharynx prior to referral for evaluation of regurgitation. All 6 dogs and 5 cats with a history of vomiting also had a history of other events that might have caused esophageal injury. Four of the 60 (7%) dogs and 5 of the 24 (21%) cats in the reference populations had a history of vomiting, and 2 (8%) cats had a history of vomiting trichobezoars within 30 days prior to admission.
The only other cause of esophageal stricture that was identified was esophageal surgery in 1 dog. This dog had had a BES prior to esophageal surgery, and multiple episodes of balloon dilation of the stricture at another referral hospital had failed to yield any improvement.
Diagnostic imaging—Thoracic radiographs obtained from 16 dogs and 6 cats with BES were available for review. Esophageal abnormalities were observed in 9 dogs and 4 cats and included focal esophageal gas (7 dogs and 4 cats), fluid in the caudal portion of the esophagus (2 dogs), and megaesophagus (1 dog). None of the animals had radiographic evidence of aspiration pneumonia at the time of admission.
Videofluoroscopic esophagraphy was performed in 14 dogs and 5 cats with liquid barium and barium mixed with solid food (10 dogs and 2 cats), liquid barium only (4 dogs), or iohexol (3 cats). Esophageal abnormalities were identified in 13 dogs and all 5 cats and included diffuse (5 dogs) or segmental (6 dogs and 5 cats) esophageal dysmotility, segmental esophageal dilation (7 dogs and 4 cats), and focal narrowing of contrast material suggestive of an esophageal stricture (6 dogs and 4 cats). In 1 dog, results of esophagraphy were unremarkable despite administration of liquid barium and barium mixed with solid food.
Esophagoscopy was performed in all 28 dogs and cats. A single stricture was observed in 10 dogs and 8 cats, and 2 strictures were observed in the remaining 10 dogs. The strictures were located cranial to the thoracic inlet in 2 dogs (3 strictures) and 1 cat, between the thoracic inlet and the heart base in 7 dogs (10 strictures) and 6 cats, and caudal to the heart base in 13 dogs (17 strictures) and 1 cat. Stricture diameter was estimated for the smallest or most cranial stricture when 2 strictures were present. Stricture diameter was estimated to be ≤ 5 mm in 9 dogs and 5 cats, > 5 but ≤ 9.8 mm in 7 dogs and 3 cats, and > 9.8 mm in 3 dogs (estimated stricture diameter was not reported in 1 dog). Although most strictures appeared to be < 1 cm long on endoscopic images, stricture length was not reliably reported. Irregular, hyperemic, or erosive esophageal mucosa consistent with esophagitis was detected in 10 dogs and 3 cats.
Esophageal bougienage—All 28 dogs and cats underwent bougienage at least once for treatment of the esophageal stricture, but a total of 125 esophageal bougienage sessions were performed. Median numbers of bougienage episodes were 3 (5th percentile, 1.9; 95th percentile, 10.0) for the dogs and 4.5 (5th percentile, 1.0; 95th percentile, 9.0) for the cats. Only 1 dog and 2 cats had a single esophageal bougienage session. For animals in which > 1 bougienage session was performed, treatment occurred over a median of 17 days (5th percentile, 5 days; 95th percentile, 96 days) in the dogs and 21 days (5th percentile, 13 days; 95th percentile, 77 days) in the cats, with a range of 2 to 48 days between sessions. Diameter of bougies used during the initial bougienage session ranged from 5 to 12 mm for most dogs and from 5 to 9 mm for most cats. Diameter of bougies used for the final bougienage session ranged from 9 to 15 mm for the dogs and from 9 to 12 mm for the cats. The largest bougie used was 15 mm in diameter.
Complications associated with esophageal bougienage were minimal. Two dogs developed mild aspiration pneumonia associated with regurgitation at the time of anesthetic induction. In 1 cat, pneumomediastinum developed following esophageal bougienage but a gastric trichobezoar was also removed endoscopically during this session. The cat was assumed to have an esophageal perforation. Treatment consisted of percutaneous endoscopically assisted placement of a gastric feeding tube and antimicrobial administration; the cat survived and underwent additional esophageal bougienage sessions without problems. Mucosal trauma following esophageal bougienage sessions was subjectively evaluated to be mild (no to small amount of hemorrhage) in 11 dogs and 6 cats, moderate (hemorrhage with small mucosal tears) in 2 dogs, and severe (hemorrhage with large mucosal tears) in 1 dog. Missing or poor-quality endoscopic images precluded evaluation of the severity of mucosal trauma following bougienage in 6 dogs and 2 cats.
Dogs and cats were treated with a variety of medications following esophageal bougienage, including orally administered glucocorticoids (18 dogs and 8 cats), proton pump inhibitors or H2 receptor antagonists (18 dogs and 5 cats), sucralfate (14 dogs and 4 cats), metoclopramide or cisapride (16 dogs and 4 cats), and various antimicrobials (8 dogs and 4 cats). Although standard drug dosages were used, the duration of administration was variable, ranging from 7 days to > 6 weeks. None of the dogs and cats received any glucocorticoid injections at the site of the stricture. Six dogs and 4 cats had a percutaneous gastric feeding tube placed at the time of esophageal bougienage.
Outcome—Owners of all 28 dogs and cats were successfully contacted and completed the telephone questionnaire regarding long-term outcome. Median time from the last esophageal bougienage session to completion of the questionnaire was 7 years (5th percentile, 1.6 years; 95th percentile, 10.8 years). Ten (50%) dogs and 4 (50%) cats were alive at the time the questionnaire was completed; follow-up time for these animals ranged from 1.3 to 9.6 years. Four (20%) dogs and 1 (13%) cat had been euthanized or died as a direct consequence of the esophageal disease between 3 weeks and 6 months after the last bougienage session. Continued regurgitation following 2 or 3 esophageal bougienage sessions was the reason for euthanasia of 3 of the dogs. The cat was euthanized because of continued regurgitation following 10 esophageal bougienage sessions. The fourth dog had a good outcome for 6 months following 5 esophageal bougienage sessions but died suddenly following an episode of suspected esophageal obstruction or injury characterized by an acute onset of gagging, ptyalism, and regurgitation in association with eating that led to severe respiratory distress. The remaining 6 dogs and 3 cats were euthanized for unrelated illnesses or were reported to have died of old age > 6 months after the last esophageal bougienage session.
Outcome of esophageal bougienage was classified as good in 14 (70%) dogs and 6 (75%) cats and poor in 6 (30%) dogs and 2 (25%) cats. Four of the dogs and 2 of the cats with a good outcome ate dry food (kibble), and the remaining 10 dogs and 4 cats ate canned food with minimal regurgitation (ie, regurgitation less than once a week). Seven dogs and 4 cats with minimal regurgitation when fed canned food were never fed dry food following diagnosis of a BES. Two of the dogs and 1 of the cats with a poor outcome were fed liquid food with minimal regurgitation but did not tolerate solid food. Two of the other dogs with a poor outcome regurgitated more often than once a week when fed solid food (canned food or kibble soaked in water) but were never fed liquid food. The remaining 2 dogs and 1 cat with a poor outcome regurgitated more than once a week despite being fed a liquid diet. Suspected cause of the esophageal stricture (ie, general anesthesia, antimicrobial use of any kind, or vomiting), stricture location (cranial vs caudal half of the esophagus), initial stricture diameter (d 5 vs > 5 mm), and presence of concurrent esophagitis did not differ significantly between dogs with a good versus a poor outcome.
Owners of 16 (57%) animals thought their pets were greatly improved following esophageal bougienage, owners of 9 (32%) animals thought their pets were mildly or moderately improved, and owners of 3 (11%) animals thought their pets were not improved at all. Owners of 19 (68%) animals indicated that they were overall satisfied with the outcome of esophageal bougienage, whereas owners of 6 (21%) animals indicated that they were slightly satisfied, and owners of 3 (11%) animals indicated that they were not satisfied at all.
Discussion
Results of the present study suggested that esophageal bougienage was a safe and effective treatment for naturally occurring BES in dogs and cats. Outcome was classified as good (ie, animal tolerated solid food with regurgitation less than once a week) in 14 of the 20 (70%) dogs and 6 of the 8 (75%) cats. This was similar to percentages of animals with good outcomes following balloon dilation in previous reports.12,14 In 1 study,12 16 of 22 (73%) animals tolerated solid food with only occasional regurgitation; in the other,14 14 of 19 (74%) animals tolerated solid food without regurgitation. Importantly, both of the previous studies12,14 involving balloon dilation excluded dogs and cats that were euthanized or died for various reasons, which may inflate the reported success rates. In contrast, in the present report, 3 dogs that were euthanized approximately 3 weeks following 2 to 3 esophageal bougienage sessions were classified as having a poor outcome and included in calculation of the success rate. If these 3 dogs had been excluded, the success rate would have been 82% (14/17) for the dogs. Although the outcome of esophageal bougienage in dogs and cats in the present study was similar to previously reported outcomes of balloon dilation, median numbers of bougienage sessions performed in the present report (3 for dogs and 4.5 for cats) were greater than median numbers of dilation sessions in those previous reports.12,14 Information on outcome for dogs and cats with BES published elsewhere8,10,15,20,21,23 could not be directly compared with results of the present report because there were insufficient details regarding the consistency of food tolerated to make meaningful comparisons.
In the authors' experience, it is common for veterinarians to believe that esophageal bougienage is associated with more complications (eg, esophageal perforation and diverticulum formation) than balloon dilation.8,24 However, this has not been found to be the case for people with BES,25,26 and esophageal perforation rate in the present study was low, both as a function of number of cases (1/28 [3.6%]) and as a function of number of bougienage sessions (1/125 [0.8%]). In addition, the esophageal perforation rate in the present study compared favorably with rates reported following balloon dilation in dogs and cats (3.6% to 9% on a per-case basis and 2% to 3% on a per-session basis).12,14,15 High esophageal perforation rates, however, have been reported following the use of freely passed bougies (ie, bougies that are passed without placement of a guide wire) in people with complex strictures.27 Because most dogs and cats with BES are likely to have complex strictures (ie, strictures < 12 mm in diameter and asymmetric or tortuous strictures), the use of freely passed bougies should probably be avoided in dogs and cats. Factors other than dilation method (bougienage vs balloon dilation), such as cause of the stricture, severity of esophagitis, presence of a diverticulum, operator experience, size of the dilator relative to size of the stricture and the animal, and amount of dilation pressure used, likely are important factors associated with esophageal perforation in dogs and cats. A potential explanation for the low esophageal perforation rate in the present study is the modest maximum diameter of bougies that were used (15 mm), compared with the 18- to 20-mm-diameter balloons used in previous reports.12,14,15 Less serious complications such as moderate to severe mucosal trauma (tears and hemorrhage) and aspiration pneumonia were identified in only 3 of 20 (15%) animals and 2 of 28 (7%) animals in the present study, respectively. This degree of mucosal trauma is similar to that reported following balloon dilation,12,14 and anesthetic technique, rather than the dilation procedure itself, appeared to be associated with the development of aspiration pneumonia.
An additional objective of the present study was to evaluate risk factors associated with development of BES in dogs and cats. Although signalment of and clinical abnormalities in dogs and cats with BES in the present study were largely consistent with findings reported previously,10,12,14,15,20 the comparison of affected animals with reference populations of unaffected animals allowed us to identify factors associated with development of BES. Specifically, female dogs in the present study were significantly more likely to have a BES than were male dogs. To our knowledge, only 3 other studies10,15,20 have described a predominance of females among dogs with BES, and this finding was attributed to the influences of progesterone and estrogen or to the high number of dogs that underwent ovariohysterectomy. However, few dogs had an ovariohysterectomy in the present study, and the role of female sex hormones on lower esophageal sphincter function in dogs is unknown. Furthermore, gender does not appear to be a risk factor for gastroesophageal reflux in people.28 Therefore, an explanation for the female predisposition to BES in dogs is not readily apparent at this time.
A history of recent general anesthesia was also found to be a significant risk factor for development of BES in dogs and cats in the present study. This was not surprising given the high prevalence of gastroesophageal reflux in dogs undergoing general anesthesia29,30 and numerous published reports10,12,14,15,23 linking anesthesia with BES. The prevalence of anesthesia-associated BES appears to be lower in cats than in dogs, however, and all of the cats with a history of recent anesthesia in the present study had other potential causes of BES. Because animals with a history of general anesthesia in the present study often also had a history of other potential causes of esophageal injury (eg, vomiting or antimicrobial administration), it was not possible to confirm the cause of stricture formation in many cases, and multiple factors may be important in the progression of esophageal injury to esophageal stricture formation.
Doxycycline-induced esophagitis was the suspected cause of BES in 3 of the 8 cats in the present study. However, we were not able to determine whether it was a risk factor because of the small number of cats. We suspect a causal relationship between doxycycline and esophageal stricture formation because of the close temporal relationship between drug administration and the onset of clinical signs of esophageal disease and the failure to identify another potential cause of esophageal injury in 2 of the 3 cats that received doxycycline. Although > 70 drugs have been associated with drug-induced esophagitis in people,31 as far as the authors are aware, drug-induced esophagitis and BES have only been reported for cats receiving doxycycline or clindamycin orally.9,13,32 One dog in the present study had received clindamycin orally, but this dog was also being treated with enrofloxacin and had recently undergone general anesthesia. Interestingly, oral antimicrobial administration was a significant risk factor for BES in dogs reported here. Although uncommon, ciprofloxacin and penicillin have been reported to cause esophagitis in people.31,33,34 All dogs in the present study with a history of oral antimicrobial administration prior to the onset of clinical signs of esophageal disease also had a history of other potential causes of esophageal injury. Therefore, further investigation is required to determine whether enrofloxacin or E-lactams are truly capable of inducing esophagitis and BES in dogs.
In previous studies10,12,14,15 of dogs and cats with BES, vomiting and esophageal foreign bodies were reported in up to 25% and 15% of cases, respectively. Distinguishing vomiting from regurgitation can be problematic in retrospective studies of esophageal disease, but vomiting was only recorded in the present study if it occurred prior to the onset of regurgitation and was clearly defined in the medical record. Therefore, percentages of dogs (6/20 [30%]) and cats (5/8 [63%]) with a history of vomiting reported in the present study may have been underestimates of the true percentages. Importantly, however, all of the animals with a history of vomiting also had a history of other potential causes of esophageal injury. Although none of the dogs in the present study had a history of esophageal foreign bodies, 4 of the 8 cats had a history of pharyngeal or esophageal trichobezoars. It seems likely that physical abrasion and chemical injury secondary to vomiting played an important role in mucosal damage and stricture formation in these cases. Interestingly, esophageal trichobezoars have been described in 4 other cats with BES12,15,17 and may represent an underappreciated cause of esophagitis and BES in cats. In agreement with a report35 of intestinal trichobezoar obstructions, most of the cats with trichobezoars in the present study were domestic longhairs.
Benign esophageal strictures secondary to nonpeptic causes, strictures with a particularly narrow diameter, and strictures associated with ongoing symptoms of reflux have all been associated with worse outcomes in people.7,36 In agreement with findings of a previous study,12 however, we were unable to identify any relationship between outcome and potential cause of BES, stricture location, initial stricture size, or presence of esophagitis for dogs in the present study, although the low number of cases likely inhibited our ability to detect any such effect. We chose not to evaluate potential relationships between number of bougienage sessions and physical properties of the stricture or outcome because the number of bougienage sessions did not always reflect the clinical response and was dictated to some extent by owner preferences and financial limitations.
The technique for performing esophageal bougienage described in the present report is relatively simple, other than the endoscopic skills needed, and was partially based on our experience and guidelines for esophageal bougienage in people.2 Although there remain unanswered questions as to the optimal size and number of bougies to use during any particular session, the procedure that we used appeared to be safe and effective for most of our dogs and cats. One advantage of esophageal bougienage, compared with balloon dilation, is that bougies are relatively cheap and durable, compared with balloon dilators. The Savary-Gilliard dilators used in the present study were approximately 20 years old, and the current price for a set of bougies ranging from 5 to 15 mm in diameter and a guide wire is approximately $2,000. By contrast, the current price for a disposable balloon dilator is approximately $145. Although disposable balloon dilators are meant to be single use, they can often be used several times. Regardless, both esophageal bougienage and balloon dilation appear to provide reasonable outcomes for dogs and cats with BES, and there is no evidence to support concerns that bougienage is associated with a higher risk of serious complications.
ABBREVIATION
| BES | Benign esophageal stricture |
Savary-Gilliard Dilators, Cook Endoscopy, Winston Salem, NC.
SAS, version 9.1.3, SAS Institute Inc, Cary, NC.
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