A retrospective and prospective study of megaesophagus in the parma wallaby (Macropus parma) at the San Diego Zoo, California, USA

At the San Diego Zoo (California, USA), 22 cases of megaesophagus were diagnosed in the parma wallaby (Macropus parma), yielding a prevalence of 21.1%. Parma wallabies often have no clinical signs until severe and chronic dilation of the esophagus is present. Clinical signs of advanced disease include weight loss, swelling of the cervical region, regurgitation without reswallowing of ingesta, short flight distance, depression, collapse, dyspnea, and sudden death. Retrospective and prospective studies at the San Diego Zoo and a multi-institutional survey in the United States were used to try to determine the cause of megaesophagus. The retrospective study did not identify an etiology. The prospective study revealed megaesophagus and severely delayed esophageal transit time in eight of eight animals. Myasthenia gravis, lead toxicosis, toxoplasmosis, and thyroid disease were eliminated as possible causes. Of 286 living and dead parma wallabies surveyed at other institutions, three cases of esophageal diverticulum and one case of megaesophagus were reported. The cause of megaesophagus in parma wallabies was not determined.     

A retrospective and prospective study of megaesophagus in the parma wallaby (Macropus parma) at the San Diego Zoo, California, USA

At the San Diego Zoo (California, USA), 22 cases of megaesophagus were diagnosed in the parma wallaby (Macropus parma); a prevalence of 21.1%. Parma wallabies often have no clinical signs until severe and chronic dilation of the esophagus is present. Clinical signs of advanced disease include weight loss, swelling of the cervical region, regurgitation without reswallowing of ingesta, short flight distance, depression, collapse, dyspnea, and sudden death. Retrospective and prospective studies at the San Diego Zoo and a multi-institutional survey in the United States were used to try to determine the cause of megaesophagus. The retrospective study did not identify an etiology. The prospective study revealed megaesophagus and severely delayed esophageal transit time in eight of eight animals. Myasthenia gravis, lead toxicosis, toxoplasmosis, and thyroid disease were eliminated as possible causes. Of 286 living and dead parma wallabies surveyed at other institutions, three cases of esophageal diverticulum and one case of megaesophagus were reported. The cause of megaesophagus in parma wallabies was not determined.     

Esophageal hiatal hernia and megaesophagus complicating tetanus in two dogs

Two dogs with tetanus developed transient megaesophagus and hiatal hernia associated with gastroesophageal reflux and regurgitation. The megaesophagus and hiatal hernia were diagnosed radiographically and resolved with resolution of the tetanus. These 2 cases, plus previously reported cases, indicate that tetanus can cause megaesophagus and esophageal dysfunction. Therefore, thoracic radiography should be included as part of the diagnostic evaluation of dogs suspected of having tetanus.     

Belt loop gastropexy in the management of gastroesophageal intussusception in a pup.

Gastroesophageal intussusception and megaesophagus were diagnosed in a 5-week-old German Shepherd Dog. Exploratory surgery was performed, and belt loop gastropexy was used to maintain proper gastric position after manual reduction of the intussusception. The pup survived surgery and was clinically normal when it was 6 months old. Follow-up contrast radiography revealed resolution of the megaesophagus and apparent permanent gastropexy. Previous reports have indicated extremely high mortality for gastroesophageal intussusception, and resolution of megaesophagus in the dog is unusual.     

Electromyographic and esophagomanometric findings in clinically normal dogs and in dogs with idiopathic megaesophagus.

Electromyography of 12 clinically normal dogs and 7 dogs with idiopathic megaesophagus revealed trains of positive sharp waves in the muscles of facial expression and in the lingual muscles of both groups. Positive waves are usually indicative of motor-unit disease; however, they are clinically insignificant in these muscles. Positive sharp waves were detected in the esophageal muscle of one dog with congenital megaesophagus. Esophageal electromyograms obtained in a dog with congenital megaesophagus and in 2 clinically normal dogs were normal. Resting caudal esophageal sphincter pressure was similar in both clinically normal dogs (mean, 22.3 mm of Hg; range, 15--37 mm of Hg) and in dogs with congenital or acquired idiopathic megaesophagus (mean, 29.6 mm of Hg; range, 20--50 mm of Hg).     

Esophageal obstruction in horses: a retrospective study of 34 cases

The major purpose of this investigation was to describe the causes, possible complications, and prognoses of horses with esophageal obstruction. Of 34 cases presenting with esophageal obstruction, 28 cases were due to impaction of ingesta. Obstruction due to pre-existing esophageal disease occurred in 4 horses with megaesophagus, in 1 horse with stricture in the upper third of the esophagus, and in 1 horse with esophageal diverticulum. There was no significant difference in the contamination of the trachea between horses that subsequently developed aspiration pneumonia and those that did not. The duration of esophageal obstruction prior to admission was significantly longer in horses that developed aspiration pneumonia (median 18, range 2-48 h) than in those horses that did not (median 4, range 0.5-48 h). Although the obstruction was relieved in all 34 horses, 4 were euthanized because of recurring obstruction due to megaesophagus (n = 2), esophageal diverticulum (n = 1), and esophageal stricture (n = 1).     

Esophageal dysmotility in young dogs

BACKGROUND: Abnormal esophageal motility can exist without megaesophagus, although its prevalence in dogs is unknown and its cause has not been elucidated. HYPOTHESIS: Esophageal dysmotility without overt megaesophagus exists in both symptomatic and asymptomatic young dogs, and motility can improve with age. ANIMALS: Dogs examined at the Department of Veterinary Medicine, University of Cambridge for regurgitation, but without evidence of megaesophagus on radiographs, and a further group of asymptomatic dogs. METHODS: Dogs underwent an initial and a repeat videofluoroscopic swallowing study. Images were reviewed and 5 criteria of esophageal motility evaluated. RESULTS: Eight affected dogs were identified (median age 9 months), and terrier dogs predominated (6 terriers of 3 breeds). Esophageal motility was reduced either globally (n = 3) or segmentally (n = 5). Repeat examination at a median of 3 months revealed that regurgitation had reduced or resolved in the majority of terrier dogs, and 4 of 6 cases demonstrated an improvement in esophageal motility. Videofluoroscopic evaluation of young (median age 11 months) asymptomatic dogs of various breeds (n = 22) revealed evidence of esophageal dysmotility in 4 of 5 control terrier dogs. Repeat evaluation demonstrated an improvement in esophageal motility in 3 dogs. CONCLUSION AND CLINICAL IMPORTANCE: Esophageal dysmotility without overt megaesophagus occurs in young terrier dogs, and affected animals can be symptomatic or asymptomatic. Further, an improvement in esophageal motility occurs with time in some dogs, and might represent a syndrome of delayed esophageal maturation.     

Surgical diseases of the esophagus

The diagnosis and management of surgical diseases of the esophagus are discussed. Esophageal foreign bodies, strictures, esophagobronchial fistulas, diverticula, gastroesophageal intussusception, hiatal hernias, and megaesophagus are included in the discussion.     

Bronchoesophageal fistula and transient megaesophagus in a dog

Bronchoesophageal fistula and megaesophagus were diagnosed in a dog. Within 2 days after surgical correction of the bronchoesophageal fistula, peristalsis in the thoracic portion of the esophagus returned to normal and the esophagus resumed its normal size. The cause of the fistula was attributed to damage from a foreign body. The cause of the transient megaesophagus likely was related to the bronchoesophageal fistula.     

Megaesophagus in two cats

Megaesophagus was diagnosed in 2 cats. Both had a history of regurgitation, and one was dyspneic. Radiography of the thorax and abdomen revealed generalized megaesophagus and gastric distention with gas. There was no esophageal motility during fluoroscopic observation. The prognosis for cats with megaesophagus is guarded. Although they may be satisfactory pets, cats with this condition should not be used for breeding because the condition is believed to be inherited through recessive genes.     

Pneumonia after intracranial surgery in dogs

OBJECTIVE: To determine factors associated with the occurrence of pneumonia after intracranial surgery in dogs. STUDY DESIGN: Retrospective cohort study. Animals-Forty-nine client-owned dogs. METHODS: The medical records of 49 dogs with space-occupying intracranial disease that underwent craniotomy were reviewed. Development of pneumonia after surgery was considered highly likely in 12 dogs (affected dogs) based on clinical signs, including acute dyspnea or coughing in association with typical radiographic findings or abnormal transtracheal wash results. Pneumonia was confirmed in 6 dogs based on necropsy findings. Affected dogs were compared with 37 dogs that did not develop pneumonia (unaffected dogs) subsequent to intracranial surgery. Based on the medical records of affected dogs, determinations were made regarding time between development of pneumonia and surgery, surgical procedure, intracranial lesion type, and intracranial lesion location. Risk factors examined for both affected and unaffected dogs included level of consciousness, body position during the postoperative recovery period, duration of anesthesia, occurrence of vomiting or regurgitation, presence of seizures, cranial nerve deficiencies, and the presence of megaesophagus before and after surgery. We also compared the feeding protocol after surgery for each group. RESULTS: Pneumonia typically occurred within the first week after surgery (median, 6.5 days); however, this was variable (range, 1-96 days). Of the factors that were present within 24 hours before the clinical signs of pneumonia, vomiting or regurgitation and megaesophagus were found to be significant risk factors. Dogs that vomited or regurgitated were 2.71 times more likely to develop pneumonia than dogs that did not. Vomiting or regurgitation occurred in 63% of the dogs that developed pneumonia in this cohort. Dogs with megaesophagus were 9.25 times more likely to develop pneumonia than dogs without megaesophagus. Seven dogs with pneumonia died. Five of these 7 dogs appeared to have died as a direct sequel to pneumonia. CONCLUSION: Dogs undergoing craniectomies for space-occupying intracranial disease may be at higher risk for development of pneumonia due to several factors, including vomiting, regurgitation, and megaesophagus.     

Acquired Myasthenia Gravis

Serum samples from 152 dogs with a clinical diagnosis of idiopathic megaesophagus without detectable generalized muscle weakness were tested for the presence of antibodies to acetylcholine receptors by immunoprecipitation radioimmunoassay. Positive serum antibody titers (mean, 3.1 nmoL/L; range, 0.77-30 nmoL/L; reference values less than 0.6 nmoL/L) were found in 40 dogs (26%), with German Shepherd dogs (8/25, 32%) and Golden Retrievers (7/20, 35%) having a greater percentage of positive submissions. By immunocytochemical methods, localization of immune complexes at the neuromuscular junction after incubation of serum with normal canine muscle was documented in an additional 17 cases (11% of all samples submitted) that did not have increased antibody titers to acetylcholine receptors. Of the 40 seropositive dogs, 17 (48%) had a clinical improvement or remission of clinical signs associated with decreasing AChR antibody titers. Idiopathic megaesophagus has been associated with a poor prognosis; however, this study demonstrates that a large percentage of the dogs have myasthenia gravis and that with supportive treatment, the clinical signs may improve or resolve.     

A review of hereditary diseases of the German shepherd dog

The German shepherd dog (GSD) is a preferred choice of many law enforcement and military agencies across the world. Unfortunately, the breed is afflicted with approximately 50 hereditary diseases. Seven major diseases afflicting the GSD are described herein: pancreatic acinar atrophy, megaesophagus, hip dysplasia, degenerative myelopathy, hemophilia A, von Willebrand disease, and hereditary multifocal renal cystadenocarcinoma and nodular dermatofibrosis. Also included is a discussion of behavior, a characteristic thought to be inherited in the dog and often problematic in larger breeds such as the GSD. Current clinical and genetic research efforts pertaining to these diseases are reviewed.     

Risk factors for acquired myasthenia gravis in cats: 105 cases (1986-1998)

OBJECTIVE: To determine prevalence of initial clinical signs and risk factors for acquired myasthenia gravis (MG) in cats. DESIGN: Retrospective case-control study. ANIMALS: 105 cats from the United States, Canada; and the United Kingdom with a confirmed diagnosis of acquired MG and 510 cats with other neuromuscular disorders, including generalized weakness, megaesophagus, and dysphagia (control group). PROCEDURES: Records were retrieved from a data-base containing results of serum samples tested for acetylcholine receptor antibodies. Signalment, including breed, age, and state or country of origin, month of onset, and initial clinical signs were obtained. An acetylcholine receptor antibody titer > 0.3 nmol/L was diagnostic for acquired MG. Unconditional logistic regression was used for statistical analysis. RESULTS: Compared with mixed-breed cats, the breed with the highest relative risk of acquired MG was the Abyssinian (including Somali). Significant differences between sexes were not detected. There was no compelling evidence for a difference in risk of developing MG between states or countries. Relative risk increased after 3 years of age. The most common clinical signs were generalized weakness without megaesophagus and weakness associated with a cranial mediastinal mass. Focal signs, including megaesophagus and dysphagia without signs of generalized weakness, were also evident. CONCLUSIONS AND CLINICAL RELEVANCE: A breed predisposition for acquired MG in Abyssinians (and related Somalis) was observed. Clinical signs were variable and included generalized weakness, megaesophagus, and dysphagia. A cranial mediastinal mass was commonly associated with MG in cats.     

Delayed primary surgical treatment in a dog with a persistent right aortic arch

A 5-year-old, 1.36-kg, neutered male Yorkshire terrier was referred for evaluation of a persistent right aortic arch with concurrent megaesophagus. The dog was 3 months old when clinical signs were first noted, 2 years of age when diagnosed with megaesophagus, and 4 years of age when diagnosed with vascular ring anomaly (VRA). Surgical correction of the VRA was performed when the dog was 5 years of age, after gastrostomy tube feeding for 1 year to maintain nutritional requirements and mitigate the degree and duration of the esophageal distention. Thirteen months after surgery, the dog was eating soft dog food with no vomiting or regurgitation.     

CONGENITAL MEGAESOPHAGUS WITH HYPERTROPHIC OSTEOPATHY IN A 6-YEAR-OLD DOG

Congenital megaesophagus is often sufficiently debilitating to a young puppy to result in an owner's request for euthanasia. If medically managed, some puppies may develop a functional esophagus and mature normally; in others, the dilation may persist, but nutritional support may be sufficient to allow skeletal maturation. Hypertrophic osteoarthropathy or hypertrophic osteopathy is well recognized in many animal species. Pulmonary neoplasia is most commonly associated with development of the secondary bone changes, but numerous other causes exist. The chronic changes of hypertrophic osteopathy were identified in a 6-year-old German Shepherd that was debilitated by persistent congenital megaesophagus. To the investigators' knowledge, a relationship between long-term esophageal dilatation and hypertrophic osteopathy has only been reported once in a human patient.     

Acquired myasthenia gravis in a poodle

An 11-year-old, spayed female, teacup poodle was evaluated for a chronic cough, lethargy, hindlimb weakness, and reluctance to exercise. Thoracic radiographs revealed megaesophagus and aspiration pneumonia. Serum antibodies against acetylcholine receptors confirmed the diagnosis of myasthenia gravis. The unusual clinical history and case outcome are discussed.     

Cryptococcal pyelonephritis in a dog

A 5-year-old castrated male Golden Retriever was evaluated for polyuria, polydipsia, and progressive regurgitation thought to be a result of bacterial pyelonephritis and megaesophagus. Bacteriologic culture of urine failed to yield clinically relevant growth, and results of a urine sediment examination were normal. With time, intention tremors and progressive neurologic dysfunction were also observed. At necropsy, a diagnosis of cryptococcal disease was confirmed histologically and immunohistochemically. Findings in the dog of this report were indicative of nephrogenic diabetes insipidus with polyuria and polydipsia caused by cryptococcal pyelonephritis. Neurologic manifestations of systemic cryptococcus infection included megaesophagus, esophageal hypomotility, and regurgitation attributed to localization of cryptococcal organisms in the brain stem in the region of the dorsal motor nucleus of the vagus nerve. To the authors' knowledge, this is the first report of polyuria secondary to cryptococcal pyelonephritis.     

Persistent right aortic arch and aberrant left subclavian artery in a white Bengal tiger (Panthera tigris).

A 3-mo-old male white Bengal tiger (Panthera tigris) presented with the chief complaint of regurgitation of solid food since weaning at 2 mo of age. Compared with its littermates, the tiger was in poor body condition and weighed only 10.3 kg when its littermates were estimated at 20-25 kg. Thoracic radiographs showed a megaesophagus cranial to the heart base. A contrast esophagram more clearly outlined the megaesophagus, and fluoroscopy demonstrated normal motility of the caudal esophagus. Endoscopic examination revealed a structure coursing dorsally from right to left over the esophagus and a constrictive band on the left of the esophagus at the heart base. Nonselective angiography confirmed the presence of a persistent right aortic arch, as well as an aberrant left subclavian artery. A left fourth intercostal thoracotomy was performed, and the ligamentum arteriosum was double ligated and divided. The left subclavian artery did not cause significant compromise of the esophagus and was not manipulated at surgery. The tiger recovered well from anesthesia and surgery. Solid food was slowly introduced over a 2-mo period without any regurgitation. The cub gained weight rapidly after surgery.     

Focal myasthenia gravis in a dog.

A 10-month-old American cocker spaniel was evaluated for megaesophagus, aspiration pneumonia, but no appendicular muscle weakness. During hospitalization, weakness of the facial muscles developed, this resolved with anticholinesterase administration. Serum antibodies against acetylcholine receptors were documented, confirming the diagnosis of focal myasthenia gravis. Diagnosis, management, and medical treatment are discussed.