Resolution of megaesophagus after treatment of concurrent hypothyroidism in a dog]

An adult mixbreed female dog is presented with a megaoesophagus. The treatment of a concomitant thyro?dism allowed the total regression of the megaoesophagus. A literature overview is presented, dealing with the correlation between megaoesophagus and hypothyro?dism. Diagnostic and therapeutic possibilities are discussed.     

Megaoesophagus in adult dogs secondary to Australian tiger snake envenomation

Four cases of megaoesophagus secondary to tiger snake envenomation are reported. History in all cases suggested megaoesophagus was not present prior to snake envenomation. Diagnosis of megaoesophagus was confirmed by thoracic radiography in all cases. One dog died of respiratory failure. The remaining three dogs recovered, with gradual resolution of clinical signs associated with megaoesophagus.     

Unusual Combination of Multiple Vascular Anomalies in a German Shepherd Puppy with Megaoesophagus

A 2‐months‐old male German shepherd puppy was referred for regurgitation and delayed growth. Radiographic and endoscopic investigations revealed a precardiac megaoesophagus and oesophageal constriction at the level of the heart base. At post‐mortem examination, a specific form of persistent right aortic arch characterized by an aberrant left subclavian artery in combination with a ligamentum arteriosum originating at the aberrant left subclavian artery (PRAA‐SA‐LA) was detected. A complete‐type persistent left cranial vena cava (PLCVC) was also observed. This is the first report describing the association between PRAA‐SA‐LA and PLCVC in a dog with megaoesophagus.     

Autoimmune myasthenia gravis and dysautonomia in a dog

A two-year-old male entire border collie dog was evaluated for a short history of mixed bowel diarrhoea, coughing, vomiting and stranguria. Physical examination revealed dyspnoea with increased ventral lung sounds and a flaccidly distended bladder. Neurological examination revealed poor pupillary light reflexes, an absent gag reflex and a poor anal tone. Thoracic radiography was consistent with megaoesophagus and aspiration pneumonia. Clinicopathological testing revealed an elevated muscular nicotinic acetylcholine receptor antibody titre. The dog was euthanased because of clinical deterioration. Cerebrospinal fluid (CSF) collected immediately post-mortem revealed macrophagic pleocytosis. Post-mortem histopathological examination was consistent with dysautonomia. This is the first report of coexisting autoimmune myasthenia gravis and dysautonomia in a non-human species. The concomitant diseases may suggest a common immunopathological aetiology.     

Gastroesophageal intussusception in a young German shepherd dog

A gastro-oesophageal intussusception in a female, six-week-old German shepherd dog was treated surgically with success. The dog was presented with acute dyspnoea and signs of shock. After laparotomy, the herniated organs were reduced from the lumen of the oesophagus into the abdomen and an imbrication of the oesophageal hiatus, an appositional fundoplica-tion and a left-sided incisional fundopexy were performed. The dog made an uneventful recovery. Eighteen months after surgery the dog is still alive, with no clinical signs despite the persistent presence of megaoesophagus.     

Spontaneous laryngeal paralysis in four white-coated German shepherd dogs

Four cases of spontaneous laryngeal paralysis in juvenile white-coated German shepherd dogs are described. The presenting signs were typical for laryngeal paralysis, with stridor present in all four cases. Laryngoscopy revealed bilateral laryngeal paralysis in three cases, and unilateral paralysis in one. Concurrent megaoesophagus was also identified in one dog. All dogs underwent surgical treatment for laryngeal paralysis. Euthanasia was performed in one case due to intractable regurgitation and aspiration pneumonia. A possible association with white coat colour is discussed.     

Paraoesophageal hiatal hernia and megaoesophagus in a three-week-old Alaskan malamute

Paraoesophageal hiatal hernia was diagnosed in a three-week-old Alaskan malamute. Reduction of the hernia was followed by an oesophagopexy and a bilateral gastropexy. During the early postoperative period, the puppy continued to have signs that were thought to be related to a concurrent megaoesophagus. At nine months of age the dog had gained weight and was well except for occasional episodes of regurgitation. These episodes responded well to medical therapy, and at the time of writing the dog had not required further treatment.     

Empty sella syndrome, hyperadrenocorticism and megaoesophagus in a dachshund

A five-year-old, entire, male dachshund was presented with a five day history of hypersalivation and regurgitation as well as polyuria and polydipsia for several months. Chest radiographs demonstrated megaoesophagus and aspiration pneumonia. Furthermore, hyperadrenocorticism was demonstrated by means of elevations in levels of serum alkaline phosphatase and cholesterol, decreased urinary specific gravity, increased response to adrenocorticotropic hormone stimulation, insufficient suppression of the post-dexamethasone plasma cortisol levels, an increased endogenous adrenocorticotropic hormone concentration and bilaterally enlarged adrenal glands on abdominal ultrasound. The dog became severely dyspnoeic and was euthanased after magnetic resonance imaging was performed. The magnetic resonance imaging and necropsy revealed the sellar region mainly filled with fluid, with only small tissue remnants, a condition defined as empty sella syndrome in human medicine. To the author's knowledge, this is the first dog described with empty sella syndrome and only the second dog described with hyperadrenocorticism secondary to ectopic adrenocorticotropic hormone production. However, the association between empty sella syndrome and hyperadrenocorticism may be no more than incidental.     

Congenital triple oesophageal stricture and megaoesophagus in a neonatal colt

Congenital oesophageal stenosis is rarely described in horses. This case report describes a neonatal colt with signs of a milky nasal discharge and cervical swelling present from birth. The diagnostic evaluation revealed a triple oesophageal stricture, identified as congenital fibromuscular oesophageal stenosis. A megaoesophagus was seen cranial to the strictures, but its aetiology remains unexplained. To the authors’ knowledge, multiple oesophageal stenosis together with megaoesophagus has not previously been described in the horse.     

Surgical correction of gastro‐oesophageal intussusception with bilateral incisional gastropexy in three dogs

Three dogs presented for evaluation of acute onset tachypnoea and dyspnoea following episodes of vomiting and/or regurgitation. Thoracic radiographs were suggestive of a gastro‐oesophageal intussusception in all three dogs; one dog also showed evidence of aspiration pneumonia. All three dogs underwent surgical correction with a bilateral incisional gastropexy. All dogs recovered from anaesthesia uneventfully and were discharged from the hospital 3 days after presentation. Persistent megaoesophagus was evident in all three dogs, and they are being chronically managed with a strict feeding regime and pro‐motility agents.     

Hiatal hernia with focal megaoesophagus in a Friesian stallion

Hiatal hernia with focal megaoesophagus was diagnosed in a 10-year-old Friesian stallion presenting to the referral hospital for further investigation of recurrent oesophageal obstruction. Oesophageal endoscopy revealed dilation of the distal oesophagus with alterations in the mucosa characteristic of gastric mucosa in the distal oesophagus. In addition, a moderate amount of feed material was identified in the distal oesophagus. Positive contrast radiography showed that approximately half of the stomach was herniated cranially through the diaphragm. Management of the disease included recommendations to elevate the patient’s torso during feeding and provide mash-only feeds. Provided that successful control of the megaoesophagus could be achieved, surgical repair of the hiatal hernia may be an option for the future. This is the first report of hiatal herniation in horses. We report the successful conservative management of a stallion with both megaoesophagus and hiatal herniation through elevated feedings and selective exercise management.     

Oesophageal compliance in naturally occurring canine megaoesophagus

SUMMARY The passive blomechanical property of oesophageal compliance (OC) was measured in 8 naturally occurring cases of canine megaoesophagus, 8 matched control and 7 vagotomised control dogs. Of the 8 dogs with megaoesophagus, 6 had congenital Idiopathic megaoesophagus and 2 had secondary megaoesophagus attributable to generalised skeletal muscle disease. Stepwise distension of the whole oesophagus was employed for measurement of OC at the 4.0 and 8.0 mL/kg Injected volume steps within the control volume range (0 to 12.0 mL/kg). At both Injected volume steps OC was higher In megaoesophagus dogs than in either matched control or vagotomised control dogs (P / 0.01 In both cases), and no significant difference was observed In OC between matched control and vagotomised control dogs. No correlation was demonstrated between OC and the estimated duration of clinical signs of dogs with megaoesophagus. These findings suggest that In most cases of canine megaoesophagus the viscoelastic properties of the oesophageal wall are significantly altered, that In such cases the disorder is unlikely to be purely dynamic and that processes other than the duration of oesophageal dilatation are responsible for the alteration in oesophageal wall blomechanical properties. The relevance of these findings to current concepts on pathophysiological mechanisms underlying the evolution and resolution of various forms of canine megaoesophagus Is discussed.     

Glycogen storage disease type II in the Lapland dog

A newly recognized inherited metabolic disease in the Lapland dog is described. The metabolic defect is a deficiency of acid-alpha-glucosidase, a lysosomal hydrolase. The clinical picture is dominated by vomiting related to megaoesophagus, and progressive muscle weakness leading to exhaustion and death before two years of age. Cardiac abnormalities are observed. The main histopathologic lesion consists of glycogen accumulation, notably in membrane-bound vacuoles (glycogenosomes), involving all kinds of muscular tissue in particular. Recessive inheritance of the disease was demonstrated by complementation analysis. The enzyme protein is present in affected tissues, although in an inactive form. Based on the gene dosage phenomenon, an attempt was made to identify carrier dogs by means of a biochemical assay. Glycogen storage disease type II in the Lapland dog appears to be a homologous model for the infantile manifestation of glycogen storage disease type II (Pompe's disease) in man.     

Glycogen storage disease type II in the Lapland dog

Summary

A newly recognized inherited metabolic disease in the Lapland dog is described. The metabolic defect is a deficiency of acid‐α‐glucosidase, a lysosomal hydrolase. The clinical picture is dominated by vomiting related to megaoesophagus, and progressive muscle weakness leading to exhaustion and death before two years of age. Cardiac abnormalities are observed. The main histopathologic lesion consists of glycogen accumulation, notably in membrane‐bound vacuoles (glycogenosomes), involving all kinds of muscular tissue in particular. Recessive inheritance of the disease was demonstrated by complementation analysis. The enzyme protein is present in affected tissues, although in an inactive form. Based on the gene dosage phenomenon, an attempt was made to identify carrier dogs by means of a biochemical assay. Glycogen storage disease type II in the Lapland dog appears to be a homologous model for the infantile manifestation of glycogen storage disease type II (Pompe's disease) in man.     

Thymoma and multiple thymic cysts in a dog with acquired myasthenia gravis

An anterior mediastinal cystic lesion in an 11-year-old mongrel dog was examined. The dog showed dysbasia and vomiting due to megaoesophagus, and anterior mediastinal round mass lesion, approximately 35 mm in diameter, was found by X ray. Based on clinical examinations, the dog was diagnosed as acquired myasthenia gravis and was successfully controlled by anticholinesterase treatment for approximately 4 months. The dog died of thermic stroke and was necropsied. Grossly, fatty tissues with cysts containing yellowish fluid and white nodules were found in the anterior mediastinal area. Histopathologically, multiple cysts, neoplastic tissues, and atrophic thymus were found within the examined tissues. The cysts were lined by thin wall consisting of ciliated long cuboidal and non-ciliated round cells and were filled with eosinophilic colloidal fluid. Some extended cysts contained neoplastic foci within their lumen and walls. The neoplastic tissues consisted of mixed population of large epithelial cells with abundant clear cytoplasm and large oval nuclei, and lymphocytes. Immunohistochemically, proliferating epithelial cells were intensely positive for keratin and cytokeratin, and more than half number of infiltrating lymphocytes were intensely positive for CD3 suggesting T cells. All these findings indicate the neoplastic lesion is thymoma and multiple cysts are considered as thymic or brachial cleft cysts.     

Canine myasthenia gravis

Decreased acetylcholine receptor content of the neuromuscular junction underlies the muscular weakness seen in both acquired and congenital myasthenia gravis. Immune mediated mechanisms account for the acquired defect while decreased membrane insertion of receptor leads to the congenital disorder. The congenital form typically presents in the first few weeks of life with generalised episodic weakness as the predominant sign. Although treatment with cholinesterase inhibitors may help temporarily, the prognosis is poor. Acquired myasthenia gravis can occur between eight months and 13 years of age and may present as megaoesophagus alone or as exercise-related weakness in conjunction with megaoesophagus. Although treatment of the immune mediated form is often successful and spontaneous remissions also occur, aspiration pneumonia secondary to megaoesophagus remains a major cause of mortality in affected dogs. Resolution of megaoesophagus must therefore be a major goal for future treatment regimes. The remarkable similarity between canine and human acquired myasthenia gravis suggests that the canine thymus gland warrants greater attention pathologically and perhaps therapeutically considering the value of thymectomy in human patients.     

Key-Gaskell syndrome in a cat in Switzerland

As far as the authors know this is the first case of Key-Gaskell-syndrome being described in Switzerland. The clinical signs of megaoesophagus, anorexia, constipation, dryness of all mucous membranes, reduced tear production, protrusion of the membrana nictitans, mydriasis, regurgitation and bradycardia are pathognomonic and can't be mistaken by any other disease. The subject of the Key-Gaskell-syndrome is a dysfunction of the autonomic nervous system. Histopathological changes are exclusively related to the autonomic nervous system and to neurons of some nuclei in the cranial nerves. Less severe changes can be found in the neurons of the spinal cord or in the dorsal root ganglia. The etiology remains still unclear. There is a relationship to the grass sickness syndrome in horses and to dysautonomia of man and dog.     

The neuropathic oesophagus. A radiographic and manometric study on the evolution of megaoesophagus in dogs with developing axonal neuropathy

Dogs given the neurotoxin acrylamide develop peripheral neuropathy and megaoesophagus. Sequential radiographic and manometric studies on the oesophagus demonstrated that the initial abnormalities consisted of a progressive decrease in the proportion of swallows that initiated peristalsis and a gradual increase in oesophageal calibre. Regurgitation, peristaltic failure and oesophageal dilatation all appeared within three days. The eating behaviour and gait abnormalities quickly resolved on stopping the neurotoxin, but the oesophagus remained dilated for longer. Previous studies have suggested that the abnormalities present in dogs which are developing a distal axonal neuropathy or in some dogs with idiopathic megaoesophagus may be limited to the proprioceptive elements of the oesophageal innervation. The present study suggests that the progressive inefficiency in the transmission of swallows and changes in oesophageal calibre in dogs with evolving megaoesophagus may be a consequence of damage to these proprioceptive elements.     

Use of radiographic measurements in distinguishing myasthenia gravis from other causes of canine megaoesophagus

OBJECTIVES: To evaluate whether dogs with megaoesophagus due to myasthenia gravis display less oesophageal dilatation radiographically than dogs with other causes of megaoesophagus. METHODS: Thoracic radiographs of 66 dogs with megaoesophagus in which concurrent acetylcholine receptor antibody titre was known were analysed retrospectively. Maximum oesophageal diameter was transformed to a "relative oesophageal diameter" using a ratio with thoracic inlet diameter. Dogs were divided into two groups according to "MG" or "non-MG" antibody status and median relative oesophageal diameter values were compared between groups and with age, weight and sex. A receiver operating characteristic plot was used to evaluate a suitable relative oesophageal diameter cut-off. RESULTS: Twenty dogs were diagnosed with myasthenia gravis and 46 with other causes of megaoesophagus. Thoracic inlet size correlated significantly with bodyweight and surface area (r(2)=0.627 and 0.669, respectively). Median values of relative oesophageal diameter for the MG group and non-MG group were 0.58 and 0.66, respectively, and these showed a small, but significant, difference (P=0.029), although there was complete overlap in the range of relative oesophageal diameter values between groups. There was no significant association between relative oesophageal diameter and sex, age or weight or significant difference in age, sex or weight between the two groups. An increased odds ratio for myasthenia gravis existed in golden retrievers and German shepherd dogs. CLINICAL SIGNIFICANCE: Relative oesophageal diameter appears to be of limited diagnostic utility in distinguishing dogs with megaoesophagus due to myasthenia gravis from those with megaoesophagus due to other causes.     

Idiopathic megaoesophagus and intermittent gastro-oesophageal intussusception in a cat

An eight-month-old domestic shorthair cat was presented with chronic vomiting for three months, with an acute increase in frequency during the past two days. A diagnosis of megaoesophagus was made by chest radiography. Diagnostic work-up for megaoesophagus was performed. A gastro-oesophageal intussusception was identified during endoscopy. Medical and nutritional therapy was instituted with a good response to the treatment.