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and specific serum assay documenting the presence
of autoantibodies against nicotinic acetylcholine receptors is available for the diagnosis of MG http:// vetneuromuscular.ucsd.edu. Endoscopic examination of the esophagus may be useful in unclear cases and to allow visualization of extent and severity of esophagitis, if present. In cases with suspected polymyositis or polyneuropathy electrodiagnostics (EMG, nerve conductions studies) and collection of muscle and nerve biopsies for histopathologic evaluation should
be considered. In endemic lesions, infection with the parasite Spirocerca lupi should be ruled out (see esophagitis lecture).
Management:
Dietary management is of central importance - it is important to try various options such as dry food kibbles, canned food in meat balls and food blended with water in different consistencies (thick or thin slurry) because each animal may respond differently. Dogs and cats
with ME should be fed a caloric-dense diet in a vertical position and be maintained in that position for 10-15 min. after the meal in order to use gravity to facilitate aboral movement of the food bolus. Small dogs can be held on a person’s lap for that time. Medium size and large dogs can be fed on stairs and maintained with their front limbs higher than their hind limbs. The Bailey chair is a useful device to keep medium size and large dogs in a vertical position during and after meals. This aspect of treatment can be a challenge for dogs with pre-existing orthopedic diseases such as coxofemoral arthritis. In severe cases, placement of a gastrostomy tube may be beneficial to ensure appropriate nutrition and timely delivery of oral medications to the stomach, and to prevent aspiration pneumonia.
Identified underlying diseases need to be treated.
For instance, recommended treatment of MG
includes administration of acetylcholinesterase
inhibitor pyridostigmine (1-3 mg/kg PO q12h, start
with a low dose to minimize risk of cholinergic crisis)
and immunosuppressive doses of prednisone or prednisolone (1-2 mg/kg PO q12h). Gastric prokinetic drugs do not significantly influence esophageal motility, while some of them increase LES tone in dogs (cisapride, erythromycin). Bethanechol is a cholinergic agent that has been shown to increase esophageal motility in some dogs and can be used in the management of clinical cases of idiopathic ME (5 to 15 mg/dog PO q8h, start with a low dose to minimize risk of cholinergic crisis). Because of the high prevalence of esophagitis in patients with
ME, sucralfate suspension should be administered to facilitate mucosal healing (0.5-1 g/dog q8h). Treatment of aspiration pneumonia is mostly supportive. If secondary bacterial infection is suspected, antibiotic treatment is best based on culture and sensitivity from a tracheal
or bronchial wash, however empiric treatment with a
broad-spectrum antibiotic may be necessary in some cases (e.g. amoxicillin and clavulanic acid, ampicillin and sulbactam).
Home management of pets with megaesophagus
is complex and time-consuming. Owners may feel overwhelmed and discouraged at first. Therefore, optimal communication between the veterinary care team and the animal’s owners is essential for successful management of this condition, and web-based (e.g. Facebook) support groups may be very helpful.
Prognosis:
Studies from Scotland and Germany reported a short median survival time of 3 months after diagnosis regardless of the etiology in dogs with ME. In the Glasgow study, 41% dogs survived 1 year, 31% were
alive at 2 years, and 22% survived for 5 years. Identified risk factors for shorter survival were dogs older than 13 months of age at the time of diagnosis and presence of aspiration pneumonia at diagnosis. Megaesophagus may be reversible when associated with endocrinopathies, but this represents only a small percentage of dogs with ME.
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