Megaesophagus
Basic Information 
Clinical Presentation
Physical Exam Findings
The findings of physical examination confirm the presenting signs, including dysphagia, hypersalivation, and nasal discharge containing food material. Distension of the cervical esophagus may be visible or palpable. The horse may be noted to eructate frequently.
Etiology and Pathophysiology
• Congenital megaesophagus may be inherited in a similar fashion to congenital megaesophagus in dogs. Some horses affected by fourth branchial arch defect may also have megaesophagus and achalasia of the upper esophageal sphincter.
• Acquired megaesophagus may be secondary to chronic or recurrent esophageal obstruction, esophageal obstruction by tumors and other masses, vascular ring anomalies, neurologic diseases (eg, equine protozoal myeloencephalitis, idiopathic vagal neuropathy), pleuropneumonia (and associated vagal neuropathy), equine grass sickness, botulism, or myasthenia gravis.
• Temporary iatrogenic megaesophagus may occur after sedation with α2-adrenergic agonists, such as detomidine.
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