Veterinary Clinical Medicine-I (General and Systemic)

PATHOPHYSIOLOGY

• Esophageal motility is decreased or absent,
• Resulting in accumulation and retention of food and liquid in the esophagus.
• Reflex esophageal motility begins when food stimulates sensory afferents in the esophageal mucosa, which then sends afferent messages to the brainstem swallowing center via the vagus nerve.
• Efferent messages from lower motor neurons in the nucleus ambiguus travel via the vagus to stimulate contraction of esophageal striated and smooth muscle.
• Lesions anywhere along this pathway, including the myoneural junction, may result in esophageal hypomotility and distention.

• Hereditary in wire-haired fox terriers and miniature schnauzers
• Familial predispositions reported in the German shepherd, Newfoundland, Great dane, Irish setter, Sharpei, Pug, Greyhound, and Siamese cats.
• Congenital megaesophagus—signs of regurgitation first appear at weaning
• Acquired forms—reported most often in young adults to middle-aged animals.