From saliva (“drool” or ptyalism) to food to color-tinged fluid to the unrecognizable, what your dog orally evacuates can take on many different appearances and create varying levels of concern.
One relatively-uncommon health concern leading to ingesta (food, liquid, etc.) erupting from a pet’s mouth is Megaesophagus.
What is Canine or Feline Megaesophagus?
Megaesophagus is a condition affecting pets where the esophagus (“food tube”) stretches beyond its normal capacity and limits the ability of food, liquids, and other substances to properly enter the stomach.
Normally, ingesta enters the mouth, is swallowed via the complex mechanism of the larynx (“voice box”), then travels through the esophagus to reach the stomach. Swallowing is a voluntary action, but once ingesta moves beyond the mouth and into the esophagus, involuntary muscular control takes over to push ingesta in a head-to-tail direction towards the stomach. A ring of muscle (esophageal sphincter) at the end of the esophagus controls the flow of contents into the stomach. The involuntary nature of this process takes the thinking out of eating for our companion canines and felines, who simply bite, chew, and swallow as part of their day-to-day survival activities.
With Megaesophagus, ingesta collects in the stretched-out esophagus instead of properly moving into the stomach. Once enough ingesta accumulates it finds the point of least resistance and erupts back out through the mouth.
What Are the Causes of Megaesophagus in Canines and Felines?
There are many potential causes of Megaesophagus, which can be can be congenital (inherited) or acquired.
Congenital Megaesophagus commonly occurs around the time of weaning (transitioning off of drinking mother’s milk and onto eating solid food) and is suspected to occur as a result of improper esophageal nerve development. As the pet matures, improved nervous system development and esophageal function can occur. Some cases of Congenital Megaesophagus are due to a vascular ring anomaly called a Persistent Right Aortic Arch (PRAA), where a remnant of fetal blood vessels remains and constricts the esophagus.
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