Its a gross topic, but it happens and here is how to tell the difference of what is actually happening and how to tell the difference.
Original link to mercola website here

“Megaesophagus is a condition in which the esophagus, a muscular tube that runs from the mouth to the stomach, is enlarged and malfunctioning. The disorder is much more common in dogs than cats.”

Another source of information on the topic is from Dr. Jean Dodds’
LINK HERE