German shepherd dogs (GSDs) are predisposed to an inherited motility disorder of the esophagus (the gullet), termed congenital idiopathic megaesophagus (CIM), in which the esophagus is enlarged and swallowing is ineffective. Affected puppies are unable to properly pass food into their stomachs and consequently regurgitate their meals and show a failure to thrive, often leading to euthanasia.
The disease affects males more than females which is thought to be due to the estrogen protection role in females.