Esophageal Strictures:
https://www.msdvetmanual.com/dog-owners/digestive-disorders-of-dogs/disorders-of-the-esophagus-in-dogs
Esophageal stricture is a narrowing of the esophagus. It may develop after trauma (for example, ingestion of a foreign object or caustic substance), anesthesia, use of certain drugs, inflammation of the esophagus, gastroesophageal reflux (gastric acid flowing back into the esophagus), or tumor invasion. Signs include regurgitation, excessive drooling, difficulty swallowing, and pain. Examining the esophagus using fluoroscopy is the preferred method for diagnosis; endoscopy can also be used. These tests enable your veterinarian to actually see the number, location, and types of strictures.

Treatment of the stricture by stretching it with a balloon catheter has been successful. The catheter is a tube that is placed in the esophagus and then advanced to where the stricture occurs. The tip of the catheter is then inflated like a balloon, which stretches the esophagus and relieves the stricture. Other methods, including surgery, have been less successful.