Cricopharyngeal achalasia is only one type of pharyngeal swallowing disorder. There are many others, some of which are caused by neuromuscular diseases that cannot be corrected by surgery. The difficulty in swallowing may originate in the mouth and not the pharynx. In young dogs, defects of the hard and soft palate can cause food and liquids to fall from the mouth and nose during eating due to an abnormal communication between the oral and nasal passages. These defects can usually be recognized during an examination of your puppy's mouth.
In young puppies, foreign bodies such as string, sticks or small chicken bones can get lodged in the mouth, pharynx or esophagus, causing drooling and difficulty swallowing. These can be difficult to detect and your puppy may require sedation or general anesthesia to ensure a thorough evaluation of the oral cavity and pharynx. Follow up X-rays of the neck or chest may also be required.
Some dental disorders in young growing puppies may lead to difficulty swallowing, but usually these problems occur after weaning, not at the time of weaning.
Megaesophagus is a disease in which the esophagus, the tube conveying food from the mouth to the stomach, loses its ability to contract and becomes baggy and flaccid. The disease can be acquired or congenital. Megaesophagus is associated with regurgitation of food rather than difficulty in swallowing. Swallowed food accumulates in the distended esophagus and will passively slide forward and out of the mouth, often in a tubular or "sausage" form. Differentiation from cricopharyngeal achalasia may be possible with plain chest x-rays, but swallowing a barium coated meal may be necessary to define this disorder.