There are a few conditions which may explain the combination of normal endoscopy and swallowing trouble. One which is sometimes overlooked is achalasia.
The Greek word achalasia means ‘non-relaxing’ of the lower esophageal sphincter (LES). In people with achalasia, the sphincter fails to relax normally with swallowing. On the contrary, the LES muscle continues to squeeze thus creating an obstruction to the passage of food and liquids into the stomach. Over time, the esophagus above the persistently contracted LES enlarges, and large volumes of food and saliva can accumulate in the dilated esophagus. This is when the condition is obvious on endoscopy, but in its early stages endoscopy may be normal. In these cases, your endoscopist will only think of the condition if he or she got a thorough history directly from you or may otherwise dismiss your symptoms as ‘functional’.
The most common symptom of achalasia is difficulty swallowing. Patients often experience the sensation that swallowed material, both solids and liquids, gets stuck in the chest. This problem often begins slowly and progresses gradually. Many people do not seek help until symptoms are advanced. Some people compensate by eating more slowly and by using maneuvers, such as lifting the neck or throwing the shoulders back, to improve emptying of the esophagus. More info on UpToDate Patient Information.
Chicago Classification of Achalasia
Due to an increased understanding of esophageal function, experts have recently changed the definition of achalasia. For the last several decades it was a requirement for the diagnosis that the esophagus above the sphincter had no contractions at all or exaggerated contractions. This is no longer the case, The following distinctions are now being made: Achalasia without peristalsis (type I), with pan-esophageal pressurization (type II), with premature (spastic) distal esophageal contractions (type III), or with preserved peristalsis (outlet obstruction) (Chicago Classification v3.0 2015).
High Resolution Manometry
The crucial test for the detection and classification of achalasia is High Resolution Manometry which is still a technique requiring special expertise and training to ensure high-quality studies. Your gastroenterologist will advise you where to have this test done if he or she suspects a condition such as achalasia.
Kahrilas, Peter J., et al. “Expert consensus document: Advances in the management of oesophageal motility disorders in the era of high-resolution manometry: a focus on achalasia syndromes.” Nature reviews. Gastroenterology & hepatology (2017).