Non-erosive reflux disease (NERD).

Non-erosive reflux disease (NERD) is characterized by the absence of esophageal mucosal damage during upper gastrointestinal endoscopy, despite the presence of typical symptoms of gastroesophageal reflux, such as heartburn and acid reflux. Almost 50 % of patients with NERD fail to respond to standard doses of proton pump inhibitors which are the first-line ther- apy for GERD. This means that acid reflux is only a minor effect on the pathophysiological mechanism of NERD and various mechanisms such as visceral hypersensitivity, esophageal motor abnormalities, weak or non-acid reflux and psychic effect have been estimated. There- fore, it is important to evaluate the pathophysiology of NERD by esophageal functional tests and to create the therapeutic strategy for each patients.