Manifestations of gastroesophageal reflux disease (GERD) have recently been classified as esophageal or extraesophageal syndromes. Clinical history, questionnaire data, and response to antisecretory therapy are not sufficient to make an accurate diagnosis of GERD. Endoscopy has low sensitivity. Recently, the advent of multichannel intraluminal impedance measurement and esophageal pH (MII-pH) monitoring have modified the diagnostic approach towards atypical manifestations of GERD. There is growing consensus that this technique should be considered the gold standard for diagnosing GERD.

Normally, peristalsis in the esophagus pushes food down to the stomach, gastric juice flows up the esophagus and then recedes. When the gastric juice overflows with a lot of acid, it will cause discomfort to the patient, inflammation of the esophageal surface and the appearance of signs of esophagitis.