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The esophagus is the main target of gastroesophageal reflux disease (GERD) and normally the esophagus is well-equipped with a number of defensive factors to protect itself from the impact of gastric (stomach) acid. Moreover, in most patients with GERD there is a normal amount of acid secreted by the stomach. So why do some people develop GERD?

Although the exact cause of GERD remains unknown, a leading theory proposed by experts implicates functional impairment of a segment of muscle at the far end of the esophagus called the lower esophageal sphincter or LES. Under normal circumstances, the LES relaxes to allow the passage of ingested substances (food; liquids) to pass from the esophagus into the stomach where the food is broken down by stomach acids. Once the ingested substances have passed into the stomach, the LES contracts and, thereby, acts as a physical barrier to prevent the acidic stomach contents from refluxing (backwashing) into the esophagus. It is thought that in people with GERD the LES muscle relaxes for an increased period of time and, thereby, exposing the esophagus to stomach acid for extended periods of time which leads to symptoms of GERD. Impairment of the reflex mechanisms in the pharynx, hypopharynx, and larynx predispose patients to atypical symptoms associated with GERD such as reflux laryngitis, asthma, and aspiration pneumonia.

A number of other factors are also thought to contribute to the development of GERD in some patients, including:

• Impaired esophageal motility
• Hiatal hernias - outpouchings from the esophagus that occur due to a weakness in the wall of the esophagus
• Previous gastric surgery - patients who have previously undergone gastric (stomach) surgery are more inclined to have reflux of not only stomach acid but also bile and pancreatic juices that can more readily damage the lining of the esophagus.