Gastroesophageal Reflux Disease (GERD) is defined as chronic symptoms or mucosal damage produced by the abnormal reflux in the esophagus/food pipe. This is commonly due to transient or permanent changes in the barrier between the esophagus and the stomach. This can be due to incompetence of the lower esophageal sphincter (LES), transient/slow LES relaxation, impaired expulsion of gastric reflux from the esophagus, or a hiatal herniation.