Many people have symptoms of Gastroesophageal Reflux Disease, or GERD, often called acid reflux. This video shows how the esophagus works and how acid can splash into the esophagus because of a hiatal hernia or weakness of the valve called the lower esophageal sphincter. Mayo Clinic has a very large team with an international reputation for its skill in diagnosing and treating reflux, Barretts esophagus and esophagus cancer. For more information, go to the Mayo Clinic website, http://www.mayoclinic.org/barretts-esophagus/