Gastroesophageal Reflux Disease (GERD) Make an Appointment Find a Doctor Ask a Question Reviewed by Jeffrey B. King, MD (February 01, 2016) Gastroesophageal reflux is a backward flow or reflux of stomach contents into the esophagus. Everybody has some reflux. Abnormal amounts of gastroesophageal reflux can cause gastroesophageal reflux disease (GERD). This occurs when the sphincter of smooth muscle between the esophagus and the stomach does not function properly. This muscle band is called the lower esophageal sphincter. A physician diagnoses GERD from a history of signs and symptoms. He or she may order tests such as a barium swallow, esophageal pH impedance probe study or endoscopy (EGD) to help diagnose this condition. Programs & Services Gastroenterology Program Clinical Trials For more than 100 years, National Jewish Health has been committed to finding new treatments and cures for diseases. Search our clinical trials.