EGD, or esophagogastroduodenoscopy, is a medical procedure that involves using an endoscope to examine the esophagus, stomach, and duodenum. There are several synonyms that are commonly used to refer to this procedure, including upper endoscopy, upper GI endoscopy, and gastroscopy. Upper endoscopy is a general term that refers to any procedure that involves examining the upper part of the gastrointestinal tract. Upper GI endoscopy is a more specific term that refers to the examination of the esophagus, stomach, and duodenum. Gastroscopy is a term that specifically refers to the examination of the stomach, and may be used interchangeably with upper endoscopy or upper GI endoscopy.