Up to 45 million people in the U.S. have an open sore in the lining of their gastrointestinal tract known as an ulcer.  An ulcer can occur in the upper portion of the small intestine (duodenal ulcer), the stomach (gastric ulcer), and the esophagus (esophageal ulcer).  Ulcers are often referred to as “peptic ulcers” to indicate they occur in the digestive tract.