Peptic ulcers are open sores that form on the inner lining of the stomach, duodenum, or esophagus due to erosion by stomach acids. The most common cause of ulcers is an infection in the stomach caused by bacteria called Helicobacter pylori (H. pylori). Symptoms of peptic ulcer usually manifest as abdominal pain. If left untreated, peptic ulcers can lead to serious complications such as internal bleeding. Therefore, it is important to consult a gastroenterologist if a peptic ulcer is suspected.