High Quality Content by WIKIPEDIA articles! A peptic ulcer, also known as ulcus pepticum, PUD or peptic ulcer disease, is an ulcer (defined as mucosal erosions equal to or greater than 0.5 cm) of an area of the gastrointestinal tract that is usually acidic and thus extremely painful. As many as 80% of ulcers are associated with Helicobacter pylori, a spiral-shaped bacterium that lives in the acidic environment of the stomach, however only 40% of those cases go to a doctor. Ulcers can also be caused or worsened by drugs such as aspirin and other NSAIDs.