A peptic ulcer is a painful sore, very much like a mouth ulcer, which forms in the lining of the stomach (gastric ulcer) or the duodenum, the first part of the small intestine (duodenal ulcer).

A very common cause for developing an ulcer is a bacterium called Helicobacter pylori. It is found in the lining of the stomach of at least half of the world's population, and its presence increases the likelihood of developing an ulcer. Another cause is the overuse of nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin or ibuprofen.

The symptoms of a peptic ulcer include pain at the top of the stomach centrally that may radiate to the back, bleeding that would result in black stools or blood in vomitus and rarely perforation, which is a hole in the lining of the digestive tract.

An upper endoscopy or gastroscopy confirms the presence of an ulcer and is one way to test for the presence of Helicobacter pylori.

Treatment of PUD involves eradicating Helicobacter pylori when it is present and reducing the stomach acid content with medications known as proton pump inhibitors (PPIs). Most ulcers heal in one to two months. Occasionally, surgery may be needed in the setting of a complication such as uncontrolled bleeding or perforation.