A peptic ulcer is a hole in the lining of the stomach or duodenum (the upper part of the small intestine), usually caused by a bacterial infection with Helicobacter pylori. The stomach produces hydrochloric acid and enzymes, including pepsin, that break down and digest food. A mucus layer coats the stomach and protects it from the acid. Prostaglandins, hormone-like substances involved in muscle contraction and the inflammatory response, also aid in protecting the lining. When these defences are not performing their job properly, acid and pepsin eat away at the lining, forming an open sore called an ulcer.
H. pylori decreases the stomach’s ability to produce mucus, making it more likely that acid will cause peptic ulcers. Although H. pylori infection is found in many people, it does not cause ulcers in all of them. However, of those who have peptic ulcers more than half have this infection.
Long-term use of non-steroidal anti-inflammatory agents (NSAIDs), such as aspirin, naproxen and ibuprofen can also cause peptic ulcers. Rarely, peptic ulcer is caused by the Zollinger-Ellison sydrome in which a tumour in the small intestine or pancreas produces large amounts of the hormone gastrin.
Smoking and heavy alcohol drinking can exacerbate peptic ulcers and slow healing.