November 1999 Up to 12 percent of Americans have ulcers at some point in life. Peptic ulcers are sores found in the lining of your stomach or of your duodenum, the upper portion of your small intestine.
Duodenal ulcers are the more common, accounting for three quarters of all cases.
Ulceration occurs when the stomach's or duodenum's mucosal lining cannot withstand the corrosive action of gastric juice, which your stomach's lining secretes to break down your meals. Gastric juice, which consists of hydrochloric acid and an enzyme, pepsin, which breaks down protein, can digest any living tissue, including your stomach and duodenum. Normally, both your stomach and duodenum are bathed constantly in gastric acid. But protective mechanisms, including the work of prostaglandins, which govern secretion of mucus from your stomach lining, and your food and saliva's ability to dilute acid, prevent your stomach from digesting itself. Some people with duodenal ulcers do secrete abnormal amounts of acid, but as many as half do not.