A peptic ulcer is a sore on the lining of the stomach or duodenum. These are the parts of the gut where acid bathes the surface. One cause of peptic ulcer is bacterial infection by Helicobacter pylori, but some ulcers are also caused by long-term use of non steroidal anti-inflammatory agents (NSAIDs), like aspirin and ibuprofen. In a few cases, cancerous tumors in the stomach or pancreas can also cause ulcers.
"It is interesting to speculate as to what diagnoses were made in the cases of duodenal ulcers prior to our present knowledge." -William J. Mayo, 1915