Illustration, based on an endoscope image, showing a gastric ulcer, a breach in the lining of the stomach caused by digestion of the mucosa (lining membrane) by acid, pepsin and bile. Symptoms include vomiting and pain in the upper abdomen shortly after eating. Complications such as bleeding, perforation and obstruction due to scarring may occur. The symptoms are alleviated by antacid medicines, but surgery may be required if the ulcer persists.