Gastric ulcer. Gross specimen of part of a human stomach containing a perforated gastric (peptic) ulcer. Ulcers are caused by excessive stomach acid (digestive juice). This acid, often combined with excess alcohol and caffeine, attacks the stomach wall, causing pain and discomfort. If the wall's protective mucus has become thinner, possibly due to mental stress or bacterial attack, the acid can eventually perforate it. Bleeding from a perforated ulcer can result in anaemia, vomiting blood (haematemesis) and bloody faeces (melaena). Ulcers can be treated with antacid drugs that neutralise the stomach acid, but surgery may be required if the ulcer persists.