Loss of blood from damaged gastric mucous membrane. This can be a complication of conditions such as a stomach ulcer or stomach cancer, or can sometimes be caused by severe damage from medicines (aspirin, particularly if used in combination with alcohol). A stomach ulcer is the commonest cause, and together with duodenal ulcer is responsible for more than half of all haemorrhage in the upper part of the alimentary canal (oesophagus, stomach, duodenum). Haemorrhage occurs when the ulcer or tumour eats into a blood vessel. Symptoms depend on the extent and rapidity of the haemorrhage. Severe haemorrhage causes vomiting blood (haematemesis), in which the blood is often brownish-black through contact with stomach acid. Such conditions cause nausea and sweating, and there is great danger of shock. Smaller haemorrhages cause blackening of the faeces (melaena); in the first instance there are no visible symptoms, and laboratory tests have to be carried out on the faeces. In rare cases the cause can be stomach cancer, penetration by a sharp object which has been swallowed, or perforation as the result of an external wound. As soon as the perforation occurs an open connection is usually established between the stomach and the abdominal cavity (open perforation).