Haematemesis is the vomiting of red blood, and indicates moderate or severe acute upper GI bleeding.

Coffee-ground vomiting is the vomiting of dark brown vomitus that resembles coffee grounds. It results from the oxidation of haem to haematin by gastric acid, and indicates minor upper GI bleeding that has slowed or stopped.

Melaena is black, tarry stool and typically indicates upper GI bleeding. Small intestinal or right colon bleeding can also cause melaena. (see Chapter 74, Table 74.1). Upper GI bleeding of >50–100 mL is required to cause melaena, which may persist for several days after bleeding has ceased. Black stool that is not melaena may result from ingestion of iron or some foods.

Haematochezia is the passage of liquid blood or clots per rectum, and usually indicates lower GI bleeding (see Chapter 74, Table 74.2), but sometimes can result from severe upper GI bleeding with rapid transit of blood through the gut.