Haematemesis is the vomiting of blood. It usually signifies pathology in the upper gastrointestinal tract. The causes of haematemesis are are given below. It is prudent to remember that the exposure of the blood to gastric acid can cause the blood to resemble coffee grounds.

The last three causes are rare.

Oesophageal varices are dilated veins which are found in the lower oesophagus. The oesophageal veins here are one of the sites of anastamosis between the hepatic portal venous system and the systemic venous system. If the flow of blood through the portal veins is impaired, as occurs in cirrhosis, the blood is shunted through one or more of these anastamoses. The lower oesophageal anastamoses are particularly vulnerable to this shunting in cirrhosis. The veins become markedly dilated and are located quite superficially in the oesophagus such that they distort the mucosal surface. They can rupture spontaneously and bleed aggressively.

A Mall ory-Weiss tear is a rip in the oesophageal mucosa that sometimes occurs during violent vomiting.

Portal hypertensive gastropathy is another complication of the portal-systemic shunting of blood in portal hypertension and cirrhosis.

Hereditary haemorrhagic telangiectasia is an autosomal dominant disease in which patients have numerous small collections of dilated, thin walled blood vessels that affect the skin, tongue, lips and nasal mucosa, together with arteriovenous malformations in internal organs, including the GI tract. Nosebleeds can be particularly troublesome in patients who have this disease. The condition is also known as Osler-Weber-Rendu disease.

Angiodysplasia is a condition in which there are small vascular malformations located close to the mucosa in the GI tract. They can be fragile and bleed from minimal provocation.

Pseudoxanthoma elasticum is an inherited disease that is usually autosomal recessive. The genetic defect results in fragile elastic connective tissue fibres and this can rarely compromise blood vessels in the gastrointestinal tract.