Lower gastrointestinal haemorrhage

Abstract

Blood originating from the sigmoid colon or distally may be dark or usually bright red and copious; that from more proximal sites in the colon or in the distal small intestine is usually dark red or black, although it does not have the sticky consistency or typical offensive smell of partially digested blood that characterizes the melaena of upper gastrointestinal bleeding. Occasionally, upper gastrointestinal haemorrhage may be brisk enough to cause the passage of unaltered blood per rectum, thus mimicking a colonic bleed.