ABSTRACT
A 73-year-old man presents with a 5-day history of passing black stools. On the fifth day he began to feel breathless and tired, particularly on climbing stairs.
A 26-year-old woman presents with a 3-week history of bloody diarrhoea. The blood is fresh and mixed in the liquid stool. Initially, she thought that she might have food poisoning, but could not recall eating anything unusual and had eaten the same food as her unaffected partner.
