Melaena
Melaena is the passage of altered blood PR. A melaena stool is black and tarry and has a characteristic smell. The blood is degraded by hydrochloric acid and intestinal enzymes high in the gastrointestinal tract. Melaena is unlikely to occur if bleeding comes from lower than the jejunum, although occasionally melaena may result from a bleeding Meckel’s diverticulum.
