In some patients, blood coming out black, sticky, and foul smelling. Black stool sticky and smelling is called melena. Melena occurs when the blood is in the colon in the long term so that the bacteria will decipher it into chemical compounds (hematin) that are black. Therefore, melena usually signifies bleeding from the upper gastrointestinal tract (eg, bleeding from the stomach or duodenal ulcer).
Sometimes, bleeding from the digestive tract is very little to progress gradually so as not to cause melena. This situation is called bleeding vague (can not be seen with the naked eye). Blood can only be determined by examining stool in the laboratory. The cause of bleeding is usually similar to faint rectal bleeding or melena, the difference is only on the intensity and duration that goes slowly. All the above types of bleeding can cause anemia due to blood loss with iron (iron deficiency anemia).