What term describes the presence of black, foul-smelling stools resulting from the digestion of blood?

The presence of black, foul-smelling stools due to the digestion of blood is referred to as melena. This term specifically indicates that there is blood in the digestive tract that has been broken down, usually originating from the upper gastrointestinal (GI) tract. The coloration and odor of melena happen because the hemoglobin in the blood undergoes chemical changes during the digestion process, resulting in the characteristic dark color. The foul smell is also a result of the breakdown products of the blood by intestinal bacteria.

In contrast, hematochezia refers to passing fresh red blood through the anus, typically indicating lower GI bleeding. Hematemesis describes vomiting blood, which can be bright red or have a "coffee grounds" appearance depending on how long it has been in the stomach. Tenesmus is a feeling of incomplete defecation or straining, which does not relate directly to the presence of digested blood in stools.

Recognizing these terms is essential for understanding gastrointestinal bleeding and helps in accurately communicating the nature of symptoms in clinical settings.