Gastrointestinal bleeding occurs as a result of blood loss from somewhere in the gastrointestinal tract, the passage that extends from the mouth to the anus.

The bleeding varies in severity from mild or undetectable through to massive, acute bleeding that can be life threatening if not managed urgently.

The upper digestive tract includes:

• The food pipe or the esophagus
• The stomach
• The upper portion of the small intestine called the duodenum

The lower digestive tract includes:

• The lower part of the small intestine
• The large intestine
• The rectum and anus

Some of the symptoms of upper gastrointestinal bleeding and lower gastrointestinal bleeding can be very different.

In upper gastrointestinal bleeding, the bleeding occurs between the pharynx and the ligament of Treitz and may lead to blood in the vomit (hematemesis) or thick, tarry stool (melena). This black-colored stool indicates the presence of blood that has been altered by digestive enzymes. Blood in the vomit may resemble ground coffee, which indicates that blood has been sitting in the stomach for a few hours.

Lower gastrointestinal bleeding usually comes form the rectum, colon or anus. Blood that is bright red usually indicates rectal bleeding, particularly in the absence of hematemesis. This passage of red, fresh blood is termed hematochezia. In lower gastrointestinal bleeding, melena may occur as a result of bleeding from anywhere within the lower small intestine through to the proximal colon.

The generalized features of severe bleeding include abdominal pain, diarrhea and the symptoms of anemia such as weakness and shortness of breath. Severe and massive bleeding can lead to shock as a result of reduced blood volume and insufficient blood flow around the body. Signs of shock include weak and rapid pulse, low blood pressure, anxiety, shallow and rapid breathing, confusion and cool, clammy skin.