Gastrointestinal, or GI bleeding, encompasses bleeding from anywhere along the GI tract, from the mouth to the anus. The GI tract is divided into the upper GI tract, including the mouth, esophagus, and stomach; and the lower GI tract, encompassing the small intestine, large intestine and rectum. Bleeding is classified as overt, or visible, and occult, meaning not visible with the naked eye. Many disorders from dilated blood vessels in the esophagus and ulcers in the stomach to cancer in the colon can cause GI bleeding. Symptoms range from dramatic to subtle.
Anemia
Occult bleeding can cause anemia, which is a low red blood count. Anemia occurs because small amounts of blood are lost from unseen bleeding. Overt bleeding can also cause anemia, but in those cases, the cause is obvious. Signs of anemia include paleness, fatigue, rapid heart rate and shortness of breath on exertion. Symptoms occur because oxygen levels drop below normal when red blood cell levels fall. Since oxygen is carried by red blood cells, oxygen deficit to all parts of the body occurs.
Vomiting Blood
Vomiting blood, an overt symptom of GI bleeding, normally garners immediate attention. Vomiting bright red blood occurs from bleeding in the upper GI tract, normally from a perforated ulcer or from dilated veins in the esophagus or stomach called varices, common in people with severe liver disease. Coffee ground emesis, so named for its dark brown, granular appearance, occurs when bleeding has slowed down or stopped. Stomach acid turns the normally red blood brown, the Merck Manual explains. Vomiting large amounts of blood can cause shock or death quickly and requires immediate medical attention.
Rectal Bleeding
Overt, or visible, rectal bleeding can occur as frank bleeding or as blood mixed in with the stool. Bleeding from the upper or lower GI tract can cause rectal bleeding, Frank blood that moves rapidly through the lower GI tract from the upper GI tract can also cause hematochezia, the medical term for passage of gross blood from the rectum. Passage of blood mixed with stool that causes black, tarry stools called melena most often indicates upper GI bleeding but can also come from the small bowel or right side of the colon, which lies farthest from the rectum. It takes between 100 to 200 milliliters of blood, slightly less than 7 ounces, to cause melena, according to the Merck Manual. Occult rectal bleeding is detected by chemically testing a stool sample.
Shock
Shock, a life-threatening decrease in blood flow to vital organs, may occur as the only sign of severe occult bleeding. Sudden collapse, low blood pressure, pallor, sweating, anxiety, dizziness, decreased urine output and rapid heartbeat may occur. Chest pain or heart attack from low blood supply to the heart may complicate the diagnosis, the Merck Manual warns.
