Gastrointestinal Bleeding
Bleeding may occur anywhere along the digestive tract, from the mouth to the anus, for a variety of reasons. Blood may be visible in the stool or in vomit or may be hidden (occult) and detectable only by diagnostic tests.
Abnormal connections between the arteries and veins (arteriovenous malformations) sometimes form in the stomach and in the small and large intestines. These abnormal blood vessels are fragile and are likely to rupture and bleed intermittently, sometimes heavily, especially in older people. Veins in the esophagus can become dilated and twisted, a condition called esophageal varices (varicose veins in the esophagus), making them fragile and prone to bleeding (see Section 10, Chapter 135).
Certain drugs, such as aspirin and many other nonsteroidal anti-inflammatory drugs (NSAIDs), can irritate the digestive tract and cause bleeding. Drugs that reduce the blood's tendency to clot (anticoagulants) or that dissolve clots once they have formed (thrombolytics such as streptokinase or tissue plasminogen activator) can cause gastrointestinal bleeding as well.
 See the table Causes of Bleeding.
Symptoms
Symptoms of gastrointestinal bleeding include vomiting blood (hematemesis), passing black tarry stools (melena), and passing visible blood from the rectum (hematochezia). Black tarry stools usually result from bleeding that occurs high up in the digestive tract--for example, in the stomach or first segment of the small intestine (duodenum); blood in the stomach turns black when exposed to stomach acid and enzymes. A single severe bleeding episode can produce tarry stools for as long as a week, so continuing tarry stools do not necessarily indicate persistent bleeding.
People with long-term bleeding that tends to occur in small amounts or intermittently may develop symptoms of anemia, such as tiring easily and looking unnaturally pale. In the absence of such symptoms, a doctor may be able to detect an abnormal drop in blood pressure when a person sits or stands up after lying down.
Symptoms indicating a serious and sudden blood loss include a rapid pulse rate, low blood pressure, and reduced urine flow. A person may also have cold, clammy hands and feet. The reduced supply of blood to the brain caused by the bleeding may lead to confusion, disorientation, sleepiness, and even shock (see Section 3, Chapter 24).
Symptoms of serious blood loss may differ, depending on whether the person has certain other diseases. For instance, a person with coronary artery disease may suddenly develop chest pain (angina) or symptoms of a heart attack. The symptoms of other diseases--such as heart failure, lung disease, and kidney failure--may worsen. In people with liver disease, bleeding into the intestine can cause a buildup of toxins that, in turn, may cause a condition called liver encephalopathy, characterized by changes in personality, awareness, and mental ability (see Section 10, Chapter 135).
Diagnosis
A doctor may suspect gastrointestinal bleeding after reviewing symptoms and examining a stool sample. If blood is not visible in the stool, a chemical (guaiac) can be added to the stool sample to reveal hidden blood (see Section 9, Chapter 119). It may be necessary to obtain a sample from the stomach; if vomit is not available to test for blood, a doctor may have to pass a tube through the mouth into the stomach to obtain the sample.
Once it has been established that bleeding has occurred or is continuing to occur, a doctor performs a rectal examination to determine the source of the bleeding. For example, a doctor feels for hemorrhoids, rectal tears (fissures), and tumors. Then, tests that may include different types of x-rays and endoscopy (examination with a flexible viewing tube) are chosen according to whether the doctor suspects that the bleeding is coming from the upper digestive tract (esophagus, stomach, and first segment of the small intestine) or lower digestive tract (lower small intestine, large intestine, rectum, and anus).
Knowing about the symptoms that led up to a bleeding episode may help a doctor determine its cause. Pain in the abdomen that is relieved by food or antacids suggests a peptic ulcer; however, bleeding ulcers often are not painful. A doctor will ask about use of aspirin or other nonsteroidal anti-inflammatory drugs, which can damage the lining of the stomach.
Cancer is suspected when bleeding is accompanied by loss of appetite and weight that occurs for no obvious reason. A person who has difficulty swallowing is examined for a narrowing of the esophagus, which could be caused by cancer. Very forceful vomiting and retching immediately before bleeding occurs suggests a torn esophagus, but about half of people with such a tear do not vomit beforehand. New or worsening constipation or diarrhea, along with bleeding or hidden blood in the stool, may be caused by cancer or a polyp in the lower intestine, particularly in someone older than 45. Fresh blood on the surface of the stool may result from rectal cancer or from another problem with the rectum, such as hemorrhoids.
Knowing that a person has certain other diseases may also help a doctor determine the cause of bleeding. For example, people with liver disease are more likely to develop arteriovenous malformations in the stomach or intestines and varicose veins in the esophagus (esophageal varices).
Treatment
In more than 80% of people with gastrointestinal bleeding, the body is able to stop the bleeding on its own. People who continue to bleed or who have symptoms of a sudden loss of a large amount of blood usually are hospitalized and often are admitted to an intensive care unit.
If a large amount of blood has been lost, fluids are given intravenously, and a blood transfusion may be needed. After a blood transfusion, the person is observed closely for evidence of continued bleeding, such as an increased pulse rate, a drop in blood pressure, or a loss of blood from the mouth or anus.
Bleeding from esophageal varices can be treated in several ways. In one method, an irritating chemical is injected into the bleeding vessels through an endoscope, causing inflammation and scarring of the veins, which stops the bleeding (sclerotherapy). In a second, more frequently used method, the varices are tied off with rubber bands during endoscopy (rubber band ligation). In a third method, now rarely used, a catheter with a deflated balloon at its tip is inserted through the mouth into the esophagus, and the balloon is then inflated to apply pressure on the bleeding area (esophageal tamponade).
Bleeding in the stomach often can be stopped with one of several procedures performed with an endoscope; these involve using an electrical current to destroy the portion of a vessel that is bleeding (cauterization) or injecting a material that causes clotting within the bleeding vessel. If these procedures fail, surgery may be needed.
Bleeding of the lower intestine usually does not require emergency treatment unless the person loses a large amount of blood quickly. Tests to locate the bleeding precisely, such as endoscopy or radionuclide scans, may be needed. Surgery can be performed if bleeding does not stop.
| 
