Hematemesis and melena are distinct but related symptoms signaling bleeding within the gastrointestinal (GI) tract. Hematemesis is the vomiting of blood, indicating a source high in the digestive system. Melena is the passage of black, tarry stools, which also points to a bleed in the upper GI tract. Recognizing these presentations is important, as the appearance of the blood or stool provides immediate clues about the location, speed, and severity of the bleeding event.
Understanding Hematemesis
Hematemesis is the expulsion of blood from the mouth during vomiting, confirming the hemorrhage source is located above the ligament of Treitz. The color and consistency of the vomited blood are informative, falling into two main categories. Bright red blood suggests a rapid and active bleed, meaning the blood has not had time to interact with the acidic environment of the stomach before being expelled.
The second presentation is “coffee-ground” emesis, which consists of dark, granular material resembling spent coffee grounds. This appearance results from the iron molecules within the red blood cells oxidizing upon exposure to stomach acid. Coffee-ground emesis indicates a bleed that has slowed, stopped, or is less brisk than bright red blood. Both forms confirm an upper GI source, including the esophagus, stomach, and the duodenum.
Understanding Melena
Melena is the term for stool that is black, sticky, and tarry in texture, often accompanied by a foul odor. The dark color is due to the digestion and alteration of hemoglobin as it travels through the intestines. Digestive enzymes and intestinal bacteria break down the blood, causing the chemical change that results in the tarry appearance.
The presence of melena suggests the bleeding originates from the upper GI tract, requiring sufficient transit time for the blood to be chemically altered. At least 50 to 100 milliliters of blood must be lost to produce this noticeable change in stool color. Melena is contrasted with hematochezia, which is the passage of bright red blood from the rectum, usually indicating a lower GI source or a very rapid upper GI bleed. The tarry consistency and offensive smell distinguish true melena from black stools caused by certain medications or foods, such as iron supplements or bismuth subsalicylate.
Common Causes of Gastrointestinal Bleeding
The underlying medical conditions causing hematemesis and melena are generally located in the upper GI tract. Peptic ulcer disease is the most frequent cause of acute upper GI bleeding. These ulcers are open sores in the lining of the stomach or duodenum, developing when the protective mucosal layer is disrupted. This allows gastric acid to erode the tissue and potentially penetrate a blood vessel.
Another source is esophageal varices, which are enlarged veins in the lower esophagus that develop due to portal hypertension. This increased pressure, often a consequence of severe liver disease like cirrhosis, makes the varices fragile and prone to rupture, leading to sudden hemorrhage.
Erosive conditions, such as gastritis and esophagitis, also result in bleeding. Gastritis is inflammation of the stomach lining, and esophagitis is inflammation of the esophageal lining. Both can be caused by factors like chronic gastroesophageal reflux disease (GERD) or nonsteroidal anti-inflammatory drug (NSAID) use. These conditions lead to superficial erosions that may cause slow, persistent bleeding or significant blood loss.
A Mallory-Weiss tear is a notable cause, characterized by a laceration in the mucous membrane at the junction of the esophagus and stomach. These tears are caused by forceful or prolonged retching and vomiting, often seen after heavy alcohol consumption, and manifest as bright red hematemesis. Cancers of the esophagus or stomach can also cause bleeding presenting as either hematemesis or melena.
When to Seek Immediate Medical Attention
Any instance of hematemesis or melena should be medically evaluated, as both symptoms indicate internal bleeding. However, accompanying signs suggesting severe blood loss require immediate emergency attention. These signs relate to the body entering hemorrhagic shock due to a rapid decrease in circulating blood volume.
Symptoms of shock include lightheadedness, dizziness, or passing out (syncope). The body attempts to compensate for blood loss by increasing the heart rate, resulting in a rapid or thready pulse. Low blood pressure, pale and clammy skin, and difficulty breathing are warning signs of hemodynamic compromise. Any change in mental status, such as confusion, agitation, or unresponsiveness, signals that the brain is not receiving sufficient oxygen and demands immediate intervention.