A gastrointestinal (GI) bleed is any blood loss occurring within the digestive tract, spanning from the esophagus to the anus. GI bleeds can be acute and sudden or chronic and slow, but they are always serious medical events requiring prompt attention. Recognizing the physical sensations and visible signs is crucial, as the appearance of the blood often provides the first clue about the location and severity of the hemorrhage.
Visible Signs of Bleeding
The most overt sign of a GI bleed is the appearance of blood in either vomit or stool. Vomiting blood, called hematemesis, presents in two ways. Bright red blood indicates fresh, active bleeding, usually suggesting a rapid hemorrhage in the upper GI tract (esophagus or stomach). If the vomited material looks dark, granular, and similar to wet coffee grounds, the blood has been partially digested by stomach acid.
Blood passed through the rectum also offers clues to the source. Melena describes stool that is black, sticky, and has a distinct tar-like consistency and odor. This results from blood that has traveled through most of the digestive tract, allowing enzymes and bacteria to chemically alter the hemoglobin.
Conversely, hematochezia is the passage of bright red or maroon-colored blood from the rectum, usually mixed with or coating the stool. This typically signals a bleed originating in the lower parts of the colon or rectum. However, a very rapid or massive bleed from the upper GI tract can also sometimes present as hematochezia if the blood moves too quickly to be chemically digested.
Systemic Effects and Physical Sensations
Blood loss from a GI bleed can trigger a range of internal physical sensations and systemic symptoms. When a significant amount of blood is lost, the body attempts to compensate for the sudden drop in circulating volume, leading to symptoms of hypovolemia. Patients often experience a profound sense of weakness and overwhelming fatigue.
The heart rate increases (tachycardia) as the heart works harder and faster to pump the remaining, reduced blood volume. This compensatory mechanism can lead to palpitations or a fluttering sensation in the chest. A person may also feel dizzy or lightheaded, especially when moving from a sitting or lying position to standing (orthostatic hypotension).
Blood loss causes a noticeable paleness of the skin and shortness of breath (dyspnea). Severe blood loss can lead to signs of organ hypoperfusion, such as feeling cold and clammy, or experiencing confusion due to reduced blood flow to the brain. Abdominal discomfort, cramping, or pain may also be felt, depending on the underlying cause of the bleeding, such as an ulcer or inflammation.
Interpreting Location: Upper Versus Lower GI Tract
The appearance of the blood is largely determined by where the bleed originates, which is broadly divided into upper and lower sections. Bleeding that occurs above the duodenum/jejunum boundary is considered an upper GI bleed, while below it is a lower GI bleed.
Upper GI bleeds, originating in the esophagus, stomach, or duodenum, are often characterized by dark blood because of exposure to stomach acid. Gastric acid chemically alters the red hemoglobin in the blood, oxidizing it into dark brown hematin. This process is responsible for the classic black, tarry appearance of melena or the coffee-ground texture of vomited blood.
Lower GI bleeds, which occur in the small intestine, colon, rectum, or anus, typically result in bright red or maroon blood. Since the bleeding site is farther down the tract, the blood has a much shorter transit time before being expelled. This limited exposure to digestive enzymes and acids prevents the significant chemical breakdown and darkening of the blood.
Recognizing When Immediate Medical Attention is Necessary
Certain signs indicate an immediate medical emergency. Any instance of passing a large volume of blood, whether through vomiting or in the stool, warrants an immediate call for emergency services.
Signs of shock are the clearest indicators that the body is severely compromised by blood loss. These signs include syncope (fainting or temporarily losing consciousness) and a feeling of profound, incapacitating dizziness. The skin may become extremely cold, pale, and clammy to the touch as the body redirects blood flow away from the extremities to protect vital organs.
An altered mental status, such as confusion or disorientation, is also a sign of critically low blood pressure and hypoperfusion of the brain. Severe, sharp abdominal pain accompanying the bleeding can indicate a potentially serious underlying cause, such as a perforated ulcer. If any of these severe indicators are present, immediate transportation to an emergency department is necessary.