Melena: What to Know About Black Stool
Medically reviewed by Kumkum S. Patel MD, MPH
Melena is when blood causes stools to appear black, tarry, and foul-smelling. The blood is dark because it is coming from somewhere in the upper digestive system, including the esophagus (food tube), stomach, and small intestine. Melena is not a disease itself but rather a symptom of a condition that's causing the bleeding.
Blood in the stool is never normal, so when melena is present, it is important to see a healthcare provider for an evaluation.
This article will describe some of the possible reasons for melena, when it might be an emergency, and the testing that might be done to determine the cause.
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What Causes Melena?
Stools may look black and appear tarry because they contain blood. The blood is dark because it is coming from somewhere in the upper digestive tract. This means that there is a medical condition present that is causing bleeding.
The amount of blood in the upper intestinal tract needs to be somewhere between 100 to 200 milliliters (about 7 to 13 tablespoons) to turn stool black. The black stools could continue for even a few days after the bleeding stops.
Peptic Ulcer (Gastric or Duodenal Ulcer)
A peptic ulcer is the most common cause of bleeding in the upper digestive tract. The stomach and small intestine have a lining, and if it wears away beyond the mucosal layers, bleeding can occur.
An ulcer in the stomach is called a gastric ulcer, and an ulcer in the first section of the small intestine (the duodenum) is called a duodenal ulcer.
It's a common myth that stress causes these ulcers. However, they are usually caused by Helicobacter pylori (H. pylori) bacteria infection. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin or Advil and Motrin (ibuprofen) can also cause these ulcers.
Some people with an ulcer have no symptoms. But when there are symptoms, they can include gnawing or burning pain in the upper chest. This pain might get better after eating or taking antacids, but sometimes when the stomach is involved, the pain doesn't follow a pattern.
Cirrhosis with Esophageal or Gastric Varices
Varices occur when a vein in the esophagus or stomach becomes dilated from too much pressure in the portal vein, which returns blood to the liver from the stomach, intestines, spleen, and pancreas. They are most commonly related to severe scarring in the liver, called cirrhosis.
Varices may have no symptoms except bleeding. The blood loss can be sudden and severe (acute). More commonly, however, the bleeding is chronic (long-lasting).
Mallory-Weiss Syndrome
A Mallory-Weiss tear is when there is a breakdown of the lining of the esophagus or upper stomach. It can be caused by forceful vomiting. It can be associated with vomiting from any cause but is sometimes associated with alcohol use disorder.
Erosive Esophagitis
Irritation or inflammation in the esophagus could lead to bleeding in some cases. Some of the symptoms could include trouble swallowing, feeling like something is caught in the throat, and a burning sensation.
There are a number of potential causes of esophagitis, including infection, vomiting, injury, gastroesophageal reflux disease (GERD), or a stuck pill.
Vascular Gastrointestinal Lesions
Vascular gastrointestinal lesions are rare. They are abnormalities in blood vessels that may cause bleeding.
These lesions can be present at birth or develop over time because of an associated condition such as kidney disease, cardiac disease, or mechanical heart valves (due to a condition called Heyde syndrome). The cecum and ascending colon are common places where these lesions might occur.
Tumors
Gastrointestinal stromal tumors may also cause bleeding that leads to melena. They are very rare and are caused by a mutation in certain genes. These tumors occur most often in people between 50 and 60 years old.
What Else Could Cause Black Stool?
Black stool could also be caused by something other than blood. Most commonly, this includes foods that are dark blue or black.
Some foods that turn stool dark are black licorice, chocolate sandwich cookies, beets, and artificial black, blue, or red food coloring. This discoloration is usually harmless and will go away after the food is digested.
Black stools could also be caused by iron supplements or bismuth subsalicylate (the active ingredient in Pepto-Bismol). As the dark color is not due to blood, it is not considered melena. If the cause is from a food or supplement, the stool will lack a tarry appearance and not have a distinctive foul-smelling odor.
What Does Melena Look Like?
True melena that's caused by blood in the stool has certain characteristics. Stool has a wide range of normal colors, but medium brown is typical. Melena causes stool to be much darker, appearing black or nearly black.
Melenic stool is also different in texture from normal stools. It is often described as tarry, meaning it is sticky and dense.
The third part of melena is the smell. Stool that contains blood has what is usually termed a "foul" smell, which is strong and unmistakable.
Other Symptoms With Melena
There may not be any other symptoms when melena starts. When there are symptoms, they will vary based on the condition that is causing it.
There could be abdominal or chest pain, especially if the cause is from an ulcer in the stomach or the small intestine. There could also be vomiting or diarrhea, depending on the reason for the melena. Significant blood loss could also be accompanied by dizziness, light-headedness, or even fainting.
How Do I Know If My Black Stool Is Melena?
When a black stool is melena, it will look tarry and smell offensive. Having other symptoms in the digestive tract may also signal blood in the stool.
However, when it's not clear that blood is in the stool, consider recent foods that you've eaten and supplements that you've taken. If any of the foods were dark in color, or if the supplements or medications could cause a dark stool, the stool might not contain blood.
Also, if the color changes back to that of a typical bowel movement and doesn't become black again, the cause likely was not blood.
If there is a true concern that blood is in the stool, contact a healthcare provider. A stool test called a fecal occult blood test might be used to detect the presence of blood.
Melena is a symptom of a problem, so there will be a need to determine the cause. The tests that might be used to find the cause of the bleeding might include:
Angiography: A type of X-ray that can be used to see blood vessels
Blood tests: Such as a complete blood count (CBC) and differential, serum chemistries, and clotting studies
Capsule endoscopy: A pill containing a tiny camera that's swallowed and takes a video of the small intestine as it passes through the body
Colonoscopy: A procedure to look at the inside of the colon using a flexible tube with a camera that's inserted through the anus
Esophagogastroduodenoscopy (EGD): A test used to look at the inside of the esophagus, stomach, and first part of the small intestine
Double balloon enteroscopy: A test to see farther into the small intestine than an EGD can reach
Gastrointestinal bleeding scan (GIBS): A noninvasive nuclear medicine test that uses contrast to find the source of bleeding
Stool culture: Tests stool for an infection
Tests for infection with H. pylori
What Is the Treatment for Melena?
The treatment for melena is based on what is causing the bleeding. In general, the goals will be as follows:
Stop the bleeding.
Treat blood loss (especially if a lot of blood has been lost).
Treat whatever is causing the blood loss.
Intravenous fluids and a blood transfusion may be needed if blood loss is significant.
If the bleeding is a tear or ulcer in the upper digestive system, an upper endoscopy might be used to not only see the cause of the bleeding but also to treat it. Ulcers in the stomach or duodenum that are caused by an infection with H. pylori will be treated with acid-reducing medication and antibiotics.
Less common causes of bleeding may require treatments that include surgery and medications to help manage ulcers and inflammation.
When to Contact a Healthcare Provider
When melena is suspected, it's important to seek medical care. Sometimes blood in the stool is clear, but if there's any doubt, ask a healthcare provider for guidance. Blood in the stool is never normal and is always a sign to see a healthcare provider.
Seek care immediately for the following symptoms that signal a large amount of blood has been lost:
A large volume of blood has passed in the stool.
Only blood is being passed.
You become dizzy, faint, light-headed, or pale.
Other signs requiring emergency care are:
Severe chest or abdominal pain
Being unable to swallow
Food that gets stuck in the esophagus
Severe pain and blood loss need care immediately and could be reasons to go to the emergency department or call 911 for an ambulance.
Summary
Blood in the stool needs to be investigated by a healthcare provider. Black or dark stools could be caused by food, medication, or supplements, but it might not be possible to tell the difference with the naked eye.
If there is any concern that blood is in the stool, it's important to consult a healthcare provider. Bleeding higher up in the digestive tract can result from several different conditions. It's important to receive a diagnosis so that treatment can begin.
Read the original article on Verywell Health.
