Black Stool Alert: Signs of Melena and Internal Bleeding

Suddenly finding that your stool has turned black can be frightening. While many people first blame something they ate, very dark, sticky, and foul-smelling stool can be an important warning sign. In medical terms, this is called melena, and it usually means that blood from higher up in the digestive tract has been altered by stomach acid and enzymes before it leaves the body (1^✔ ✔Trusted Source
Causes of Melena and Effective Examination Strategies in Children

Go to source). When blood spends enough time inside the gut, the red pigment is broken down and oxidized, changing the stool to a black, tar-like appearance. This is different from simple stool darkening caused by food or supplements, which usually does not look sticky or smell strongly.

How Much Bleeding Can Turn Stool Black?

Melena is often a marker of upper gastrointestinal bleeding, which means bleeding from the esophagus, stomach, or the first part of the small intestine. Clinical research on patients with gastrointestinal bleeding has shown that even a modest volume of blood in the stomach can change stool color. Research published in Gastroenterology Research and Practice reported that as little as about 50 to 100 milliliters of blood in the upper gut may be enough to produce melena, and the black stools can continue for several days even after the bleeding has stopped.

Common causes behind this type of bleeding include:

• Peptic ulcers in the stomach or duodenum
• Inflammation or erosion of the stomach lining
• Swollen veins in the esophagus or stomach (varices) that rupture
• Tears in the lining of the upper digestive tract
• Less commonly, growths or tumors in the upper gut

Many of these problems can develop silently, with little or no pain, so a sudden change in stool can sometimes be the first visible clue.

What A Pediatric Study Revealed About Melena

Although melena is often discussed in adults, it can also occur in children. A study published in the journal Frontiers in Pediatrics examined 55 children who were investigated for black, tar-like stool. Doctors were able to identify the precise source of bleeding in 39 of them.

The analysis showed that:

• 34 of the 39 children with a known source had bleeding from the upper digestive tract.
• Duodenal ulcer was the single most common diagnosis, found in 22 children.
• Other upper gut causes included stomach ulcers, inflammation of the esophagus, and enlarged veins that had bled.
• In 5 children, the bleeding came from the small intestine, highlighting that melena can sometimes come from deeper segments of the bowel.

The study also stressed that a careful upper endoscopy is the key first test when melena is present. When standard endoscopy does not find a cause, small bowel tests such as capsule endoscopy can help uncover bleeding sites that are otherwise missed.

When Black Stool Might Be Harmless

Not every dark stool means internal bleeding. Certain foods and medicines can stain the stool black without any blood being present. Examples include:

• Iron tablets and some multivitamins
• Bismuth-containing stomach remedies
• Foods like black licorice, blueberries, or blood sausage
• Activated charcoal is taken for indigestion or poisoning

In these cases, the stool is usually not sticky or tarry and does not have a particularly bad smell. The color often returns to normal once the food or medicine is stopped (2^✔ ✔Trusted Source
Availability of Blood Urea Nitrogen/Creatinine Ratio in Gastrointestinal Bleeding with Melena in Children

Go to source).

However, if stool is black and tar-like, or stays dark over several bowel movements, it should always be treated seriously, especially if there are other symptoms such as dizziness, weakness, paleness, rapid heartbeat, shortness of breath, or vomiting.

How Doctors Investigate Melena

Evaluation typically begins with blood tests to check for anemia and to estimate how much blood has been lost. A stool test can confirm the presence of blood. The most important investigation is usually an upper endoscopy, where a flexible camera is guided through the mouth into the esophagus, stomach, and duodenum.

During endoscopy, doctors can:

• Look for ulcers, inflamed areas, tears, or abnormal vessels
• Take small tissue samples if needed
• Treat some bleeding sites immediately using clips, injections, or heat-based methods

If the bleeding source is still unclear, additional tests such as capsule endoscopy, imaging scans, or specialized deep endoscopy of the small intestine may be recommended. Treatment might include acid-reducing medicines, drugs that reduce pressure in gut veins, transfusions, or, rarely, surgery.

Takeaway: Do Not Ignore New Black, Tarry Stool

A one-time dark stool after eating certain foods is usually harmless. In contrast, new, black, sticky, and foul-smelling stool is a classic warning sign of melena, which often reflects bleeding in the upper digestive tract. Research in both adults and children shows that peptic ulcers and other upper gut problems are major causes, and even relatively small bleeds can visibly change stool color.

The safest approach is straightforward: if you notice black, tar-like stool, especially with weakness, dizziness, paleness, or vomiting, seek medical care promptly. Early diagnosis and treatment can control the bleed, address the underlying cause, and significantly lower the risk of serious complications.

References:

1. Causes of Melena and Effective Examination Strategies in Children - (https://pmc.ncbi.nlm.nih.gov/articles/PMC8692886/)
2. Availability of Blood Urea Nitrogen/Creatinine Ratio in Gastrointestinal Bleeding with Melena in Children - (https://pmc.ncbi.nlm.nih.gov/articles/PMC4391998/)

Source-Medindia