Black stools and melena: causes and treatment in adults and infants

By Cristiano Antonino On Jul 3, 2022

The presence of blood in stools gives them a very dark colour, tending to black. This is blood coming from the upper part of the gastrointestinal tract, i.e. from the oesophagus, stomach and small intestine. If the blood came from the lower part of the intestine (closer to the anus), the blood would be bright red and not dark brown tending to black

Black stools due to bleeding are called ‘melena’

Not all black stools are necessarily due to bleeding: “false melena” are those stools that appear dark or black, but do not actually contain blood.

Black stools can be caused by various causes, such as ingestion of certain substances or taking iron supplements.

However, as mentioned earlier, black stools can also be caused by a serious condition, namely bleeding in the digestive tract due to a peptic ulcer.

Some of the most common causes of black stools include:

stomach ulcer (peptic ulcer);
inflammation of the gastrointestinal tract;
use of non-steroidal anti-inflammatory drugs.

Black stools may be a habit for people who have undergone colectomy surgery, because food is not digested in the most complete way.

However, if gastrointestinal bleeding has occurred in the past, stools have a bad smell or the problem goes on for more than a couple of days, consult your doctor immediately.

Black stools and melena: causes and treatment in adults and infants

One of the possible causes of melena is a bleeding ulcer: an ulcer is a wound that appears on the stomach lining and can cause bleeding and melena.

Contrary to popular belief, stomach ulcers are not usually caused by stress or spicy food (although these can aggravate an existing ulcer).

In fact, they are caused by an infection due to a bacterium called Helicobacter pylori (H. pylori).

Antibiotics are normally prescribed to eliminate the infection, and sometimes an acid reducer.

Another cause of stomach ulcers is the long-term use of pain-relieving drugs known as NSAIDs (non-steroidal anti-inflammatory drugs).

NSAIDs can irritate the stomach, weakening the lining’s ability to resist the acid produced in the stomach.

For this same reason, NSAIDs have a negative effect on Crohn’s disease and ulcerative colitis.

NSAIDs are common drugs such as ibuprofen, naproxen sodium and aspirin. Some NSAIDs are prescribed by doctors.

Stomach ulcers, caused by NSAIDs, usually heal after the offending drug is discontinued.

Gastritis (inflammation of the stomach lining) can also result in black stools.

This inflammation can be caused by too much alcohol or food, spicy food, smoking, bacterial infection or prolonged use of NSAIDs.

Gastritis can also develop after surgery or trauma, or it can be associated with pre-existing medical conditions.

Oesophageal varices are dilated veins in the stomach wall, either in the upper or lower oesophagus, and can also lead to black stools.

When these veins rupture, they can cause bleeding, which can result in blood appearing in the stool or vomiting.

Oesophageal varices are a serious complication resulting from portal hypertension (high blood pressure) caused by liver cirrhosis.

What symptoms accompany the appearance of black stools?

Black stools may be accompanied by other symptoms, which vary depending on the root cause.

Symptoms and signs that may accompany black stools include:

abdominal pain
abdominal bloating;
change in bowel habits;
diarrhoea;
indigestion;
flu-like symptoms ;
malodorous stools;
nausea and vomiting;
poor appetite;
general malaise;
asthenia;
rectal pain or burning sensation;
unexpected weight loss.

How is black stools diagnosed?

The underlying cause of black stools is generally diagnosed by the doctor by means of a medical history, an objective examination and various laboratory and imaging tests.

These tests may include:

X-rays;
ultrasound scans;
blood tests;
stool tests;
detection of blood in the stool;
colonoscopy;
gastroscopy;
stool culture.

What is the treatment for black stools?

Treatment varies depending on the cause of the problem, so it can be pharmacological, surgical or other, depending on the case.

Black stools in children and infants

It is possible for stools to take on this colouration due to an excessive intake of iron if the child has been fed a lot of vegetables.

If, on the other hand, the colouring is completely black, then it is necessary to have the child examined by the paediatrician immediately, as this could be a symptom of bleeding in the upper digestive tract and the dark colour could be due to the presence of digested blood.

If, on the other hand, small bright red streaks of blood are seen along with the stools, the most common cause is small fissures or excoriations of the anal mucosa, due to the expulsion of harder stools; the mother (or paediatrician) notices them because they are clearly visible around the anus.

To avoid them, all one has to do is to soften the stools, treating any constipation; to soothe the discomfort, one can apply healing ointments, e.g. phytostimulines, or a little zinc oxide ointment, which has the function of protecting the skin when stools pass.

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