Black Stool: Causes, Diagnosis and Treatment

Black stools aren’t always a health problem. Sometimes it’s caused by your diet, supplements, and medication. Other times, it can be due to health conditions like bleeding from the digestive system.

It’s good to report it to your doctor to be sure what exactly is causing it.

Causes Of Black Stool

1. Dark Foods

Foods that have dark pigments – black, dark blue, dark green, may end up darkening the color of the stool. This is because there is no other way for the body to get rid of these pigments, so they are dumped in your stool.

Examples of foods that cause black poop are:

  • Blueberries
  • Black licorice
  • Dark chocolate
  • Beets
  • Cranberries
  • Purple juice
  • Prunes
  • Dark-green leafy vegetables such as spinach and kale

If you have taken any of these and you noticed your poop turned black, you may have found the cause. These foods aren’t harmful but you can avoid them for a few days and observe your stool afterward.

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If it remains dark or black, then you may have something else going on that is unrelated to your diet.

However, if your stools revert to their normal color, it means that the blackening of your stool was due to your diet. There is no cause for alarm in this situation.

2. Medicines

Another very common cause of black stools is Iron supplements or Iron-containing medication. The Iron ingested undergoes some changes in the gut that can lead to black discoloration of the stools.

When you start taking Iron-containing medications, most doctors will inform you of this well-known side effect of blackened stools.

Another popular stool darkening medicine is Pepto-Bismol or bismuth-containing drugs.

Analgesics like Aspirin, Ibuprofen and other NSAIDs (Non-Steroidal Anti-Inflammatory Drugs) can cause black stools but in a more worrisome manner. Prolonged use of these drugs can damage the inner lining of the stomach and cause bleeding. When this blood mixes with poop, it turns black.

If you have been using these NSAIDs for a long period for conditions like chronic pain and arthritis and have recently developed black stools, you may be bleeding in your gut. Please see your doctor as soon as possible for further evaluation.

3. Gastro-Enteritis

Gastroenteritis is the inflammation of the stomach and small intestines usually due to an infection. The infection causes the gut to be sore (inflamed) and some amount of blood is released which then ends up in the stool.

It is not a common cause of black stools and the infection would have to be very severe. Gastroenteritis more commonly causes nausea, vomiting, diarrhea, abdominal cramps, fever and loss of appetite.

If you have symptoms of gastroenteritis and you notice black or bloody stools, please see your doctor immediately.

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4. Gastro-Intestinal Bleeding

This is by far the commonest medical cause of black stools.

When there is bleeding in the gut, it undergoes some chemical changes and ends up coloring the poop black.

The human gut is very extensive and a bleed anywhere from the esophagus to the intestines can cause black stools. There are specific conditions which have been known to cause black stools, the commonest ones are:

Esophageal Varices – This is a condition usually seen in persons with liver disease. The blood vessels around the esophagus swell and eventually rupture releasing a lot of blood into the stomach and intestines. The blood becomes mixed in with poop turning it black.

If you have liver disease and have not been evaluated for esophageal varices, please see your doctor immediately if you notice your stool has turned black.

Mallory-Weiss tear – This is a tear in the lower part of the esophagus that usually results from prolonged, violent vomiting and retching or coughing. Blood oozes from the tear into the gut and ends up in the stool.

If you have had a recent episode of violent vomiting or coughing and afterward you observed dark stools, you may need to see your doctor for further investigations.

Peptic ulcer disease – Peptic ulcer is one of the commonest gastrointestinal conditions worldwide. It is the presence of sores on the inner lining of the stomach that can cause bleeding. There is usually an associated abdominal pain.

Ulcer is one of the first things that is checked for when there is a complaint of black stools and the mild causes (food and supplements) have been ruled out. It is a very common cause of black stools and if severe or left untreated, it can be fatal.

Peptic ulcer disease can be well managed and treated by your doctor. If it is caused by an infection, you’ll need a course of antibiotics to eradicate the bacteria.

Gastritis – This is the inflammation of the stomach. It can be caused by an infection, auto-immune disease (the body fighting itself) or drugs like NSAIDs.

The inflammatory process causes the stomach to bleed, releasing blood into the stool and turning it black. This also must be managed by your doctor.

5. Gastrointestinal Cancer

Cancer anywhere from the esophagus to the intestines can cause a bleed in the gut. This blood turns the stool black.

A person who is older (above 50 years), has persistent black stools and unexplained weight loss may have GI cancer and needs to consult a doctor as soon as possible.

There may be no pain or abdominal swelling. Conditions like intestinal polyps and inflammatory bowel disease increase a person’s chances of developing cancer. If there is a history of these, immediate evaluation is required if black stools are observed.

Diagnostic Tests

The first step in determining the cause of any medical problem is a medical interview and a physical examination. It is during this interview that the doctor would determine if the cause may be from your diet,  current medications or a medical condition.

A blood and stool sample might be taken and analyzed to help with the diagnosis. If blood is found in your stool and/ or your blood level is decreased you may have to have an endoscopy done. This is basically viewing your digestive tract to look for sources of bleeding.

Scans like a CT scan or MRI scan may also be requested by your doctor.

Treatment Options

Treatment is always dependent on the cause.

Dietary Change

If the cause is food and medication, the obvious treatment option would be avoidance. When you avoid the things in your diet causing your stool to be black, you won’t have black stools anymore.

Medications

In conditions like Inflammatory bowel disease, peptic ulcer, and infections, medication will be prescribed to treat the underlying cause.

Endoscopy

In more serious cases where the bleeding is brisk or continuous, the source of the bleed has to be identified and stopped. A long flexible tube with a tiny camera attached (called an endoscope) is passed through the mouth to view along the esophagus, the stomach and some parts of the small intestine.

If the source of the bleed is found, using the same endoscope, your doctor can stop the bleeding by applying heat or binding it.

Colonoscopy

This is essentially the same as the endoscopy except the tube goes in through the anus. The source of the bleed is searched for and when identified, it is stopped by heat or binding.

GI Camera

A slow bleed coming from the middle of the small intestine may be missed by both upper and lower endoscopy. In such cases, you may be asked to swallow a small pill-like camera which takes thousands of pictures of your gut and transmits them to a computer for your doctor to view.

When the location of the bleeder is seen, surgery may then be carried out in the exact location to stop the bleeding.

Surgery

Sometimes, gut bleeding might need surgery to locate and treat the problem.

Summary

Black stools might be due to your diet, medications or a bleed somewhere in your digestive system.

If you have black stools, a visit to your physician is necessary to determine the cause and for prompt treatment.

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