Health & Fitness

Why is my stool black?


Q:Over the past three months, I have been having episodes of dark stool. Initially, I thought it was due to the large amounts of spicy foods that I eat but my stool is still dark even after changing to a bland diet. I went to my doctor who explained that I was likely having some internal bleeding in either my stomach or my intestines. She suggested that I get a procedure known as an endoscopy to look for the culprit. Honestly, I am very uncomfortable with invasive procedures and have been hesitant to go for this test. Are there other alternatives to this test? Could this internal bleeding by a sign of cancer?


Black, tarry stool is referred to as melena. As your doctor correctly stated, it is usually a sign of bleeding from the digestive system. The stool becomes dark as it passes through the digestive due to the breakdown of the blood in the stool.

There are several causes of bleeding from the digestive tract. The most common is peptic ulcers.

Peptic ulcers are erosions of either the stomach lining or the first part of the intestine. Severe inflammation of the stomach wall in a condition known as gastritis can also result in bleeding into the digestive system.

(If the inflammation is in the small intestine, it is known as duodenitis). Peptic ulcers and gastritis have been found to be mostly caused by a bacterium known as H.pylori.

In some cases, it can be due to long-term use of harsh painkillers or the effects of smoking. Critically ill patients are also at risk of developing stress related ulcers and gastritis.

Liver damage (cirrhosis) results in a condition known as varices in the food pipe (oesophagus). Varices are enlarged veins in the food pipe, which are at a high risk of bleeding. Varices can also, sometimes, form in the upper part of the stomach due to a clot in the vein that drains blood from the spleen (the vessels of intra-abdominal organs are interconnected). Cirrhosis is a complication of liver infection (hepatitis), drug or alcohol abuse.

There are several unusual causes of bleeding in the digestive tract and this include bleeding from either the liver or pancreas and the presence of abnormal vessels in the stomach. Forceful vomiting can sometimes result in either a tear or even rupture of the food pipe, which can present with bleeding.

How can you identify cause of bleeding?

You will require an endoscopy to find out the exact cause of the bleed.

An endoscopy is a procedure in which a flexible ‘tube’ with a camera is inserted into your mouth and guided down your food pipe and into your stomach and intestines.

This allows your doctor to look for ulcers, varices and all possible causes of your bleeding. It is often done as an office procedure and you need not be sedated or anaesthetised during the process.

The entire process usually takes five to 10 minutes. Sometimes, the doctor may take specimens (biopsies) from your stomach or intestines for further assessment in the laboratory.

What are my other diagnostic options?

Well, it is possible to do stool or blood tests to check for infection with H.pylori and you can get treatment based on this.

However, this route of management presumes that your bleeding is related to peptic ulcers or gastritis or duodenitis. If you have another underlying problem, you will still need to get an endoscopy to identify them. A test to check for bleeding known as ‘fecal occult blood test’ can be done to confirm that you are actually bleeding from your digestive system but it does not add much value to identifying where the bleeding is coming from.

What is the treatment?

The treatment depends on the underlying cause. Ulcers may need to be injected or coagulated during the endoscopy if they are actively bleeding. If that fails, then surgery is often necessary. Otherwise, if they are not bleeding at the time of the endoscopy, they tend to respond well to medical treatment. It is also important to get rid of any offending painkillers and stop smoking. Varices usually need to have a rubber band put around them to prevent them from bleeding.

Can bleeding resolve on its own?

Yes, it can. However, if it does not, you could have potentially life endangering complications. In the worst-case scenario, you could bleed torrentially and require emergency intervention (including surgery).

Other more subtle issues involve the development of anaemia. In this condition, the blood levels become very low resulting in constant fatigue, palpitations, dizziness and even fainting spells.

Could the bleeding be a sign of cancer?

Yes, it can. Stomach cancer, in particular, can present as a bleeding ulcer. For this reason, it is crucial that you find the cause of your bleeding and get it addressed effectively.

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