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What causes greenish black stools?

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General & Family Physician
Practicing since : 1991
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Recently I have noticed that my stools are very dark - greenish black. Does this mean something bad?
Fri, 4 May 2018 in Digestion and Bowels
Answered by Dr. Bonnie Berger-Durnbaugh 1 hour later
Brief Answer:

Detailed Answer:
Hello Mr. XXXX,

If your stools are black and tarry appearing, then this can represent bleeding from the upper gastrointestinal tract (stomach or esophagus). This is because stomach acid changes blood to a black tarry appearance.

Pepto Bismol can also cause black appearing stools.

A greenish color can be from foods that have green in them such as green leafy vegetables (for example, kale), foods with green food coloring in them, and some herbal supplements.

It can also be freon a fast transit time through the intestines which doesn't allow enough time for bile salts from the gall bladder to be broken down. Bile acid/bile salts have a greenish color. If this is what is happening, usually there are other symptoms to go with it such as a shorter time from eating to having a BM, or loose stools.

You ask if it is something bad: If it is mostly black and tarry, then do go in to be seen now, as it can be stomach bleeding. If it is diarrheal, talk with your doctor about the color associated with this as it can be related to an infection in your digestive tract.

I hope this gives you enough information for how to proceed. Please let me know if I can provide further information or clarification.
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