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A 19-year-old male asked:

Is black stool a symptom of colon cancer or ulcer?

3 doctor answers7 doctors weighed in
Dr. Gurmukh Singh
Pathology 49 years experience
Depends: There are many causes of black tarry stool. The common issue is bleeding in the intestine. Bleeding may be due to ulcers in the stomach, or intestine. Oral iron intake may produce dark stool. Colon cancer is one of the causes of bleeding in the intestine. It would be prudent to see your doctor to determine the cause of dark stools, especially if it is due to bleeding in the intestine.
Dr. Myron Arlen
Surgical Oncology 64 years experience
Ulcer: Bleeding from a tumor of the colon results in the presence of blood in the stool. This blood is for the most part red, but may have signs of some decomposition. When blood is released from a stomach ulcer, the acid that is present breaks the Hgb down to result in a black appearing stool which is not seen is colon malignancies.
Dr. Richard Perlman
Orthopedic Surgery 58 years experience
Dr Arlen is a very smart man. You should not ignore these symptoms (unless you are taking excessive amounts of iron supplements. Even so, you should be checked out by a physician.
Jun 21, 2015
Dr. Daniel Popowich
A Verified Doctoranswered
A US doctor answeredLearn more
It can be: Black stool is a sign of blood within the GI tract visually from the upper GI tract (stomach and small bowel). It is ALWAYS worth while to get checked out by a gastroenterologist to be certain.

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TX
A 35-year-old male asked:

Do all rectal/colon cancer have bloody or black stool?

1 doctor answer1 doctor weighed in
Dr. Saptarshi Bandyopadhyay
Hospital-based practice 21 years experience
No. Microscopic poss: Not all colon cancers cause changes to stool that u can see w/ your eye. Some polyps (pre-cancerous lesions) cause MICROscopic blood in the stool that only sensitive lab tests can pick up. Bright red stool is thought 2 b from rectum, maroon red stool from intestine, & dark / black stool (melena) from stomach; however, it depends on how brisk bleeding is. Slow bleeds may not discolor stool at all.

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Last updated Dec 19, 2018

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