Thank you for the query.
Any blood in stool
should be investigated as soon as possible. Dark blood in stool can be caused by bleeding from peptic ulcer
, gastric cancer
, colon polyps, colon cancer
, Crohn`s disease or by vessels malformation. Such symptom should not be neglected, even if not associated with any other symptoms like stomach pain, nausea, weight lost, etc.
So first of all you should have colonoscopy and upper GI endoscopy. Abdominal ultrasound and fool blood work should be performed as well.
Hope this will help.