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Abdomen pain with blood in stool can be due to various causes as Inflammatoy Bowel Disease,Chron's Disease,Colon disorders etc.It is also to be corelated with other symptoms if present as nausea,vomitting,weight loss etc.Since how long has been this pain and blood in stool present?You require a clinical examination along with investigations as Endoscopy/Colonoscopy to rule out whether the bleeding is from the Upper or Lower GI tract.A proper evaluation is must for the correct diagnosis.
Consider visiting a Physician and wait for the Endoscopy results.
Take Care!