Blood in stools indicate that there have been active bleeding in then gastrointestinal tract secondary to gastric, duodenal or intestinal ulceration. A bleeding to shown in stools has to be greater than 60ml , beyond which it is seen as active bleed per rectum while defecation.
Drinking alcohol is the most common cause of gastric ulcerations and thereby bloody diarrhoea or dysentery. It is suggested that you may visit your physician to undergo a planned endoscopy to look for ulcers and thereby direct the treatment in form of H2 blockers and other antibiotics. Alcohol can cause severe gastritis and dyspepsia , which presents with moderate to severe pain in abdomen especially epigastric region and more likely cause if either worsening ulceration or even perforation sometimes.
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