The Quantity of Blood Required to Produce a Tarry Stool. How much? Melena, characterized by black tarry stools, can occur with as little as 50 cc of blood in the stomach. How Different stool colours can provide important clinical clues related to digestion, bleeding, liver disease, malabsorption, infection, or bowel inflammation. Disclaimer For educational purposes only. Not medical advice. Consult a qualified Your Poop Is Talking .. Are You Listening? Your stool is your gut's daily report card. The shape, color, and texture tell you exactly what's going on inside. Here's a quick doctor style Dark Stools and Abdominal Pain: A Case Study of Mr. Arnold's Course Hero Hematochezia vs Melena: Symptoms, Causes, Diagnosis, Treatment