Is Hematochesia or Melanin a Cause of Cancer?

The most morbid hypothesis is that he has a brisk upper GI bleed. It's much more likely for an upper GI bleed to result in hematochesia than for a lower GI bleeding to result in melanin. Hematochesia gives you a 75% chance of having a lower GI bleed. And I think that's the tiebreaker.