Strange stool changes

I'm 25. About a year ago I stopped taking tagamet for my GERD (which has just about disappeared now) and since I've been having some very strange bowel problems. It started with undigested food of all sorts showing up at random intervals, from black olives to chunks of tomatoes to spinach and greens. Now I'm seeing small reddish areas in my stool (spots, not streaks that I still think might be tomatoes) but I'm starting to worry because with each bowel movement a yellow/brown (not red) color leeches from the stool into the bowl water at a very fast rate no matter the consistency (loose or solid stool.) My doctor recommended me for a colonoscopy and a in-office occult test showed me negative for blood. I haven't returned my samples for guaiac fecal occult tests (the first sample I gave they accidentally ran the wrong tests on) so I don't actually know if there's blood in my stool or not. Should I go ahead and have the colonoscopy without these results? I don't want to do this if it's not totally necessary.

[Ratnakar Kini, MD]

Hi,
Undigested food particles and vegetable matter in stool can be normal.
If occult blood test is positive , then colonoscopy may be needed.