Are you thin/slim? Did they rule out abdominal aortic aneurism? I can feel my aortic pulse all the time because I'm thin. It runs vertically up your torso just next to your belly button. Occasionally I can feel a "lump", but assume it's just related to poor digestion. It comes and goes infrequently, so I'm not too worried. I'm kind of surprised your doc is like, "I dunno ((shrug))..." If he thinks the mass has something to do with your issues and he's not sure what it is, why oh why didn't he call for an MRI or CT Scan? I'd probably look for a new MD that would take a little more interest in your case. You could have a tumor for all he knows! I doubt you do, but geesh...