Looking For A Zebra in a Flock of Ducks

So, Tylor has been sick for 15 days. He is nauseous, dizzy (even laying down), no appetite (has lost 6 lbs so far), and food/liquid makes matters worse (doesn't matter what kind). We have been through one, "If it quacks like a duck and walks like a duck then it's probably a duck.", visit to the doctor and two other, "Well, it's not (blank, blank or blank).". Tylor has taken blood being drawn to the Medieval Torture level involving two smallish women, two regular sized guys and an Uber-mom hauling, dragging, kicking (I have bruises to prove it!) and screaming bloody murder, and I do mean bloody murder, to get done. We have now moved on from lower intestinal virus (still possible) to hepititus (nope) to liver issues (none) and several other things that weren't imortant enough for me to remember to an ultra-sound this Tuesday of his gallbladder. I told him it was brain surgery next ... made him smile. So, I was wondering if in our wealth of knowledge anyone has any thoughts on Zebras?