My niece is very sick... someone help us!?

My niece turned 5 today. She has been in isolation at the hospital for 12 days now. Throwing up, cant keep anything down. Diarrhea. Yellow pale skin. abdominal cramping. Doctors have tested EVERYTHING under the sun. They did catscans, MRI's... blood work... etc. Cannot find anything wrong. Saying might be viral flu, but its been going on for 13 days already and no improvement in her condition. They want to fly her to the childrens hospital in ST. LOUIS to have a pediatric specialist do an upper GI and scope her stomache. And there is not a specialist in Springfield to work on babies. I am looking to yahoo for suggestions on what it may be... so any help would be wonderful. Praying for Abbigail!