Suggest Treatment For Persistent Vomiting, Exhaustion, Dehydration, Lethargy And Excessive Sleep For Over A Week

MY NEPHEW HAS SUDDEN ONSET NON-STOP VOMITING - HE HAS BEEN TESTED BY 4 HOSPITAL VISITS IN THE LAST 2 MONTHS - NOT DIABETES, RUNS IN FAMILY, NOT CELIAC OR ANY OTHER NORMAL TESTING - ONCE HE STARTS VOMITING, HE CANT STOP FOR DAYS 5-7 - THEN HE IS EXHAUSTED, DEHYDRATED, LETHARGIC... JUST DRAINED - THEN HE SLEEPS AND STARTS TO EAT IN SMALL DOSES FOR 2 OR 3 DAYS BEFORE HE IS WELL ENOUGH TO GO BACK TO WORK - THIS HAS BEEN GOING ON FOR SEVERAL YEARS - AND IS INTERMITANT - DO YOU HAVE ANY SUGGESTIONS OF TESTING HE SHOULD FOLLOW UP WITH... THANK YOU