How To Treat Persistent Vomiting, Fever And Diarrhea In A Teenager?
Most likely viral gastroenteritis
Detailed Answer:
Hello XXXXXXX
If your son is not able to retain any fluids, then he might be getting dehydrated and losing electrolytes from the vomiting and diarrhea, which would be a reason to take him in.
I think it would be reasonable to take him in to the ER. Sometimes just getting an IV and electrolyte replacement (potassium in particular) and nothing by mouth for a few hours is enough to quiet it down, but in addition, they can also give him an antiemetic IV or IM which will help too.
So yes, if he isn't able to counter this with enough fluids, it is time to take him in.
In addition, although you didn't mention other alarming symptoms, while this is most likely a viral gastroenteritis ("stomach flu"), other things can present with these symptoms (appendicitis, etc) and this can be evaluated in the ER too.
I hope this information helps. Please let me know if I can provide further information.