Research question

This might seem like a weird request, but I'm tossing this out there because I don't know where to start and don't know anyone in the medical field.  I'm writing a short story and the heroine has a 9 yr old son.  I want the son to be getting treated for some disease or illness in a hospital.  I don't want it to necessarily be life-threatening, but I would like it if he had to make a few trips to the hospital/clinic for treatments and when he's there it would take a few hours for those treatments.  He's a smart little boy, and sits and does his homework while getting the medical attention.

So any suggestions to possible disease or condition this boy could have that would see him in the hospital as mentioned above?
Thanks!
M