J.S.
My second child, boy, has hydronophrosis.. which is almost the same thing.. different name, and his kidney did not drain. It was found at birth also.. he also had to take antibiotics. He is not 16 months.. it has gone from severe to moderate... so he is outgrowing it. He also no longer has to take antibiotics.
The specialist that we saw in Texas was really good. According to him there are people that live with it forever and never have to have surgery... it just has to be monitored. However, in children, especially boys, the norm is that eventually outgrown it through puberty.
Hope this gives you some relief!! Good luck!!