Hi! I faced the same problem while my kid was in my tummy 7 yrs ago. I cried and cried but onlly one doctor told me that my kid might be too naughty and not wanted to drink water only.
His stomach was full of water and his kidney was in good condition too. Other doctors said he might be suffered from brain problem... but we finally pray to God and wait.
Today, my boy is a healthy and happy kid. He had no sign of any problems that mentioned above.
BTW, he was playing bubble at his mouth (吹口水波) while I saw him first sight at he surgery room, i think this is the main reason why the tummy water was out of llimit!