Hello, my son who is now 15, has been experiencing polyurination, in ither words although normal urination during the day but as soon as he goes to bed, he gets up anywhere from 2 to 4 times to pee, but has just drops at a time. It s been going on for about 4 years. This spring, he had 2 full ultrasounds of all if his organs, at the Chikdren s hospital. Tests are normal. What could be causing this ? Thank you Bruna