My two year old son, currently has hydronephrosis of the Left Kidney. He is undergoing exploratory tommorrow, and will probably have the valve corrected after that....
Yeah, it is usually diagnosed early in life, and fairly easily corrected (or it corrects itself) before any damage occurs to the kidney. In my case, its been there since infancy, undetected until now. It has destroyed my left kidney, and is now a bag of pi$$ the size of a large grapefruit in my torso... weird image I tell ya.