Multicystic kidney in fetus

Our 19 week ultrasound showed a slighty enlargement to a 30% portion of one kidney in the male fetus.  A subsequent ultrasound 2 weeks later showed no change in the kidney appearance, but the radiologist suspects a multicystic kidney with the rest of the kidney likely affected.  Amneotic fluid in normal and the other kidney does not seem affected.  There are no other noticable abnormalities in an otherwise healthy fetus.

I have several questions.  My father (deceased) had an enlarged, non-functioning kidney removed when he was 3.
Is a multicystic kidney hereditary?  I obviously cannot ask him about the specific diagnosis, but does a multicystic kidney continue to grow to the point of requiring surgery 3 years after birth?  Don't they usually involute and show no symptoms?

Perhaps this is a father's wishful thinking, but could there be any confusion on a prenatal ultrasound between hydronephrosis and a multicystic kidney?  Especially when the ultrasound appears to indicate a kidney is present and only a portion was originally affected.

Thanks