What happens if the fetal kidneys are enlarged?

Q: During an ultrasound (pregnancy 21 week), the doctor said that my baby boy's kidneys are enlarged measuring 4.6 mm and 4.3 mm. Is this dangerous for the baby?

A:In boys if both kidneys are dilated, we also need to know if the ureters (the pipes draining urine from kidneys to urinary bladder) are also dilated. Also whether the urinary bladder is emptying and what is the amount of amniotic fluid. This information will help us to decide the possible cause of this problem.