multicystic kidney in fetus

Our 19 week ultrasound showed a slight enlargement to a 30% portion of one kidney in a 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 is 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, approximately 65 years ago.  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 (UPJ) and a multicystic kidney?  When listening to what doctors have said, the ultrasound appears to indicate kidney tissue is present and only a portion was originally affected.

Thanks

[Yao Sun, MD, PhD]

In the absence of other abnormalities, multicystic dysplastic kidney (MCDK) is not usually considered to be hereditary.  There are some rare genetic syndromes that include MCDK as a feature, but this is less of a concern since the ultrasounds so far show no other anomalies.

MCDK can occasionally be mistaken for other urinary obstructive problems such as uretero-pelvic junction obstruction.  Further ultrasounds may better delineate the kidney structure to allow your doctors to better differentiate whether this is MCDK or another kidney problem.

It is a good sign that the other kidney is not affected and the amniotic fluid volume has been normal.  Whether the problem in the affected kidney is MCDK or another form of urinary tract obstruction, the long term prognosis for your baby is good if no other abnormalities are found.