Fetal Renal Volume and Fetal Renal Artery Doppler in Normal and Intrauterine Growth Restricted Fetuses

Background: Human fetal kidney undergoes constant changes throughout the pregnancy to attain final maturity in terms of structural and functional aspect. Approximately one million nephrons are seen on either side at birth in term fetuses. Many factors both maternal and fetal affect nephrogenesis viz. maternal malnutrition, maternal hyperglycemia, Intrauterine Growth Restriction (IUGR), vitamin A deficiency, and fetal exposure to some drugs. The aim of this study was to evaluate changes in the fetal renal artery Doppler parameter and fetal kidney volume measured by 3D ultrasound system with (VOCAL) method in normally grown and growth restricted fetuses after 26 weeks of gestation.

Methods: This prospective study include 60 pregnant women divided in to two groups, first one (A) contains 30 pregnant women with intrauterine growth restricted fetuses, and the second one (B) contains 30 pregnant women with normally grown fetuses.

Results: There was insignificant differences between two groups as regard gestational age by date but gestational age by US there was significant decrease in group A. There were insignificant differences between two groups as regard length of kidney either right or left. There was significant decrease in kidney width right and left side in group A versus group B. There was significant decrease in kidney depth right and left side in group A versus group B. There was significant decrease in kidney volume right and left side in group A versus group B. There was significant decrease in combined kidney volume in group A versus group B. There was significant increase in renal artery PI, RI in group A versus group B.

Conclusions: Fetal hypoxemia which occurs in growth restricted fetuses leads to reduction in the percentage of the cardiac output reaching the kidneys which was reflected on Doppler as increase in the renal artery pulsatility index causing reduced renal perfusion. This reduction in the renal perfusion was responsible for impaired nephrogenesis and thus decreased kidney volume in growth restricted fetuses as compared to normal fetuses.