o_1977r8vv9vk1ts2ms0kd8pksa.pdf

216 J. C. Veille
Table 15.2. Resistance index (RI) of the renal artery in normal
fetuses and children
Age group Number RI
Fetuses (3rd trimester) 32 0.67±0.88
0±1 month 30 0.57±0.90
1±3 months 20 0.60±0.84
3±6 months 11 0.65±0.75
creased significantly after maternal meal ingestion in
normally grown fetuses during late pregnancy
(n=14) (fasting = 2.36Ô0.16 versus fed =2.09 Ô 0.33;
P=0.021). These authors postulated that the decrease
in the resistance may be associated with increased
fetal urine production after maternal meals [25].
Renal Artery Doppler Studies
in IUGR Fetuses
Using duplex Doppler ultrasound and a low wall filter
(50 Hz), Veille and Kanaan could not demonstrate absent
end-diastolic flow of the fetal renal artery in a
group of asymmetric fetuses who were suffering intrauterine
growth restriction (IUGR) [13]. The PI in
the IUGR fetuses was significantly higher than in
normally grown fetuses. Among the IUGR group, fetuses
with signs of hypoxia had an even higher S/D
ratio than the fetuses without signs of hypoxia [13].
These investigators suggested that local mechanisms
are operational in the fetal kidneys that may in turn
influence renal blood flow.
Vyas and Campbell found that 64% of small-forgestational-age
(SGA) human fetuses had a PI higher
than the 90th percentile confidence interval of the reference
range for gestation (Fig. 15.6) [15]. They found
no association between the change in PI and a
Fig. 15.6. The 5th, 50th, and 90th percentiles for the fetal
renal artery pulsatility index (PI) and gestational age. Sixtyfour
percent of small-for-gestational age fetuses had a PI
above the 90th percentile. (Reprinted from [15] with permission)
change in umbilical cord PO 2 concentration. In this
group of SGA fetuses, 20 of 48 (42%) had oligohydramnios.
The PI of 16 of 20 fetuses with oligohydramnios
(80%) were above the 95th percentile of
their normal reference range [15]. The authors concluded
that as the impedance to fetal renal blood flow
increases, which indicates a higher PI, it is associated
with a decrease in fetal urine production.
In a prospective longitudinal study, the changes
within the fetal renal circulation were assessed by
Doppler sonography in preterm severely growth-restricted
fetuses during the period of gradual deterioration
prior to delivery; the relationship between
Doppler measurements, amniotic fluid index, birth
weight, and fetal condition at birth were examined.
Sixteen preterm growth-restricted fetuses between 26
and 35 weeks of gestational age were studied. Serial
Doppler measurements were made of the renal artery,
umbilical artery, middle cerebral artery, and ductus
venosus. The PI in the renal artery did not show any
correlation with cord blood pH, birth weight, or amniotic
fluid index corrected for gestational age (Delta/
SDAFI). Peak systolic velocities in the renal artery
showed a significant reduction with time (n=7,
P