Assessment of renal volume by 3D VOCAL Ultrasonography method in late-onset growth-restricted fetuses with normal amniotic fluid index.

Objectives: The aim of this study was to study renal volumetric alterations and renal artery doppler changes in late-onset fetal growth restricted (FGR) fetuses with normal amniotic fluid compared to healthy pregnancies.

Material And Methods: This prospective study was composed of pregnant women with late-onset FGR and a control group of uncomplicated pregnancies within 32-37 weeks of gestation. Following the assessment of umbilical, bilateral uterine, middle cerebral using Doppler Ultrasonography (US), three dimensional (3D) US Virtual Organ Computer-aided Analysis (VOCAL) was executed to calculate bilateral renal volumes.

Results: A total of 76 fetuses with FGR and 51 healthy fetuses (control group) were evaluated. Umbilical artery Doppler systole/diastole and Pulsatility index values were found to be significantly different between the two groups (p = 0.001 and p = 0.001, respectively). Middle cerebral, bilateral uterine, and bilateral renal arteries' Doppler indices revealed no difference between the two groups. Right, left, and mean renal volume of the fetuses with FGR were smaller than the control group, and the differences were statistically significant (p = 0.025, p = 0.004, p = 0.004, respectively). Left renal volume was significantly greater than the right renal volume in the control group (p = 0.009).

Conclusion: Although not accompanied by oligohydramnios, and having similar renal vascular resistance as the control group, renal volumes of fetuses with late-onset FGR were still observed lower than the control group. This difference was explained by not decreased blood flow via redistribution but other mechanisms like glomeruli reduction and glomerular apoptosis.