Fetal renal growth as assessed through renal parenchymal area derived from prenatal and perinatal ultrasonography.

PURPOSE: Few quantitative parameters allow for comparison of serial studies in children with prenatally detected genitourinary abnormalities. We establish the first ultrasonographically based fetal renal parenchymal growth curve that could serve as a standard for fetal renal growth assessment.
MATERIALS AND METHODS: Longitudinal ultrasounds of 246 normal fetal kidneys from 16 to 38 weeks of gestation were scanned with renal parenchymal area calculated and growth curves plotted. Our previously determined nomogram from birth to adolescence was then combined with this fetal nomogram to produce a composite renal growth curve. Data were plotted as mean parenchymal area +/- 2 SD using lines determined by polynomial regression.
RESULTS: Renal growth curves were constructed independently for the right and left fetal kidneys as well as the total fetal renal parenchymal area. The polynomial regression equation for the right renal parenchymal area was y = -0.0076x(2) + 0.7141x - 8.5344 (r(2) = 0.91). The polynomial regression equation for the left renal parenchymal area was y = -0.0036x(2) + 0.5161x - 6.2337 (r(2) = 0.96). The polynomial regression equation for the total fetal renal parenchymal area was y = -0.0113x(2) + 1.234x - 14.814 (r(2) = 0.95).
CONCLUSIONS: We propose a new quantitative standard to evaluate appropriate fetal kidney size the prenatal renal parenchymal area growth curve. Renal parenchymal growth curves for the normal fetal kidney may serve as a valuable tool to assess fetal renal pathology.