Fetal MRI with diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) assessment in the evaluation of renal development: preliminary experience in normal kidneys

The study aimed to investigate the correlation between apparent diffusion coefficient (ADC) and gestational age by applying diffusion-weighted imaging (DWI) in the study of normal fetal kidneys. We performed magnetic resonance (MR) imaging on 88 fetuses (gestational age range 17-40 weeks) after ultrasound had ruled out urinary system malformations. A multiplanar study of the urinary system was obtained by using conventional T2-weighted sequences and echoplanar imaging (EPI). DW sequences with ADC maps were subsequently acquired, and kidney ADC values were correlated with gestational age by diving the fetuses into six groups according to age. We found a correlation between ADC values and gestational age. The ADC values, ranging from 0.99 to 1.62x10(-3) mm(2)/s [mean 1.22; 95% confidence interval (CI) 1.19-1.25, standard deviation (SD) 0.147], showed a tendency to decrease with increasing gestational age. The relationship between ADC values and gestational age was expressed by a linear regression equation: ADC (mm(2)/s)=1.69-0.0169 (GA) (R(2)=37.7%, R(2) ADJ=37.0%, p < 0.005, Pearson correlation=-0.614). DWI with ADC mapping provides functional information on fetal renal parenchyma development and may thus become a useful tool in the management of pregnancy and treatment of the newborn child.