MR volumetry of the normal fetal kidney: reference values.

Objective The aim of this study is to provide reference values for normal fetal kidney growth based on magnetic resonance (MR) volumetry Differences in side and gender will be investigated

Method The institute s database was reviewed for all fetal MR examinations of singleton pregnancies performed between January 2003 and December 2009 Exclusion criteria for renal volumetry were presence of urogenital anomalies intrauterine growth retardation polymalformative disorders oligo- or anhydramnios and maternal diabetes On anatomical images renal volumetry was evaluated by delineating kidneys on all slices and combining these into one volume measurement per kidney Polynomial regression analysis was performed to examine volume evolution over gestational age (GA)

Results Bilateral renal volumes of 274 MR examinations in 240 fetuses with GAs between 20 and 37 weeks were calculated The renal volumes strongly correlated with GA (polynomial regression analysis p <0 001) No significant difference could be observed between the left and right renal volume and between male and female (p = 0 12 and 0 68 respectively) For fetuses GA >= 30 weeks the right kidney was slightly larger than the left side (n = 100 p = 0 039)

Conclusion The present study provides reference data for normal fetal renal volumes, which may enable to identify fetuses at risk to develop congenital oligonephropathy.

Keywords:MR, fetal, renal, kidney, volume