Are renal volumes measured by magnetic resonance imaging and three-dimensional ultrasound in the term neonate comparable?

Renal volume, but not renal length, has been shown to be positively correlated with renal function. Three-dimensional (3D) ultrasound and magnetic resonance imaging (MRI) are two modalities used to assess renal volume. The aim of our study was to determine whether 3D ultrasound measurements of renal volume in the neonate are comparable to those of MRI measurements. Preterm and term neonates had an MRI and 3D ultrasound to determine renal volume at the same time as they had an MRI brain scan for other clinical conditions. The preterm neonates were all term corrected age, and the term neonates were 1-4 weeks of age. None of the kidneys examined were abnormal. There were no significant differences in the weight or length of the preterm and term infants at the time of their MRI scan. The left renal length was significantly longer according to MRI measurements than according to 3D ultrasound measurements (p=0.02). Renal volumes of both the left and right kidney were greater when measured by MRI than by 3D ultrasound (p<0.0001, respectively). Total volumes of the kidneys were greater when measured by MRI than by 3D ultrasound (p=0.008). Renal volume in neonates was significantly less when evaluated by 3D ultrasound than by MRI. These results demonstrate that MRI and 3D ultrasound renal volumes are not comparable in the neonatal population and, therefore, the same radiological modality should be used if repeat volume measurements are to be performed.

Does extreme prematurity affect kidney volume at term corrected age?

OBJECTIVE: Extreme prematurity exposes the neonate to a number of potential renal insults that may result in a reduced number of glomeruli and/or renal size. This may predispose these individuals to cardiovascular disease later in life. The objective was to determine using magnetic resonance imaging (MRI) whether extreme prematurity results in decreased renal volume. METHODS: Neonates <29 weeks' gestation and term infants undergoing MRI of the brain were enrolled in the study. An MRI was performed at term corrected age in the premature neonate and within the first 4 weeks of life in the term neonate. RESULTS: Seventeen preterm infants and 13 term infants had MRIs performed. There was no significant difference in weight and length at the time of MRI (p = 0.76 and 0.11, respectively). There was no significant difference in total renal volume or total kidney volume to weight ratio between the preterm and term neonates (p = 0.83 and 0.6, respectively). CONCLUSIONS: At term corrected age, extremely premature neonates have the same renal volume as term infants. It is unclear whether renal volume is a good indicator of glomerular number.