Liver Stiffness Values Are Lower in Pediatric Subjects than in Adults and Increase with Age: A Multifrequency MR Elastography Study.

Purpose To determine if healthy hepatic mechanical properties differ between pediatric and adult subjects at magnetic resonance (MR) elastography. Materials and Methods Liver shear moduli in 24 healthy pediatric participants (13 children aged 5-14 years [seven boys, six girls] and 11 adolescents aged 15-18 years [six boys, five girls]) and 10 healthy adults (aged 22-36 years [five men, five women]) were obtained with 3-T MR elastography at 28, 56, and 84 Hz. Relationships between shear moduli and age were assessed with Spearman correlations. Differences between age groups were determined with one-way analysis of variance and Tukey multiple comparisons tests. Results Liver stiffness values (means ± standard deviations) were significantly lower in children and adolescents than in adults at 56 Hz (children, 2.2 kPa ± 0.3; adolescents, 2.2 kPa ± 0.2; adults, 2.6 kPa ± 0.3; analysis of variance, P = .009) and 84 Hz (children, 5.6 kPa ± 0.8; adolescents, 6.5 kPa ± 1.2; adults, 7.8 kPa ± 1.2; analysis of variance, P = .0003) but not at 28 Hz (children, 1.2 kPa ± 0.2; adolescents, 1.3 kPa ± 0.3; adults, 1.2 kPa ± 0.2; analysis of variance, P = .40). At 56 and 84 Hz, liver stiffness increased with age (Spearman correlation, r = 0.38 [P = .03] and r = 0.54 [P = .001], respectively). Stiffness varied less with frequency in children and adolescents than in adults (analysis of variance, P = .0009). No significant differences were found in shear moduli at 28, 56, or 84 Hz or frequency dependence between children and adolescents (P = .38, P = .99, P = .14, and P = .30, respectively, according to Tukey tests). Conclusion Liver stiffness values are lower and vary less with frequency in children and adolescents than in adults. Stiffness increases with age during normal development and approaches adult values during adolescence. Comparing pediatric liver stiffness to adult baseline values to detect pediatric liver mechanical abnormalities may not allow detection of mild disease and may lead to underestimation of severity. © RSNA, 2016 Online supplemental material is available for this article.