Performance of two--dimensional ultrasound shear wave elastography: reference values of normal liver stiffness in children

Background Two-dimensional (2-D) shear wave elastography is a new sonographic elastography method for noninvasive measurement of liver stiffness. Objective The aim of this study was to establish reference values of normal liver stiffness on 2-D shear wave elastography in children. Materials and methods Two-dimensional shear wave elastography values were measured in 202 children with no liver disease from the neonatal period to puberty, who were divided into 4 age groups: newborns and infants, preschoolers, elementary school children and adolescents. We investigated the effects of age, depth of elastography measurement, transducer, number of measurements per child, liver size and Doppler parameters of hepatic blood flow on liver elasticity values. Results The mean normal liver elasticity value in the study population was: 4.29±0.59 kilopascals (kPa). In neonates and infants, mean liver elasticity value was 4.63 (± 0.6) kPa, in preschoolers and elementary school children, 4.05 (± 0.57) kPa and 4.15 (± 0.52) kPa, respectively, and in adolescents, 4.39 (± 0.55) kPa. Values in neonates and infants as well as adolescents were significantly higher than in preschoolers and elementary school children (Kruskal-Wallis, P <0.001; Mann-Whitney U tests, P <0.05). There was no significant association between liver elasticity values and size of the right lobe or Doppler parameters of hepatic blood flow. Different depths and the number of elastography measurements had no effect on liver elasticity values. Conclusion Two-dimensional shear wave elastography is achievable in a wide range of age in children. We established the reference values of normal liver stiffness on 2-D shear wave elastography in children.