Purpose or Case Report: Our aim is to determine the normal elastography liver stiffness values in children and if sampling depth is a factor.
Methods & Materials: The study population included 127 children (68 male, 59 female) age 8 to 18 (mean 12.8 years, SD 3 years) who had liver ultrasound with elastography. Patients with abnormal liver ultrasound were separated from those with normal studies. The liver was normal in 69 children and abnormal in 58 children. All examinations were performed for clinical indications. Elastography was performed using acoustic radiation force impulse ultrasound and point shear-wave elastography technique. Measurements were performed at two depths: 2 cm and 4 cm. Ten measurements were performed at each depth. The median stiffness (k Pa) of those measurements at each depth was analyzed by utilizing a repeated measures analysis of covariance. Average median stiffness for different groups was compared using model-based t tests with the Bonferroni correction for multiple comparisons.
Results: A linear association between median stiffness and age, adjusting for whether or not liver findings are abnormal, depth, and the interaction between liver findings and depth, was identified (p=0.0095). The estimated corresponding slope is about 0.16 k Pa per 1 year of age (95% confidence interval (CI): (0.04, 0.28)).
Average median stiffness in k Pa adjusted for age in normal group increased from 3.72 at 2 cm to 4.15 at 4 cm and for the abnormal group from 4.61 to 5.84. There is a statistically significant difference between the average median stiffness at 2 cm and 4 cm for patients with normal liver findings adjusting for age (p=0.0119; 95% CI: (-0.78, -0.08), Bonferroni-adjusted) and for patients with abnormal liver findings adjusting for age (p < 0.0001; 95% CI: (-1.66, -0.79), Bonferroni-adjusted).
Regarding the difference between the average median stiffness at 2 cm and 4 cm for patients with normal liver findings and the corresponding difference for patients with abnormal liver findings, there is sufficient statistical evidence to suggest that there is a difference between those two differences, adjusting for age (p=0.0016; 95% CI: (0.31, 1.28)).
Conclusions: A small increase in k Pa with age was detected. Measurements at 4 cm depth are greater than 2 cm depth. The increase in median stiffness in abnormal livers is significantly greater than in normal livers suggesting a method for increasing sensitivity in detecting abnormal liver stiffness.