## 3 The Opportunities and Challenges of Ultrasound-Based Elastography in Children NAFLD
\begin{tabular}{c c c c c c c} \multicolumn{9}{c}{Table 2: Cont.} \\ \hline \hline  & & & \multicolumn{3}{c}{**Elastography Method**} \\ \multicolumn{9}{c}{**Author, Year, and Country Patients**} & **Study Type/No of** & **Age (Vears)** & \multicolumn{3}{c}{**(TE/P-SWE/2D-SWE/SD)**} \\ \cline{4-7}
**Author, Year, and Country** & **Study Type/No of** & **Age (Vears)** & \multicolumn{3}{c}{**(TE (KPa)**} \\ \multicolumn{9}{c}{**County**} \\ \multicolumn{9}{c}{**Patients**} & **Mean/Median \({}^{*}\)** & **TE (KPa)** & \multicolumn{3}{c}{**p-SWE/ART (m/s)**} \\ \multicolumn{9}{c}{**Mean/Median \({}^{*}\)**} \\ \multicolumn{9}{c}{**Mean/Median \({}^{*}\)**} \\ \[PERSON] et al., 2013, Thailand [82] & Prospective/20 & 9.5 & 5.00 \({}^{*}\) & - & - & - \\ \[PERSON] et al., 2013, Germany [75] & Prospective/20 & 6.0 \({}^{*}\)(all 547) & 4.50 \({}^{*}\)(MG) & - & - & - \\ \[PERSON] et al., 2013, Switzerland [83] & Prospective/103 & 6.3 \({}^{*}\) & - & 1.12 \({}^{*}\) & - & - \\ \hline [PERSON] et al., 2013, Republic of Korea [84] & Prospective/202 & 8.1 \({}^{*}\) & - & 1.12 \({}^{*}\) & - & - \\ \[PERSON] et al., 2012, Romania [85] & Prospective/32 & 5.9 \({}^{*}\) & - & 1.18 \({}^{*}\) & - & - \\ \[PERSON] et al., 2012, Portugal [86] & Prospective/20 & 7.0 \({}^{*}\) & - & 1.11 \({}^{*}\) & - & - \\ \[PERSON] et al., 2012, Germany [87] & Prospective/240 & 9.3 (female) \({}^{*}\) & 4.70 \({}^{*}\) & - & - & - \\ \[PERSON] et al., 2012, Germany [88] & Prospective/132 & 9.2 \({}^{*}\) & - & 1.16 \(\pm\) 0.14 & - & - \\ \hline [PERSON] et al., 2010, Belgium [89] & Prospective/31 & 8.5 \({}^{*}\) & 4.30 (M) & - & - & - \\ \hline [PERSON] et al., 2009, Belgium [90] & Prospective/99 & 10.2 \({}^{*}\) & \(<\)12 \(y>\) 5.63) \(>\)12 \(y>\) 6.50 & - & - & - \\ \hline [PERSON] et al., 2009, France [91] & Prospective/19 & 12.7 \({}^{*}\) & 4.34 \({}^{*}\)(M) & - & - & \\ \hline [PERSON] et al., 2008, Italy [82] & Prospective/175 & \(8\pm 3.6\) & -3-7 & - & - & 4.8 \(\pm\) 1.9 with P probe \\ \hline \multicolumn{9}{c}{**Legend-TE - transient elastography, FSWE = point shear-wave elastography, FSWE = real-time shear-wave elastography; TE is measured in kPa, FSWE in m/s, rFSWE in both kPa and m/s. Probe type. M = d-s are probe, \({}^{*}\) p-s’- versus; Mean age calculated from mean of the three age groups in the study.**} \\ \end{tabular}   
The most recent confounding factor identified in a study performed on patients with Hepatitis C virus (HCV) is represented by serum transaminases hypothesized to increase liver stiffness measurements. Thus, [PERSON] et al. proved as a result of a study on 110 patients with HCV that the probability of liver fibrosis overestimation of two or more grades equals 50% for AST of 99 IU/L and ALT of 90.5 IU/L; 80% for AST of 123.5 IU/L and ALT of 101.5 IU/L; and up to 100% for AST of 211 IU/L and ALT of 140 IU/L [93]. Nevertheless, no data is available to date in pediatric patients regarding the impact of serum transaminases on liver stiffness measurements. Blood flow is another potential confounding factor of liver stiffness since previous studies underlined that increased blood flow as a result of food intake leads to an increased liver stiffness [94]. Thus, a period of at least 4 h of fasting is recommended before the examination in order to avoid this confounding factor [95]. It is well-documented that elastography is of major importance in assessing portal hypertension, but it was proved that severe portal hypertension impairs the correlations between liver stiffness and hepatic venous pressure gradient, emphasizing that the assessment of spleen stiffness could be more reliable in these cases [96]. In terms of spleen stiffness assessment, a recent study performed on HCV patients proved that spleen stiffness increased by 3.220 kPa for each mm of portal vein diameters and by 0.7 kPa for each cm/s of portal vein velocity, underlining that it might be an accurate parameter for portal hypertension stratification [97].