Letter to the Editor: Influence of liver stiffness heterogeneity on staging fibrosis in patients with nonalcoholic fatty liver disease

To the editor, We read with great enthusiasm the article by Kawamura et al entitled “Influence of liver stiffness heterogeneity on staging fibrosis in patients with nonalcoholic fatty liver disease”.1 We were fortuitous to peruse this impressive article, and we congratulate the authors for their excellent efforts. We support their main findings that discordance between biopsy and magnetic resonance elastography (MRE)-based fibrosis staging is associated with heterogeneity in liver stiffness measurement (LSM), as depicted with MRE. However, we consider it essential to incorporate further elements to enhance the article’s quality and contribute to the existing literature. First, the study mentioned that while conducting MRE, the regions of interest included “parenchyma of the right lobe, avoiding the edges of the liver and large blood vessels.” Yet, the authors could not clarify if normal liver fissures, bile ducts, and gallbladder/fossa were avoided at all. These regions are shown to affect the accuracy of LSMs2 by producing low-quality elastograms. Therefore, the authors should have provided a more detailed delineation of these regions to augment the robustness of the outcomes. Second, MRE provides state-of-the-art non-invasive means to LSM; nevertheless, it has a major drawback of being non-diagnostic in certain body conditions of iron overload, such as hemochromatosis or hemosiderosis.3 The authors did not take any measures to address the possibility of these conditions in any of the patients, the presence of which could have altered the findings in these patients. Third, in color elastography, liver hot spots (LHS) should be identified and excluded from measurements to accurately assess the LSM.4 LHS are focal areas of elevated liver stiffness that are artifactual. Including LHS measurements may result in an erroneous classification of a normal liver, such as abnormal or over-estimation of liver fibrosis staging. To reinforce the validity of their findings, the authors should have furnished additional details regarding the presence or exclusion of LHS in their findings. Fourth, despite showing superior accuracy for fibrosis staging in comparison to vibration-controlled transient elastography (VCTE), the routine and repeated utilization of MRE in LSM is not recommended in the current guidelines due to its limited availability and unfavorable cost-effectiveness. Consequently, we believe that studies examining the clinical significance of variations in VCTE-based LSM are necessary. Finally, well-powered studies with large sample sizes are necessary to understand better the role of LSM heterogeneity in staging fibrosis in NAFLD patients, which can improve their prognosis and treatment.