Two-dimensional shear wave elastography and ultrasound-guided attenuation parameter for progressive non-alcoholic steatohepatitis

Performance of Magnetic Resonance Imaging and Ultrasound for Identifying the Different Degrees of Hepatic Steatosis: A Systematic Review and Meta-analysis

BACKGROUND

MRI proton density fat fraction (MRI-PDFF), controlled attenuation parameters (CAP), and attenuation coefficients (AC) are capable of steatosis characterization and may be useful as noninvasive alternatives for diagnosing hepatic steatosis.

PURPOSE

This meta-analysis aimed to evaluate the performance of MRI-PDFF, CAP, and AC in grading hepatic steatosis, using histology as the reference standard.

METHODS

We conducted a comprehensive search of the PubMed, Cochrane Library, Embase, and Web of Science databases until June 2024. The quality of eligible studies was assessed. Pooled sensitivity, specificity, and area under receiver operating characteristic (AUC) curves were calculated using a bivariate random-effects model. Meta-regression analysis, subgroup analysis, and Deeks' test were performed to explore heterogeneity and assess publication bias.

RESULTS

This meta-analysis included 38 studies with 5056 patients with metabolic dysfunction-associated steatotic liver disease. The AUC values for grading steatosis ≥S1, ≥S2, and ≥S3 were 0.99, 0.89, and 0.90 for MRI-PDFF, 0.95, 0.84, and 0.77 for CAP, and 0.97, 0.90, and 0.89 for AC, respectively. CAP demonstrated lower accuracy for detecting steatosis grades ≥S2 and ≥S3 compared to MRI-PDFF (0.89 vs. 0.84, p<0.001; 0.90 vs. 0.77, p<0.001) and AC (0.90 vs. 0.84, p<0.001; 0.89 vs. 0.77, p<0.001). Subgroup analyses revealed that MRI-PDFF and CAP exhibited superior diagnostic performance in diagnosing ≥S2 and ≥S3 steatosis among individuals in Asia, with a body mass index ≤30 kg/m2, and age <51 years.

CONCLUSION

A direct comparison with CAP showed greater accuracy for MRI-PDFF and AC in diagnosing moderate and severe steatosis, and similar diagnostic performance for MRI-PDFF and AC. For patients with steatosis, AC should be incorporated into routine ultrasound screening.

Impact of shear wave elastography and attenuation imaging for predicting life-threatening event in patients with metabolic dysfunction-associated steatotic liver disease

We aimed to elucidate the value of ultrasound-based biomarkers for predicting the major life-threatening events in metabolic dysfunction-associated steatotic liver disease (MASLD). We established a prospective cohort of 279 patients who underwent two-dimensional shear wave elastography (2D-SWE), ultrasound-guided attenuation parameter (UGAP). An area under the curve analysis was performed to determine the cutoff values of liver stiffness measurements (LSM) by 2D-SWE and attenuation coefficient (AC) by UGAP for a moderate fibrosis and a moderate steatosis. We then classified the cohort into Groups A (low LSM and low AC), B (low LSM and high AC), C (high LSM and high AC), and D (high LSM and low AC). We compared the incidence of events between the groups, and estimated the hazard ratios (HRs) with 95% confidence intervals (CIs). The LSM and AC cut off values were 8.37 kPa and 0.62 dB/cm/MHz, respectively. The cumulative incidence rate in Groups A, B, C, and D were 11.2%, 12.2%, 29.5%, and 31.0%/5years, respectively (p < 0.05). LSM (HRs = 1.20, 95%CIs: 1.09-1.32, p < 0.01), and AC (HRs = 1.62, 95%CIs: 1.04-2.51, p = 0.03) were associated with life-threatening events. A combination of 2D-SWE and UGAP may help identify patients with MASLD at high risk for subsequent life-threatening events.

Comparison of the diagnostic accuracy of shear wave elastography with transient elastography in adult nonalcoholic fatty liver disease: a systematic review and network meta-analysis of diagnostic test accuracy

PURPOSE

To compare the diagnostic test accuracy (DTA) of shear wave elastography (SWE) to that of transient elastography (TE) for liver fibrosis grade assessment in nonalcoholic fatty liver disease adults.

METHODS

MEDLINE, The Cochrane Library, and Web of Science were searched. Inclusion criteria were primary studies examining DTA of TE, point SWE (pSWE), two-dimensional SWE (2D-SWE), or magnetic resonance elastography (MRE) with liver biopsy. Network meta-analysis was conducted using a Bayesian bivariate mixed-effects model.

RESULTS

For fibrosis grade 2 or higher, 15 studies with 25 observations (16 observations for TE, 1 for MRE, 4 for pSWE and 2D-SWE; 2,066 patients) were included; the pooled sensitivity and specificity were 0.79 (95% credible interval (CrI) 0.70-0.86; 95% prediction interval (PI) 0.36-0.96) and 0.73 (95% CrI 0.62-0.82; 95% PI 0.23-0.96) for TE, 0.68 (95% CrI 0.48-0.83; 95% PI 0.23-0.94) and 0.75 (95% CrI 0.53-0.88; 95% PI 0.24-0.97) for pSWE, 0.85 (95% CrI 0.70-0.93; 95% PI 0.40-0.98) and 0.72 (95% CrI 0.49-0.86; 95% PI 0.20-0.96) for 2D-SWE, respectively. The proportion of studies classified as unclear in QUADAS-2 was high, and the results were heterogeneous.

CONCLUSION

2D-SWE could be recommended as TE is for liver fibrosis assessment. The protocol of this systematic review and network meta-analysis has been registered in PROSPERO (CRD42022327249). All included primary papers have already been published and the information and data can be used freely.

Novel subharmonic-aided pressure estimation for identifying high-risk esophagogastric varices

BACKGROUND

Subharmonic-aided pressure estimation (SHAPE) is a technique for determining changes in ambient pressure. We aimed to analyze a novel SHAPE integrated into ultrasound diagnostic equipment to predict patients with liver cirrhosis at high risk of esophagogastric varices (EV).

METHODS

This prospective study included 111 patients with liver cirrhosis diagnosed between 2020 and 2023. We obtained liver stiffness measurements (LSM) and spleen stiffness measurements (SSM) using shear wave elastography and hepatic vein-portal vein (HV-PV) gradient using the SHAPE method. The EV risk was determined either as null, low, or high by esophagoscopy and Child-Pugh stage.

RESULTS

HV-PV gradient increased concordantly with the increase in EV risk (- 7.0 dB in null-risk, - 4.4 dB in low-risk, and - 2.0 dB in high-risk) with statistically significant difference among any two groups. The most appropriate cut-off value of the HV-PV gradient was - 3.5 dB, and sensitivity, specificity, and positive and negative predictive values were 80.0%, 89.0%, 80.0%, and 88.0%, respectively. The areas under the curve values for predicting the high-risk EV were 0.920, 0.843, and 0.824 for the HV-PV gradient, LSM, and SSM, respectively.

CONCLUSIONS

The novel SHAPE system demonstrated high accuracy in identifying patients with liver cirrhosis at a high risk of EV.

Imaging-based noninvasive liver disease assessment for staging liver fibrosis in chronic liver disease: A systematic review supporting the AASLD Practice Guideline

BACKGROUND AND AIMS

Transient elastography (TE), shear wave elastography, and/or magnetic resonance elastography (MRE), each providing liver stiffness measurement (LSM), are the most studied imaging-based noninvasive liver disease assessment (NILDA) techniques. To support the American Association for the Study of Liver Diseases guidelines on NILDA, we summarized the evidence on the accuracy of these LSM methods to stage liver fibrosis (F).

APPROACH AND RESULTS

A comprehensive search for studies assessing LSM by TE, shear wave elastography, or MRE for the identification of significant fibrosis (F2-4), advanced fibrosis (F3-4), or cirrhosis (F4), using histopathology as the standard of reference by liver disease etiology in adults or children from inception to April 2022 was performed. We excluded studies with <50 patients with a single disease entity and mixed liver disease etiologies (with the exception of HCV/HIV coinfection). Out of 9447 studies, 240 with 61,193 patients were included in this systematic review. In adults, sensitivities for the identification of F2-4 ranged from 51% to 95%, for F3-4 from 70% to 100%, and for F4 from 60% to 100% across all techniques/diseases, whereas specificities ranged from 36% to 100%, 74% to 100%, and 67% to 99%, respectively. The largest body of evidence available was for TE; MRE appeared to be the most accurate method. Imaging-based NILDA outperformed blood-based NILDA in most comparisons, particularly for the identification of F3-4/F4. In the pediatric population, imaging-based NILDA is likely as accurate as in adults.

CONCLUSIONS

LSM from TE, shear wave elastography, and MRE shows acceptable to outstanding accuracy for the detection of liver fibrosis across various liver disease etiologies. Accuracy increased from F2-4 to F3-4 and was the highest for F4. Further research is needed to better standardize the use of imaging-based NILDA, particularly in pediatric liver diseases.

Attenuation Measuring Ultrasound Shearwave Elastography (AMUSE) as Noninvasive Imaging Biomarker for Liver Acute Cellular Rejection

OBJECTIVE

There are over 9000 liver transplants in the United States per year, with acute cellular rejection (ACR) being a prevalent early post-transplant complication (20%-40%) treated using corticosteroids. Ischemia-reperfusion injury (IRI), another early post-transplant pathology, has similar laboratory results but typically resolves without therapy. ACR confirmation requires invasive liver biopsy, bearing risks like hemorrhage and pneumothorax. Attenuation Measuring Ultrasound Shearwave Elastography (AMUSE) assesses shear wave velocity (c) and attenuation (α) without rheological models and have shown potential for noninvasive tissue characterization.

METHODS

We analyzed 58 transplanted livers suspected for ACR by comparing AMUSE measurements to biopsy findings. Thirteen patients underwent longitudinal tracking from ACR diagnosis on day 7 to therapy initiation and repeat biopsy on day 14. Statistical methods and support vector machine (SVM) were used for performance analysis.

RESULTS

AMUSE measurements at 100, 200, and 300 Hz showed statistical significance (p < 0.001) for ACR presence, with 200 Hz exhibiting the highest Spearman correlation coefficients for c and α (0.68 and -0.83). High c (> 2.2 m/s) and low α (< 130 Np/m) at 200 Hz correlated with ACR diagnostic, while low c and high α indicated no ACR. Combining c and α into a single biomarker α/c improved patient differentiation, yielding an F1-score of 0.97. SVM was used to evaluate AMUSE ACR staging capabilities using all available frequencies, reaching 0.95 F1-score for categorical classification, with an AUROC of 0.99. When evaluating the presence of ACR the SVM reached 0.99 F1-score, with 1.00 sensitivity/recall.

CONCLUSION

These findings support the use of AMUSE potential for detection and staging of liver ACR.

Diagnostic accuracy of 2D-SWE ultrasound for liver fibrosis assessment in MASLD: A multilevel random effects model meta-analysis

BACKGROUND AND AIMS

Metabolic dysfunction-associated steatotic liver disease (MASLD) imposes significant health care burdens. Early detection of advanced fibrosis and cirrhosis in MASLD is essential due to their unfavorable outcomes. This multilevel random-effects meta-analysis aimed to provide the best evidence for the diagnostic accuracy of 2-dimensional shear wave elastography in detecting liver fibrosis in biopsy-proven MASLD.

APPROACH AND RESULTS

This study involves systematic search in PubMed/MEDLINE, Embase, Scopus, Web of Science, LILACS, and Cochrane Library electronic databases for full-text articles published in any language up to February 26, 2024. Included studies reported liver stiffness measurement by 2-dimensional shear wave elastography and used histological diagnosis as the gold standard. A linear mixed-effects multiple thresholds model was employed, and summary estimates for sensitivity, specificity (Sp), and summary area under the receiver operator characteristic curve were computed. Twenty observational studies (SuperSonic Imagine, General Electric Healthcare, and Canon Medical Systems) fulfilled the inclusion criteria, comprising 2223 participants with biopsy-proven MASLD. The prevalence of mild fibrosis (F1), significant fibrosis (F2), advanced fibrosis (F3), and cirrhosis (F4) was 30.0%, 18.5%, 17.9%, and 10.9%, respectively. The summary area under the receiver operator characteristic curve [95% CI] in detecting ≥F1, ≥F2, ≥F3, and F4 for all ultrasound machines considered together were 0.82 [0.16-0.98], 0.82 [0.76-0.88], 0.86 [0.77-0.93], and 0.89 [0.80-0.95], respectively. The optimal cutoff values were 6.432 kPa for ≥F1, 8.174 kPa for ≥F2, 9.418 kPa for ≥F3, and 11.548 kPa for F4, respectively.

CONCLUSIONS

Our meta-analysis identified optimized cutoffs for fibrosis staging by 2-dimensional shear wave elastography in etiology-specific chronic liver diseases (MASLD), with excellent diagnostic performance, underscoring the potential for standardizing cutoff values.

Body mass index of 23 or greater is relevant to hepatic steatosis and fibrosis in patients with harmful alcohol use

BACKGROUND

Steatotic liver disease, characterized by a combination of metabolic dysfunction, alcohol use, or specific etiologies, is a leading cause of chronic liver disease. However, the role of metabolic dysfunction in chronic liver disease with harmful alcohol use remains unclear. This study aimed to investigate factors associated with hepatic steatosis and fibrosis in patients with harmful alcohol use.

METHODS

Over a 2-year period, we registered patients with harmful alcohol use, defined by an Alcohol Use Disorders Identification Test score of 8 or higher. We retrospectively analyzed background information, blood test results, ultrasound-guided attenuation parameter (attenuation coefficient), and liver stiffness measurement. Hepatic steatosis was defined as attenuation coefficient ≥0.65 dB/cm/MHz, and fibrosis as liver stiffness measurement ≥7.5 kPa.

RESULTS

The study included 131 patients (82% men, median age 59 years). Linear regression analysis revealed significant associations with attenuation coefficient for body mass index ≥23 (0.08, p < 0.0001) and age (-0.002, p = 0.002). Liver stiffness measurement was associated with body mass index ≥23 (2.52, p = 0.001), aspartate aminotransferase (0.02, p = 0.0189), gamma-glutamyl transpeptidase (0.008, p < 0.0001), platelet count (-0.02, p = 0.001), and prothrombin international normalized ratio (26.40, p < 0.0001). Among the four groups classified by the presence or absence of steatosis and fibrosis, patients with fibrosis, but without steatosis, demonstrated the lowest liver reserve. In contrast, patients with both steatosis and fibrosis showed higher aspartate aminotransferase and gamma-glutamyl transpeptidase levels.

CONCLUSIONS

Body mass index is associated with both hepatic steatosis and fibrosis in patients with harmful alcohol use.

Choline-deficient, high-fat diet-induced MASH in Göttingen Minipigs: characterization and effects of a chow reversal period

The prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) and metabolic dysfunction-associated steatohepatitis (MASH) is increasing, and translational animal models are needed to develop novel treatments for this disease. The physiology and metabolism of pigs have a relatively high resemblance to humans, and the present study aimed to characterize choline-deficient and high-fat diet (CDAHFD)-fed Göttingen Minipigs as a novel animal model of MASLD/MASH. Göttingen Minipigs were fed CDAHFD for up to 5 mo, and the phenotype was investigated by the analysis of plasma parameters and repeated collection of liver biopsies. Furthermore, changes in hepatic gene expression during the experiment were explored by RNA sequencing. For a subset of the minipigs, the diet was changed from CDAHFD back to chow to investigate whether the liver pathology was reversible. Göttingen Minipigs on CDAHFD gained body weight, and plasma levels of cholesterol, AST, ALT, ALP, and GGT were increased. CDAHFD-fed minipigs developed hepatic steatosis, inflammation, and fibrosis, which in 5 of 16 animals progressed to cirrhosis. During an 11-wk chow reversal period, steatosis regressed, while fibrosis persisted. Regarding inflammation, the findings were less clear, depending on the type of readout. MASH Human Proximity Scoring (combined evaluation of transcriptional, phenotypic, and histopathological parameters) showed that CDAHFD-fed Göttingen Minipigs resemble human MASLD/MASH better than most rodent models. In conclusion, CDAHFD-fed minipigs develop a MASH-like phenotype, which, in several aspects, resembles the changes observed in human patients with MASLD/MASH. Furthermore, repeated collection of liver biopsies allows detailed characterization of histopathological changes over time in individual animals.NEW & NOTEWORTHY The physiology and metabolism of pigs have a relatively high resemblance to humans. This study characterizes a new animal model of MASLD/MASH using CDAHFD-fed Göttingen Minipigs. Göttingen Minipigs fed CDAHFD gained weight and developed hepatic steatosis, inflammation, fibrosis, and cirrhosis. After an 11-wk chow-reversal period, hepatic steatosis and some inflammatory parameters reversed. Combined evaluation of phenotypic, transcriptional, and histological parameters revealed the minipig model showed a higher resemblance to human disease than many rodent models.

Non-Invasive Ultrasound Diagnostic Techniques for Steatotic Liver Disease and Focal Liver Lesions: 2D, Colour Doppler, 3D, Two-Dimensional Shear Wave Elastography (2D-SWE), and Ultrasound-Guided Attenuation Parameter (UGAP)

We conducted a comprehensive literature review to evaluate the efficacy of combining two-dimensional shear wave elastography (2D-SWE) and ultrasound-guided attenuation parameter (UGAP) in assessing the risk of progressive metabolic dysfunction-associated steatohepatitis (MASH). This narrative review explores the applications of liver ultrasound in diagnosing metabolic liver diseases, focusing on recent advancements in diagnostic techniques for steatotic liver disease (SLD). Liver ultrasound can detect a spectrum of SLD manifestations, from metabolic dysfunction-associated liver disease (MASLD) to fibrosis and cirrhosis. It is also possible to identify inflammation, hepatitis, hepatocellular carcinoma (HCC), and various other liver lesions. Innovative ultrasound applications, including elastography and UGAP, can significantly enhance the diagnostic capabilities of ultrasound in accurately interpreting liver diseases. Understanding the pathogenesis of liver diseases requires a thorough analysis of their etiology and progression in order to develop sound diagnostic and therapeutic approaches. Chronic liver diseases (CLD) vary in origin, with MASLD affecting approximately 20-25% of the general population. The insidious progression of CLD from inflammation to fibrosis and cirrhosis underscores the need for effective early detection methods. This review aims to highlight the evolving role of non-invasive ultrasound-based diagnostic tests in the early detection and staging of liver diseases. By synthesizing current evidence, we aim to provide an updated perspective on the utility of advanced ultrasound techniques in redefining the diagnostic landscape for metabolic liver diseases.

Quantitative Ultrasound and Ultrasound-Based Elastography for Chronic Liver Disease: Practical Guidance, From the AJR Special Series on Quantitative Imaging

Quantitative ultrasound (QUS) and ultrasound-based elastography techniques are emerging as non-invasive effective methods for assessing chronic liver disease. They are more accurate than B-mode imaging alone and more accessible than MRI as alternatives to liver biopsy. Early detection and monitoring of diffuse liver processes such as steatosis, inflammation, and fibrosis play an important role in guiding patient management. The most widely available and validated techniques are attenuation-based QUS techniques and shear-wave elastography techniques that measure shear-wave speed. Other techniques are supported by a growing body of evidence and are increasingly commercialized. This review explains general physical concepts of QUS and ultrasound-based elastography techniques for evaluating chronic liver disease. The first section describes QUS techniques relying on attenuation, backscatter, and speed of sound. The second section discusses ultrasound-based elastography techniques analyzing shear-wave speed, shear-wave dispersion, and shear-wave attenuation. With an emphasis on clinical implementation, each technique's diagnostic performance along with thresholds for various clinical applications are summarized, to provide guidance on analysis and reporting for radiologists. Measurement methods, advantages, and limitations are also discussed. The third section explores developments in quantitative contrast-enhanced and vascular ultrasound that are relevant to chronic liver disease evaluation.

Reliability and stability of ultrasound-guided attenuation parameter in evaluating hepatic steatosis

PURPOSE

This study aimed to explore the reliability and stability of ultrasound-guided attenuation parameter (UGAP) values obtained by two measuring methods and different measuring times.

METHODS

Patients who underwent liver UGAP examinations in our hospital from September 2022 to December 2022 were retrospectively analyzed. The clinical data and UGAP measurements results were collected. Two different measuring methods: static single-frame multi-point measuring and dynamic multi-frame single-point measuring, were performed for each patient, and 10 UGAP values of each measuring method were recorded. The medians of the UGAP values of the 1st-3rd, 1st-5th, 1st-7th and 1st-10th by each measuring method were taken as the final UGAP values of measuring 3, 5, 7 and 10 times. The UGAP values obtained by the two different measuring methods and different measuring times (3, 5, 7 or 10 times) were compared.

RESULTS

206 patients were included in this study. There was no statistical difference between UGAP values measured by static single-frame multi-point measuring and dynamic multi-frame single-point measuring (P = 0.689, P = 0.270, P = 0.298, P = 0.091), regardless of measuring times (3, 5, 7, 10 times). No significant difference between the UGAP values obtained by 3, 5, 7 and 10 measurements was found (P = 0.554, P = 0.916).

CONCLUSION

The UGAP values obtained by the two different measuring methods and different measuring times (3, 5, 7 and 10 times) are stable and reliable. Additionally, 3 times of UGAP measurements might be enough for each patient in clinical practice.

Coincidental items in the definition of metabolic dysfunction-associated fatty liver are useful in identifying patients having significant fibrosis with fatty liver

AIM

We aimed to establish a method that will identify patients at a high risk for progressive phenotype of fatty liver.

METHODS

Patients with fatty liver who underwent liver biopsy between July 2008 and November 2019 were included as cohort 1, and those who underwent abdominal ultrasound screening examination by general physicians between August 2020 and May 2022 served as cohort 2. According to the definition of metabolic dysfunction-associated fatty liver (MAFLD), the subjects were classified by body mass index of ≥23, diabetes mellitus, and coexistence of two or more metabolic risk items. The progressive phenotype of MAFLD is defined by significant fibrosis complicated with either nonalcoholic fatty liver disease activity score ≥4 (BpMAFLD) or steatosis grade ≥2 by ultrasound examination (UpMAFLD).

RESULTS

One hundred sixty-eight patients and 233 patients were enrolled in cohorts 1 and 2, respectively. In cohort 1, the prevalence of BpMAFLD was 0% in patients without a complicating factor (n = 10), 13% in those with one complicating factor (n = 67), 32% in those with two (n = 73), and 44% in those with all three complicating factors (n = 36). A logistic regression analysis revealed that factors in the MAFLD definition were significantly associated with BpMAFLD. In cohort 2, a criterion of two or more positive MAFLD definitions was found to have a 97.4% negative predictive value for the diagnosis of UpMAFLD.

CONCLUSION

Patients with two or more complicating factors in the MAFLD definition should have further evaluation for liver fibrosis.

Novel multi-parametric diagnosis of non-alcoholic fatty liver disease using ultrasonography, body mass index, and Fib-4 index

BACKGROUND

Shear wave speed (SWS), shear wave dispersion (SWD), and attenuation imaging (ATI) are new diagnostic parameters for non-alcoholic fatty liver disease. To differentiate between non-alcoholic steatohepatitis (NASH) and non-alcoholic fatty liver (NAFL), we developed a clinical index we refer to as the “NASH pentagon” consisting of the 3 abovementioned parameters, body mass index (BMI), and Fib-4 index.

AIM

To investigate whether the area of the NASH pentagon we propose is useful in discriminating between NASH and NAFL.

METHODS

This non-invasive, prospective, observational study included patients diagnosed with fatty liver by abdominal ultrasound between September 2021 and August 2022 in whom shear wave elastography, SWD, and ATI were measured. Histological diagnosis based on liver biopsy was performed in 31 patients. The large pentagon group (LP group) and the small pentagon group (SP group), using an area of 100 as the cutoff, were compared; the NASH diagnosis rate was also investigated. In patients with a histologically confirmed diagnosis, receiver-operating characteristic (ROC) curve analyses were performed.

RESULTS

One hundred-seven patients (61 men, 46 women; mean age 55.1 years; mean BMI 26.8 kg/m²) were assessed. The LP group was significantly older (mean age: 60.8 ± 15.2 years vs 46.4 ± 13.2 years; P < 0.0001). Twenty-five patients who underwent liver biopsies were diagnosed with NASH, and 6 were diagnosed with NAFL. On ROC curve analyses, the areas under the ROC curves for SWS, dispersion slope, ATI value, BMI, Fib-4 index, and the area of the NASH pentagon were 0.88000, 0.82000, 0.58730, 0.63000, 0.59333, and 0.93651, respectively; the largest was that for the area of the NASH pentagon.

CONCLUSION

The NASH pentagon area appears useful for discriminating between patients with NASH and those with NAFL.

Non-invasive evaluation of liver steatosis with imaging modalities: New techniques and applications

In the world, nonalcoholic fatty liver disease (NAFLD) accounts for majority of diffuse hepatic diseases. Notably, substantial liver fat accumulation can trigger and accelerate hepatic fibrosis, thus contributing to disease progression. Moreover, the presence of NAFLD not only puts adverse influences for liver but is also associated with an increased risk of type 2 diabetes and cardiovascular diseases. Therefore, early detection and quantified measurement of hepatic fat content are of great importance. Liver biopsy is currently the most accurate method for the evaluation of hepatic steatosis. However, liver biopsy has several limitations, namely, its invasiveness, sampling error, high cost and moderate intraobserver and interobserver reproducibility. Recently, various quantitative imaging techniques have been developed for the diagnosis and quantified measurement of hepatic fat content, including ultrasound- or magnetic resonance-based methods. These quantitative imaging techniques can provide objective continuous metrics associated with liver fat content and be recorded for comparison when patients receive check-ups to evaluate changes in liver fat content, which is useful for longitudinal follow-up. In this review, we introduce several imaging techniques and describe their diagnostic performance for the diagnosis and quantified measurement of hepatic fat content.

Indian National Association for Study of the Liver (INASL) Guidance Paper on Nomenclature, Diagnosis and Treatment of Nonalcoholic Fatty Liver Disease (NAFLD)

Nonalcoholic fatty liver disease (NAFLD) is a major cause of chronic liver disease globally and in India. The already high burden of NAFLD in India is expected to further increase in the future in parallel with the ongoing epidemics of obesity and type 2 diabetes mellitus. Given the high prevalence of NAFLD in the community, it is crucial to identify those at risk of progressive liver disease to streamline referral and guide proper management. Existing guidelines on NAFLD by various international societies fail to capture the entire landscape of NAFLD in India and are often difficult to incorporate in clinical practice due to fundamental differences in sociocultural aspects and health infrastructure available in India. A lot of progress has been made in the field of NAFLD in the 7 years since the initial position paper by the Indian National Association for the Study of Liver on NAFLD in 2015. Further, the ongoing debate on the nomenclature of NAFLD is creating undue confusion among clinical practitioners. The ensuing comprehensive review provides consensus-based, guidance statements on the nomenclature, diagnosis, and treatment of NAFLD that are practically implementable in the Indian setting.

How to Identify Advanced Fibrosis in Adult Patients with Non-Alcoholic Fatty Liver Disease (NAFLD) and Non-Alcoholic Steatohepatitis (NASH) Using Ultrasound Elastography-A Review of the Literature and Proposed Multistep Approach

Non-alcoholic fatty liver disease (NAFLD), and its progressive form, non-alcoholic steatohepatitis (NASH), represent, nowadays, real challenges for the healthcare system. Liver fibrosis is the most important prognostic factor for NAFLD, and advanced fibrosis is associated with higher liver-related mortality rates. Therefore, the key issues in NAFLD are the differentiation of NASH from simple steatosis and identification of advanced hepatic fibrosis. We critically reviewed the ultrasound (US) elastography techniques for the quantitative characterization of fibrosis, steatosis, and inflammation in NAFLD and NASH, with a specific focus on how to differentiate advanced fibrosis in adult patients. Vibration-controlled transient elastography (VCTE) is still the most utilized and validated elastography method for liver fibrosis assessment. The recently developed point shear wave elastography (pSWE) and two-dimensional shear wave elastography (2D-SWE) techniques that use multiparametric approaches could bring essential improvements to diagnosis and risk stratification.

Validation of attenuation imaging coefficient, shear wave elastography, and dispersion as emerging tools for non-invasive evaluation of liver tissue in children

Introduction

The number of children with acute and chronic liver disease is rising. Moreover, liver involvement may be limited to subtle changes in organ texture especially in early childhood and some syndromic conditions, such as ciliopathies. Attenuation imaging coefficient (ATI), shear wave elastography (SWE), and dispersion (SWD) are emerging ultrasound technologies providing data about attenuation, elasticity, and viscosity of liver tissue. This additional and qualitative information has been correlated with certain liver pathologies. However, limited data are available for healthy controls and have mainly been raised in adults.

Methods

This prospective monocentric study was conducted at a university hospital with a specialization in pediatric liver disease and transplantation. Between February and July 2021, 129 children aged 0-17.92 years were recruited. Study participants attended outpatient clinics due to minor illnesses excluding liver or cardiac diseases, acute (febrile) infections or other conditions affecting liver tissue and function. ATI, SWE, and SWD measurements were performed on an Aplio i800 (Canon Medical Systems) with an i8CX1 curved transducer by two different investigators with long-standing experience in pediatric ultrasound according to a standardized protocol.

Results

Considering multiple potential covariates, we derived percentile charts for all 3 devices relying on the Lambda-Mu-Sigma (LMS) approach. 112 children were considered for further analysis, excluding those with abnormal liver function and under-/overweight (BMI SDS<-1.96/> 1.96, respectively). Age range was 0-17.92 years (mean 6.89±0.50SD), 58% were male. The mean duration of the ultrasound examination (basic ultrasound plus SWE, SWD, and ATI) was 6.67±0.22 minutes and it was well tolerated in 83% (n=92) of cases. While ATI was related to age, SWD was found to depend on BMI SDS, and SWE on abdominal wall thickness and sex. ATI correlated with neither SWE nor SWD, but SWE was correlated with SWD.

Conclusions

Our study provides norm values and reference charts for ATI, SWE, and SWD considering important covariates including age, sex and, BMI. This may help to implement these promising tools into imaging diagnostics of liver disease and to improve the diagnostic relevance of liver ultrasound. In addition, these noninvasive techniques proved to be time-effective and highly reliable, which make them ideal for application in children.

Utility of Ultrasound-Guided Attenuation Parameter for Grading Steatosis With Reference to MRI-PDFF in a Large Cohort

BACKGROUND & AIMS

Ultrasound-guided attenuation parameter (UGAP) is recently developed for noninvasive evaluation of steatosis. However, reports on its usefulness in clinical practice are limited. This prospective multicenter study analyzed the diagnostic accuracy of grading steatosis with reference to magnetic resonance imaging-based proton density fat fraction (MRI-PDFF), a noninvasive method with high accuracy, in a large cohort.

METHODS

Altogether, 1010 patients with chronic liver disease who underwent MRI-PDFF and UGAP were recruited and prospectively enrolled from 6 Japanese liver centers. Linearity was evaluated using intraclass correlation coefficients between MRI-PDFF and UGAP values. Bias, defined as the mean difference between MRI-PDFF and UGAP values, was assessed by Bland-Altman analysis. UGAP cutoffs for pairwise MRI-PDFF-based steatosis grade were determined using area under the receiver-operating characteristic curve (AUROC) analyses.

RESULTS

UGAP values were shown to be normally distributed. However, because PDFF values were not normally distributed, they were log-transformed (MRI-logPDFF). UGAP values significantly correlated with MRI-logPDFF (intraclass correlation coefficient = 0.768). Additionally, Bland-Altman analysis showed good agreement between MRI-logPDFF and UGAP with a mean bias of 0.0002% and a narrow range of agreement (95% confidence interval [CI], -0.015 to 0.015). The AUROCs for distinguishing steatosis grade ≥1 (MRI-PDFF ≥5.2%), ≥2 (MRI-PDFF ≥11.3%), and 3 (MRI-PDFF ≥17.1%) were 0.910 (95% CI, 0.891-0.928), 0.912 (95% CI, 0.894-0.929), and 0.894 (95% CI, 0.873-0.916), respectively.

CONCLUSIONS

UGAP has excellent diagnostic accuracy for grading steatosis with reference to MRI-PDFF. Additionally, UGAP has good linearity and negligible bias, suggesting that UGAP has excellent technical performance characteristics that can be widely used in clinical trials and patient care. (UMIN Clinical Trials Registry, Number: UMIN000041196).

Liver Stiffness Measurements by 2D Shear-Wave Elastography: Effect of Steatosis on Fibrosis Evaluation

BACKGROUND. Hepatic steatosis has been found not to affect liver stiffness measurements (LSM) from MR elastography (MRE). However, the effect of steatosis on LSM from 2D shear-wave elastography (SWE) remains controversial. OBJECTIVE. The purpose of this study was to evaluate the effect of hepatic steatosis on the diagnostic performance of LSM from 2D SWE (LSM2D SWE) for evaluation of liver fibrosis with LSM from MRE (LSMMRE) as the reference standard. METHODS. This retrospective study included 888 patients (442 women, 446 men; median age, 67 years) with chronic liver disease who underwent LSM by both 2D SWE and MRE within a 3-month window. Steatosis was also assessed on ultrasound examinations by ultrasound-guided attenuation parameter (UGAP) and on MRI examinations by proton density fat fraction (PDFF). Fibrosis stages and steatosis grades were classified according to previously established thresholds. The effect of steatosis on LSM2D SWE was evaluated by Kruskal-Wallis tests with post hoc tests and ROC analysis. RESULTS. LSM2D SWE were significantly higher in patients with severe steatosis than those without steatosis by MRI PDFF among patients with F0 fibrosis (5.5 kPa [IQR, 4.7-6.0 kPa] vs 4.7 kPa [IQR, 4.2-5.5 kPa], p = .009) and F1 fibrosis (6.3 kPa [IQR, 6.0-7.2 kPa] vs 5.9 kPa [IQR, 5.0-6.6 kPa], p = .009). LSM2D SWE were significantly higher in patients with severe steatosis than those without steatosis by UGAP among patients with F1 fibrosis (6.6 kPa [IQR, 5.9-7.3 kPa] vs 5.9 kPa [IQR, 5.1-6.5 kPa], p = .008). Otherwise, LSM2D SWE did not vary significantly across steatosis grades at a given fibrosis stage (all p > .05). Sensitivity and specificity for ≥ F1 fibrosis were 63.8% and 91.5% in patients without versus 60.4% and 80.9% in patients with severe steatosis by MRI PDFF and were 62.4% and 91.5% in patients without versus 72.1% and 78.3% in patients with severe steatosis by UGAP. CONCLUSION. Severe hepatic steatosis may result in overestimation of LSM2D SWE in patients without or with mild steatosis, reducing the specificity of liver fibrosis detection. CLINICAL IMPACT. Assessment of UGAP at 2D SWE may help identify patients in whom LSM2D SWE should be assessed with caution. In patients with no or mild steatosis by 2D SWE and severe steatosis by UGAP, MRE helps provide a more reliable measure of liver fibrosis.

Ultrasound Methods for the Assessment of Liver Steatosis: A Critical Appraisal

The prevalence of the non-alcoholic fatty liver disease has reached major proportions, being estimated to affect one-quarter of the global population. The reference techniques, which include liver biopsy and the magnetic resonance imaging proton density fat fraction, have objective practical and financial limitations to their routine use in the detection and quantification of liver steatosis. Therefore, there has been a rising necessity for the development of new inexpensive, widely applicable and reliable non-invasive diagnostic tools. The controlled attenuation parameter has been considered the point-of-care technique for the assessment of liver steatosis for a long period of time. Recently, many ultrasound (US) system manufacturers have developed proprietary software solutions for the quantification of liver steatosis. Some of these methods have already been extensively tested with very good performance results reported, while others are still under evaluation. This manuscript reviews the currently available US-based methods for diagnosing and grading liver steatosis, including their classification and performance results, with an appraisal of the importance of this armamentarium in daily clinical practice.

New horizon of ultrasound for screening and surveillance of non-alcoholic fatty liver disease spectrum

Non-alcoholic fatty liver disease (NAFLD) affects almost one quarter of adults worldwide, and its progressive subtype, non-alcoholic steatohepatitis can progress to advanced fibrosis/cirrhosis and even hepatocellular carcinoma. It is critical to screen and grade NAFLD patients for management decisions to rationalize the utilization of medical resources. Conventional ultrasound is widely applied for NAFLD screening, however, some inherent weaknesses hinder its utility. This limitation has spurred the development of acoustic parameters-based quantitative ultrasound techniques that allow a more accurate evaluation of the histological features of NAFLD (e.g. steatosis, necroinflammation, fibrosis/cirrhosis). Herein, this paper reviews the research advances in emerging ultrasound techniques for screening and surveillance across NAFLD spectrum and summarize their principles, feasibility, accuracy, reproducibility, and limitations of each technique. The challenges and future directions are also discussed to advance clinical practice.

Efficacy of B-mode ultrasound-based attenuation for the diagnosis of hepatic steatosis: a systematic review/meta-analysis

The accuracy of attenuation coefficients and B-mode ultrasound for distinguishing between S0 (healthy, < 5% fat) and S1-3 (steatosis ≥ 5%) livers compared to a controlled attenuation parameter is unclear. This meta-analysis aimed to comprehensively assess the diagnostic performance of B-mode ultrasound imaging for evaluating steatosis of ≥ 5%. We searched the PubMed, Embase, and Web of Science databases for studies on the accuracy of B-mode ultrasound for differentiating S0 from S1-3 in adults with chronic liver disease. A bivariate random-effects model was performed to estimate the pooled sensitivity, specificity, positive (PLR) and negative likelihood ratios (NLR), and diagnostic odds ratios (DORs). Subgroup analyses by attenuation coefficient, conventional B-mode ultrasound findings, and B-mode ultrasound findings without semi-quantification methods were performed. Liver steatosis was scored as follows: S0, < 5%; S1, 5-33%; S2, 33-66%; and S3, > 66%. Nineteen studies involving 3240 patients were analyzed. The pooled sensitivity and specificity of B-mode ultrasound for detecting S1 were 0.70 (95% confidence interval [CI], 0.63-0.77) and 0.86 (95% CI 0.82-0.89), respectively. The pooled PLR, NLR, and DOR were 4.90 (95% CI 3.69-6.51), 0.35 (95% CI 0.27- 0.44), and 14.1 (95% CI 8.7-23.0), respectively. The diagnostic accuracy was better in patients with attenuation coefficients (area under the curve [AUC], 0.89; sensitivity, 0.75; specificity, 0.86) than in those with conventional B-mode findings (AUC, 0.80; sensitivity, 0.59; specificity, 0.83). In particular, the diagnostic value was better when the attenuation coefficient guided by B-mode ultrasound was utilized. To screen patients with steatosis of ≥ 5%, attenuation coefficient should be used.

The Concept of Indeterminable NASH Inducted by Preoperative Diet and Metabolic Surgery: Analyses of Histopathological and Clinical Features

Practitioners routinely perform intraoperative liver biopsies during laparoscopic sleeve gastrectomy (LSG) to evaluate nonalcoholic fatty liver disease (NAFLD). In some patients, hepatocyte ballooning, inflammation, and fibrosis without steatosis are observed, even in the absence of other etiologies. We call this finding indeterminable nonalcoholic steatohepatitis (Ind-NASH). In this study, we clarified the prevalence, as well as histopathological and clinical features, of Ind-NASH through intraoperative liver biopsy in Japanese patients presenting with severe obesity. We enrolled 63 patients who had undergone LSG and intraoperative liver biopsy. In patients diagnosed with histopathological NASH, we performed protocol liver biopsies at 6 and 12 months after LSG. We statistically analyzed these histopathological findings and clinical parameters and found the prevalence rate of Ind-NASH discovered through intraoperative biopsy to be 15.9%. Protocol liver biopsy also revealed that Ind-NASH was an intermediate condition between NASH and normal liver. The clinical features of patients with Ind-NASH are a higher body weight compared to NASH (134.9 kg vs. 114.7 kg; p = 0.0245), stronger insulin resistance compared to nonalcoholic fatty liver (homeostasis model assessment–insulin resistance: 7.1 vs. 4.9; p = 0.0188), and mild liver dysfunction compared to NASH. Patients with Ind-NASH observed positive weight-loss effects from a preoperative diet compared to the postoperative course (percentage total weight loss: 32.0% vs. 26.7%; p < 0.0001). Patients with Ind-NASH may also be good candidates for metabolic surgery owing to their good treatment response; therefore, efforts should be made by specialists in the near future to deeply discuss and define Ind-NASH.

Diagnostic accuracy of ultrasound-guided attenuation parameter as a noninvasive test for steatosis in non-alcoholic fatty liver disease

The purpose of this study was to evaluate the diagnostic accuracy of the ultrasound-guided attenuation parameter (UGAP) using the LOGEQ E10 for hepatic steatosis in non-alcoholic fatty liver disease (NAFLD) patients and directly compare UGAP with attenuation imaging (ATI) and controlled attenuation parameter (CAP). We prospectively analyzed 105 consecutive patients with NAFLD who underwent UGAP, ATI, CAP, and liver biopsy on the same day between October 2019 and April 2021. The diagnostic ability of the UGAP-determined attenuation coefficient (AC) was evaluated using receiver operating characteristic (ROC) curve analysis, and its correlation with ATI-determined AC values or CAP values was investigated. The success rate of UGAP was 100%. The median IQR/med obtained by UGAP was 4.0%, which was lower than that of ATI and CAP (P < 0.0001). The median ACs obtained by UGAP for grades S0 (control), S1, S2, and S3 were 0.590, 0.670, 0.750, and 0.845 dB/cm/MHz, respectively, demonstrating a stepwise increase with increasing hepatic steatosis severity (P < 0.0001). The areas under the ROC curve of UGAP for identifying ≥ S1, ≥ S2, and S3 were 0.890, 0.906, and 0.912, respectively, which were significantly better than the results obtained with CAP for identifying S3. Furthermore, the correlation coefficient between UGAP-AC and ATI-AC values was 0.803 (P < 0.0001), indicating a strong relationship. Our results indicate that UGAP has high diagnostic accuracy for detecting and grading hepatic steatosis in patients with NAFLD.