Clinical application of magnetic resonance elastography in chronic liver disease

Recent Advances in the Pathogenesis and Clinical Evaluation of Portal Hypertension in Chronic Liver Disease

In chronic liver disease, hepatic stellate cell activation and degeneration of liver sinusoidal endothelial cells lead to structural changes, which are secondary to fibrosis and the presence of regenerative nodules in the sinusoids, and to functional changes, which are related to vasoconstriction. The combination of such changes increases intrahepatic vascular resistance and causes portal hypertension. The subsequent increase in splanchnic and systemic hyperdynamic circulation further increases the portal blood flow, thereby exacerbating portal hypertension. In clinical practice, the hepatic venous pressure gradient is the gold-standard measure of portal hypertension; a value of ≥10 mm Hg is defined as clinically significant portal hypertension, which is severe and is associated with the risk of liver-related events. Hepatic venous pressure gradient measurement is somewhat invasive, so evidence on the utility of risk stratification by elastography and serum biomarkers is needed. The various stages of cirrhosis are associated with different outcomes. In viral hepatitis-related cirrhosis, viral suppression or elimination by nucleos(t)ide analog or direct-acting antivirals results in recompensation of liver function and portal pressure. However, careful follow-up should be continued, because some cases have residual clinically significant portal hypertension even after achieving sustained virologic response. In this study, we reviewed the current and future prospects for portal hypertension.

Validity of the Algorithm for Liver Resection of Hepatocellular Carcinoma in the Caudate Lobe

BACKGROUND

We aimed to validate our algorithm for resecting Hepatocellular carcinoma (HCC) in the caudate lobe based on tumor location, tumor size, and indocyanine green clearance rate.

METHODS

Patients who underwent curative resections for solitary HCC in the caudate lobe were included. The surgical outcomes of patients with HCC in the caudate lobe were compared with those of patients with HCC in other sites of the liver.

RESULTS

After one-to-one matching, the caudate-lobe group (n = 150) had longer operation time, greater amount of bleeding, lower weight of resected specimens, and shorter distance between tumor and resection line than the other-sites group (n = 150), but the complication rates were not different between the groups (38.0% vs. 34.1%, P = 0.719). After a median follow-up period of 3.0 years (range, 0.3-16.2 years), the median overall survivals were 6.5 (95% confidence interval [CI], 5.3-7.9) and 7.5 years (95% CI, 6.3-9.7) in the caudate-lobe and other-site groups, respectively (P = 0.430). Median recurrence-free survivals in the caudate-lobe group (1.9 years; 95% CI, 1.4-2.7) had a tendency to be shorter than those in the other-sites group (2.3 years; 1.7-3.4) (P = 0.052).

CONCLUSIONS

Patients' survival and complication rates in the caudate-lobe group were comparable to those in the other-sites group; therefore, our algorithm for resecting HCC in the caudate lobe is of clinical use.

OUP accepted manuscript

Background

This study aimed to assess the performance of transient elastography (TE), two-dimensional shear wave elastography (2D-SWE), and magnetic resonance elastography (MRE) for staging significant fibrosis and cirrhosis in untreated chronic hepatitis B (CHB) patients.

Methods

Pubmed, Embase, Web of Science, and Cochrane Library were searched for terms involving CHB, TE, 2D-SWE, and MRE. Other etiologies of chronic liver disease, previous treatment in patients, or articles not published in SCI journals were excluded. Hierarchical non-linear models were used to evaluate the diagnostic accuracy of TE, 2D-SWE, and MRE. Heterogeneity was explored via analysis of threshold effect and meta-regression.

Results

Twenty-eight articles with a total of 4,540 untreated CHB patients were included. The summary areas under the receiver-operating characteristic curves (AUROCs) using TE, 2D-SWE, and MRE for predicting significant fibrosis (SF) were 0.84, 0.89, and 0.99, respectively. The AUROC values of TE, 2D-SWE, and MRE for staging cirrhosis were 0.9, 0.94, and 0.99, respectively. Based on the meta-analysis of studies with head-to-head comparison, 2D-SWE is superior to TE (0.92 vs 0.85, P < 0.01) in staging significant fibrosis.

Conclusion

TE, 2D-SWE, and MRE express acceptable diagnostic accuracies in staging significant fibrosis and cirrhosis in untreated CHB patients. 2D-SWE outperforms TE in detecting significant fibrosis in treatment-naive people with hepatitis B virus.

[Magnetic resonance elastography of the liver : Worth knowing for clinical routine]

BACKGROUND

Magnetic resonance elastography (MRE) is a noninvasive, quantitative, MRI-based method to evaluate liver stiffness. Beside biopsy and ultrasound elastography, this imaging method plays in many places a significant role in the detection and additive characterization of chronic liver disease.

OBJECTIVES, MATERIALS AND METHODS

Based on the literature, a brief review of the underlying method and the commercially available products is given. Furthermore, the practical procedure, the analysis, and the interpretation of clinically relevant questions are illustrated and a comparison with ultrasound elastography is provided.

RESULTS

This relative "young" MRI method allows extensive evaluation of mechanical properties of the liver and is an important diagnostic tool especially in follow-up examinations. The MRE of the liver is with a maximum technical failure rate of 5.8% a robust technique with high accuracy and an excellent re-test reliability as well as intra- and interobserver reproducibility. There is a high diagnostic certainty within the framework of most important clinical indications, the quantification of fibrosis, and with a very good correlation with the "gold standard" biopsy.

CONCLUSION

Based on its rising clinical relevance and the broad usage, MRE of the liver is increasingly used in many centers and in routine liver protocols. Therefore, basic knowledge of this method is essential for every radiologist.

The stratification of cirrhosis

Cirrhosis is traditionally seen as an irreversible stage of chronic liver disease although its clinical course may last several years. Overall, the clinical management of patients with cirrhosis is based on the observation of clinical events mostly related to complications of portal hypertension. Each event of cirrhosis decompensation has clear prognostic implications although it is not precisely predictable. In practice, the advancement in the knowledge of the mechanisms responsible for disease progression is not yet translated in clinical tools allowing the stratification of the cirrhotic stage according to pathophysiological mechanisms. This article provides a review of the main clinical and histopathological features of liver cirrhosis that are relevant for its clinical stratification together with the advancements provided by the introduction of non-invasive measures of portal hypertension. Other clinical aspects that have a major impact on the quality of life and the possibility of liver transplantation are also discussed.

Liver stiffness does not affect ultrasound-guided attenuation coefficient measurement in the evaluation of hepatic steatosis

AIM

Recently, a new method has been developed to diagnose hepatic steatosis with attenuation coefficients based on the ultrasound-guided attenuation parameter (UGAP). We investigated whether fibrosis identified by hepatic stiffness measurements based on magnetic resonance elastography (MRE) affects attenuation coefficient measurement using UGAP for the evaluation of hepatic steatosis.

METHODS

A total of 608 patients with chronic liver disease were analyzed. Correlations between magnetic resonance imaging-determined proton density fat fraction (PDFF) or MRE value and attenuation coefficients were evaluated. In addition, the interaction between hepatic fibrosis and the attenuation coefficient was analyzed.

RESULTS

The correlation coefficient (r) between PDFF values and attenuation coefficient values was 0.724, indicating a strong relationship. Conversely, the r between MRE values and attenuation coefficient values was -0.187, indicating almost no relationship. In the multiple regression assessment of the effect of PDFF and MRE on the attenuation coefficient based on UGAP, the P-values for PDFF, MRE, and PDFF × MRE were < 0.001, 0.277, and 0.903, respectively. In patients with non-alcoholic fatty liver disease (n = 169), the r between PDFF values and attenuation coefficient values was 0.695, indicating a moderate relationship. Conversely, the r between MRE values and attenuation coefficient values was -0.068, indicating almost no relationship. In the multiple regression assessment of the effect of PDFF and MRE on the attenuation coefficient based on UGAP, the P-values for PDFF, MRE, and PDFF × MRE were <0.001, 0.948, and 0.706, respectively.

CONCLUSION

UGAP-determined attenuation coefficient was weakly affected by liver stiffness, an indicator of hepatic fibrosis.

Assessing the risk of hepatocellular carcinoma by combining liver stiffness and the controlled attenuation parameter

AIM

Ultrasound technology can now be used for liver stiffness measurement (LSM) and for evaluating the amount of hepatic fat quantitatively known as the controlled attenuation parameter (CAP). This study aimed to determine the applicable cut-off values of LSM and the CAP for primary hepatocellular carcinoma (HCC), and to investigate their clinical usefulness for assessing HCC risk in patients with chronic liver disease.

METHODS

A total of 1054 patients (88 with primary HCC and 966 without HCC) whose LSM and the CAP were measured by transient elastography with clinically evident hepatitis C virus (419 patients), hepatitis B virus (377 patients), and non-alcoholic fatty liver disease (258 patients) were enrolled in this study. Subsequently, a total of 966 patients who did not have HCC initially were followed, and the usefulness of the cut-off values of LSM and CAP for HCC development were evaluated.

RESULTS

In hepatitis C virus patients, the incidence of HCC development was significantly higher among those with a combination of LSM ≥8.0 kPa and CAP ≤221 dB/m than among those with other values (log-rank test 0.0239, hazard ratio 2.66, 95%CI 1.07-6.47, P = 0.0362). In non-alcoholic fatty liver disease patients, the incidence of HCC development was significantly higher among those with a combination of LSM ≥5.4 kPa and CAP ≤265 dB/m than among others (log-rank test 0.0040, hazard ratio 8.91, 95% CI 1.47-67.97, P = 0.0192).

CONCLUSION

In the hepatitis C virus and non-alcoholic fatty liver disease groups, a combination of LSM and the CAP cut-off values would be useful for screening to identify the high-risk group for primary HCC development.

Current Imaging Techniques for Noninvasive Staging of Hepatic Fibrosis

OBJECTIVE. The purpose of this article is to discuss quantitative methods of CT, MRI, and ultrasound (US) for noninvasive staging of hepatic fibrosis. Hepatic fibrosis is the hallmark of chronic liver disease (CLD), and staging by random liver biopsy is invasive and prone to sampling errors and subjectivity. Several noninvasive quantitative imaging methods are under development or in clinical use. The accuracy, precision, technical aspects, advantages, and disadvantages of each method are discussed. CONCLUSION. The most promising methods are the liver surface nodularity score using CT and measurement of liver stiffness using MR elastography or US elastography.

Prediction of esophageal varices by liver and spleen MR elastography

OBJECTIVES

We aimed to assess the diagnostic performance of MR elastography (MRE) in predicting esophageal varices (EVs) in patients with chronic liver disease.

METHODS

We prospectively performed liver (LSM) and spleen stiffness measurements (SSM) using MRE and endoscopic screening for EVs to determine if patients with hepatocellular carcinoma were eligible for resection. We investigated whether LSM, SSM, and other non-invasive preoperative parameters were associated with the presence of EVs. In order to predict EVs, 211 patients were divided into training (n = 140) and test (n = 71) groups. A nomogram was built using independent factors based on logistic regression analysis in the training group and its accuracy was validated using an independent cohort.

RESULTS

Forty-six patients (21.8%) were diagnosed as having EVs (mild, n = 36; severe, n = 10). According to multiple regression analysis, LSM (odds ratio, 2.362; 95% confidence interval [CI], 1.341-4.923; p = 0.001) and SSM (1.489; 1.095-2.235; p = 0.010) were independent predictors of EVs in the training group. The nomogram showed good discrimination, with a C-index of 0.942 (95% CI, 0.892-0.974) through internal validation, and good calibration. Application of the nomogram in the test group still gave good discrimination (C-index, 0.948; 95% CI, 0.868-0.995).

CONCLUSIONS

The combination of LSM and SSM using MRE is an accurate tool to identify patients at risk for EVs.

KEY POINTS

• Performance of MR elastography can estimate the presence of esophageal varices non-invasively. • Liver and spleen stiffness measurements are independent predictors for esophageal varices. • The nomogram using a combination of liver and spleen stiffness measurements allows for the risk of esophageal varices.

Efficiency of acoustic radiation force impulse imaging for the staging of graft fibrosis after liver transplantation

AIM

Liver biopsy is the gold standard for assessing liver fibrosis (LF) after liver transplantation (LT), but its invasiveness limits its utility. This study aimed to evaluate the usefulness of liver stiffness measurement (LSM) using acoustic radiation force impulse (ARFI) imaging to assess LF after LT.

METHODS

Between September 2013 and January 2017, 278 patients who underwent liver biopsy after LT in Kyoto University Hospital (Kyoto, Japan) were prospectively enrolled. Liver stiffness measurement was carried out using ARFI imaging; its value was expressed as shear wave velocity (Vs) [m/s]. The LF was evaluated according to METAVIR score (F0-F4). The diagnostic performance of Vs for F2≤ and F3≤ was assessed and compared with that of laboratory tests using receiver operating characteristic (ROC) analysis.

RESULTS

The median Vs values increased according to the progression of LF (F0, 1.18 (0.78-1.92); F1, 1.35 (0.72-3.54); F2, 1.55 (1.05-3.37); F3, 1.84 (1.41-2.97)). The Vs had the highest area under the ROC curve (AUROC) for the prediction of both F2 ≤ and F3 ≤ fibrosis (F2, 0.77; and F3, 0.85). With the cut-off value of Vs >1.31, sensitivity, specificity, positive predictive value, and negative predictive value were 89.4%, 53.3%, 37.3%, and 94.2% in predicting F2≤, respectively. Shear wave velocity diagnosed LF better than any laboratory tests regardless of the type of primary disease.

CONCLUSIONS

Acoustic radiation force impulse helps to assess graft LF after LT. The high sensitivity suggested that ARFI might reduce the frequency of liver biopsies by detecting patients who are unlikely to have significant fibrosis after LT. (Unique trial no. UMIN R000028296.).