Magnetic resonance imaging for the assessment of pathological hepatic findings in nonalcoholic fatty liver disease

Noninvasive assessment of liver fibrosis and its clinical significance in nonalcoholic fatty liver disease

Liver fibrosis is the most important prognostic factor in patients with nonalcoholic fatty liver disease (NAFLD). Several noninvasive markers for fibrosis, including blood-based markers and imaging based-markers have been developed. Indirect fibrosis markers (e.g., fibrosis-4 index and NAFLD fibrosis score) consist of standard laboratory data and clinical parameters. Given its availability and high negative predictive value for advanced fibrosis, these markers are suitable for screening at primary care. Blood-based fibrogenesis markers (enhanced liver fibrosis and N-terminal propeptide of type 3 collagen), ultrasound-based modalities (vibration-controlled transient elastography, point shear wave elastography [SWE], and two-dimensional SWE), and magnetic resonance elastography have high diagnostic accuracy for liver fibrosis and are suitable for diagnosing liver fibrosis at secondary care centers. Sequential use of these markers can increase diagnostic accuracy and reduce health care costs. Furthermore, combining noninvasive makers may assist in identifying candidates for pharmacological trials and reducing screening failure. Emerging data suggest that these noninvasive markers are associated with liver-related events (hepatocellular carcinoma and decompensation) and mortality. Furthermore, delta change in noninvasive markers over time is also associated with time-course change in fibrosis, liver-related event risk, and mortality risk. However, the association between liver fibrosis and cardiovascular disease (CVD) risk is still controversial. CVD risk may decrease in patients with decompensated liver disease and noninvasive markers may be useful for assessing CVD risk in these patients. Therefore, noninvasive markers may be utilized as measures of fibrosis as well as real-time prognostic tools, in place of liver biopsy.

The effect of the skin-liver capsule distance on the accuracy of ultrasound diagnosis for liver steatosis and fibrosis

PURPOSE

Transient elastography (TE) and the controlled attenuation parameter (CAP) have been used for diagnosis of liver fibrosis and steatosis. Obesity is a limiting factor to the accuracy of elastography; however, an XL probe was validated for use in obese patients. Two-dimensional shear wave elastography (2D-SWE) and attenuation imaging (ATI) have also been developed. It is unknown if obesity affects 2D-SWE/ATI values for evaluation of liver fibrosis and steatosis. We assessed the reliability of the measurement rate and the diagnostic performance of TE/CAP versus SWE/ATI.

METHODS

The patients (n = 85) underwent TE/CAP, 2D-SWE/ATI, and liver biopsy on the same day. They were diagnosed with chronic hepatitis based on liver biopsy. The patients were divided into three groups by skin-liver capsule distance (SCD).

RESULTS

The reliability of the measurement rate for the M probe was lower than that for the XL probe in the group with SCD over 22.5 mm. The rate achieved with 2D-SWE was high in all groups regardless of the SCD. In the assessment of the diagnostic performance, there was no difference between the area under the receiver-operating curve (AUROC) of TE compared to 2D-SWE to stratify the fibrosis stage. There was no difference in the AUROC for the stratification of the steatosis grades between CAP and ATI. The diagnostic accuracy of TE for F ≥ 3 fibrosis evaluated with the M probe and 2D-SWE was lower than that of TE evaluated with the XL probe in the group with SCD over 22.5 mm.

CONCLUSION

The ability of 2D-SWE to stratify fibrosis stage and steatosis grade was as good as FibroScan. However, 2D-SWE had a high reliability in the measurement rate regardless of the SCD with one probe. And the XL probe showed high diagnostic accuracy for severe fibrosis in the group with SCD over 22.5 mm.

High frequency and long persistency of ballooning hepatocyte were associated with glucose intolerance in patients with severe obesity

Nonalcoholic steatohepatitis (NASH) and glucose intolerance are associated with an increased risk of mortality in patients with severe obesity; however, whether histological findings of the liver are related to glucose intolerance in these patients remain unknown. Sixty-nine consecutive patients who underwent metabolic surgery between June 2008 and February 2020 were included; histological findings of the liver and laboratory data were analyzed. Twenty patients with biopsy-proven NASH were chronologically evaluated using sequential biopsies; data before metabolic surgery was considered as the baseline. Glucose intolerance—demonstrated by an increased area under the curve (AUC) for blood sugar (BS) during the 75-g oral glucose tolerance test—and increased homeostatic model assessment for insulin resistance (HOMA-IR) correlated with the grade of hepatocyte ballooning in patients. Patients with persistent ballooning at the follow-up biopsy had a higher HOMA-IR, high AUC for BS, and lower adiponectin level than those in patients in whom ballooning was eliminated, while there was no significant difference in body weight. We concluded that glucose intolerance was associated with the grade of hepatocyte ballooning; additionally, persistent hepatocyte ballooning sustained glucose intolerance, while elimination of hepatocyte ballooning improved the condition. Glucose intolerance may, thus, mediate balloon formation of the hepatocyte.

Attenuation coefficient (ATT) measurement for liver fat quantification in chronic liver disease

Liver fat is one of the main clinical features in chronic liver disease, and the number of fatty liver patients is increasing as the prevalence of obesity and metabolic syndrome increases globally. Noninvasive and quantitative assessment of liver fat content was made possible by recent technological advances. Attenuation coefficient (ATT) measurement is a noninvasive and quantitative liver fat measurement method used in clinical practice. The ATT value is significantly associated with histological steatosis grade. The diagnostic accuracy of ATT for histological steatosis grade is equivalent to controlled attenuation parameter (CAP), and ATT has a lower measurement failure rate than CAP because ATT can be measured on a B-mode image with the exact location of the region of interest. Furthermore, ATT measurement has high interobserver reproducibility. Since ATT measurement and other ultrasound-based modalities for liver fat quantification are easy to perform and inexpensive, these modalities are suitable for point-of-care and screening. Although emerging data suggest that quantitative liver fat content and its changes over time may be associated with disease progression in nonalcoholic fatty liver disease, the association between ATT and disease progression has not been evaluated yet. Therefore, further investigation and validation studies are necessary to strengthen the clinical significance of ATT measurement in chronic liver disease.

Ultrasonographic grayscale findings related to fibrosis in patients with non-alcoholic fatty liver disease: comparison with transient elastography and Fib-4 index

PURPOSE

Fibrosis is a predictor of mortality in patients with non-alcoholic fatty liver disease (NAFLD). In our institution, abdominal ultrasonography has been performed based on a unified method consisting of 25 images. We investigated ultrasonographic grayscale findings related to fibrosis in patients with NAFLD.

METHODS

This retrospective study comprised 41 cases of pathologically proven fatty liver between January 2015 and September 2020. A total of 26 ultrasonographic findings were subjectively evaluated. These findings, transient elastography (TE) with M probe, and FIB-4 index were compared with fibrosis stage.

RESULTS

The frequency of roughness of the dorsal side of the surface (p < 0.001), heterogenicity of the parenchyma (p = 0.003), narrowing of the hepatic vein (p = 0.004), and splenomegaly (p < 0.001) were strongly correlated with the fibrosis stage. Logistic regression analysis for stage ≥ 3 showed narrowing of the hepatic vein (odds ratio [OR] 5.860, p = 0.031) and splenomegaly (OR 6.290, p = 0.028). Logistic regression analysis for stage 4 showed roughness of the ventral side of the surface (OR 42.0, p = 0.019). The AUROC for stage 3 and stage 4 with the number of positive ultrasonographic findings was 0.856, and 0.940, respectively. The AUROC for F3 and F4 with TE was 0.831 and 0.861, respectively. The AUROC for stage 3 and stage 4 with FIB-4 index was 0.815 and 0.806, respectively.

CONCLUSIONS

Narrowing of the hepatic vein, roughness of the dorsal side of the surface, heterogenicity of the parenchyma, and splenomegaly and their combination could predict fibrosis in patients with NAFLD.

A review of physical and engineering factors potentially affecting shear wave elastography

It has been recognized that tissue stiffness provides useful diagnostic information, as with palpation as a screening for diseases such as cancer. In recent years, shear wave elastography (SWE), a technique for evaluating and imaging tissue elasticity quantitatively and objectively in diagnostic imaging, has been put into practical use, and the amount of clinical knowledge about SWE has increased. In addition, some guidelines and review papers regarding technology and clinical applications have been published, and the status as a diagnostic technology is in the process of being established. However, there are still unclear points about the interpretation of shear wave speed (SWS) and converted elastic modulus in SWE. To clarify these, it is important to investigate the factors that affect the SWS and elastic modulus. Therefore, physical and engineering factors that potentially affect the SWS and elastic modulus are discussed in this review paper, based on the principles of SWE and a literature review. The physical factors include the propagation properties of shear waves, mechanical properties (viscoelasticity, nonlinearity, and anisotropy), and size and shape of target tissues. The engineering factors include the region of interest depth and signal processing. The aim of this review paper is not to provide an answer to the interpretation of SWS. It is to provide information for readers to formulate and verify the hypothesis for the interpretation. Therefore, methods to verify the hypothesis for the interpretation are also reviewed. Finally, studies on the safety of SWE are discussed.