Point Shear Wave Elastography for Assessment of Liver Stiffness in Normal Individuals and in Patients With Non-alcoholic Fatty Liver Disease

Abstract

Background Non-alcoholic fatty liver disease (NAFLD) is an increasing health issue worldwide, driven by rising rates of diabetes, obesity, and hypertriglyceridemia. Often asymptomatic, NAFLD is diagnosed through blood tests, imaging, and sometimes liver biopsy. Some cases advance to non-alcoholic steatohepatitis (NASH), which can lead to complications like liver cirrhosis and liver failure. While liver biopsy is the standard test for diagnosis, non-invasive methods such as shear wave elastography (SWE) offer a simpler and more reproducible alternative for diagnosing NAFLD. This is crucial for early intervention and preventing the progression of liver damage. Objectives The objectives of the study were to measure and compare liver stiffness in healthy individuals and patients with NAFLD using point shear wave elastography (pSWE), as well as to correlate liver stiffness in NAFLD patients with the ultrasonographic grades of fatty liver. Materials and methods This observational study was carried out at Dr. D. Y. Patil Medical College, Hospital and Research Centre in Pune, India, from December 2022 to April 2024. The study involved 82 participants in total, with 41 patients diagnosed with NAFLD (cases) and 41 healthy individuals with a sonographically normal liver (controls). pSWE was performed on each participant to measure liver stiffness, with results expressed in kilopascals (kPa). The procedure was conducted using a Samsung HS70A ultrasound machine (Samsung Electronics Pvt. Ltd., Seoul, South Korea). Data analysis was performed using IBM SPSS Statistics for Windows, Version 26.0 (Released 2019; IBM Corp., Armonk, New York, USA). Non-parametric tests, such as the Mann-Whitney test and Kruskal-Wallis test, were used to evaluate the significance of differences. A p-value of less than 0.05 was considered statistically significant. Results The mean liver stiffness, measured in kilopascals (kPa), was higher in NAFLD patients (cases) (10±5.1 kPa) than in normal individuals (controls) (4.4±0.7 kPa). This difference was statistically significant, with a p-value of less than 0.001. A positive correlation (rho=0.848, p<0.001) was found between the ultrasonographic grade of fatty liver and liver stiffness in NAFLD patients. Conclusion Our study demonstrated that individuals with NAFLD exhibited significantly higher liver stiffness compared to healthy individuals, as measured by ultrasound SWE. These findings suggest that pSWE could serve as a valuable, non-invasive diagnostic tool for assessing liver stiffness in NAFLD patients. Additionally, pSWE holds the potential for evaluating and monitoring the progression of the disease. However, further research with larger sample sizes is necessary to determine the prognostic significance of liver stiffness in these patients.

Keywords: fatty liver; liver stiffness; non‐alcoholic fatty liver disease; point shear wave elastography; ultrasound elastography.

Figure 1. Ultrasound image utilized to assess liver stiffness. The ROI is marked by a small square (yellow box), and the liver stiffness is measured within this area

ROI: region of interest; pSWE: point shear wave elastography

Figure 2. Box-and-whisker plot showing the comparison of liver stiffness between cases and controls

The box-and-whisker plot demonstrates that the cases (NAFLD patients) exhibited higher median liver stiffness values as well as a broader range compared to the controls (normal individuals). The blue boxes represent the IQR of liver stiffness for each group, with the dark blue lines indicating the median values. The black whiskers extend to the minimum and maximum values within 1.5 times the IQR from the first and third quartiles. The circles outside of the whiskers represent the outliers. IQR: interquartile range; NAFLD: non-alcoholic fatty liver disease

Figure 3. The positive statistical correlation between ultrasonographic grades of fatty liver and liver stiffness (kPa). The data points are represented by blue marks, and the red line represents the line drawn through the data points