Elucidation of spleen elasticity and viscosity in a carbon tetrachloride rat model of liver cirrhosis using a new ultrasound elastography

Relationship Between Spleen Pathologic Changes and Spleen Stiffness in Portal Hypertension Rat Model

OBJECTIVE

The aim of the study described here was to explore the influence of splenic pathology and hemodynamic parameters on spleen stiffness in portal hypertension (PH).

METHODS

A Sprague‒Dawley rat model of PH (n = 34) induced by CCl4 was established, and 9 normal rats were used as controls. All animals underwent a routine ultrasound examination, spleen stiffness measurement (SSM), liver stiffness measurement (LSM), portal vein pressure (PVP) measurement and histopathologic assessment. The diagnostic performance of SSM and LSM in PH was evaluated. SSMs were compared among the groups at different pathologic and hemodynamic levels. Multiple linear regression was used to analyze the factors affecting SSM.

RESULTS

SSM had excellent diagnostic efficacy for PH (area under the receiver operating characteristic curve [AUC] = 0.900) and was superior to LSM (AUC = 0.794). In a rat model of PH, pathologic changes such as splenic sinus widening, thickening of the splenic capsule and an increase in collagen fibers were observed in the spleen. There were significant differences in SSM at different splenic capsule thicknesses and splenic sinus widths (all p values <0.05), but there were no significant differences in the SSM at different levels of the splenic collagen fiber area and red pulp area (all p values >0.05). In addition, there were significant differences in SSM at different levels of portal vein diameter, blood flow and congestion index (all p values <0.05). Multiple linear regression analysis revealed that PVP, portal vein congestion index and splenic capsule thickness were significantly associated with SSM.

CONCLUSION

SSM is a good non-invasive way to assess PH. PVP, splenic capsule thickness and portal vein congestion index are responsible for spleen stiffness but not the proliferation of splenic fibrous tissue.

Enlargement of the Spleen Index Is a Predictor of the Occurrence of Esophageal Varices and Hepatocellular Carcinoma after Administering Direct-acting Antiviral Agents

Objective Direct-acting antiviral agents (DAAs) can eliminate hepatitis C virus at a high rate, although the long-term incidence of portal hypertension and hepatocellular carcinoma (HCC) has not yet been elucidated. In this observational study, we clarified the predictors associated with the incidence of esophageal varices (EVs) and HCC after DAAs treatment based on ultrasound findings and blood examinations. Methods A total of 78 patients treated with DAAs were enrolled in this study. The primary endpoint was to identify the predictors associated with EVs and HCC occurrence using univariate and multivariate analyses. Secondary endpoints were to extract the cutoff values for EVs and HCC occurrence and clarify the changes in liver stiffness (LS), spleen stiffness (SS), spleen index (SI), portal venous flow volume (PVF), and blood examination at 12 weeks after the end of DAAs treatment. Results The mean observation period was 1,402±546 days. SI change (SI after DAAs-SI before DAAs) was a predictor of EVs occurrence in multivariate analysis (p=0.045). The treatment history of HCC, albumin value before DAAs, and SI change were predictors of HCC occurrence in multivariate analysis (p=0.002, p=0.032, and p=0.009, respectively). LS, SS, PVF, SI, and liver function significantly improved after DAAs treatment. Conclusion Portal hypertension seems to improve after DAAs treatment over a long period. Patients with splenomegaly deterioration after DAAs treatment need to be carefully monitored for the occurrence of EVs and HCC.

Shear Wave Dispersion in Chronic Liver Disease: From Physical Principles to Clinical Usefulness

The development of new applications in ultrasound (US) imaging in recent years has strengthened the role of this imaging technique in the management of different pathologies, particularly in the setting of liver disease. Improved B-mode imaging (3D and 4D), contrast-enhanced US (CEUS) and especially US-based elastography techniques have created the concept of multiparametric ultrasound (MP-US), a term borrowed from radiological sectional imaging. Among the new elastography techniques, shear wave dispersion is a newly developed imaging technology which enables the assessment of the shear waves' dispersion slope. The analysis of the dispersion qualities of shear waves might be indirectly related to the tissue viscosity, thus providing biomechanical information concerning the pathologic state of the liver such as necroinflammation. Some of the most recent US devices have been embedded with software that evaluate the dispersion of shear waves/liver viscosity. In this review, the feasibility and the clinical applications of liver viscosity are reviewed based on the preliminary findings of both animal and human studies.

Spleen stiffness in patients with chronic liver disease evaluated by 2-D shear wave elastography with ultrasound multiparametric imaging

BACKGROUND

The novel 2-D shear wave elastography (2D-SWE) can measure two ultrasound parameters: shear wave dispersion (SWD) and shear wave speed (SWS). We investigated the ability of 2D-SWE in measuring spleen stiffness using ultrasound multiparametric imaging.

METHODS

This cross-sectional study included patients with chronic liver disease who underwent esophagogastroduodenoscopy and ultrasonographic examinations of the spleen between September 2018 and December 2021. In total, 157 patients were enrolled in this study: 81 and 67 patients were included in the pilot set for hepatic venous pressure gradient (HVPG) measurements and validation cohort without HVPG measurements, respectively. To confirm reproducibility between the two examiners, an additional 30 patients were enrolled.

RESULTS

The Bland-Altman plots revealed no significant bias in the SWD as measured by two examiners. The splenic SWS (r = 0.752) and SWD (r = 0.444) were correlated with the HVPG. Regarding high-risk varices, as per the Youden index, the cut-off value for splenic SWS was 3.30 m/s, with a sensitivity of 85.7%, specificity of 92.5%, positive predictive value of 85.7%, and negative predictive value of 92.4% in the pilot set. In the validation set, good diagnostic performance by the splenic SWS was observed. However, SWD did not perform as well as SWS.

CONCLUSIONS

The splenic SWS, measured using ultrasound multiparametric imaging, was closely correlated with the HVPG. Thus, SWS is a useful predictive marker for high-risk varices.

Liver and spleen stiffness on ultrasound elastography are predictors of the occurrence of esophagogastric varices after balloon-occluded retrograde transvenous obliteration

BACKGROUND

Balloon-occluded retrograde transvenous obliteration (BRTO) is an effective treatment for gastric varices, but predictors associated with overall survival rate (OS) and occurrence of esophagogastric varices (EGV) have not yet been clarified. In this study, we clarified these predictors by performing ultrasound elastography and blood tests at various time points.

METHODS

A total of 34 patients were enrolled. The primary endpoint was to identify predictors associated with OS and EGV occurrence by univariate and multivariate analyses. Secondary endpoints were to extract the cutoff values for OS and EGV occurrence, and to clarify chronological changes in liver stiffness (LS), spleen stiffness (SS), spleen index (SI), and portal vein flow volume (PVF). Time points were set as before BRTO (Bf), and 1 day (D1), 7 days (D7), 1 month (1M), 3 months (3M), and 6 months (6M) after BRTO.

RESULTS

Albumin-bilirubin score Bf, fibrin-4 index change 6M, and branched chain amino acids tyrosine molar ratio (BTR) 1M were predictors of OS on univariate analysis (p = 0.021, 0.033, and 0.019, respectively) but were not extracted by multivariate analysis. The factors of LS 6M > 19.9 kPa and SS D7 > 21.7 kPa were predictors of the occurrence of EGV on multivariate analysis (p = 0.029 and 0.025, respectively). PVF significantly increased with time after BRTO.

CONCLUSION

Albumin-bilirubin score and BTR had the possibility to associated with OS, and the predictors of reduced occurrence of EGV were LS < 19.9 and SS < 21.7.