Ultrasound shear wave elastography for the evaluation of renal pathological changes in adult patients

Impact of Ultrasonographically Measured Elastography Scores on Renal Prognosis in Kidney Transplant Recipients

BACKGROUND

The aim of this study was to investigate the relationship between ultrasonographic elastography score and long-term renal prognosis in renal transplant patients.

METHODS

A retrospective cohort study of 100 patients who underwent renal transplantation in our hospital between 2005 and 2022 was performed. Patients were divided into two groups as those with elastography scores higher than 8.45 kPa (n = 50) and those with elastography scores equal to or lower than 8.45 kPa (n = 50). Elastography measurements were performed with Siemens Acuson S2000 ultrasound system and the scores were compared with renal function parameters and other clinical characteristics.

RESULTS

Patients with high elastography scores had smaller kidney size (P = .010), lower eGFR (P = .002), and higher proteinuria and albuminuria levels (P < .05) than patients with low elastography scores. There was a significant association between elastography score and the risk of renal dysfunction (OR = 1.039, P = .006).

CONCLUSIONS

A large elastography score may act as a significant biomarker for prognosing the risk of renal dysfunction in subjects undergoing kidney transplantation. These findings suggest that elastography may become an invaluable noninvasive tool during the long-term follow-up of patients with renal transplants.

Defining normal enthesis stiffness range in a healthy adult population

OBJECTIVES

This study explores the correlation between volunteer demographics with enthesis stiffness and intra- and interobserver agreements using shear wave elastography (SWE).

METHODS

Ninety-eight healthy volunteers were recruited. SWE was performed on quadriceps, suprapatellar, infrapatellar, and Achilles entheses. The stiffness measurements were measured in shear wave velocity (SWV).

RESULTS

Mann-Whitney test revealed insignificant difference in SWV among gender. Wilcoxon signed-rank test showed significant difference in SWV between left and right Achilles entheses. Spearman correlation test revealed moderate negative correlation between SWV and age group in quadriceps (ρ, -0.45, P < .01), and weak negative correlation in suprapatellar (ρ, -0.31, P < .01), and left Achilles (ρ, -0.29, P < .01). Multiple linear regression analysis showed subjects' demographic significantly predicted quadriceps, suprapatellar, and left Achilles entheses stiffness with only age statistically significantly to the prediction (P < .05). Kruskal-Wallis showed significant differences in SWV for quadriceps (P = .01), suprapatellar (P = .03), and left Achilles (P = .01) among different age groups. Good interobserver [0.79-0.86 (95% CI, 0.32-0.94)] and interobserver agreement [0.78-0.89 (95% CI, 0.62-0.95)] were found in all the entheses.

CONCLUSION

SWE emerges as a reproducible method for entheses stiffness quantification, with the study highlighting age as a significant factor impacting SWV in quadriceps, suprapatellar, and left Achilles entheses. Among the studied entheses, SWV for Achilles enthesis is the highest in all age groups.

ADVANCES IN KNOWLEDGE

The study significantly contributes to the understanding of enthesis stiffness by exploring the influence of gender, BMI, and age.

Ultrasound viscoelastic imaging in the noninvasive quantitative assessment of chronic kidney disease

BACKGROUND

This study aims to evaluate the clinical application value of ultrasound viscoelastic imaging in noninvasive quantitative assessment of chronic kidney disease (CKD).

METHODS

A total of 332 patients with CKD and 190 healthy adults as a control group were prospectively enrolled. Before kidney biopsy, ultrasound viscoelastic imaging was performed to measure the mean stiffness value (Emean), mean viscosity coefficient (Vmean), and mean dispersion coefficient (Dmean) of the renal. CKD patients were divided into three groups based on estimated glomerular filtration rate. The differences in clinic, pathology, ultrasound image parameters between the control and patient groups, or among different CKD groups were compared. The correlation between viscoelastic parameters and pathology were analyzed.

RESULTS

Emean, Vmean, and Dmean in the control group were less than the CKD group (p < 0.05). In the identification of CKD from control groups, the area under curve of Vmean, Dmean, Emean, and combining the three parameters is 0.90, 0.79, 0.69, 0.91, respectively. Dmean and Vmean were increased with the decline of renal function (p < 0.05). Vmean and Dmean were positively correlated with white blood cell, urea, serum creatinine, and uric acid (p < 0.05). Vmean is positively correlated with interstitial fibrosis and inflammatory cell infiltration grades (p < 0.001).

CONCLUSIONS

Ultrasound viscoelastic imaging has advantages in noninvasive quantitative identification and evaluating renal function of CKD. Emean > 6.61 kPa, Vmean > 1.86 Pa·s, or Dmean > 7.51 m/s/kHz may suggest renal dysfunction. Combining Vmean, Dmean, and Emean can improve the efficiency of identifying CKD.

Application value of real-time shear wave elastography for quantitative evaluation of chronic kidney disease in pediatric patients

OBJECTIVE

To evaluate the effectiveness of real-time shear wave elastography (SWE) in quantitative evaluation of chronic kidney disease (CKD) in pediatric patients.

METHODS

SWE was conducted on 58 pediatric patients with CKD (CKD group) and 70 healthy volunteers (Control group). Computer-assisted quantitative analysis was utilized to determine the percentage of interstitial fibrosis (IF) in images from the CKD group, categorizing them into mild, moderate, and severe groups according to IF% values. The differences in Young's modulus (YM) and estimated Glomerular Filtration Rate (eGFR) between the renal cortex and medulla in these groups were compared. Additionally, the relationships between YM and IF% as well as YM and eGFR, were analyzed.

RESULTS

The YM values in right lower pole cortex and medulla of the CKD group were significantly higher than those in the control group (all P < 0.05). Significant differences were observed in eGFR among mild, moderate, and severe CKD patients (F = 40.882). YM demonstrated a correlation with eGFR in both the renal cortex and medulla (r = -0.329, P = 0.012; r = 0.417, P = 0.001). YM values increased with the severity of renal interstitial fibrosis in a pronounced trend across groups (F = 109.962, F = 72.950, all P < 0.001). Additionally, YM correlated with IF% in both the renal cortex and medulla (r = 0.362, P = 0.006; r = 0.483, P < 0.001). The optimal cut-off value of renal cortex YM for distinguishing between CKD and control group was 4.05 kPa.

CONCLUSION

SWE enables quantitative assessment of kidney YM values, revealing significantly higher values in children with CKD compared to healthy individuals. YM is correlated with the severity of renal interstitial fibrosis, thereby establishing SWE as a valuable non-invasive tool for quantitative evaluation of pediatric CKD.

Interpretable machine learning model integrating clinical and elastosonographic features to detect renal fibrosis in Asian patients with chronic kidney disease

BACKGROUND

Non-invasive renal fibrosis assessment is critical for tailoring personalized decision-making and managing follow-up in patients with chronic kidney disease (CKD). We aimed to exploit machine learning algorithms using clinical and elastosonographic features to distinguish moderate-severe fibrosis from mild fibrosis among CKD patients.

METHODS

A total of 162 patients with CKD who underwent shear wave elastography examinations and renal biopsies at our institution were prospectively enrolled. Four classifiers using machine learning algorithms, including eXtreme Gradient Boosting (XGBoost), Support Vector Machine (SVM), Light Gradient Boosting Machine (LightGBM), and K-Nearest Neighbor (KNN), which integrated elastosonographic features and clinical characteristics, were established to differentiate moderate-severe renal fibrosis from mild forms. The area under the receiver operating characteristic curve (AUC) and average precision were employed to compare the performance of constructed models, and the SHapley Additive exPlanations (SHAP) strategy was used to visualize and interpret the model output.

RESULTS

The XGBoost model outperformed the other developed machine learning models, demonstrating optimal diagnostic performance in both the primary (AUC = 0.97, 95% confidence level (CI) 0.94-0.99; average precision = 0.97, 95% CI 0.97-0.98) and five-fold cross-validation (AUC = 0.85, 95% CI 0.73-0.98; average precision = 0.90, 95% CI 0.86-0.93) datasets. The SHAP approach provided visual interpretation for XGBoost, highlighting the features' impact on the diagnostic process, wherein the estimated glomerular filtration rate provided the largest contribution to the model output, followed by the elastic modulus, then renal length, renal resistive index, and hypertension.

CONCLUSION

This study proposed an XGBoost model for distinguishing moderate-severe renal fibrosis from mild forms in CKD patients, which could be used to assist clinicians in decision-making and follow-up strategies. Moreover, the SHAP algorithm makes it feasible to visualize and interpret the feature processing and diagnostic processes of the model output.

Comparison of resistive index and shear-wave elastography in the evaluation of chronic kidney allograft dysfunction

BACKGROUND

Detection of early chronic changes in the kidney allograft is important for timely intervention and long-term survival. Conventional and novel ultrasound-based investigations are being increasingly used for this purpose with variable results.

AIM

To compare the diagnostic performance of resistive index (RI) and shear wave elastography (SWE) in the diagnosis of chronic fibrosing changes of kidney allograft with histopathological results.

METHODS

This is a cross-sectional and comparative study. A total of 154 kidney transplant recipients were included in this study, which was conducted at the Departments of Transplantation and Radiology, Sindh Institute of Urology and Transplan tation, Karachi, Pakistan, from August 2022 to February 2023. All consecutive patients with increased serum creatinine levels and reduced glomerular filtration rate (GFR) after three months of transplantation were enrolled in this study. SWE and RI were performed and the findings of these were evaluated against the kidney allograft biopsy results to determine their diagnostic utility.

RESULTS

The mean age of all patients was 35.32 ± 11.08 years. Among these, 126 (81.8%) were males and 28 (18.2%) were females. The mean serum creatinine in all patients was 2.86 ± 1.68 mg/dL and the mean estimated GFR was 35.38 ± 17.27 mL/min/1.73 m2. Kidney allograft biopsy results showed chronic changes in 55 (37.66%) biopsies. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of SWE for the detection of chronic allograft damage were 93.10%, 96.87%%, 94.73%, and 95.87%, respectively, and the diagnostic accuracy was 95.45%. For RI, the sensitivity, specificity, PPV, and NPV were 76.92%, 83.33%, 70.17%, and 87.62%, respectively, and the diagnostic accuracy was 81.16%.

CONCLUSION

The results from this study show that SWE is more sensitive and specific as compared to RI in the evaluation of chronic allograft damage. It can be of great help during the routine follow-up of kidney transplant recipients for screening and early detection of chronic changes and selecting patients for allograft biopsy.

2D shear wave elastography for the assessment of quadriceps entheses-a methodological study

OBJECTIVE

To establish the scanning protocol for 2-dimensional shear wave elastography (SWE) on normal entheses by investigating the possible confounding factors that may increase the variability of measured elasticity.

MATERIAL AND METHODS

30 normal quadriceps entheses were scanned using SWE to compare the stiffness and coefficient variation by changing the ultrasonic coupling gel thickness, knee position, region of interest size, and scanning plane.

RESULTS

No significant difference in median shear wave velocity (SWV) was observed in different coupling gel thicknesses. The median SWV was higher in the knee flexion position than in the extended position (p < 0.001). Increased knee flexion led to stiffer quadriceps enthesis and higher SWV (ρ = 0.8, p < 0.001). The median SWV was higher when the diameter region of interest was 4.0 mm than 2.0 mm (p = 0.001). The median SWV was higher in the transverse plane than in the longitudinal plane (p < 0.001). Strong correlation was found between SWV and the degree of the shear wave to muscle fiber direction (ρ = 0.8, p < 0.001). The coefficient variation was lower in a gel thickness of 2.5 cm, with an extended knee, a region of interest of 2.0 mm, and a longitudinal plane (p > 0.05). For interobserver reliability for the proposed protocol, the intraclass correlation coefficients was 0.763.

CONCLUSION

In this study, we determined supine position with the knee extended; using 2.0 mm diameter region of interest and image acquisition at the longitudinal plane with thicker layer coupling gel seems most appropriate to reliably image healthy quadriceps entheses with SWE.

Shear wave elastography in chronic kidney disease - the physics and clinical application

Chronic kidney disease is a leading public health problem worldwide. The global prevalence of chronic kidney disease is nearly five hundred million people, with almost one million deaths worldwide. Estimated glomerular filtration rate, imaging such as conventional ultrasound, and histopathological findings are necessary as each technique provides specific information which, when taken together, may help to detect and arrest the development of chronic kidney disease, besides managing its adverse outcomes. However, estimated glomerular filtration rate measurements are hampered by substantial error margins while conventional ultrasound involves subjective assessment. Although histopathological assessment is the best tool for evaluating the severity of the renal pathology, it may lead to renal insufficiency and haemorrhage if complications occurred. Ultrasound shear wave elastography, an emerging imaging that quantifies tissue stiffness non-invasively has gained interest recently. This method applies acoustic force pulses to generate shear wave within the tissue that propagate perpendicular to the main ultrasound beam. By measuring the speed of shear wave propagation, the tissue stiffness is estimated. This paper reviews the literature and presents our combined experience and knowledge in renal shear wave elastography research. It discusses and highlights the confounding factors on shear wave elastography, current and future possibilities in ultrasound renal imaging and is not limited to new sophisticated techniques.