Relationship between Novel Elastography Techniques and Renal Fibrosis-Preliminary Experience in Patients with Chronic Glomerulonephritis

Role of shearing wave elastography in detecting early diabetic nephropathy

BACKGROUND

Diabetes mellitus is one of the systemic diseases affecting the kidneys that eventually develop end-stage kidney disease. Shear wave elastography (SWE) is a reliable and non-invasive ultrasonography test used to determine tissue elasticity. The aim of this study is to detect early diabetic nephropathy by measuring renal stiffness using shear wave elastography (SWE), renal resistivity indices, and laboratory findings in DN patients.

METHODS

Shear wave elastography and color duplex sonography assessments were performed in 60 diabetic nephropathy patients (divided according to eGFR into 3 stages: stage I-II-III diabetic nephropathy with equal groups of 20 patients in each stage) and 20 healthy age-matched control subjects. The SWE-derived mean value of the tissue stiffness, given in kilopascals (kPa), was correlated to patients' clinico-laboratory data (serum creatinine and eGFR) and resistive index.

RESULTS

There is a statistically significant increase in SWE and RI in the diabetic group than control group and a statistically significant increase in SWE (mean) in CKD stage II and III when compared with CKD stage I, SWE can be used to discriminate between diabetic groups and control group at a cutoff level of > 10.5 (kPa), and also, SWE (mean) can be used to discriminate between CKD stage II and III patients at a cutoff level of > 41 (kPa), with 66.7% sensitivity and 64.9% specificity.

CONCLUSION

Shear wave elastography is a sensitive, non-invasive, and specific diagnostic tool for the detection of diabetic nephropathy and differentiation between different stages of DN.

Role of 2D shear wave elastography in assessing chronic kidney disease and its correlation with point shear wave elastography and eGFR

The study was conducted with the aim of calculating renal stiffness through shear wave sonoelastography (SWE) in chronic kidney disease (CKD) and in normal kidneys, to find out a cut off value to differentiate between the two. This cross-sectional study included 80 participants (40 CKD patients and 40 subjects with normal renal function) with eGFR calculated using serum creatinine taken as a biochemical parameter. All participants underwent 2D and point SWE. Values obtained as young's modulus statistical analysis was done. CKD patients had higher mean 2D elasticity of 7.92 kPa (SD ± 1.94) and mean point elasticity of 7.93 kPa (SD ± 3.83) compared to the control group. At a cutoff point of > 5.2, Elast Q provides the reliable balance between sensitivity (95%) and specificity (97.5%) for predicting CKD. To conclude, Young's modulus values derived by 2D and point SWE found to be greater in diseased kidneys than healthy kidneys. 2D SWE (Elast Q) outperforms point SWE (Elast PQ) in predicting CKD due to its higher area under the curve, better sensitivity, specificity making it more reliable diagnostic tool for CKD.

Shear wave elastography primer for the abdominal radiologist

PURPOSE

Shear wave elastography (SWE) provides a means for adding information about the mechanical properties of tissues to a diagnostic ultrasound examination. It is important to understand the physics and methods by which the measurements are made to aid interpretation of the results as they relate to disease processes.

METHODS

The components of how ultrasound is used to generate shear waves and make measurements of the induced motion are reviewed. The physics of shear wave propagation are briefly described for elastic and viscoelastic tissues. Additionally, shear wave propagation in homogeneous and inhomogeneous cases is addressed.

RESULTS

SWE technology has been implemented by many clinical vendors with different capabilities. Various quality metrics are used to define valid measurements based on aspects of the shear wave signals or wave velocity estimates.

CONCLUSION

There are many uses for SWE in abdominal imaging, but it is important to understand how the measurements are performed to gauge their utility for diagnosis of different conditions. Continued efforts to make the technology robust in complex clinical situations are ongoing, but many applications actively benefit from added information about tissue mechanical properties for a more holistic view of the patient for diagnosis or assessment of prognosis and treatment management.

Noninvasive assessment of pediatric glomerular disease: multimodal ultrasound

Background

Traditional 2-dimensional (2D) ultrasound is a noninvasive method in the assessment of glomerular disease. Ultrasound elastography shows promise in evaluating renal fibrosis, which plays a key role in glomerular disease progression. However, research in pediatric cohorts is limited. This study aimed to assess the diagnostic efficacy of multimodal ultrasound in pediatric patients with glomerular disease.

Methods

Pediatric patients undergoing kidney elasticity examination were recruited. Participants were categorized into a control group, nephritic group, and nephrotic group based on clinical presentation and pediatric nephrologist diagnosis. The nephritic group included cases with hematuria, proteinuria, kidney function impairment, and potentially edema or hypertension. The nephrotic group included cases with nephrotic syndrome. All participants underwent multimodal ultrasound of the right kidney to obtain 2D parameters, hemodynamic parameters, and elasticity values. Sound touch quantification (STQ) is a new shear wave elastography (SWE) technology that has been used in clinical applications in recent years. In this study, it was used to obtain kidney elasticity values. The diagnostic efficacy of multimodal ultrasound was evaluated through receiver operating characteristic (ROC) curve analysis. Logistic regression was further utilized to investigate the combined diagnostic efficacy of multiple parameters.

Results

This study included 154 females and 187 males with ages ranging from 4 to 16 years (mean age: 9.78±3.20 years). Cortical STQ and medullary STQ exhibited lower sensitivity but higher specificity. In logistic regression modeling, multimodal ultrasound showed good diagnostic performance. Between the nephritic group and the control group, the ROC curve yielded an area under the curve (AUC) of 0.71 [95% confidence interval (CI): 0.64-0.77]; sensitivity, 58.10%; specificity, 76.26% (P<0.01). Between the nephrotic group and the control group, the ROC curve yielded an AUC of 0.75 (95% CI: 0.69-0.82); sensitivity, 75.26%; specificity, 62.59% (P<0.01).

Conclusions

Ultrasound elastography demonstrates potential in detecting glomerular disease. Multimodal ultrasound can serve as a noninvasive approach for assessing glomerular disease, exhibiting good diagnostic performance.

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.

Prediction of acute rejection in renal allografts using shear-wave dispersion slope

OBJECTIVES

To evaluate the role of shear-wave dispersion slope for predicting renal allograft dysfunction.

METHODS

We retrospectively reviewed 128 kidney transplant recipients (median age, 55 years [interquartile range, 43-62 years]; male, 68) who underwent biopsy for allograft evaluation from November 2022 to February 2023. Cortex and renal sinus fat stiffness and shear-wave dispersion slope were obtained at shear-wave elastography (SWE). Cortex-to-sinus stiffness ratio (SR) and dispersion slope ratio (DSR)-related clinical and pathologic factors were evaluated using multivariable linear regression analysis. We conducted univariate and multivariate analyses for multiparametric ultrasound (US) parameters for identifying acute rejection and calculated the area under the receiver operating curve (AUC) values.

RESULTS

Of 128 patients, 31 (24.2%) demonstrated acute rejection. The SR value did not differ between patient groups (1.21 vs. 1.20, p = 0.47). Patients with acute rejection demonstrated a higher DSR than those without rejection (1.4 vs. 1.21, p < 0.01). Interstitial fibrosis and tubular atrophy grade (IFTA; coefficient, 0.11/grade; p = 0.04) and renal transplant and biopsy interval (coefficient, 0.00007/day; p = 0.03) were SR determinant factors, whereas only IFTA grade (coefficient, 0.10/grade; p = 0.01) for DSR. Multivariate analysis revealed mean resistive index (odds ratio [OR] 1.08, 95% confidence interval [CI] 1.02-1.14, p = 0.01) and DSR value (OR 16.0, 95% CI 3.0-85.8, p = 0.001) as independent factors for predicting acute rejection. An AUC of 0.74 for detecting acute rejection was achieved by combining the resistive index and DSR value.

CONCLUSION

Shear-wave dispersion slope obtained at SWE may help identify renal allograft dysfunction.

CLINICAL RELEVANCE STATEMENT

Acute rejection in renal allografts is a major cause of allograft failure, but noninvasive diagnosis is a challenge. Shear-wave dispersion slope can identify acute rejection non-invasively.

KEY POINTS

• The interstitial fibrosis and tubular atrophy grade was a determinant factor for stiffness ratio and shear-wave dispersion slope ratio between cortex and renal sinus fat. • Shear-wave dispersion slope ratio between cortex and renal sinus fat could identify acute rejection in renal allografts. • A shear-wave dispersion slope has a potential to reduce unnecessary renal biopsy for evaluating renal allografts.

Canadian Anatomic Kidney Score: Quantitative Macroscopic Assessment of Donor Kidney Quality for Transplantation

Background

The Canadian Anatomic Kidney Score (CAKS) is a novel 6-point grading system that standardizes the gross description of a donor kidney across 3 components-vessels, anatomy, and sticky fat. We hypothesized that the CAKS predicts allograft functional outcomes and provides additional information to the Kidney Donor Profile Index (KDPI) and histologic assessment of the donor kidney.

Methods

Single-center cohort of 145 patients who underwent renal transplantation with CAKS analysis between 2018 and 2021. CAKS was prospectively determined before transplantation. Preimplantation core biopsies were assessed according to the Remuzzi score (RS). The primary outcome was 1-y allograft function represented by an estimated glomerular filtration rate (eGFR).

Results

Linear regression without adjustment for KDPI or RS showed a significant association between the CAKS and 1-y eGFR (-8.7 mL/min/1.73 m2 per point increase in CAKS; 95% CI, -13.0 to -4.4; P < 0.001). Most of that association was attributed to the vessel component (-12.1; -19.4 to -4.8; P = 0.002). Adjustment for KDPI and RS attenuated the relationship between 1-y function and CAKS (-4.6; -9.5 to 0.3; P = 0.065) and vessel component (-7.4; -15.2 to 0.5; P = 0.068).

Conclusions

Anatomic assessment of donor kidneys at the time of transplantation associates with allograft function at 1 y. Vascular assessment appears to make the dominant contribution.

Evaluation of Robustness of S-Transform Based Phase Velocity Estimation in Viscoelastic Phantoms and Renal Transplants

Ultrasound shear wave elastography (SWE) methods are being used to differentiate healthy versus diseased tissue on the basis of their viscoelastic mechanical properties. Tissue viscoelasticity is often studied by analyzing shear wave phase velocity dispersion curves, which is the variation of phase velocity with frequency or wavelength. Recently, a unique approach using a generalized Stockwell transformation (GST-SFK) was proposed for the calculation of dispersion curves in viscoelastic media over expanded frequency band. In this work, the method's robustness was evaluated on data from five custom-made viscoelastic tissue-mimicking phantoms and sixty in vivo renal transplants. For each phantom, 15 shear wave motion data acquisitions were taken, while 10-13 acquisitions were acquired for renal transplants measured in the renal cortex. For each data-set mean and standard deviation (SD) of estimated phase velocity dispersion curves were studied. In addition, the viscoelastic parameters of the Zener model were examined, which were preceded by a convergence analysis. For viscoelastic phantoms scanned with a research ultrasound scanner, and for the in vivo renal transplants scanned with a clinical scanner, the decisive advantage of the GST-SFK method over the standard two-dimensional Fourier transform (2D-FT) method was shown. The GST-SFK method provided dispersion curve estimates with lower SD over a wider frequency band in comparison to the 2D-FT method. These advantages are relevant to the analysis of the mechanical properties of tissues in clinical practice to discriminate healthy from diseased tissue.

The value of shear wave elasticity and shear wave dispersion imaging to evaluate the viscoelasticity of renal parenchyma in children with glomerular diseases

BACKGROUND

To study the value of shear wave elasticity and shear wave dispersion imaging to evaluate the viscoelasticity of renal parenchyma in children with glomerular diseases.

METHODS

Forty-three children with glomerular diseases were prospectively evaluated by shear wave elasticity (SWE) and shear wave dispersion imaging (SWD); 43 healthy volunteers served as the control group. The shear wave velocities (SWV) and the dispersion slopes were measured at the upper, middle, and lower poles of both kidneys. The analysis of mean SWV and mean dispersion slope in control and patient groups was used to further evaluate the value of SWE and SWD in the viscoelasticity of renal parenchyma in children with glomerular disease.

RESULTS

The mean SWV in children with glomerular disease was higher than that in the healthy control group (1.61 ± 0.09 m/s vs. 1.43 ± 0.07 m/s, p < 0.001). Compared with healthy group, the mean dispersion slope in children with glomerular disease was significantly increased (13.5 ± 1.39 (m/s)/kHz vs. 12.4 ± 1.40 (m/s)/kHz, p < 0.001). Correlation analysis showed absence of correlation between the SWV and dispersion slope of occult blood, serum creatinine, 24-h urine protein, blood albumin, BMI and ROI box depth of children with glomerular disease.

CONCLUSIONS

The present study shows that it is feasible to use SWE and SWD to evaluate the difference of viscoelasticity of the renal parenchyma between healthy children and those with glomerular disease.