ARFI-based tissue elasticity quantification in comparison to histology for the diagnosis of renal transplant fibrosis

Role of Shear Wave Elastography for Assessment of Renal-Allograft Fibrosis and its Correlation With Histopathology

OBJECTIVES

To investigate whether shear wave elastography (SWE) can accurately identify interstitial fibrosis and tubular atrophy (IFTA) in chronic renal allograft injury (CRAI) and whether it can differentiate between different grades of IFTA.

MATERIALS AND METHODS

Prospective observational study on renal transplant recipients who presented with CRAI. Patient selection was done on the basis of clinical presentation, serum creatinine, and eGFR levels. Biopsy and SWE were performed and SWE values were correlated with histopathological findings according to Banff schema. Receiver operating characteristic (ROC) was also analyzed to assess the diagnostic efficacy of SWE.

RESULTS

Sxity-one patients were evaluated. Ten patients had no IFTA, 33 patients had mild IFTA, 16 patients had moderate IFTA, and 2 patients had severe IFTA. Mean parenchymal stiffness values in no IFTA, mild IFTA, moderate IFTA and severe IFTA were 39.86 ± 2.17 kPa (3.64 ± 0.09 m/s), 41.59 ± 3.36 kPa (3.71 ± 0.15 m/s), 47.59 ± 3.34 kPa (3.98 ± 0.14 m/s), and 53.83 ± 1.41 kPa (4.25 ± 0.03 m/s), respectively. SWE values of parenchymal stiffness reached statistical significance to differentiate between mild, moderate, and severe IFTA. ROC analysis revealed cut-off values of 45.09 kPa (3.89 m/s) to differentiate between mild IFTA and moderate IFTA, 52.06 kPa (4.18 m/s) to differentiate between moderate IFTA and severe IFTA with acceptable sensitivity and specificity.

CONCLUSION

SWE is a non-invasive and cost-effective imaging tool to evaluate the disease status of renal allografts affected by CRAI. Thus, it can be of paramount importance if added to the regular follow-up imaging protocol of renal allograft along with grayscale and Doppler imaging.

Shear wave elastography of transverse carpal ligament increased with simulated carpal tunnel pressure

BACKGROUND

Elevation of carpal tunnel pressure is known to be associated with carpal tunnel syndrome. This study aimed to correlate the shear wave elastography in the transverse carpal ligament (TCL) with carpal tunnel pressures using a cadaveric model.

METHODS

Eight human cadaveric hands were dissected to evacuate the tunnels. A medical balloon was inserted into each tunnel and connected to a pressure regulator to simulate tunnel pressure in the range of 0-210 mmHg with an increment of 30 mmHg. Shear wave velocity and modulus was measure in the middle of TCL.

RESULTS

SWV and SWE were significantly dependent on the pressure levels (p < 0.001), and positively correlated to the tunnel pressure (SWV: R = 0.997, p < 0.001; SWE: R = 0.996, p < 0.001). Regression analyses showed linear relationship SWV and pressure (SWV = 4.359 + 0.0263 * Pressure, R2 = 0.994) and between SWE and pressure (SWE = 48.927 + 1.248 * Pressure, R2 = 0.996).

CONCLUSION

The study indicated that SWV and SWE in the TCL increased linearly as the tunnel pressure increased within the current pressure range. The findings suggested that SWV/SWE in the TCL has the potential for prediction of tunnel pressure and diagnosis of carpal tunnel syndrome.

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.

Ultrasound-based quantitative tools in predicting renal involvement in asymptomatic primary hyperparathyroidism

PURPOSE

Asymptomatic primary hyperparathyroidism (aPHPT) has been recognized as a condition that can lead to renal complications. Timely identification of prognostic indicators for renal impairment holds the potential to facilitate proactive monitoring and treatment strategies in these patients. This study aims to investigate the utility of acoustic radiation force impulse (ARFI) imaging and renal resistive index (RRI), in identifying renal parenchymal and vascular changes in patients with aPHPT.

METHODS

Forty-two patients with aPHPT and 42 controls matched for age, sex, and body mass index were included in the study. The presence of renovascular changes was evaluated by RRI measurement with Doppler ultrasonography, and the presence of renal parenchymal involvement was evaluated by ARFI quantification, given as shear wave velocity (SWV).

RESULTS

In aPHPT patients, both the mean RRI and mean SWV values exhibited substantial elevation compared to the control group (P < 0.001 for both). Significant associations were observed between SWV values and serum calcium, parathyroid hormone (PTH), and adenoma size within the patient group (P < 0.001, P < 0.001, P = 0.016, respectively). Similarly, the mean RRI demonstrated positive correlations with serum calcium and PTH levels in the patient group (P< 0.001, P = 0.011, respectively). Multivariate linear regression analysis underscored the connection between mean RRI and mean SWV values with serum calcium levels within the patient group. In addition, serum PTH levels affected mean SWV positively and significantly.

CONCLUSION

The use of ARFI imaging and RRI measurements appears to hold potential in identifying renal involvement in patients with aPHPT.

Evidence and therapeutic implications of biomechanically regulated immunosurveillance in cancer and other diseases

Disease progression is usually accompanied by changes in the biochemical composition of cells and tissues and their biophysical properties. For instance, hallmarks of cancer include the stiffening of tissues caused by extracellular matrix remodelling and the softening of individual cancer cells. In this context, accumulating evidence has shown that immune cells sense and respond to mechanical signals from the environment. However, the mechanisms regulating these mechanical aspects of immune surveillance remain partially understood. The growing appreciation for the 'mechano-immunology' field has urged researchers to investigate how immune cells sense and respond to mechanical cues in various disease settings, paving the way for the development of novel engineering strategies that aim at mechanically modulating and potentiating immune cells for enhanced immunotherapies. Recent pioneer developments in this direction have laid the foundations for leveraging 'mechanical immunoengineering' strategies to treat various diseases. This Review first outlines the mechanical changes occurring during pathological progression in several diseases, including cancer, fibrosis and infection. We next highlight the mechanosensitive nature of immune cells and how mechanical forces govern the immune responses in different diseases. Finally, we discuss how targeting the biomechanical features of the disease milieu and immune cells is a promising strategy for manipulating therapeutic outcomes.

Investigating the role of ultrasound-based shear wave elastography in kidney transplanted patients: correlation between non-invasive fibrosis detection, kidney dysfunction and biopsy results-a systematic review and meta-analysis

INTRODUCTION

Interstitial fibrosis and tubular atrophy are leading causes of renal allograft failure. Shear wave elastography could be a promising noninvasive method for providing information on the state of the kidney, with specific regard to fibrosis but currently available data in the literature are controversial. Our study aimed to analyze the correlation between shear wave elastography and various kidney dysfunction measures.

METHODS

This review was registered on PROSPERO (CRD42021283152). We systematically searched three major databases (MEDLINE, Embase, and CENTRAL) for articles concerning renal transplant recipients, shear wave elastography, fibrosis, and kidney dysfunction. Meta-analytical calculations for pooled Pearson and Spearman correlation coefficients (r) were interpreted with 95% confidence intervals (CIs). Heterogeneity was tested with Cochran's Q test. I2 statistic and 95% CI were reported as a measurement of between-study heterogeneity. Study quality was assessed with the QUADAS2 tool.

RESULTS

In total, 16 studies were included in our meta-analysis. Results showed a moderate correlation between kidney stiffness and interstitial fibrosis and tubular atrophy, graded according to BANFF classification, on biopsy findings for pooled Pearson (r = 0.48; CI: 0.20, 0.69; I2 = 84%) and Spearman correlations (r = 0.57; CI: 0.35, 0.72; I2 = 74%). When compared to kidney dysfunction parameters, we found a moderate correlation between shear wave elastography and resistive index (r = 0.34 CI: 0.13, 0.51; I2 = 67%) and between shear wave elastography and estimated Glomerular Filtration Rate (eGFR) (r = -0.65; CI: - 0.81, - 0.40; I2 = 73%). All our outcomes had marked heterogeneity.

CONCLUSION

Our results showed a moderate correlation between kidney stiffness measured by shear wave elastography and biopsy results. While noninvasive assessment of kidney fibrosis after transplantation is an important clinical goal, there is insufficient evidence to support the use of elastography over the performance of a kidney biopsy.

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.

Ultrasound elastography in chronic kidney disease: a systematic review and meta-analysis

Ultrasound elastography (USE) is a noninvasive technique for assessing tissue elasticity, and its application in nephrology has aroused growing interest in recent years. The purpose of this article is to systematically review the clinical application of USE in patients with chronic kidney disease (CKD), including native and transplanted kidneys, and quantitatively investigate differences in elasticity values between healthy individuals and CKD patients. Furthermore, we provide a qualitative analysis of the studies included, discussing the potential interplay between renal stiffness, estimated glomerular filtration rate, and fibrosis. In January 2022, a systematic search was carried out on the MEDLINE (PubMed) database, concerning studies on the application of USE in patients with CKD, including patients with transplanted kidneys. The results of the included studies were extracted by two independent researchers and presented mainly through a formal narrative summary. A meta-analysis of nine study parts from six studies was performed. A total of 647 studies were screened for eligibility and, after applying the exclusion and inclusion criteria, 69 studies were included, for a total of 6728 patients. The studies proved very heterogeneous in terms of design and results. The shear wave velocity difference of - 0.82 m/s (95% CI: - 1.72-0.07) between CKD patients and controls was not significant. This result agrees with the qualitative evaluation of included studies that found controversial results for the relationship between renal stiffness and glomerular filtration rate. On the contrary, a clear relationship seems to emerge between USE values and the degree of fibrosis. At present, due to the heterogeneity of results and technical challenges, large-scale application in the monitoring of CKD patients remains controversial.

Shear wave elastography evaluation of kidneys in children with familial mediterranean fever

Background and Aim

Familial Mediterranean fever (FMF) is an autosomal recessive disorder. Typical clinical manifestations are self-limiting attacks of recurrent fever, abdominal pain, arthralgia, and chest pain due to aseptic polyserositis. Renal involvement is common in FMF patients. Shear wave elastography (SWE) is a noninvasive method that provides the measurement of tissue stiffness. In this study, we aimed to show that SWE can be used as an adjunctive method for evaluating renal involvement in children with FMF.

Materials and Methods

Our study group consists of 79 pediatric FMF patients and 79 control individuals. The study was planned prospectively. The variables, such as age, height, weight, and body mass index (BMI) of the patient and control groups, were kept in a similar way in order not to be affected by the differences. The right and left kidney sizes, parenchymal thicknesses, and SWE values in both groups were compared. The parenchymal stiffness degrees of the kidneys were quantified by shear modulus values in kilopascals.

Results

In our study, no statistically significant difference was found between the control and patient groups in terms of the right and left kidney longitudinal dimensions, transverse dimensions, and parenchymal thicknesses. When the kidneys were evaluated in terms of the right and left kidney stiffness values, the stiffness values in the patient group were significantly higher in both kidneys compared with those in the control group (P < 0.001).

Conclusions

SWE can be a noninvasive quantitative imaging method that can be used to evaluate kidney involvement by detecting changes in kidney stiffness in children with FMF.

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

OBJECTIVE

Many studies have conflicting findings in using shear wave elastography (SWE) to assess renal fibrosis. This study reviews the use of SWE to evaluate pathological changes in native kidneys and renal allografts. It also tries to elucidate the confounding factors and care taken to ensure the results are consistent and reliable.

METHODS

The review was carried out according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Literature search was conducted in Pubmed, Web of Science and Scopus database up to 23 October 2021. To evaluate risk and bias applicability, the Cochrane risk-of bias tool and GRADE was used. The review was registered under PROSPERO CRD42021265303.

RESULTS

A total of 2921 articles were identified. 104 full texts were examined and 26 studies included in systematic review. 11 studies performed on native kidneys and 15 studies on transplanted kidney. A wide range of impact factors was found that affect the accuracy of SWE of renal fibrosis in adult patients.

CONCLUSIONS

Compared to point SWE, two-dimensional SWE with elastogram could enable better selection of the region of interest in kidneys, leading to reproducible results. Tracking waves were attenuated as the depth from skin to region of interest increased, therefore, SWE is not recommended for overweight or obese patients. Variable transducer forces might also affect SWE reproducibility, thus, training of operators to ensure consistent operator-dependent transducer forces may be helpful.

ADVANCES IN KNOWLEDGE

This review provides a holistic insight on the efficiency of using SWE in evaluating pathological changes in native and transplanted kidneys, thereby contributing to the knowledge of its utilisation in clinical practice.

The kidney matrisome in health, aging, and disease

Dysregulated extracellular matrix is the hallmark of fibrosis, and it has a profound impact on kidney function in disease. Furthermore, perturbation of matrix homeostasis is a feature of aging and is associated with declining kidney function. Understanding these dynamic processes, in the hope of developing therapies to combat matrix dysregulation, requires the integration of data acquired by both well-established and novel technologies. Owing to its complexity, the extracellular proteome, or matrisome, still holds many secrets and has great potential for the identification of clinical biomarkers and drug targets. The molecular resolution of matrix composition during aging and disease has been illuminated by cutting-edge mass spectrometry-based proteomics in recent years, but there remain key questions about the mechanisms that drive altered matrix composition. Basement membrane components are particularly important in the context of kidney function; and data from proteomic studies suggest that switches between basement membrane and interstitial matrix proteins are likely to contribute to organ dysfunction during aging and disease. Understanding the impact of such changes on physical properties of the matrix, and the subsequent cellular response to altered stiffness and viscoelasticity, is of critical importance. Likewise, the comparison of proteomic data sets from multiple organs is required to identify common matrix biomarkers and shared pathways for therapeutic intervention. Coupled with single-cell transcriptomics, there is the potential to identify the cellular origin of matrix changes, which could enable cell-targeted therapy. This review provides a contemporary perspective of the complex kidney matrisome and draws comparison to altered matrix in heart and liver disease.

Kidney Ultrasound for the Nephrologist: A Review

Ultrasound imaging is a key investigatory step in the evaluation of chronic kidney disease and kidney transplantation. It uses nonionizing radiation, is noninvasive, and generates real-time images, making it the ideal initial radiographic test for patients with abnormal kidney function. Ultrasound enables the assessment of both structural (form and size) and functional (perfusion and patency) aspects of kidneys, both of which are especially important as the disease progresses. Ultrasound and its derivatives have been studied for their diagnostic and prognostic significance in chronic kidney disease and kidney transplantation. Ultrasound is rapidly growing more widely accessible and is now available even in handheld formats that allow for bedside ultrasound examinations. Given the trend toward ubiquity, the current use of kidney ultrasound demands a full understanding of its breadth as it and its variants become available. We described the current applications and future directions of ultrasound imaging and its variants in the context of chronic kidney disease and transplantation in this review.

The stiffness of transplanted kidneys changes with time after renal transplantation

BACKGROUND

Kidney transplantation is one of the most effective ways to treat end-stage kidney disease. However, 5000 renal transplant recipients start or restart dialysis because of chronic allograft nephropathy (CAN) every year in the United States. Detecting changes in the stiffness of transplanted kidneys can help diagnose transplanted kidney disease.

PURPOSE

To explore changes in the stiffness of transplanted kidneys after renal transplantation using shear wave elastography (SWE).

MATERIAL AND METHODS

This study conducted consecutive follow-up observations on 10 patients after kidney transplantation. SWE examination was performed in the first week, second week, first month, second month, third month, fourth month, fifth month, and sixth month after surgery. This study also analyzed the graft stiffness of 86 patients with stable renal function recovery one month after surgery.

RESULTS

The results show that there is a change in the stiffness of the transplanted kidney over time after renal transplantation. It decreases rapidly within one month after renal transplantation and tends to be stable after one month. The mean renal cortical and pyramidal stiffness of patients with stable renal function were 28.48 ± 4.27 kPa and 21.97 ± 3.90 kPa, respectively.

CONCLUSION

Consecutive stiffness measurement of transplanted kidneys is an effective method for monitoring the function of transplanted kidneys. According to the change in transplanted kidney stiffness, we can designate a more scientific review plan to determine the functional status of the transplanted kidney.

Novel Uses of Ultrasound to Assess Kidney Mechanical Properties

Ultrasound is a key imaging tool for evaluating the kidney. Over the last two decades, methods to measure the mechanical properties of soft tissues have been developed and used in clinical practice, although use in the kidney has not been as widespread as for other applications. The mechanical properties of the kidney are determined by the structure and composition of the renal parenchyma and perfusion characteristics. Because pathologic processes change these factors, the mechanical properties change and can be used for diagnostic purposes and for monitoring treatment or disease progression. Ultrasound-based elastography methods for evaluating the mechanical properties of the kidney use focused ultrasound beams to perturb the kidney and then high frame-rate ultrasound methods are used to measure the resulting motion. The motion is analyzed to estimate the mechanical properties. This review will describe the principles of these methods and discuss several seminal studies related to characterizing the kidney. Additionally, an overview of the clinical use of elastography methods in native and kidney allografts will be provided. Perspectives on future developments and uses of elastography technology along with other complementary ultrasound imaging modalities will be provided.

Diagnostic value of real-time shear wave elastography in children with chronic kidney disease

OBJECTIVE

To evaluate the diagnostic value of real-time shear wave elastography (SWE) in children with chronic kidney disease (CKD).

METHODS

Children with CKD diagnosed by the ultrasound-guided biopsy between January 2018 and May 2019 were enrolled as the case group. Age- and sex- matched healthy children were selected as the control group. The Young's Modulus (YM) of the renal cortex was measured by SWE after the traditional ultrasound examination. Variance analysis was performed to compare the values of YM between the two groups. Receiver operating characteristic curve (ROC) analysis was used to compare the values of YM, and explore the cut-offs of the YM.

RESULTS

In the case group (n = 60, 45% male, mean age of 9.2 years), the kidney YM modulus on the left side (16.8±4.8 kPa vs. 8.3±2.1 kPa) and the right side (16.0±4.7 kPa vs. 8.3±2.4 kPa) were both higher than the control group (all P values < 0.001). With the progress of CKD, the YM value of the left and right kidneys gradually increased. ROC analysis showed that when the left and right kidney YM value was 11.7 kPa and 11.0 kPa, the diagnostic sensitivity and specificity were the highest (left: respectively 93.3% and 95.0%; right: respectively 93.3 % and 91.7%).

CONCLUSION

The increase of YM in CKD is related to the progression of renal dysfunction which may provide a new method for early diagnosis of CKD, dynamic monitoring of disease progression, and evaluation of curative effect and prognosis.

The association between renal elasticity evaluated by Real-time tissue elastography and renal fibrosis

BACKGROUND

The progression of chronic kidney disease (CKD) depends on the extent of fibrosis in the kidneys; however, a renal biopsy is necessary to evaluate the severity of renal fibrosis. Real-time tissue elastography (RTE), which measures heartbeat-induced tissue displacement, can assess the elasticity of organs. Here, we aimed to investigate the correlation between renal elasticity and the extent of fibrosis in renal biopsy samples.

METHODS

We investigated 29 consecutive patients who underwent a renal biopsy at Ehime University Hospital from February 2018 to August 2019. Renal fibrosis was categorized into three grades, mild (< 25%), moderate (25-50%), and severe (> 50%), based on the total affected area within the biopsy sample. The association between renal elasticity assessed by RTE and the grade of renal fibrosis was evaluated, and a receiver operating characteristic curve was used to distinguish the severity of renal fibrosis.

RESULTS

The mean age and estimated glomerular filtration rate (eGFR) were 58.8 years and 55.2 mL/min/1.73 m², respectively. The median urine protein-to-creatinine ratio was 1.24 g/gCr. The mean renal elasticity of mild, moderate, and severe renal fibrosis was 3.40, 3.98, and 4.77, respectively. Renal elasticity of native kidneys was significantly positively correlated with the grade of renal fibrosis (ρ = 0.529, P = 0.003). At the cutoff point of 3.81, the area under the curve, sensitivity, and specificity were 0.778, 68.4%, and 81.8%, respectively.

CONCLUSION

Real-time tissue elastography is a promising, non-invasive method for assessing renal fibrosis in patients with CKD.

Elastography: a surrogate marker of renal allograft fibrosis - quantification by shear-wave technique

Purpose

Renal fibrosis is the most common cause of allograft failure in kidney transplantations. Evaluation of renal abnormalities has progressed considerably over the past years. Currently, the diagnosis of intrarenal fibrosis and quantification of its development with non-invasive assessment tools is possible. This may help in early detection of renal allograft dysfunction. This study sought to assess the efficacy of 2D real-time shear-wave elastography (SWE) in the quantitative measurement of renal allograft dysfunction.

Methods

A total of 172 patients were included in our study. SWE was performed in all these patients just before renal allograft biopsy. The cortical elasticity was assessed and described in terms of Young’s modulus (kPa). Banff histopathological grading obtained from transplant kidney tissue biopsy was taken as the reference standard. The potential correlation between SWE scores and Banff classification was performed.

Results

There was a significant correlation between the Banff grade and mean SWE score, with a correlation coefficient of 0.665 (p < 0.001). The individual correlation coefficients of interstitial fibrosis and tubular atrophy with mean SWE score stood at 0.667 and 0.649 respectively (p < 0.001). The correlation of resistive indices was insignificant when compared to mean polar SWE score in respective poles and the Banff grading of fibrosis.

Conclusions

Renal stiffness quantified by 2D SWE showed significant correlation with histopathological renal fibrosis. Thus, the study suggests that shear-wave elastography could be used as a surrogate marker for early detection of renal fibrosis.

Shear wave elastography findings in Immunoglobulin A Nephropathy patients: is it more specific and sensitive for interstitial fibrosis or interstitial fibrosis/tubular atrophy?

Background

Prediction of prognosis in Immunoglobulin A Nephropathy (IgAN) and taking appropriate precautions may reduce annual incidence of chronic kidney disease. This may be possible by close follow-up for the development and progression of interstitial fibrosis (IF) or interstitial fibrosis/tubular atrophy (IFTA) in IgAN patients.

Aim

To investigate whether Young’s elastic modulus (YM) which measured shear wave elastography (SWE) might be used for follow-up of IF or IFTA in IgAN patients.

Methods

Prospective study was approved by Human Research Ethics Committee. Group 1 consisted of patients with IgAN. Group 2 consisted of healthy control participants. Young’s elastic modulus which is a value of stiffness along with longitudinal stiffness was used to evaluate tissue elasticity. Specificity, sensitivity, positive predictive value (PPV) of YM for the presence of IF and IFTA were evaluated.

Results

Group 1 consisted of 30 participants, and group 2 consisted of 32 participants. Sensitivity and specificity of SWE to diagnose presence of IF for YM > 15 kPa were 89% and 90%, respectively. PPV among the ones whom IF was diagnosed by YM >15 kPa was 91%. Sensitivity and specificity of SWE to diagnose presence of IFTA for YM > 15 were 65% and 51%, respectively. PPV among the ones whom IFTA was diagnosed by YM >15 kPa was 78.1%.

Conclusions

YM which measured SWE is highly specific and sensitive in the diagnosis of IF, but not for IFTA in IgAN patients. Therefore, progression for IF in IgAN may be followed by SWE.

Renal tissue elasticity by acoustic radiation force impulse: A prospective study of healthy kidney donors

BACKGROUND

Some studies reported the correlations between renal parenchymal stiffness measured by transient elastography or acoustic radiation force impulse (ARFI) and the extent of interstitial fibrosis. This study was prospectively designed to evaluate the correlation between clinical, histological findings and the kidney shear wave velocity (SWV, m/s) assessed by ARFI elastography to identify factors affecting the kidney SWV in normal patients.

METHODS

Seventy-three adult living kidney transplantation donors were enrolled in our center between September 2010 and January 2013. Before transplantation, all donors were evaluated by ARFI elastography to identify the range of SWV in kidneys. Time-zero biopsies were performed on all graft kidneys before implantation.

RESULTS

Mean age of donors was 42.0 ± 11.3 years. The mean SWV and depth were 2.21 ± 0.58 m/s and 5.37 ± 1.06 cm. All histological findings showed mild degree of the Banff score, only grade I. In univariate analyses, the SWV was not associated with all histological parameters. Age (r = -0.274, P = .019) diastolic blood pressure (DBP, r = -0.255, P = .030) and depth for SWV measurement (r = -0.345, P = .003) were significantly correlated with the SWV. In multivariate linear regression analysis, age, gender, body mass index (BMI), and depth for SWV measurement were significantly correlated with the SWV (P = .003, .005, .002, and .004, respectively).

CONCLUSIONS

We demonstrated that all histological findings are not correlated with the SWV of donor kidney. Otherwise, factors influencing the kidney SWV assessed by ARFI elastography are age, gender, BMI, and depth for the SWV measurement in donors for kidney transplantation.

The role of real-time shear wave elastography in the diagnosis of idiopathic nephrotic syndrome and evaluation of the curative effect

PURPOSE

To evaluate the use of real-time shear wave elastography (SWE) in the assessment of renal elasticity and the efficacy of steroid treatment in adult idiopathic nephrotic syndrome (INS).

METHODS

This study included 120 patients with INS. Patients were divided into steroid-sensitive and steroid-resistant groups. Renal biopsy was performed. Thirty healthy subjects were recruited as controls. Young's modulus (YM) of the renal parenchyma was measured by SWE. The YM values in each group were compared using glomerular sclerosis index (GI) and renal interstitial fibrosis (RIF).

RESULTS

The YM values were significantly different between the INS and control groups, as well as between the steroid-sensitive and steroid-resistant groups (P < 0.05). Higher YM values were associated with steroid sensitivity. The area under the receiver operating characteristic curve for the YM value in the INS group vs. control group was 0.871 (95% CI 0.815-0.927) and in the steroid-resistant group vs. control, and steroid-sensitive groups was 0.836 (95% CI 0.765-0.908). The corresponding cut-off values were 7.96 and 10.73 m/s, with 81.7% and 86.0% sensitivities, 93.3% and 77.9% specificities, and Youden index 0.750 and 0.639, respectively. Spearman correlation analysis showed that the YM value in the renal parenchyma was positively correlated with GI (r = 0.631, P < 0.05) and RIF (r = 0.606, P < 0.05).

CONCLUSION

SWE technology is a potential method for non-invasive quantitative measurement of renal parenchyma stiffness to determine the pathological changes of INS renal parenchyma and evaluate the effectiveness of steroid therapy.

Magnetic resonance elastography vs. point shear wave ultrasound elastography for the assessment of renal allograft dysfunction

PURPOSE

To investigate the utility of magnetic resonance elastography (MRE) vs. ultrasound (US) point shear wave elastography (pSWE) for the assessment of chronic renal allograft dysfunction, prediction of outcome and determine the correlation with Banff pathology scores.

METHODS

In this IRB approved prospective study, 27 enrolled patients with functional (n = 15) and chronic dysfunctional (n = 12) renal allografts underwent same day 2D MRE and pSWE. Histogram parameters [including mean, median, standard deviation, kurtosis and skewness] of the magnitude of the complex shear modulus (MRE) and median Young's modulus (pSWE) were measured in the cortex (MRE and pSWE) and combined corticomedullary regions (MRE). Histopathology was available for 16 patients (4 functional, 12 dysfunctional).

RESULTS

MRE and pSWE stiffness were not significantly different between functional and dysfunctional groups (p range 0.139-0.347). The skewness of MRE corticomedullary stiffness was significantly lower (p = 0.04) in patients with chronic dysfunction and correlated significantly with Banff histopathologic scores (range r=-0.518-0.567, p = 0.035-0.040). MRE cortical and corticomedullary mean stiffness showed strong performance in predicting graft loss/relist (AUC 0.958, p = 0.011 for both). Reliable pSWE measurements were obtained in 13 patients (48 %). pSWE stiffness did not correlate with Banff scores and did not predict outcome.

CONCLUSIONS

The skewness of MRE corticomedullary stiffness is sensitive to changes in chronic allograft dysfunction, while mean/median MRE renal stiffness and median US stiffness did not differentiate patients with stable function vs those with chronic renal allograft dysfunction. MRE corticomedullary mean stiffness appears to be a predictor of graft loss/relist. pSWE was not found to be a useful method for assessing renal allografts.

Shear-Wave Elastography Variability Analysis and Relation with Kidney Allograft Dysfunction: A Single-Center Study

Shear-wave elastography (SWE) showed the absence or presence of significant differences among stable kidney allograft function and allograft dysfunction. We evaluated the variability of kidney allograft stiffness in relation to allograft dysfunction, respectively, in terms of a correlation of stiffness with patients' characteristics. A single-center prospective study on patients who had undergone renal transplantation was conducted between October 2017 and November 2018. Patients were clinically classified as having a stable allograft function or allograft dysfunction. SWE examinations performed by the same radiologist with a LOGIQ E9 were evaluated. Ten measurements were done for Young's modulus (kPa) at the level of allograft cortex and another ten at the level of medulla. Eighty-three SWE examinations from 63 patients, 69 stable allografts, and 14 allografts with dysfunction were included in the analysis. The intra-examinations stiffness showed high variability, with the quantile covariation coefficient ranging from 2.21% to 45.04%. The inter-examinations stiffness showed heterogeneity (from 28.66% to 42.38%). The kidney allograft cortex stiffness showed significantly higher values in cases with dysfunction (median = 28.70 kPa, interquartile range (IQR) = (25.68-31.98) kPa) as compared to those with stable function (median = 20.99 kPa, interquartile range = (16.08-27.68) kPa; p-value = 0.0142). Allograft tissue stiffness (both cortex and medulla) was significantly negatively correlated with body mass index (-0.44, p-value < 0.0001 for allograft cortex and -0.42, p-value = 0.0001 for allograft medulla), and positively correlated with Proteinuria/Creatinuria ratio (0.33, p-value = 0.0021 for allograft cortex and 0.28, p-value = 0.0105 for allograft medulla) but remained statistically significant only in cases with stable function. The cortical tissue stiffness proved significantly higher values for patients with allograft dysfunction as compared to patients with stable function, but to evolve as an additional tool for the evaluation of patients with a kidney transplant and to change the clinical practice, more extensive studies are needed.

Ultrasound elastography correlations between anthropometrical parameters in kidney transplant recipients

Ultrasound elastography (USE) is a method to assess the stiffness of parenchymatous organs. Shear wave elastography (SWE) is considered to be the most suitable elastography method for the non-invasive kidney transplant (KTx) elasticity assessment. The aim of this study was to assess the implementability of SWE for the evaluation of kidney transplant elasticity measurement depending on the depth of an allograft, body mass index (BMI) and donor age. Secondly, to investigate the associations between SWE stiffness measurements and the clinical parameters. This cross-sectional prospective study involved consecutive 100 KTx patients were grouped according to time from transplantation and their BMI (in BMI<25 group the mean was 22.1±2.4, n=42 and in BMI≥25 group the mean BMI was 29.9±3.3, n=58). Mean estimated glomerular filtration rate was almost similar in both groups: <25 group 54.3 and ≥25 group 53.4 mL/min. Mean elastography results were found statistically different (p=0.006) BMI<25 (8.95±5.84 kPa) and BMI≥25 (5.95±3.16 kPa) groups. Significant correlation was found between SWE and the depth of the measurement (r=-0.4, p<0.05). The variations in USE stiffness values were smallest in patients group with lower BMI. In conclusion, we demonstrated that the non-invasive USE measurement stiffness result depends on a patient's BMI, the depth of renal allograft and donor age.

Efficacy of the Sonoelastography Method for Diagnosis of Fibrosis in Renal Transplant Patients

OBJECTIVES

Although biopsy is the most important method for diagnosing the cause of renal allograft dysfunction, sonoelastography, a new ultrasonography method, can be used to distinguish between the soft or hard nature of lesions. In this study, our aim was to investigate whether sonoelastography could diagnose fibrosis in renal transplant patients.

MATERIALS AND METHODS

In this prospective study, we included patients over 18 years old who were recommended for clinical biopsy. Sonoelastographic evaluation was made by conducting acoustic radiation force impulse measurements for each patient after they were admitted to the clinic for biopsy. Measurements were performed just before the biopsy procedure. All results were examined by 2 experienced radiologists using the Siemens S3000 Ultrasound Machine (Erlangen, Germany). Comparisons of ultrasonographic values with biopsy results were made with SPSS software (SPSS: An IBM Company, version 20, IBM Corporation, Armonk, NY, USA).

RESULTS

Of the 65 patients included in this study, pathology showed acute T-cell-mediated rejection in 37 patients. There was a significant correlation between the pathologic Banff scores and the sonographic acoustic radiation force impulse values (P = .002), where the degree of Banff increased as the mean acoustic radiation force impulse values elevated. A rise in mean impulse values correlated with increased degree of interstitial fibrosis in renal allografts. Renal parenchymal echogenicity of patients significantly differed by sex (P = .009), with an average renal echogenicity of grade 1 in women and grade 0 in men. Also, a statistically significant difference was found between age of the renal transplant recipient and resistive index values.

CONCLUSIONS

Our study showed a significant correlation between Banff degree and the acoustic radiation force impulse values of renal transplant patients. In addition to biopsy, sonoelastography can be beneficial for the diagnosis of fibrosis in renal transplant patients.

Virtual Touch Tissue Quantification for Assessing Renal Pathology in Idiopathic Nephrotic Syndrome

The aim of this study was to evaluate Virtual Touch tissue quantification in assessing renal interstitial fibrosis in patients with idiopathic nephrotic syndrome. Ninety patients with idiopathic nephrotic syndrome were assigned to mild, moderate and severe groups depending on the degree of renal interstitial fibrosis on histopathologic examination of renal biopsy specimens. Thirty healthy patients were also selected as the control group. Virtual Touch tissue quantification was performed to measure the shear wave velocity of the renal parenchyma. There was no statistically significant difference in shear wave velocity between the mild and control groups (p > 0.05); however, the moderate and severe groups did significantly differ compared with the control (p <0.001). The area under the receiver operating characteristic curve value for the shear wave velocity of renal interstitial fibrosis in the moderate group versus the control and mild groups together was 0.869 (95% confidence interval: 0.791-0.947) and that in the severe group versus the control, mild and moderate groups together was 0.954 (95% confidence interval: 0.917-0.998). The corresponding best cutoff points were 2.41 and 2.77 m/s, with sensitivities of 91.7% and 86.8%, specificities of 78.0% and 92.0%, negative predictive values 0.907 and 0.907, positive predictive values 0.800 and 0.971 and Youden index values of 0.697 and 0.788, respectively. Virtual Touch tissue quantification may non-invasively and quantitatively estimate the degree of renal interstitial fibrosis in patients with idiopathic nephrotic syndrome as a baseline for monitoring progression and treatment response.

Utility of Shear Wave Elastography for Assessing Allograft Fibrosis in Renal Transplant Recipients: A Pilot Study

OBJECTIVES

To evaluate the utility of ultrasound-based shear wave elastography (SWE) as a noninvasive method to accurately detect and potentially stage the severity of renal allograft fibrosis and assess its user reproducibility.

METHODS

In this Institutional Review Board-approved, Health Insurance Portability and Accountability Act-compliant prospective study, 70 renal transplant recipients underwent an SWE evaluation of their allograft followed directly by biopsy. Two radiologists performed separate SWE measurement acquisitions and the mean, median, and standard deviation of 10 SWE measurements, obtained separately within the cortex and the medulla, were automatically computed. Each patient's SWE results were subsequently compared to their histologic fibrosis scores. The Fisher exact test and univariate logistic regression models were fit to test for associations between the presence of fibrosis (yes/no) as well as categorical SWE results based on the fibrosis severity, ranging from F0 (no fibrosis) to F3 (severe fibrosis), correlating with histologic scores according to the 2007 Banff classification system. Interobserver and intraobserver correlations were also examined.

RESULTS

Our median medulla SWE values reached statistical significance (P = .04) in association with fibrosis. Furthermore, for every unit increase in the median medulla SWE measurement, the odds of fibrosis increased by approximately 20%. No statistical significance was found for mean cortical, median cortical, or mean medullary SWE values (P = .32, .37, and .06, respectively) in association with fibrosis.

CONCLUSIONS

The use of SWE for assessing renal allograft fibrosis is challenging but promising. Further investigation with a larger sample size remains to validate our initial results and establish clinical relevance.

Renal shear wave elastography for the assessment of nephron hypertrophy: a cross-sectional study in chronic kidney disease

PURPOSE

To investigate the association of renal elasticity to microscopic findings of nephron hypertrophy and nephrosclerosis.

METHODS

Patients who underwent renal biopsy were enrolled. Renal elasticity was measured by acoustic radiation force impulse, and nephron size (glomerular volume, non-sclerotic glomerular density, and mean profile tubular area) and nephrosclerosis (globally sclerotic glomeruli and interstitial fibrosis) were estimated. Nephron hypertrophy was indicated by larger glomerular volume, larger tubular area, and lower non-sclerotic glomerular density. Nephrosclerosis was indicated by a higher percentage of globally sclerotic glomeruli and higher severity of fibrosis.

RESULTS

Renal elasticity was negatively correlated with glomerular volume (r = - 0.480, P = 0.024) and mean tubular area (r = - 0.469, P = 0.028), but it was not correlated with non-sclerotic glomerular density (r = 0.205, P = 0.359), percentage of globally sclerotic glomeruli (r = 0.057, P = 0.800), and severity of fibrosis (r = 0.014, P = 0.950). In a multiple linear regression analysis, glomerular volume and mean tubular area were independently associated with renal elasticity (std β = - 0.454, P = 0.015 and std β = - 0.577, P = 0.007, respectively).

CONCLUSION

Renal elasticity was correlated with microstructural findings of nephron hypertrophy. Measuring renal elasticity could help in detecting kidney disease.

Extracellular matrix as a driver of progressive fibrosis

The extracellular matrix (ECM) is dynamically tuned to optimize physiological function. Its major properties, including composition and mechanics, profoundly influence cell biology. Cell-ECM interactions operate through an integrated set of sensor and effector circuits that use several classes of receptors and signal transduction pathways. At the single-cell level, the ECM governs differentiation, metabolism, motility, orientation, proliferation, and survival. At the cell population level, the ECM provides higher-order guidance that is essential for physiological function. When pathological changes in the ECM lead to impairment of organ function, we use the term "fibrosis." In this Review, we differentiate fibrosis initiation from progression and focus primarily on progressive lung fibrosis impairing organ function. We present a working model to explain how the altered ECM is not only a consequence but also a driver of fibrosis. Additionally, we advance the concept that fibrosis progression occurs in a fibrogenic niche that is composed of a fibrogenic ECM that nurtures fibrogenic mesenchymal progenitor cells and their fibrogenic progeny.

Application of Ultrasound Elastography for Chronic Allograft Dysfunction in Kidney Transplantation

Interstitial fibrosis is the main characteristic of chronic allograft dysfunction, which remains the key factor affecting long-term allograft survival after kidney transplantation. Ultrasound elastography (UE), including real-time elastography, transient elastography, and acoustic radiation force impulse, has been applied widely in breast, thyroid, and liver diseases, especially in the assessment of liver fibrosis. Recently, numerous studies have reported the efficacy of UE methods in evaluating renal allograft fibrosis. This review aims to investigate the clinical applications, limitations, and future roles of UE in current clinical practice in light of changing management paradigms. In current clinical practice, UE methods, especially transient elastographic measurement, appear to be useful for ruling out fibrosis but do not have sufficient accuracy to distinguish between various stages of allograft fibrosis. Moreover, there remain considerable issues to be solved for the application of UE in kidney transplantation. Thus, UE methods cannot replace the crucial role of renal allograft biopsy in the diagnosis and evaluation of allograft fibrosis in kidney transplantation. Perhaps UE methods could be of more importance in the long-term observation and evaluation of allograft fibrosis during follow-up.

Evaluation of Stiffness in Postmastectomy Lymphedema Using Acoustic Radiation Force Impulse Imaging: A Prospective Randomized Controlled Study for Identifying the Optimal Pneumatic Compression Pressure to Reduce Stiffness

PURPOSE

We aimed to assess the improvement in stiffness in patients with postmastectomy lymphedema (PMLE) after intermittent pneumatic compression (IPC) using acoustic radiation force impulse (ARFI) imaging and evaluate the effects of different IPC pressures.

METHODS

We randomly assigned 45 patients with PMLE (stage II) to three groups based on the IPC pressure: 25, 35, and 45 mmHg. Patients received a single session of IPC for 30 minutes. We recorded the subcutaneous tissue thickness of the proximal upper limbs using ultrasonography and circumference of the upper limbs and stiffness using ARFI before and immediately after IPC.

RESULTS

Arm circumference and subcutaneous tissue thickness were significantly decreased after IPC in all groups. The shear wave velocity (SWV) decreased after IPC in all groups, but significantly decreased only in the 35 mmHg group. The subcutaneous tissue thickness and SWV in the 35 mmHg group were significantly decreased compared to the other groups.

CONCLUSION

IPC can reduce stiffness and subcutaneous tissue thickness of the proximal upper arm in patients with PMLE. A pressure of 35 mmHg yields the largest improvement of stiffness; higher compression pressure did not yield any additional improvement.

Does standoff material affect acoustic radiation force impulse elastography? A preclinical study of a modified elastography phantom

PURPOSE

This study was conducted to determine the influence of standoff material on acoustic radiation force impulse (ARFI) measurements in an elasticity phantom by using two different probes.

METHODS

Using ARFI elastography, 10 observers measured the shear wave velocity (SWV, m/sec) in different lesions of an elasticity phantom with a convex 4C1 probe and a linear 9L4 probe. The experimental setup was expanded by the use of an interposed piece of porcine muscle as standoff material. The probe pressure on the phantom was registered.

RESULTS

Faulty ARFI measurements occurred more often when quantifying the hardest lesion (74.0 kPa 4.97 m/sec) by the 9L4 probe with the porcine muscle as a standoff material interposed between the probe and the phantom. The success rate for ARFI measurements in these series was 52.4%, compared with 99.5% in the other series. The SWV values measured with the 9L4 probe were significantly higher (3.33±1.39 m/sec vs. 2.60±0.74 m/sec, P<0.001 in the group without muscle) and were closer to the reference value than those measured with the 4C1 probe (0.25±0.23 m/sec vs. 0.85±1.21 m/sec, P<0.001 in the same group). The SWV values measured when using the muscle as a standoff material were lower than those without the muscle (significant for 9L4, P=0.040). The deviation from the reference value and the variance increased significantly with the 9L4 probe if the muscle was in situ (B=0.27, P=0.004 and B=0.32, P<0.001). In our study, the pressure exerted by the operator had no effect on the SWV values.

CONCLUSION

The presence of porcine muscle acting as a standoff material influenced the occurrence of failed measurements as well as the variance and the accuracy of the measured values. The linear high-frequency probe was particularly affected.

Usefulness of Multiparametric Ultrasound for Evaluating Structural Abnormality of Transplanted Kidney: Can We Predict Histologic Abnormality on Renal Biopsy in Advance?

OBJECTIVE

The purpose of this study was to investigate the associations between microscopic abnormalities of transplanted kidneys and sonography-based imaging biomarkers, including elasticity, venous impedance index, arterial resistive index, and size.

MATERIALS AND METHODS

Between 2011 and 2015, 159 recipients underwent sonography and biopsy of a transplanted kidney at our institution; 104 adult patients were included in this study. The maximal longitudinal length on gray-scale images, arterial resistive index, and venous impedance index on Doppler images and shear wave velocity on acoustic radiation force impulse imaging or Young modulus on supersonic shear imaging were measured before biopsy. The Banff criteria (2009 update), an international standardized classification and scoring system for renal allograft pathology, were used to evaluate the biopsy samples. Sonography parameters and clinical variables were analyzed with individual and summed Banff scores.

RESULTS

Spearman rank correlation coefficients and ordinal logistic regression showed no association between sonography parameters and summed Banff scores. Only the interval between transplant and biopsy was significantly associated with summed Banff scores (p < 0.05). Univariate logistic regression analysis with individual Banff scores showed associations of one Banff feature with arterial resistive index, three with venous impedance index, and six with interval between transplant and biopsy (p < 0.05). Sonoelastography parameters were not associated with any individual Banff score.

CONCLUSION

Neither sonoelastography parameter was associated with any histopathologic change of renal allografts. Although arterial resistive index and venous impedance index were related to a few individual Banff scores, length of time between transplant and biopsy showed stronger correlation than any imaging biomarkers with renal allograft deterioration.

Renal Cortical Elastography: Normal Values and Variations

Introduction

Renal cortical elastography has shown conflicting but promising results in evaluation of chronic kidney disease and other renal disorders. The purpose of this study was to establish a normogram of renal cortical elasticity values and assess their variation between right and left kidney and their relation with age, gender, body mass index, renal dimensions and skin to cortex distance.

Methods

The study was a hospital based cross sectional study performed at Tribhuvan University Teaching Hospital, a tertiary care center in Kathmandu, Nepal. All individuals referred for Ultrasound from General Health Check up clinic were included in the study. Patient with abnormal ultrasound findings and abnormal renal function test were excluded from the study. Renal morphometry including length, cortical thickness, and skin to cortex distance were measured in B mode imaging and renal cortical elastography was measured with region of interest box of 1 × 0.5 cm. All analyses were done using Statistical Package for Social Sciences 20.0 soft ware.

Results

A total of 95 individuals who met the inclusion criteria were included in the study. The mean values of right and left renal cortical shear wave velocity were 1.49 ± 0.19 m/s and 1.54 ± 0.19 m/s respectively. Statistical significant difference was observed between the renal cortical shear wave velocity of right and left kidney. The renal shear wave velocity was seen to decrease with age, however the correlation was not statistically significant. No significant difference was also noted in renal shear wave velocity among various sex or Body mass index groups. Statistically significant negative correlation was noted between skin to cortex distance and renal cortical shear wave velocities. However no statistically significant correlation was noted between renal dimensions and renal cortical shear wave velocities.

Conclusions

The normal cortical elasticity values in terms of shear wave velocity of right and left kidney were established. Renal elasticity is independent of the age, gender, Body mass index and renal dimensions.

Characterization of histological subtypes of clear cell renal cell carcinoma using contrast-enhanced ultrasound (CEUS)

INTRODUCTION

The aim of this study was to analyze the histological subtypes of clear cell renal cell carcinoma (RCC) examined by means of contrast-enhanced ultrasound (CEUS) and a second generation blood pool agent (SonoVue®, Bracco, Milan, Italy) during the pre-operative phase.

MATERIALS AND METHODS

29 patients with histologically proven subtypes of clear cell RCC were examined. A total of three patients were diagnosed with highly differentiated clear cell RCC, 21 out of 29 cases with moderately differentiated clear cell RCC and five out of 29 patients had insufficiently differentiated clear cell RCC. An experienced radiologist examined the patients with CEUS. The following parameters were analyzed: maximum signal intensity (PEAK), time elapsed until PEAK is reached (MTT), local blood flow (RBF), area under the time intensity curve (AUC) and the signal intensity (SI) during the course of time. For the groups all comparisons are made based on healthy renal parenchyma.

RESULTS

In the clear cell RCC significant differences (significance level p < 0.05) between cancerous tissue and the healthy renal parenchyma were noticed in all four parameters. Therefore, the clear cell RCC stands out due to its reduced blood volume. However, it reached the PEAK reading relatively rapidly and its signal intensity was always lower than that of the healthy renal parenchyma. In the arterial phase retarded absorption of the contrast agent was observed, followed by fast washing out of the contrast agent bubbles.In all three histological subgroups no significant differences were noticed in PEAK and SI. However, the diagrams showed the possible bias, that the group of the insufficiently differentiated clear cell RCC had the highest PEAK-value and the highest signal intensity when compared with highly and moderately differentiated clear cell RCC.

CONCLUSION

Our study suggests that CEUS may be an additional tool for non-invasive characterisation and differentiation of the three histological subtypes of clear cell RCC. Furthermore, it seems to have an additional diagnostic value in daily clinical.

Clinical application of Acoustic Radiation Force Impulse Imaging with Virtual Touch IQ in breast ultrasound: diagnostic performance and reproducibility of a new technique

Background Virtual Touch IQ (VTIQ) is a novel technique of quantitative sonoelastography that applies acoustic radiation force impulse (ARFI). Purpose To evaluate breast ARFI imaging with VTIQ in the clinical setting, with regard to reproducibility and diagnostic performance, and to specify cutoff limits for the differentiation of benign and malignant lesions. Material and Methods This retrospective study included 83 patients with 85 breast lesions (51 benign, 34 malignant) who received ARFI imaging with VTIQ. Two independent ARFI measurements of each lesion were performed and shear wave velocities (SWV) of the lesion and the adjacent tissues were measured. A lesion-to-fat velocity ratio (L/F Ratio) was calculated for each lesion. Diagnostic performance of SWV measurements and L/F Ratios was evaluated with receiver operating curve (ROC) analysis. The intraclass correlation coefficient and Bland-Altman plots were used to evaluate measurement reproducibility. Results All measurements showed equal diagnostic performance, as measured by the area under the ROC curve (0.853 for SWV, 0.882 for the L/F Ratio). At a cutoff value of 3.23 m/s, sensitivity and specificity were 82.4% and 80.4%, respectively. An L/F Ratio cutoff value of 2.23 revealed a sensitivity and specificity of 89.7% and 76.5%. The reproducibility of the SWV measurements was moderate (limits of agreement, 40.3-44.4%) and higher than that of the L/F Ratios (54.5-60.2%). Conclusion ARFI imaging with VTIQ is a novel, moderately reproducible, quantitative elastography technique, which provides useful information for the differentiation of benign and malignant breast lesions in the clinical setting.

Renal acoustic radiation force impulse elastography in the evaluation of coronary artery disease

Background Renal insufficiency may occur in patients with coronary artery disease (CAD). Acoustic radiation force impulse (ARFI) is a method for quantifying tissue elasticity, which could be used as an additional diagnostic test for renal insufficiency and provide an additional contribution to the determination of CAD. Purpose To evaluate ARFI elastography with shear wave velocity (SWV) measurements in the diagnosis of mild-to-moderate chronic kidney disease (CKD) in CAD patients, and to analyze the relationship between the severity of CAD assessed by the Gensini scoring system and kidney stiffness. Material and Methods The study included 76 CAD patients and 79 healthy volunteers. SWV was measured for each kidney in the both groups. The CAD group was divided into two subgroups based on Gensini score: mild CAD and severe CAD. SWV values of the CAD patients were compared to those of the healthy volunteers; values of subgroups were also compared with each other. Results The patient group had significantly lower renal mean SWV values than those of the healthy group (1.87 ± 0.58 vs. 2.34 ± 0.38, P < 0.01). The SWV value decreased as the eGFR level decreased. Mean SWV values for kidneys of the patients with severe CAD were lower than those of the mild CAD patients (1.64 ± 0.39 vs. 2.42 ± 0.60, P < 0.01). Conclusion renal mean SWV values of CAD patients decreased in proportion to the reduction in eGFR, and the SWV values decreased as the severity of CAD increased. ARFI elastography is a novel technique for diagnosing CKD and defining illness severity in CAD patients.

Shear wave elastography imaging for assessing the chronic pathologic changes in advanced diabetic kidney disease

Objective

The assessment of the grade of renal fibrosis in diabetic kidney disease (DKD) requires renal biopsy, which may be associated with certain risks. To assess the severity of chronic pathologic changes in DKD, we performed a quantitative analysis of renal parenchymal stiffness in advanced DKD, using shear wave elastography (SWE) imaging.

Patients and methods

Twenty-nine diabetic patients with chronic kidney disease (CKD) grades 3–4 due to DKD, and 23 healthy subjects were enrolled. Combined conventional ultrasound and SWE imaging were performed on all participants. The length, width, and cortical thickness and stiffness were recorded for each kidney.

Results

Cortical thickness was lower in patients with DKD than in healthy subjects (13.8±2.2 vs 14.8±1.6 mm; P=0.002) and in DKD patients with CKD grade 4 than in those with grade 3 (13.0±3.5 vs 14.7±2.1 mm; P<0.001). Cortical stiffness was greater in patients with DKD than in healthy subjects (23.72±14.33 vs 9.02±2.42 kPa; P<0.001), in DKD patients with CKD grade 4 than in those with grade 3 (30.4±16.2 vs 14.6±8.1 kPa; P<0.001), and in DKD patients with CKD grade 3b, than in those with CKD grade 3a (15.7±6.7 vs 11.0±4.2 kPa; P=0.03). Daily proteinuria was higher in DKD patients with CKD grade 4 than in those with grade 3 (5.52±0.96 vs 1.13±0.72; P=0.001), and in DKD patients with CKD grade 3b, than in those with CKD grade 3a (1.59±0.59 vs 0.77±0.48; P<0.001). Cortical stiffness was inversely correlated with the estimated glomerular filtration rate (r=−0.65, P<0.001) and with cortical thickness (r=−0.43, P<0.001) in patients with DKD.

Conclusions

In patients with advanced DKD, SWE imaging may be utilized as a simple and practical method for quantitative evaluation of the chronic morphological changes and for the differentiation between CKD grades.

Research on pediatric glomerular disease and normal kidney with shear wave based elastography point quantification

PURPOSE

To evaluate the renal cortex stiffness in children with glomerular disease by shear wave based elastography point quantification (ElastPQ), and to investigate the association between shear wave velocity (SWV) in the renal cortex and age in normal children, and the inter-gender differences.

MATERIALS AND METHODS

One hundred and five children who were pathologically confirmed with glomerular diseases were selected as the disease group. Meanwhile, 120 healthy children were selected as the control group. Effective values were measured 5 times at the same kidney sites on each side.

RESULTS

Comparisons of SWV measurements between left and right kidneys in the disease and control groups all showed significant differences (left kidney t = 6.896, P = 0.004; right kidney t = 7.415, P = 0.001). In the control group, left and right kidney SWV measurements were all positively correlated with age (left kidney r = 0.792, P = 0.003; right kidney r = 0.794, P = 0.004). Moreover, inter-gender difference was present in the right kidney measurements.

CONCLUSIONS

ElastPQ technology has certain advantages in predicting pediatric glomerular disease compared to conventional ultrasound. ElastPQ technology contributes to the early diagnosis of the disease.

Prediction of Renal Allograft Acute Rejection Using a Novel Non-Invasive Model Based on Acoustic Radiation Force Impulse

Point shear wave elastography based on acoustic radiation force impulse is a novel technology used to quantify tissue stiffness by measuring shear wave speed. A total of 115 kidney transplantation recipients were consecutively enrolled in this prospective study. The patients were subdivided into two groups using 1 mo post-transplantation as the cutoff time for determining the development of acute rejection (AR). Shear wave speed was significantly higher in the AR group than in the non-AR group. We created a model called SEV, comprising shear wave speed, estimated glomerular filtration rate and kidney volume change, that could successfully discriminate patients with or without AR. The area under the receiver operating characteristic curve of SEV was 0.89, which was higher than values for other variables; it was even better in patients within 1 mo post-transplantation (0.954), but was lower than the estimated glomerular filtration rate in patients after 1 mo post-transplantation. Therefore, the SEV model may predict AR after renal transplantation with a high degree of accuracy, and it may be more useful in the early post-operative stage after renal transplantation.

Preclinical evaluation of acoustic radiation force impulse measurements in regions of heterogeneous elasticity

Purpose

The purpose of this study was to compare the reliability of ultrasound-based shear wave elastography in regions of homogeneous versus heterogeneous elasticity by using two different probes.

Methods

Using acoustic radiation force impulse (ARFI) elastography, we measured the shear wave velocity (SWV) in different lesions of an elastography phantom with the convex 4C1 probe and the linear 9L4 probe. The region of interest (ROI) was positioned in such a way that it was partly filled by one of the lesions (0%, 25%, 50%, 75%, and 100%) and partly by the background of the phantom (100%, 75%, 50%, 25%, and 0%, respectively).

Results

The success rate was 98.5%. The measured value and the reference value of SWV correlated significantly (r=0.89, P<0.001). Further, a comparison of the two probes revealed that there was no statistical difference in either the mean or the variance values. However, the deviation of SWV from the reference was higher in the case of the 9L4 probe than in the case of the 4C1 probe, both overall and in measurements in which the ROI contained structures of different elasticity (P=0.021 and P=0.002). Taking into account all data, for both probes, we found that there was a greater spread and deviation of the SWV from the reference value when the ROI was positioned in structures having different elastic properties (standard deviation, 0.02±0.01 m/sec vs. 0.04±0.04 m/sec; P=0.010; deviation from the reference value, 0.21±0.12 m/sec vs. 0.38±0.27 m/sec; P=0.050).

Conclusion

Quantitative ARFI elastography was achievable in structures of different elasticity; however, the validity and the reliability of the SWV measurements decreased in comparison to those of the measurements performed in structures of homogeneous elasticity. Therefore, a convex probe is preferred for examining heterogeneous structures.

Acoustic radiation force impulse with shear wave speed quantification of pancreatic masses: A prospective study

BACKGROUND

Acoustic Radiation Force Impulse (ARFI) is a new ultrasound technique that evaluates mechanical properties of tissues. To evaluate the use of ARFI with shear waves speed quantification for pancreatic masses characterization during the ultrasound examination.

METHODS

123 pancreatic lesions were prospectively evaluated. Median shear waves speeds were compared with Mann-Whitney U test. Two reading methods were applied for the characterization of adenocarcinoma: more than one measurement above the top shear waves speed (SWS) value. Two reading methods were applied to diagnose mucinous lesion: at least 2 (method 1) or 3 (method 2) numerical measurements. Sensitivity, specificity, positive and negative predictive values and accuracy of each reading method were calculated. Forty volunteers were included for normal ARFI values.

RESULTS

In the adenocarcinoma group median SWS value was 2.74 m/s. In the volunteers group the median SWS value was 1.17 m/s. Significant difference between SWS median values of adenocarcinoma and normal pancreas was found (P < 0.05). For the diagnosis of pancreatic solid masses if more than one measurement is above the top SWS value of 4.00 m/s results in the study, the diagnosis of ductal adenocarcinoma is highly specific with specificity and PPV of 100%. Good sensitivity (73.3%) and specificity (83.3%) were obtained for the characterization of mucinous cystic lesions.

CONCLUSIONS

Acoustic Radiation Force Impulse imaging could help in the non-invasive characterization of solid and cystic lesions of the pancreas during a conventional US examination.

Acoustic Radiation Force Impulse Measurement in Renal Transplantation: A Prospective, Longitudinal Study With Protocol Biopsies

Interstitial fibrosis and tubular atrophy (IF/TA) is a common cause of kidney allograft loss. Several noninvasive techniques developed to assess tissue fibrosis are widely used to examine the liver. However, relatively few studies have investigated the use of elastographic methods to assess transplanted kidneys. The aim of this study was to explore the clinical implications of the acoustic radiation force impulse (ARFI) technique in renal transplant patients. A total of 91 patients who underwent living donor renal transplantation between September 2010 and January 2013 were included in this prospective study. Shear wave velocity (SWV) was measured by ARFI at baseline and predetermined time points (1 week and 6 and 12 months after transplantation). Protocol biopsies were performed at 12 months. Instead of reflecting IF/TA, SWVs were found to be related to time elapsed after transplantation. Mean SWV increased continuously during the first postoperative year (P < 0.001). In addition, mixed model analysis showed no correlation existed between SWV and serum creatinine (r = -0.2426, P = 0.0771). There was also no evidence of a relationship between IF/TA and serum creatinine (odds ratio [OR] = 1.220, P = 0.7648). Furthermore, SWV temporal patterns were dependent on the kidney weight to body weight ratio (KW/BW). In patients with a KW/BW < 3.5 g/kg, mean SWV continuously increased for 12 months, whereas it decreased after 6 months in those with a KW/BW ≥ 3.5 g/kg.No significant correlation was observed between SWV and IF/TA or renal dysfunction. However, SWV was found to be related to the time after transplantation. Renal hemodynamics influenced by KW/BW might impact SWV values.

Shear wave elastography in chronic kidney disease: a pilot experience in native kidneys

Background

There currently is a need for a non-invasive measure of renal fibrosis. We aim to explore whether shear wave elastography (SWE)-derived estimates of tissue stiffness may serve as a non-invasive biomarker that can distinguish normal and abnormal renal parenchymal tissue.

Methods

Participants with CKD (by estimated GFR) and healthy volunteers underwent SWE. Renal elasticity was estimated as Young’s modulus (YM) in kilopascals (kPa). Univariate Wilcoxon rank-sum tests were used.

Results

Twenty-five participants with CKD (median GFR 38 mL/min; quartile 1, quartile 3 28, 42) and 20 healthy controls without CKD underwent SWE performed by a single radiologist. CKD was associated with increased median YM (9.40 [5.55, 22.35] vs. 4.40 [3.68, 5.70] kPa; p = 0.002) and higher median intra-subject inter-measurement estimated YM’s variability (4.27 [2.89, 9.90] vs. 1.51 [1.21, 2.05] kPa; p < 0.001).

Conclusions

SWE-derived estimates of renal stiffness and intra-subject estimated stiffness variability are higher in patients with CKD than in healthy controls. Renal fibrosis is a plausible explanation for the observed difference in YM. Further studies are required to determine the relationship between YM, estimated renal stiffness, and renal fibrosis severity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-015-0120-7) contains supplementary material, which is available to authorized users.

Evaluation of kidney allograft status using novel ultrasonic technologies

Early diagnosis of kidney allograft injury contributes to proper decisions regarding treatment strategy and promotes the long-term survival of both the recipients and the allografts. Although biopsy remains the gold standard, non-invasive methods of kidney allograft evaluation are required for clinical practice. Recently, novel ultrasonic technologies have been applied in the evaluation and diagnosis of kidney allograft status, including tissue elasticity quantification using acoustic radiation force impulse (ARFI) and contrast-enhanced ultrasonography (CEUS). In this review, we discuss current opinions on the application of ARFI and CEUS for evaluating kidney allograft function and their possible influencing factors, advantages and limitations. We also compare these two technologies with other non-invasive diagnostic methods, including nuclear medicine and radiology. While the role of novel non-invasive ultrasonic technologies in the assessment of kidney allografts requires further investigation, the use of such technologies remains highly promising.

Evaluation of Stiffness of the Spastic Lower Extremity Muscles in Early Spinal Cord Injury by Acoustic Radiation Force Impulse Imaging

Objective

To investigate intrinsic viscoelastic changes using shear wave velocities (SWVs) of spastic lower extremity muscles in patients with early spinal cord injury (SCI) via acoustic radiation force impulse (ARFI) imaging and to evaluate correlation between the SWV values and spasticity.

Methods

Eighteen patients with SCI within 3 months and 10 healthy adults participated. We applied the ARFI technique to measure SWV of gastrocnemius muscle (GCM) and long head of biceps femoris muscle. Spasticity of ankle and knee joint was assessed by original Ashworth Scale.

Results

Ten patients with SCI had spasticity. Patients with spasticity had significantly faster SWV for GCM and biceps femoris muscle than those without spasticity (Mann-Whitney U test, p=0.007 and p=0.008) and normal control (p=0.011 and p=0.037, respectively). The SWV values of GCM correlated with the ankle spasticity (Spearman rank teat, p=0.026). There was significant correlation between the SWV values for long head of biceps femoris muscle and knee spasticity (Spearman rank teat, p=0.022).

Conclusion

ARFI demonstrated a difference in muscle stiffness in the GCM between patients with spastic SCI and those without spasticity. This finding suggested that stiffness of muscles increased in spastic lower extremity of early SCI patients. ARFI imaging is a valuable tool for noninvasive assessment of the stiffness of the spastic muscle and has the potential to identify pathomechanical changes of the tissue associated with SCI.

Acoustic radiation force impulse imaging for evaluation of renal parenchyma elasticity in diabetic nephropathy

OBJECTIVE. The goal of this study is to evaluate the changes in the elasticity of the renal parenchyma in diabetic nephropathy using acoustic radiation force impulse imaging. SUBJECTS AND METHODS. The study included 281 healthy volunteers and 114 patients with diabetic nephropathy. In healthy volunteers, the kidney elasticity was assessed quantitatively by measuring the shear-wave velocity using acoustic radiation force impulse imaging based on age, body mass index, and sex. The changes in the renal elasticity were compared between the different stages of diabetic nephropathy and the healthy control group. RESULTS. In healthy volunteers, there was a statistically significant correlation between the shear-wave velocity values and age and sex. The shear-wave velocity values for the kidneys were 2.87, 3.14, 2.95, 2.68, and 2.55 m/s in patients with stage 1, 2, 3, 4, and 5 diabetic nephropathy, respectively, compared with 2.35 m/s for healthy control subjects. Acoustic radiation force impulse imaging was able to distinguish between the different diabetic nephropathy stages (except for stage 5) in the kidneys. The threshold value for predicting diabetic nephropathy was 2.43 m/s (sensitivity, 84.1%; specificity, 67.3%; positive predictive value, 93.1%; negative predictive value 50.8%; accuracy, 72.1%; positive likelihood ratio, 2.5; and negative likelihood ratio, 0.23). CONCLUSION. Acoustic radiation force impulse imaging could be used for the evaluation of the renal elasticity changes that are due to secondary structural and functional changes in diabetic nephropathy.

A Preliminary Investigation of Normal Pancreas and Acute Pancreatitis Elasticity Using Virtual Touch Tissue Quantification (VTQ) Imaging

BACKGROUND

The aim of this study was to prospectively evaluate the use of elastometry in healthy volunteers and patients with acute pancreatitis using virtual touch tissue quantification (VTQ) imaging technology performed on the pancreas.

MATERIAL AND METHODS

We enrolled 210 healthy volunteers and 44 acute pancreatitis patients in the study between March 2012 and June 2013. Healthy subjects were divided into 3 groups: young (18-30 years), middle-aged (30-50 years), and elderly (>50 years). VTQ was performed on the pancreatic head and body regions to obtain shear wave velocity (SWV) measurements, which were used to evaluate the elasticity values of tissues.

RESULTS

The pancreatic head SWV value in the whole healthy group was 1.18±0.23 m/s, and that in the pancreatic body was 1.21±0.20 m/s. In patients with acute pancreatitis, the mean SWV measurements at the head were 1.18±0.20 m/s, compared to 1.25±0.19 m/s in the pancreatic body. There was no statistically significant difference between whole healthy volunteers and the acute pancreatitis group.

CONCLUSIONS

VTQ is a new method that shows promise for the quantification of pancreatic elasticity, but further studies are warranted.

Relationship between the estimated glomerular filtration rate and kidney shear wave speed values assessed by acoustic radiation force impulse elastography: a pilot study

OBJECTIVES

The aim of the study was to establish the relationship between the estimated glomerular filtration rate (GFR) and kidney shear wave speed values assessed by acoustic radiation force impulse (ARFI) elastography.

METHODS

Our study included 104 patients with or without chronic kidney disease in which the kidney shear wave speed was evaluated by ARFI elastography and correlated with the estimated GFR. Five ARFI measurements were performed in the parenchyma of each kidney. A median value expressed as meters per second was calculated.

RESULTS

Five valid ARFI elastographic measurements were obtained in the right kidney in all patients and in the left kidney in 97.1% of patients. The mean kidney shear wave speed values ± SD in the right and left kidneys were similar: 2.17 ± 0.81 versus 2.06 ± 0.75 m/s (P = .30). The mean kidney shear wave speed decreased with the decrease in the estimated GFR. Statistically significant differences were obtained only when kidney shear wave speed values obtained in patients with an estimated GFR of greater than 90 mL/min/1.73 m(2) were compared to values in patients with stage 4 (estimated GFR, 15-29 mL/min/1.73 m(2)) and stage 5 (estimated GFR, <15 mL/min/1.73 m(2)) chronic kidney disease: 2.32 ± 0.83 versus 1.62 ± 0.75 m/s (P = .03) and 2.32 ± 0.83 versus 1.66 ± 0.72 m/s (P = .04), respectively. For a cutoff value of 2.26 m/s or lower, kidney shear wave speed had 86.7% sensitivity, 48.3% specificity, a 22.1% positive predictive value, and a 95.6% negative predictive value (area under the receiver operating characteristic curve, 0.692; P = .008) for predicting the presence of an estimated GFR of less than 30 mL/min/1.73 m(2).

CONCLUSIONS

Kidney shear wave speed values obtained by ARFI elastography decrease with the decrease in the estimated GFR.

Acoustic radiation force impulse (ARFI) elastography for detection of renal damage in children

BACKGROUND

Acoustic radiation force impulse (ARFI) imaging is a promising method for noninvasive evaluation of the renal parenchyma.

OBJECTIVE

To investigate the contribution of ARFI quantitative US elastography for the detection of renal damage in kidneys with and without vesicoureteral reflux (VUR).

MATERIALS AND METHODS

One hundred seventy-six kidneys of 88 children (46 male, 42 female) who had been referred for voiding cystourethrography and 20 healthy controls were prospectively investigated. Patients were assessed according to severity of renal damage on dimercaptosuccinic acid (DMSA) scintigraphy. Ninety-eight age- and gender-matched healthy children constituted the control group. Quantitative shear wave velocity (SWV) measurements were performed in the upper and lower poles and in the interpolar region of each kidney. DMSA scintigraphy was performed in 62 children (124 kidneys). Comparisons of SWV values of kidneys with and without renal damage and/or VUR were done.

RESULTS

Significantly higher SWV values were found in non-damaged kidneys. Severely damaged kidneys had the lowest SWV values (P < 0.001). High-grade (grade V-IV) refluxing kidneys had the lowest SWV values, while non-refluxing kidneys had the highest values (P < 0.05). Significant negative correlations were found between the mean quantitative US elastography values and DMSA scarring score (r = -0.788, P < 0.001) and VUR grade (r = -0.634, P < 0.001). SWV values of the control kidneys were significantly higher than those of damaged kidneys (P < 0.05).

CONCLUSION

Our findings suggest decreasing SWV of renal units with increasing grades of vesicoureteric reflux, increasing DMSA-assessed renal damage and decreasing DMSA-assessed differential function.