Predictive value of contrast-enhanced ultrasonography for the early diagnosis of renal dysfunction after kidney transplantation: A systematic review and meta-analysis

OBJECTIVES

We aimed to evaluate the changes in renal cortical microperfusion and quantitative contrast-enhanced ultrasonography (CEUS) parameters after kidney transplantation, and to determine the evidence-based value of CEUS in predicting renal dysfunction.

METHODS

The Embase, MEDLINE, Web of Science, and Cochrane Library databases were searched for relevant studies published from 2000 to 2023 on the use of CEUS to assess the renal cortical microcirculation after kidney transplantation. Subject terms and related keywords were combined, and a meta-analysis and systematic review were performed according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines.

RESULTS

The search yielded six studies involving 451 patients with moderate to high overall quality. The peak intensity (standardized mean difference [SMD]: -0.64, 95% confidence interval [CI] -1.13 to -0.15, p = 0.01) of CEUS was significantly lower in patients with renal dysfunction than in those with stable renal function. However, the time to peak (SMD: 0.28, 95% CI 0.04 to 0.52, p = 0.02) was significantly shorter in patients with renal dysfunction than in those with stable renal function. The total renal cortical microperfusion and renal cortical perfusion intensity were decreased, and the perfusion time was prolonged, in patients with renal dysfunction after kidney transplantation.

CONCLUSION

CEUS parameters can reflect real-time changes in renal cortical microperfusion, thus providing a basis for the early diagnosis of renal dysfunction after kidney transplantation.

Standardized evaluation methodology for renal cortical blood perfusion in elderly patients using contrast-enhanced ultrasound: A Chinese expert consensus (2024 edition)

As a sensitive and non-invasive method for assessing changes in renal cortical blood perfusion in the elderly, contrast-enhanced ultrasound (CEUS) can indirectly reflect changes in kidney filtration and reabsorption function, thus providing feasibility for early evaluation of renal function changes. However, significant differences exist among researchers in terms of operational methods, contrast agent selection, post-data analysis, and many other aspects, leading to substantial heterogeneity in results. This hinders horizontal comparisons and greatly limits the clinical application of contrast-enhanced ultrasound for evaluating renal cortical blood flow perfusion. Based on the latest domestic and overseas literature and discussions with clinical experts, this consensus provides recommended guidelines for the evaluation of renal cortical blood flow perfusion using contrast-enhanced ultrasound. It is hoped that this consensus will promote a better understanding of CEUS among medical practitioners at all levels and standardize the examination of renal cortical blood flow perfusion with CEUS.

EFSUMB Technical Review - Update 2023: Dynamic Contrast-Enhanced Ultrasound (DCE-CEUS) for the Quantification of Tumor Perfusion

Dynamic contrast-enhanced ultrasound (DCE-US) is a technique to quantify tissue perfusion based on phase-specific enhancement after the injection of microbubble contrast agents for diagnostic ultrasound. The guidelines of the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) published in 2004 and updated in 2008, 2011, and 2020 focused on the use of contrast-enhanced ultrasound (CEUS), including essential technical requirements, training, investigational procedures and steps, guidance regarding image interpretation, established and recommended clinical indications, and safety considerations. However, the quantification of phase-specific enhancement patterns acquired with ultrasound contrast agents (UCAs) is not discussed here. The purpose of this EFSUMB Technical Review is to further establish a basis for the standardization of DCE-US focusing on treatment monitoring in oncology. It provides some recommendations and descriptions as to how to quantify dynamic ultrasound contrast enhancement, and technical explanations for the analysis of time-intensity curves (TICs). This update of the 2012 EFSUMB introduction to DCE-US includes clinical aspects for data collection, analysis, and interpretation that have emerged from recent studies. The current study not only aims to support future work in this research field but also to facilitate a transition to clinical routine use of DCE-US.

Contrast-enhanced ultrasonography-based renal blood perfusion in brain-dead donors predicts early graft function

PURPOSE

The aim of this study was to quantify renal microcirculatory perfusion in braindead donors using contrast-enhanced ultrasonography (CEUS), and to establish an accurate, noninvasive, and convenient index for predicting delayed graft function (DGF) post-transplantation.

METHODS

In total, 90 brain-dead donor kidneys (training group, n=60; validation group, n=30) examined between August 2020 and November 2022 were recruited in this prospective study. CEUS was performed on the kidneys of brain-dead donors 24 hours before organ procurement and time-intensity curves were constructed. The main measures were arrival time, time to peak, and peak intensity of the kidney segmental arteries, cortex, and medulla. Recipients were divided into DGF and non-DGF groups according to early post-transplant graft function. The area under the receiver operating characteristic curve (AUC) was used to assess diagnostic performance.

RESULTS

The arrival time of the kidney segmental artery and cortex and the time interval between the time to peak of the segmental artery and cortex were identified as independent factors associated with DGF by multivariate stepwise regression analysis. A new index for the joint prediction model of three variables, the contrast-enhanced ultrasonography/Kidney Donor Profile index (CEUS-KDPI), was developed. CEUS-KDPI showed high accuracy for predicting DGF (training group: AUC, 0.91; sensitivity, 90.5%; specificity, 92.3%; validation group: AUC, 0.84; sensitivity, 75.0%; specificity, 92.3%).

CONCLUSION

CEUS-KDPI accurately predicted DGF after kidney transplantation. CEUS may be a potential noninvasive tool for bedside examinations before organ procurement and may be used to predict early renal function after kidney transplants kidneys from donors after brain death.

Evaluation of Early Diabetic Kidney Disease Using Ultrasound Localization Microscopy: A Feasibility Study

OBJECTIVE

The purpose of this study is to detect the hemodynamic changes of microvessels in the early stage of diabetic kidney disease (DKD) and to test the feasibility of ultrasound localization microscopy (ULM) in early diagnosis of DKD.

METHODS

In this study, streptozotocin (STZ) induced DKD rat model was used. Normal rats served as the control group. Conventional ultrasound, contrast-enhanced ultrasound (CEUS), and ULM data were collected and analyzed. The kidney cortex was divided into four segments, which are 0.25-0.5 mm (Segment 1), 0.5-0.75 mm (Segment 2), 0.75-1 mm (Segment 3), and 1-1.25 mm (Segment 4) away from the renal capsule, respectively. The mean blood flow velocities of arteries and veins in each segment were separately calculated, and also the velocity gradients and overall mean velocities of arteries and veins. Mann-Whitney U test was used for comparison of the data.

RESULTS

Quantitative results of microvessel velocity obtained by ULM show that the arterial velocity of Segments 2, 3, and 4, and the overall mean arterial velocity of the four segments in the DKD group are significantly lower than those in the normal group. The venous velocity of Segment 3 and the overall mean venous velocity of the four segments in the DKD group are higher than those in the normal group. The arterial velocity gradient in the DKD group is lower than that in the normal group.

CONCLUSION

ULM can visualize and quantify the blood flow and may be used for early diagnosis of DKD.

Value of conventional ultrasound and contrast-enhanced ultrasound for the assessment of renal allograft dysfunction and prognosis

BACKGROUND

Ultrasound (US) is the primary imaging modality for the assessment of transplanted kidneys. This study aims to investigate the ability of conventional US and contrast-enhanced US (CEUS) in assessing renal allograft function and prognosis.

METHODS

A total of 78 consecutive renal allograft recipients were enrolled. Patients were classified as normal allograft function (n = 41) and allograft dysfunction (n = 37) groups. All patients underwent US and parameters were measured. The independent-samples t-test or Mann-Whitney U test, logistic regression analysis, Kaplan-Meier survival plots, and Cox regression analysis were used.

RESULTS

In multivariable analysis, cortical echo intensity (EI) and cortical peak intensity (PI) were determinant US parameters for renal allograft dysfunction (p = .024 and p = .003, respectively). The combination of cortical EI and PI showed an area under the receiver operating characteristic curve (AUROC) of .785 (p < .001). Of 78 patients (median follow-up: 20mo), 16 (20.5%) exhibited composite end points. Cortical PI had a general prediction accuracy with an AUROC of .691, sensitivity of 87.5%, and specificity of 46.8% at the threshold of 22.08 dB in predicting prognosis (p = .019). The combination of estimated-glomerular filtration rate (e-GFR) and PI in predicting prognosis showed an AUROC of .845 with a cut-off value of .836, sensitivity of 84.0%, and specificity of 67.3% (p < .001).

CONCLUSION

This study indicates that cortical EI and PI are useful US parameters for evaluating renal allograft function and e-GFR combined with PI may provide a more accurate predictor of survival.

Contrast Enhanced Ultrasonography of Kidney in Chronic Intermittent Hypoxia Rat Model

OBJECTIVES

The objective of our study was to assess the ability of contrast-enhanced ultrasound (CEUS) in evaluating renal microperfusion in an animal model.

METHODS

Twenty Sprague-Dawley rats were subdivided into two groups: the normal and chronic intermittent hypoxia (CIH) groups. In the CIH model, 10 Sprague-Dawley rats were exposed to CIH for 8 weeks to mimic obstructive sleep apnea (OSA). The CEUS parameters of the renal cortex and medulla were obtained and compared between groups. The pathological changes of the kidney tissues were examined by histological staining such as hematoxylin and eosin (H&E) and Masson's trichrome.

RESULTS

CIH caused morphological damage to kidneys. In the cortex, the peak intensity (PI) (P = .009) was significantly lower and time to peak (Ttop) (P = .019) was significantly prolonged in the CIH group compared with the controls. The area under ascending curve (WiAUC) in the medulla and cortex were both significantly lower in the CIH group than those in the control group (P both <.05). CEUS parameters (including PI and WiAUC of the cortex and WiAUC of the medulla) were negatively correlated with serum creatinine (P all <.05). In the medulla, the area under descending curve (WoAUC) was positively correlated with serum creatinine (P = .027), PI was negatively correlated with uric acid (P = .034).

CONCLUSION

CEUS parameters (including Ttop, PI, WoAUC, and WiAUC) reflect renal microvascular changes in CIH. CEUS could be a safe and accurate imaging method to assess renal microvascular damage in CIH rats.

Classifying Kidney Disease in a Vervet Model Using Spatially Encoded Contrast-Enhanced Ultrasound Perfusion Parameters

Early stages of diabetic kidney disease (DKD) are difficult to diagnose in patients with type 2 diabetes. This work was aimed at identifying contrast-enhanced ultrasound (CEUS) perfusion parameters, a microcirculatory biomarker indicative of early DKD progression. CEUS kidney flash-replenishment data were acquired in control, insulin resistant and diabetic vervet monkeys (N = 16). By use of a mono-exponential model, time-intensity curve parameters related to blood volume (A), velocity (β) and flow rate (perfusion index [PI]) were extracted from 10 concentric kidney layers to study spatial perfusion patterns that could serve as strong indicators of disease. Mean squared error (MSE) was used to assess model performance. Features calculated from the perfusion parameters were inputs for the linear regression models to determine which features could distinguish between cohorts. The mono-exponential model performed well, with average MSEs (±standard deviation) of 0.0254 (±0.0210), 0.0321 (±0.0242) and 0.0287 (±0.0130) for the control, insulin resistant and diabetic cohorts, respectively. Perfusion index features, with blood pressure, were the best classifiers between cohorts (p < 0.05). CEUS has the potential to detect early microvascular changes, providing insight into disease-related structural changes in the kidney. The sensitivity of this technique should be explored further by assessing various stages of DKD.

Is it time to re-think FAST? A systematic review and meta-analysis of Contrast-Enhanced Ultrasound (CEUS) and conventional ultrasound for initial assessment of abdominal trauma

BACKGROUND

The Focused Assessment with Sonography for Trauma (FAST) examination using conventional ultrasound has limited utility for detecting solid organ injury. Therefore, this systematic review and meta-analysis compares the performance of contrast-enhanced ultrasound (CEUS) to conventional ultrasound when used as the initial assessment for abdominal trauma prior to computed tomography (CT) imaging.

METHODS

A systematic literature search of major databases was conducted of human studies investigating the diagnostic accuracy of conventional ultrasound and CEUS occurring prior to CT imaging for abdominal trauma. The study followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement. The quality of studies was evaluated using the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies 2) tool. Paired pooled sensitivity and specificity between conventional ultrasound and CEUS were compared using data extracted from the eligible studies. Diagnostic odds ratio, number needed to diagnose values, and likelihood ratios were also determined.

RESULTS

Ten studies were included. More than half of the included studies demonstrated low risk of bias. Using McNemar's test to assess for paired binary observations, we found that CEUS had statistically higher sensitivity (0.933 vs. 0.559; two-tailed, P < 0.001) and specificity (0.995 vs. 0.979; two-tailed, P < 0.001) than conventional ultrasound in the setting of abdominal trauma, respectively. When divided into particular findings of clinical interest, CEUS had statistically higher sensitivity than conventional ultrasound in screening for active bleeding and injuries to all abdominal solid organs. CEUS also had superior diagnostic odds ratios, number needed to diagnose values, and likelihood ratios than conventional ultrasound.

CONCLUSION

The diagnostic value of CEUS was higher than that of conventional ultrasound for differentiating traumatic abdominal injuries when used as the initial assessment in the emergency department.

Evaluating renal microcirculation in patients with acute kidney injury by contrast-enhanced ultrasonography: a protocol for an observational cohort study

BACKGROUND

Acute kidney injury (AKI) in critically ill patients has poor renal outcome with high mortality. Changes in intra-renal microcirculation and tissue oxygenation are currently considered essential pathophysiological mechanisms to the development and progression of AKI. This study aims to investigate the characteristics of contrast-enhanced ultrasonography (CEUS) derived parameters in biopsy-proven AKI patients, and examine the predictive value of these markers for renal outcome.

METHODS AND DESIGN

This prospective observational study will enroll AKI patients who are diagnosed and staging following KDIGO (Kidney Disease: Improving Global Outcomes) criteria. All patients undergo a kidney biopsy and pathological tubulointerstitial nephropathy is confirmed. The CEUS examination will be performed at 0, 4 and 12 weeks after biopsy to monitor renal microcirculation. The percentage decrease of serum creatinine, 4-week and 12-week eGFR (estimated glomerular filtration rate) will also be reviewed as renal prognosis. The relationship of CEUS parameters with clinical and pathological markers will be analyzed. We perform a lassologit procedure to select potential affecting variables, including clinical, laboratory indexes and CEUS markers, to be included in the logistic regression model, and examine their predictive performance to AKI outcomes.

DISCUSSION

If we are able to show that CEUS derived parameters contribute to diagnosis and prognosis of AKI, the quality of life of patients will be improved while healthcare costs will be reduced.

TRIAL REGISTRATION

This study is retrospectively registered on the Chinese Medical Research Registration information System( https://61.49.19.26/login ) on December 31, 2021: MR-11-22-003,503. This study has been approved by the Ethics and Scientific Research Department of Peking University First Hospital.

Ultrasonography Combined with Blood Biochemistry on the Early Diagnosis of Diabetic Kidney Disease

Objective

Diabetic kidney disease (DKD) has been well recognized as a microvascular complication of diabetes mellitus. Perfusion of intrarenal arteries is closely related with development of DKD. The aim of the present study was to investigate relation of ultrasonography performance of intrarenal arteries and grade of DKD.

Methods

From May to December at 2021, a total of 54 DKD patients and 36 non-DKD cases were recruited. Ultrasonography performance of intrarenal and arteries at lower extremity was examined by high-resolution ultrasound diagnostic equipment; maximum (Vsmax) as well as minimum (Vdmin) blood velocity of arteries were recorded, and resistance index (RI) of arteries were calculated. Blood routine and biochemical parameters were determined from clinical laboratory of our hospital.

Results

According to eGFR grading, 42.50% of the 54 DKD cases are at Grade 1, and 18.52%, 11.11%, 9.26%, and 18.52% cases were at Grade 2, 3a, 3b, and 4-5, respectively. Blood urea and creatinine were significantly positively related with progress of DKD, while level of Hb was negatively related with DKD. By ultrasonography; we found that Vsmax and Vdmin of main renal artery (MRA), segmental renal artery (SRA), and interlobular renal artery (IRA) were significantly reduced compared with healthy cases; IR of the above arteries was dramatically elevated, and changes of the above data were more obvious than that of lower extremity. Vdmin of MRA, SRA, and IRA was negatively related with grading of DKD, while RI was positively related with the grading. Converging from RI and level of Hb, we found that the level of Hb is positively related with healthy status of the kidney, while RI of the arteries is negatively with that.

Conclusions

Resistance index (RI) of intrarenal arteries, obtained from ultrasonography combining with level of hemoglobin (Hb), is the predictor of progress of DKD.

Assessment of Renal Transplant Perfusion by Contrast-Enhanced Ultrasound after Switch from Calcineurin Inhibitor to Belatacept: A Pilot Study

Calcineurin inhibitors (CNIs) have improved short-term kidney allograft survival but are nephrotoxic and vasoconstrictive. Vasoconstriction is potentially reversible after switching from CNIs to belatacept. The kidney allograft shows optimal requirements for dynamic perfusion imaging using contrast-enhanced ultrasound (CEUS). We performed standardized CEUS in patients after switching from CNIs to belatacept for clinical indication to study the suitability of CEUS, in order to assess the effects of CNI cessation on kidney allograft perfusion. Eleven kidney transplant patients were enrolled from February 2020 until November 2020. Demographic, clinical, and laboratory parameters, as well as perfusion imaging, were assessed at baseline and 6 months after switching immunosuppression. Quantification of perfusion imaging on CEUS was performed using a post-processing software tool on uncompressed DICOM cine loops. After CNI cessation, estimated glomerular filtration rate increased by 4.8 mL/min/1.73 m² (16%). Despite good quality of fit and comparable regions of interest in baseline and follow-up CEUS examinations, quantification of perfusion imaging showed a slightly improved cortical perfusion without reaching statistical significance after CNI cessation. This is the first study that systematically investigates the suitability of CEUS to detect changes of microvascular perfusion in kidney transplant recipients in vivo. No significant differences could be detected in perfusion measurements before and after CNI cessation.

Gray-Scale, Color Doppler, Spectral Doppler, and Contrast-Enhanced Renal Artery Ultrasound: Imaging Techniques and Features

Renal artery stenosis (RAS) is increasingly being detected in elderly patients as life expectancy increases. RAS induces hypertension or reduces renal function. Computed tomography or magnetic resonance angiography are objective in detecting RAS but may cause iodine-induced nephrotoxicity or nephrogenic systemic fibrosis in patients with RAS. Ultrasound (US) is, by contrast, a noninvasive and real-time imaging modality useful in patients with reduced renal function. Renal US is not as sensitive for detecting RAS because this technique indirectly assesses the renal artery by analyzing intrarenal hemodynamic changes. Although, ideally, US would be used to directly evaluate the renal artery, its current utility for RAS detection remains unclear. The purpose of this review is to introduce how to assess renal artery with US, to describe imaging features of renal artery US, to compare renal artery US and renal US, and to show how to perform work-up in patients in whom RAS is suspected.

Evaluation of renal microperfusion in hyperuricemic nephropathy by Contrast-Enhanced Ultrasound imaging

Diagnostic tools for the early detection of renal injury caused by hyperuricemia are still lacking. Here, we investigated whether contrast-enhanced ultrasound (CEUS) could be used as a diagnostic tool for hyperuricemic nephropathy (HN). In the HN rat model, CEUS detected a significant decline in renal cortical perfusion compared with that in control rats. Peak intensity (PI) values correlated significantly with serum KIM-1 levels and fibrosis scores in HN rats. An early decline in PI values was also observed in chronic kidney disease (CKD) stage 1 patients with HN compared with the controls (61.1±4.52 dB versus 65.80±7.10 dB) and correlated with renal function in the patients with HN. In contrast, an increase in time to reach PI values was detected in HN patients with stage 1 CKD (15.14±1.75 s versus 14.52±4.75 s) and was more pronounced in CKD stage 4 patients (67.32±3.29 s). CEUS was able to detect abnormal renal perfusion in early CKD with HN, which correlated with renal function decline, suggesting that CEUS could be used as a noninvasive tool for assessing renal function in patients with HN.

Repeatability of Contrast-Enhanced Ultrasound to Determine Renal Cortical Perfusion

Alterations in renal perfusion play a major role in the pathogenesis of renal diseases. Renal contrast-enhanced ultrasound (CEUS) is increasingly applied to quantify renal cortical perfusion and to assess its change over time, but comprehensive assessment of the technique’s repeatability is lacking. Ten adults attended two renal CEUS scans within 14 days. In each session, five destruction/reperfusion sequences were captured. One-phase association was performed to derive the following parameters: acoustic index (AI), mean transit time (mTT), perfusion index (PI), and wash-in rate (WiR). Intra-individual and inter-operator (image analysis) repeatability for the perfusion variables were assessed using intra-class correlation (ICC), with the agreement assessed using a Bland–Altman analysis. The 10 adults had a median (IQR) age of 39 years (30–46). Good intra-individual repeatability was found for mTT (ICC: 0.71) and PI (ICC: 0.65). Lower repeatability was found for AI (ICC: 0.50) and WiR (ICC: 0.56). The correlation between the two operators was excellent for all variables: the ICCs were 0.99 for PI, 0.98 for AI, 0.87 for mTT, and 0.83 for WiR. The Bland–Altman analysis showed that the mean biases (± SD) between the two operators were 0.03 ± 0.16 for mTT, 0.005 ± 0.09 for PI, 0.04 ± 0.19 for AI, and −0.02 ± 0.11 for WiR.

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.

In Vivo assessment of hypertensive nephrosclerosis using ultrasound localization microscopy

PURPOSE

As a typical chronic kidney disease (CKD), hypertensive nephrosclerosis (HN) is a common syndrome of hypertension, characterized by chronic kidney microvascular damage. Early diagnosis of microvascular damage using conventional ultrasound imaging encounters challenges in sensitivity and specificity owing to the inherent diffraction limit. Ultrasound localization microscopy (ULM) has been developed to obtain microvasculature and microvascular hemodynamics within the kidney, and would be a promising tool for early diagnosis of CKD.

METHODS

In this study, the advantage of quantitative indexes obtained by using ULM (mean arterial blood flow speeds of different segments of interlobular arteries) over indexes obtained using conventional clinical serum (β2-microglobulin, serum urea nitrogen and creatinine) and urine (24-hour urine volume and urine protein) tests and ultrasound Doppler imaging [peak systolic velocity (PSV), end-diastolic velocity (EDV) and resistance index (RI)] and contrast-enhanced ultrasound imaging [CEUS; rise time (RT), peak intensity (IMAX), mean transit time (mTT) and area under the time-intensity curve (AUC)] for early diagnosis of HN was investigated. Examinations were carried out on 6 spontaneously hypertensive rats (SHR) and 5 normal Wistar-Kyoto (WKY) rats at the age of 10 weeks.

RESULTS

The experimental results showed that the indicators derived from conventional clinical inspections (serum and urine tests) and ultrasound imaging (PSV, EDV, RI, RT, IMAX, mTT and AUC) did not show significant difference between hypertensive and healthy rats (p > 0.05), while the TTP of the SHR group (28.52 ± 5.52 s) derived from CEUS is significantly higher than that of the WKY group (18.68 ± 7.32 s; p < 0.05). The mean blood flow speed in interlobular artery of SHR (12.47 ± 1.06 mm/s) derived from ULM is significantly higher than that of WKY rats (10.13 ± 1.17 mm/s; p < 0.01).

CONCLUSION

The advantages of ULM over conventional clinical inspections and ultrasound imaging methods for early diagnosis of HN were validated. The quantitative results showed that ULM can effectively diagnose HN at the early stage by detecting the blood flow speed changes of interlobular arteries. ULM may promise a reliable technique for early diagnosis of HN in the future. This article is protected by copyright. All rights reserved.

Quantitative assessment of renal perfusion in children with UPJO by contrast enhanced ultrasound: A pilot study

BACKGROUND

Contrast-enhanced ultrasound (CEUS) is a new potential modality for the quantitative evaluation of the microvascular perfusion of a parenchymal organ.

OBJECTIVE

To prospectively and quantitatively analyse the role of CEUS in evaluating renal perfusion for assessing renal function in children with ureteropelvic junction obstruction (UPJO).

METHODS

The study protocol was approved by the local ethics committee, and written informed consent was obtained from the patients' parents or guardians. Ultrasonography, CEUS, and radioisotope renography were performed for 51 children (42 boys, 9 girls; mean age, 6.75 ± 4.14 years) with unilateral UPJO. The slope of the ascending curve (A), time to peak (TTP), peak intensity (PI), and area under the curve (AUC) were recorded during CEUS; quantitative data were calculated by QLab system (semiautomated border tracking, Philips Healthcare) software. Sensitivity and specificity values were determined for CEUS with respect to radioisotope renography.

RESULTS

CEUS was used to evaluate 102 kidneys in 51 patients, for which the perfusion time-intensity curve (TIC) was determined. The TIC of renal cortical perfusion in all groups showed an asymmetrical single-peak curve, which could be clearly distinguished between the experimental group and the control group. Compared with the control group, the experimental group showed a markedly prolonged TTP but a significantly decreased A (P < 0.05). There was no significant correlation between the AUC, PI and differential renal function (DRF), but the correlation coefficient between TTP, A and DRF remained significant (p < 0.001).The receiver operating characteristic (ROC) curves drawn to differentiate DRF using the TTP value yielded an area under the ROC curve (AUROC) of 0.86. For a quantitative assessment of DRF less than 40% by CEUS, the sensitivity and specificity values were 92.86% and 76.14%, respectively.

DISCUSSION

Unlike in previous studies, no significant difference in the AUC or PI was found between the control group and the experimental group in this study (P > 0.05). Renal blood perfusion could not be evaluated overall by CEUS. Parenchymal thinning may be considered a limitation to CEUS.

CONCLUSIONS

This preliminary experience represents the first report of evaluating the diagnostic value of CEUS in assessing renal function in children with UPJO. CEUS is a highly sensitive, rapid, and cost-effective diagnostic imaging modality for detecting and monitoring renal function noninvasively.

Contrast-enhanced ultrasonography for assessing histopathology in pediatric immunoglobulin A nephropathy and Henoch-Schönlein purpura nephritis

BACKGROUND

Glomerular disease, including immunoglobulin A nephropathy (IgAN) and Henoch-Schönlein purpura nephritis, is one of the most common kidney diseases in children. The diagnosis of these diseases depends on pathological biopsy, although this procedure is seriously limited by its invasive and high-risk nature.

OBJECTIVE

To investigate the potential of contrast-enhanced ultrasonography (CEUS) for evaluating the histopathological severity of IgAN and Henoch-Schönlein purpura nephritis (HSPN).

MATERIALS AND METHODS

We investigated a total of 13 children with IgAN and 12 children with HSPN confirmed by renal histopathology. We reevaluated the pathological lesions of the children according to the Oxford classification and the Lee grading system and then all the children underwent CEUS. Using SonoLiver software, we constructed time-intensity curves of CEUS for regions of interest in the renal cortex. We analyzed CEUS quantitative parameters for IgAN and HSPN and used Spearman correlation analysis to examine the correlation between CEUS parameters and clinicopathological indexes in the study cohort.

RESULTS

The CEUS parameters rise time (RT) and time to peak (TTP) were significantly higher in children with Lee grade IV than in those with Lee grades II or III. Spearman correlation analysis revealed a positive correlation between rise time and time to peak with Lee grade in the overall cohort of children, and a positive correlation between rise time and time to peak and severity of crescents in the Oxford classification scoring system.

CONCLUSION

Contrast-enhanced US may be used as a noninvasive imaging technique to evaluate the severity of renal pathology and formation of crescents in children with IgAN and HSPN.

Interobserver reproducibility of contrast-enhanced ultrasound in diabetic nephropathy

OBJECTIVE

To investigate the interobserver reproducibility of contrast-enhanced ultrasound (CEUS) in patients with diabetic nephropathy.

METHODS

A total of 40 patients with diabetic nephropathy were enrolled in this retrospective study. We measured peak intensity (PEAK), time-to-peak (TP), area under the curve (AUC) and mean transit time (MTT) of renal CEUS in each patient. Each parameter was performed by two independent observers. The interobserver reproducibility was assessed using intraclass correlation coefficients (ICCs) with 95% confidence intervals (CIs) and Bland-Altman plots by mean difference with 95% limits of agreement (LOAs).

RESULTS

The parameters of the left and right kidneys showed moderate or good reliability. The best was the left kidney AUC parameters (ICC,0.945),with a 95% CI of 0.896-0.971.The Bland-Altman plots showed that the mean differences between the right renal parameters (PEAK, TP, AUC and MTT) obtained between the observers 1 and 2 were -6.63%,2.54%,-11.30%,-2.22%, and the 95% LOAs are -30.78 to 17.52%, -30.15 to 35.23%, -43.95 to 21.35%, -44.50 to 40.06%. While the left ones were -2.89%, 0.32%, -8.26%, 1.25% , and the 95% LOAs were -38.50 to 32.72%, -31.98 to 32.62%, -57.89 to 41.37%, -37.21 to 39.71%, respectively.

CONCLUSION

Quantitative CEUS can show good interobserver reproducibility, which is better for the right kidney. It seems necessary to establish standardized techniques for obtaining contrast-enhanced quantitative analysis of renal blood perfusion.

ADVANCES IN KNOWLEDGE

Quantitative assessment of renal perfusion by CEUS in patients with diabetic nephropathy provides diagnostic information. Furthermore, renal perfusion assessment in patients with diabetic nephropathy using CEUS has good reproducibility.

Usefulness of Contrast-enhanced Ultrasound in the Evaluation of Chronic Kidney Disease

BACKGROUND

Contrast-enhanced ultrasound (CEUS) can provide more improved images of renal blood flow and much more information of both macro- and microcirculation of the kidney as compared to Doppler US.

OBJECTIVE

To investigate the usefulness of CEUS by analyzing differences in perfusion-related parameters among the three chronic kidney disease (CKD) subgroups and the control group.

METHODS

Thirty-eight patients with CKD and 21 controls who were age-matched (20-49 years) were included. Included CKD patients were stratified into three groups according to their eGFR: group I, eGFR ≥ 60 ml/min/1.73 m2 (GFR category I and II); group II, 30 ml/min/1.73 m² ≤ eGFR < 60 ml/min/1.73 m² (GFR category III); and group III, eGFR < 30 ml/min/1.73 m² (GFR category IV and V). Comparisons with the controls (eGFR > 90 ml/min/1.73 m²) were performed. Real-time and dynamic renal cortex imaging was performed using CEUS. Time-intensity curves and several bolus model quantitative perfusion parameters were created using the VueBox® quantification software. We compared the parameters among the CKD subgroups and between the CKD and control groups.

RESULTS

Eight patients were included in group I, 12 patients in group II, and 18 patients in group III. Significant differences were noted in the wash-in and wash-out rates between the CKD and control groups (p = 0.027 and p = 0.018, respectively), but not between those of the CKD subgroups. There were no significant differences of other perfusion parameters among the CKD subgroups and between the CKD and control groups.

CONCLUSION

A few perfusion related CEUS parameters (WiR and WoR) can be used as markers of renal microvascular perfusion relating renal function. CEUS can effectively and quantitatively exhibit the renal microvascular perfusion in patients with CKD as well as normal control participants.

Evaluation of Renal Microperfusion in Diabetic Patients With Kidney Injury by Contrast-Enhanced Ultrasound

OBJECTIVES

To conduct a quantitative analysis of renal microvascular perfusion in diabetic patients with kidney injury using contrast-enhanced ultrasound (CEUS).

METHODS

A total of 172 patients with type 2 diabetes mellitus and kidney injury were recruited from May 2017 to November 2019. After collection of clinical characteristics, a CEUS examination was performed after injection of the contrast agent SonoVue (Bracco SpA, Milan, Italy). Time-intensity curves and renal perfusion parameters were analyzed. Ultrasound-guided renal biopsy was performed. The patients were divided into a diabetic nephropathy (DN) group and a nondiabetic renal disease (NDRD) group according to renal pathologic results. The discrimination of perfusion parameters between the groups was analyzed statistically with SPSS version 19.0 software (IBM Corporation, Armonk, NY). Receiver operating characteristic curves were used to illustrate the diagnostic performance of indicators.

RESULTS

Ninety-eight patients, including 45 with DN (29 male; mean age ± SD, 57.76 ± 10.47 years) and 53 with NDRD (40 male; mean age, 48.7 ± 13.88 years) were included in this study. The peak enhancement (PE), wash-in the area under the curve (AUC), wash-in rate, wash-in perfusion index, wash-out AUC, wash-in and wash-out AUC, and wash-out rate were significantly different between the groups (P < .05). There were no differences in time-related parameters between the DN and NDRD groups (P > .05). The receiver operating characteristic curve analysis showed that the AUC for PE was 0.727, and PE lower than 7712.426 had diagnostic potential, with sensitivity of 81% and specificity of 40% in discriminating between NDRD and DN.

CONCLUSIONS

The quantification of CEUS parameters can discriminate DN in diabetic patients with kidney injury. The PE and AUC may be feasible parameters.

Cortical perfusion as assessed with contrast-enhanced ultrasound is lower in patients with chronic kidney disease than in healthy subjects but increases under low salt conditions

Background

Disturbances in renal microcirculation play an important role in the pathophysiology of chronic kidney disease (CKD), but the lack of easy accessible techniques hampers our understanding of the regulation of the renal microcirculation in humans. We assessed whether contrast-enhanced ultrasound (CEUS) can identify differences in cortical perfusion and alterations induced by different dietary salt intakes in CKD patients and controls.

Methods

Participants underwent CEUS twice: once after 5 days of high-salt (HS) intake, and again after 5 days of low salt (LS) diet. Sonovue® (0.015 mL/kg/min) was perfused as contrast agent and four consecutive destruction–reperfusion sequences were analysed per visit. The primary outcome measure was the (change in) mean perfusion index (PI) of the renal cortex.

Results

Forty healthy volunteers (mean age ± standard deviation 50 ± 8 years) and 18 CKD Stages 2–4 patients [aged 55 ± 11 years, estimated glomerular filtration rate (eGFR) 54 ± 28 mL/min/1.73 m2] were included and underwent CEUS without side effects. Under HS conditions, cortical PI was significantly lower in CKD patients [1618 ± 1352 versus 3176 ± 2278 arbitrary units (a.u) in controls, P = 0.034]. Under LS, renal PI increased in CKD patients (with +1098 to 2716 ± 1540 a.u., P = 0.048), whereas PI remained stable in controls. In the continuous analysis, PI correlated with eGFR (Spearman’s r = 0.54, P = 0.005) but not with age, sex, blood pressure or aldosterone levels.

Conclusions

CEUS identified important reductions in cortical micro-perfusion in patients with moderate CKD. Lowering salt intake increased perfusion in CKD patients, but not in controls, underlining the benefits of an LS diet in CKD patients. Whether a low PI is an early sign of kidney damage and predicts renal function decline needs further study.

Application of dynamic contrast enhanced ultrasound in the assessment of kidney diseases

PURPOSE OF REVIEW

Many forms of acute and chronic disease are linked to changes in renal blood flow, perfusion, vascular density and hypoxia, but there are no readily available methods to assess these parameters in clinical practice. Dynamic contrast enhanced ultrasound (DCE-US) is a method that provides quantitative assessments of organ perfusion without ionising radiation or risk of nephrotoxicity. It can be performed at the bedside and is suitable for repeated measurements. The purpose of this review is to provide updates from recent publications on the utility of DCE-US in the diagnosis or assessment of renal disease, excluding the evaluation of benign or malignant renal masses.

RECENT FINDINGS

DCE-US has been applied in clinical studies of acute kidney injury (AKI), renal transplantation, chronic kidney disease (CKD), diabetic kidney disease and to determine acute effects of pharmacological agents on renal haemodynamics. DCE-US can detect changes in renal perfusion across these clinical scenarios and can differentiate healthy controls from those with CKD. In sepsis, reduced DCE-US measures of perfusion may indicate those at increased risk of developing AKI, but this requires confirmation in larger studies as there can be wide individual variation in perfusion measures in acutely unwell patients. Recent studies in transplantation have not provided robust evidence to show that DCE-US can differentiate between different causes of graft dysfunction, although it may show more promise as a prognostic indicator of graft function 1 year after transplant. DCE-US can detect acute haemodynamic changes in response to medication that correlate with changes in renal plasma flow as measured by para-aminohippurate clearance.

SUMMARY

DCE-US shows promise and has a number of advantages that make it suitable for the assessment of patients with various forms of kidney disease. However, further research is required to evidence its reproducibility and utility before clinical use can be advocated.

Derepression of glomerular filtration, renal blood flow and antioxidant defence in patients with type 2 diabetes at high-risk of cardiorenal disease

BACKGROUND

The role of antioxidant status on microvascular blood flow and glomerular filtration (eGFR) in patients with type 2 diabetes and hypertension whose risk of progressive renal disease varies by ethnicity is unknown.

METHODS

Adult, non-Caucasian (n = 101) and Caucasian (n = 69) patients with type 2 diabetes, hypertension and/or microalbuminuria and an eGFR > 45 mL/min/1.73 m² were randomised to receive 400 IU vitamin E and/or 20 μg selenium daily or matching placebo. eGFR (CKD-EPI) was measured at baseline, 3,6 and 12 months and renal blood flow by contrast-enhanced ultrasonography in a sub-group (n = 9) at baseline and 3 months by assessing the area under the time intensity curve (TIC). Circulating glutathione peroxidase 3 (GPx-3) activity was measured as a biomarker of oxidative defence status.

RESULTS

The time to change in eGFR was shortest with combined vitamin E and selenium than usual care (5.6 [4.0-7.0] vs 8.9 [6.8-10.9 months]; p = 0.006). Area under the TIC was reduced compared to baseline (38.52 [22.41-90.49] vs 123 [86.98-367.03]dB.s; P ≤ 0.05 and 347 [175.88-654.92] vs 928.03 [448.45-1683]dB.s; P ≤ 0.05, respectively] at 3 months suggesting an increase in rate of perfusion. The proportional change in eGFR at 12 months was greater in the group whose GPx-3 activity was above, compared with those below the cohort median (360 U/L) in the non-Caucasian and the Caucasian groups (19.1(12.5-25.7] % vs 6.5[-3.5 to 16.5] % and 12.8 [0.7 to 24] % vs 0.2 [-6.1 to 6.5] %).

CONCLUSION

In these patients with type 2 diabetes and early CKD, antioxidant treatment derepresses renal blood flow and a rise in eGFR correlated directly with GPx-3 activity.

SIGNIFICANCE

Diabetes mellitus is the world's leading cause of end-stage renal disease which has a predilection for black and minor ethnic groups compared with Caucasians. The differences in risk despite the benefits of conventional care may be related to oxidative stress. We found that glomerular filtration and renal blood flow is suppressed when renal function is preserved in high-risk patients with type 2 diabetes. Conventional care supplemented with selenium - the co-factor for glutathione peroxidase-3 (GPx-3) - improves renal perfusion and increase glomerular filtration according to host antioxidant defence determined by GPx-3 activity. Circulating GPx-3 activity warrants further investigation as a novel biomarker of reversible haemodynamic changes in early diabetic kidney disease to better enable targeting of renoprotective strategies.

Improving Prognostic and Chronicity Evaluation of Chronic Kidney Disease with Contrast-Enhanced Ultrasound Index-Derived Peak Intensity

The capability of contrast-enhanced ultrasound (CEUS) to assess the prognosis and chronicity of chronic kidney disease (CKD) was evaluated in patients diagnosed with CKD in 2014 at Ren Ji Hospital, Shanghai, China. Time-intensity curves and quantitative indexes were created using QLab quantification software. Kidney biopsies were analyzed with α-smooth muscle actin immunohistochemistry. According to the renal chronicity score, patients were divided into four groups: minimal (n = 14), mild (n = 73), moderate (n = 49) and severe (n = 31). Multivariate logistic regression analysis revealed that the derived peak intensity (DPI) was independently associated with the renal chronicity score. Of 167 CKD patients (median follow-up: 30.4 ± 18.7 mo), 31 (18.6%) exhibited CKD progression, with a decline in the glomerular filtration rate of more than 25% or end-stage renal disease. Multivariate Cox regression analysis revealed that a lower DPI was independently associated with CKD progression. This study indicates that DPI is a reliable CEUS parameter for evaluating chronic renal changes and an independent prognostic factor of CKD.

Contrast enhanced ultrasound: A review of radiology applications

Ultrasound contrast agents have been used for decades in Europe and Asia for cardiac and abdominal imaging and are now being more commonly utilized in the United States for radiology applications. Our article reviews the basics of contrast-enhanced ultrasound including how the contrast agent works, advantages and disadvantages, as well as pearls and pitfalls to help the radiologist efficiently integrate this technology into day-to-day clinical practice. We also discuss the diagnosis of focal hepatic lesions as well as off-label applications such as evaluation of renal masses.

Clinical significance of contrast-enhanced ultrasound in chronic kidney disease: a pilot study

BACKGROUND

Contrast-enhanced ultrasound (CEUS) has the potential to improve the imaging of renal blood flow and renal lesional vascularity in real time with high temporal and spatial resolution.

PURPOSE

This study investigated the clinical significance of real-time CEUS in cases of chronic kidney disease (CKD).

MATERIALS AND METHODS

Included patients were stratified according to their estimated glomerular filtration rate (eGFR): Group I (CKD stage I and II), eGFR ≥ 60 ml/min/1.73 m²; group II (CKD stage III), eGFR of 30 ≤ eGFR < 60 ml/min/1.73 m²; and group III (CKD stage IV and V), eGFR of eGFR < 30 ml/min/1.73 m². Real-time and dynamic imaging of the renal cortex was performed using CEUS. Several bolus model perfusion and laboratory parameters were compared. The differences in perfusion or laboratory parameters among the groups and correlation between perfusion or laboratory parameters and eGFR were assessed.

RESULTS

Of the 24 patients, 4 were classified into group I, 13 into group II, and 7 into group III. No significant differences were found among the three groups in the perfusion parameter analysis. No parameter was significantly positively correlated with eGFR. In the laboratory parameter analysis, significant differences in several parameters (RBC, BUN, SCr, glucose, TCh, phosphorus, TP, p < 0.05) were detected among the three groups. These parameters significantly correlated with eGFR (correlation coefficient, R = - 0.7625 to 0.6026).

CONCLUSIONS

Kidney perfusion parameters in CEUS do not correlate with kidney function in this pilot study.

Renal perfusion parameters measured by contrast-enhanced ultrasound in healthy dogs demonstrate a wide range of variability in the long-term

Contrast-enhanced ultrasound may be helpful for detecting early renal microvascular damage and dysfunction in dogs. However, before this noninvasive imaging method can be tested as an early-stage screening tool in clinical patients, an improved understanding of long-term variation in healthy animals is needed. In this prospective, secondary, longitudinal, serial measurements study, variability of contrast-enhanced ultrasound renal perfusion parameters was described for eight healthy dogs, using seven time points and a period of 83 weeks. Dogs were sedated with butorphanol (0.4 mg/kg), and contrast-enhanced ultrasound of each kidney was performed after an intravenous bolus injection of a microbubble contrast agent (0.04 mL/kg). Time-intensity curves were created from regions-of-interest drawn in the renal cortex and medulla. Intensity-related parameters representing blood volume and time-related parameters representing blood velocity were determined. A random-effects model using restricted maximum likelihood was used to estimate variance components. Within-dog coefficient of variation was defined as the ratio of the standard deviation over the mean. Time-related parameters such as time-to-peak, rise and fall time had lowest within-dog variability. Intensity-related parameters such as peak enhancement, wash-in and wash-out area under the curve, total area under the curve, and wash-in and washout rates had high within-dog variability (coefficient of variation > 45%). Authors therefore recommend the use of time-related parameters for future studies of renal perfusion. Within-dog variability for bilateral kidney measurements was extremely low, therefore contrast-enhanced ultrasound may be particularly useful for detecting unilateral changes in renal perfusion. Future studies are needed to compare contrast-enhanced ultrasound findings in healthy dogs versus dogs with renal disease.

Contrast-enhanced ultrasonography for assessment of tubular atrophy/interstitial fibrosis in immunoglobulin A nephropathy: a preliminary clinical study

PURPOSE

To investigate the potential of contrast-enhanced ultrasonography (CEUS) for evaluating the severity of tubular atrophy/interstitial fibrosis (TA/IF) in immunoglobulin A nephropathy (IgAN) patients.

MATERIALS AND METHODS

A total of 80 patients with IgAN and 33 healthy adults were investigated. Patients were divided into three groups according to the TA/IF (T) grade of the Oxford classification: T0 (n = 28), T1 (n = 35), and T2 (n = 17). Patients and control subjects underwent conventional ultrasound (US) and CEUS. Time-intensity curves of CEUS were drawn for regions of interest located in the renal cortex and medulla using QLab software. Conventional US and CEUS quantitative parameters were analyzed. One-way analysis of variance (ANOVA), binary logistic regression, and receiver operating characteristic (ROC) curves were used.

RESULTS

There were no significant differences in renal size, cortical thickness, and medullary perfusion parameters (P > 0.05), whereas the differences in peak intensity (PI), area under the time-intensity curve (AUC) and wash-in slope (WIS) of cortical perfusion parameters between the control subjects and patients were significant (P < 0.05). PI was significantly lower with the increasing degree of T (P < 0.05). PI was associated independently with the degree of T in IgAN patients (P < 0.05). ROC analysis revealed that using the optimal cutoff values of 15.38 dB for diagnosis of T0-T1 (sensitivity 83.30% and specificity 63.00%) and 14.69 dB for diagnosis of T2 (sensitivity 100.00% and specificity 66.70%), the corresponding areas under the ROC curve were found to be 0.782 and 0.952, respectively.

CONCLUSIONS

CEUS can potentially be used as a noninvasive imaging marker to evaluate the severity of TA/IF in IgAN patients.

Quantitative parameters of contrast-enhanced ultrasonography for assessment of renal pathology: A preliminary study in chronic kidney disease

OBJECTIVE

To assess the severity of renal pathology in patients with chronic kidney disease (CKD) using contrast-enhanced ultrasonography (US).

METHODS

275 patients with CKD who were proven by renal biopsy and 30 healthy adults were examined using conventional US and contrast-enhanced US. Ultrasonic parameters included renal length, cortical thickness, rise time (RT), peak intensity (PI), area under the time-intensity curve (AUC), wash-in slope (WIS) and time to peak (TTP). Based on pathological scores, CKD patients were classified into mild, and moderate to severe CKD groups. The logistic regression analysis and receiver operating characteristic (ROC) curves were used.

RESULTS

PI and AUC differed significantly among the controls, mild and moderate to severe CKD groups (P < 0.05). There was significant difference in PI among the different pathology types (P < 0.05). The multivariate logistic regression analysis showed that PI was associated independently with the severity of renal pathology in patients with CKD (P < 0.05). PI less than 13.87 dB had a certain diagnostic ability, and the sensitivity and specificity were 72.5% and 64.0%, respectively.

CONCLUSIONS

Contrast-enhanced US may be useful for noninvasive assessment of the severity of renal pathology. PI may be potentially valuable for guiding therapy and follow-up in patients with CKD.

Repeatability of Contrast-Enhanced Ultrasonography of the Kidneys in Healthy Cats

Contrast-enhanced ultrasound can be used to image and quantify tissue perfusion. It holds great potential for the use in the diagnosis of various diffuse renal diseases in both human and veterinary medicine. Nevertheless, the technique is known to have an inherent relatively high variability, related to various factors associated with the patient, the contrast agent and machine settings. Therefore, the aim of this study was to assess week-to-week intra- and inter-cat variation of several perfusion parameters obtained with CEUS of both kidneys of 12 healthy cats. Repeatability was determined by calculating the coefficient of variation (CV). The contrast-enhanced ultrasound parameters with the lowest variation for the renal cortex were time-to-peak (CV 6.0%), rise time (CV 13%), fall time (CV 19%) and mean transit time (24%). Intensity-related parameters and parameters related to the slope of the time-intensity curve had a CV of >35%. Lower repeatability was present for perfusion parameters derived from the renal medulla compared with the renal cortex. Normalization to the inter-lobar artery does not cause a reduction in variation. In conclusion, time-related parameters for the cortex show a reasonable repeatability; whereas poor repeatability is present for intensity-related parameters and parameters related to in- and outflow of contrast agent. Poor repeatability is also present for all perfusion parameters for the renal medulla, except for time to peak, which has a good repeatability.

Contrast enhanced ultrasound guided biopsies of liver lesions not visualized on standard B-mode ultrasound-preliminary experience

Background

To assess the technical success of contrast enhanced ultrasound (CEUS) guided biopsies of liver lesions poorly visualized on B-mode ultrasound.

Methods

Patients were selected during the procedure based on the real-time clinical scenario of unsatisfactory B-mode ultrasound lesion visualization and all patients would have otherwise undergone CT guided liver lesion biopsy. A total of 26 patients underwent CEUS guided biopsy and were included in this retrospective analysis. The review of the patients' files included demographic information, lesion characteristics on imaging, procedural details and pathology outcome. Technical success was defined as concordance between the radiological findings, pathology report and clinical follow-up-demonstrating lack of need for re-biopsy or re-biopsy with identical pathological results. Patients with less than 2 months follow-up were excluded from the study.

Results

CEUS guided liver biopsy was successful in 23 out of 26 patients (88.5%). The average procedure time was 30.7±12.3 minutes and the average lesion size was 2.2±1.7 cm. The majority of lesions (80.8%) were hypoenhancing on the delayed phase of CEUS. The mean number of samples taken from each lesion per procedure was 3.2 (±1.7).

Conclusions

CEUS guidance biopsies of focal liver lesions (FLL) that were difficult to visualize on B-mode ultrasound demonstrated high success rate and may be an evolving image guidance modality in selected patients to avoid CT guided procedures.

Contrast-Enhanced Ultrasound Examination for the Assessment of Renal Perfusion in Cats with Chronic Kidney Disease

Background

Contrast‐enhanced ultrasound examination (CEUS) is a functional imaging technique allowing noninvasive assessment of tissue perfusion. Studies in humans show that the technique holds great potential to be used in the diagnosis of chronic kidney disease (CKD). However, data in veterinary medicine are currently lacking.

Objectives

To evaluate renal perfusion using CEUS in cats with CKD.

Animals

Fourteen client‐owned cats with CKD and 43 healthy control cats.

Methods

Prospective case‐controlled clinical trial using CEUS to evaluate renal perfusion in cats with CKD compared to healthy control cats. Time‐intensity curves were created, and perfusion parameters were calculated using off‐line software. A linear mixed model was used to examine differences between perfusion parameters of cats with CKD and healthy cats.

Results

In cats with CKD, longer time to peak and shorter mean transit times were observed for the renal cortex. In contrast, a shorter time to peak and rise time were seen for the renal medulla. The findings for the renal cortex indicate decreased blood velocity and shorter total duration of enhancement, likely caused by increased vascular resistance in CKD. Increased blood velocity in the renal medulla has not been described before and may be because of a different response to regulatory factors in cortex and medulla.

Conclusions and Clinical Importance

Contrast‐enhanced ultrasound examination was capable of detecting perfusion changes in cats with CKD. Further research is warranted to assess the diagnostic capabilities of CEUS in early stage of the disease process.

Evaluation of Renal Perfusion in Hyperthyroid Cats before and after Radioiodine Treatment

Background

Hyperthyroidism and chronic kidney disease (CKD) are common in elderly cats. Consequently, both diseases often occur concurrently. Furthermore, renal function is affected by thyroid status. Because changes in renal perfusion play an important role in functional renal changes in hyperthyroid cats, investigation of renal perfusion may provide novel insights.

Objectives

To evaluate renal perfusion in hyperthyroid cats with contrast‐enhanced ultrasound (CEUS).

Animals

A total of 42 hyperthyroid cats was included and evaluated before and 1 month after radioiodine treatment.

Methods

Prospective intrasubject clinical trial of contrast‐enhanced ultrasound using a commercial contrast agent (SonoVue) to evaluate renal perfusion. Time‐intensity curves were created, and perfusion parameters were calculated by off‐line software. A linear mixed model was used to examine differences between pre‐ and post‐treatment perfusion parameters.

Results

An increase in several time‐related perfusion parameters was observed after radioiodine treatment, indicating a decreased blood velocity upon resolution of the hyperthyroid state. Furthermore, a small post‐treatment decrease in peak enhancement was present in the renal medulla, suggesting a lower medullary blood volume.

Conclusions and Clinical Importance

Contrast‐enhanced ultrasound indicated a higher cortical and medullary blood velocity and higher medullary blood volume in hyperthyroid cats before radioactive treatment in comparison with 1‐month post‐treatment control.

Ultrasound-Based Shear Wave Elastography in the Assessment of Patients with Diabetic Kidney Disease

In previous studies of acoustic radiation force impulse (ARFI) elastography, using Virtual Touch tissue quantification (VTQ) (Siemens Acuson S2000), it was reported that the measurement of renal shear wave speed in patients with chronic kidney disease (CKD) is not influenced exclusively by renal fibrosis. The purpose of the present study was to analyze the role of VTQ in patients with diabetic kidney disease, considered the main cause of CKD. The study group included 164 patients: 80 patients with diabetic kidney disease (DKD) and 84 without renal disease or diabetes mellitus. In each subject in lateral decubitus, five valid VTQ measurements were performed in each kidney and a median value was calculated, the result being expressed in meters/second. The following means of the median values were obtained In DKD patients, the means of the median values were for VTQ right kidney, 2.21 ± 0.71 m/s, and for VTQ left kidney, 2.13 ± 0.72 m/s, whereas in the normal controls statistically significant higher values were obtained: 2.58 ± 0.78 m/s for VTQ right kidney (p = 0.0017) and 2.46 ± 0.81 m/s for VTQ left kidney (p = 0.006). Patients with an estimated glomerular filtration rate (eGFR) >60 mL/min (DKD stages 1 and 2 together with normal controls) had a significantly higher kidney shear wave speed compared with patients with an eGFR <60 mL/min (2.53 m/s vs. 2.09 m/s, p < 0.05). In the DKD group, there was a significant correlation between eGFR and VTQ levels for the right kidney (r = 0.28, p = 0.04). There was no correlation of VTQ values with proteinuria level, stage of diabetic retinopathy or glycated hemoglobin. Our study indicates that shear wave speed values in patients with diabetic kidney disease and eGFRs <60 mL/min are significantly lower compared with those of patients with eGFRs >60 mL/min (either normal controls or diabetic patients with DKD stages 1 and 2), and values decrease with the decrease in eGFR. However, proteinuria, diabetic retinopathy and glycated hemoglobin have no influence on VTQ.

Limited Accuracy of Colour Doppler Ultrasound Dynamic Tissue Perfusion Measurement in Diabetic Adults

Dynamic tissue perfusion measurement (DTPM) is a pre-described and available method in pediatric ultrasound to quantify tissue perfusion in renal Doppler ultrasound by particular video analysis software. This study evaluates DTPM during single and between repeated visits after 6 months, calibrates repeated DTPM within different region of interest (ROI) and compares DTPM with kidney function markers in adult patients with early diabetic nephropathy (n = 17). During repeated measurements, no association of readings at the same patients in the same (n = 3 readings) as well as repeated visit (n = 2 visits) could be retrieved. No association between DTPM, MDRD-GFR, albuminuria, age and duration of diabetes was observed. These negative results are presumably related to inconsistency of DTPM due to non-fixed ROI position as could be shown in calibrating series. Further development of the method should be performed to enable reproducible DTPM readings in adults.

Assessment of renal perfusion with contrast-enhanced ultrasound: Preliminary results in early diabetic nephropathies

OBJECTIVE

We performed a prospective study to evaluate the value of contrast-enhanced ultrasound (CEUS) in quantitative evaluation of renal cortex perfusion in patients suspected of early diabetic nephropathies (DN), with the estimated GFR (MDRD equation) as the gold standard.

METHODS

The study protocol was approved by the hospital review board; each patient gave written informed consent. Our study included 46 cases (21 males and 25 females, mean age 55.6 ± 4.14 years) of clinical confirmed early DN patients. After intravenous bolus injection of 1 ml sulfur hexafluoride microbubbles of ultrasound contrast agent, real time CEUS of renal cortex was performed successively using a 2-5 MHz convex probe. Time-intensity curves (TICs) and quantitative indexes were created with Qlab software. Receiver operating characteristic (ROC) curves were used to predict the diagnostic criteria of CEUS quantitative indexes, and their diagnostic efficiencies were compared with resistance index (RI) and peak systolic velocity (PSV) of renal segmental arteries by chi square test. Our control group included forty-five healthy volunteers. Difference was considered statistically significant with P <  0.05.

RESULTS

Changes of area under curve (AUC), derived peak intensity (DPI) were statistically significant (P <  0.05). DPI less than 12 and AUC greater than 1400 had high utility in DN, with 71.7% and 67.3% sensitivity, 77.8% and 80.0% specificity. These results were significantly better than those obtained with RI and PSV which had no significant difference in early stage of DN (P > 0.05).

CONCLUSIONS

CEUS might be helpful to improve early diagnosis of DN by quantitative analyses. AUC and DPI might be valuable quantitative indexes.

Evaluation of Feline Renal Perfusion with Contrast-Enhanced Ultrasonography and Scintigraphy

Contrast-enhanced ultrasound (CEUS) is an emerging technique to evaluate tissue perfusion. Promising results have been obtained in the evaluation of renal perfusion in health and disease, both in human and veterinary medicine. Renal scintigraphy using ^99mTc-Mercaptoacetyltriglycine (MAG₃) is another non-invasive technique that can be used to evaluate renal perfusion. However, no data are available on the ability of CEUS or ^99mTc- MAG₃ scintigraphy to detect small changes in renal perfusion in cats. Therefore, both techniques were applied in a normal feline population to evaluate detection possibilities of perfusion changes by angiotensin II (AT II). Contrast-enhanced ultrasound using a bolus injection of commercially available contrast agent and renal scintigraphy using ^99mTc-MAG₃ were performed in 11 healthy cats after infusion of 0,9% NaCl (control) and AT II. Angiotensin II induced changes were noticed on several CEUS parameters. Mean peak enhancement, wash-in perfusion index and wash-out rate for the entire kidney decreased significantly after AT II infusion. Moreover, a tendency towards a lower wash-in area-under-the curve was present. Renal scintigraphy could not detect perfusion changes induced by AT II. This study shows that CEUS is able to detect changes in feline renal perfusion induced by AT II infusion.

The Natural History of Kidney Graft Cortical Microcirculation Determined by Real-Time Contrast-Enhanced Sonography (RT-CES)

Background

Kidney transplantation is the therapy of choice for end-stage kidney disease. Graft’s life span is shorter than expected due in part to the delayed diagnosis of various complications, specifically those related to silent progression. It is recognized that serum creatinine levels and proteinuria are poor markers of mild kidney lesions, which results in delayed clinical information. There are many investigation looking for early markers of graft damage. Decreasing kidney graft cortical microcirculation has been related to poor prognosis in kidney transplantation. Cortical capillary blood flow (CCBF) can be measured by real-time contrast-enhanced sonography (RT-CES). Our aim was to describe the natural history of CCBF over time under diverse conditions of kidney transplantation, to explore the influence of donor conditions and recipient events, and to determine the capacity of CCBF for predicting renal function in medium term.

Patients and Methods

RT-CES was performed in 79 consecutive kidney transplant recipients during the first year under regular clinical practice. Cortical capillary blood flow was measured. Clinical variables were analyzed. The influence of CCBF has been determined by univariate and multivariate analysis using mixed regression models based on sequential measurements for each patient over time. We used a first-order autoregression model as the structure of the covariation between measures. The post-hoc comparisons were considered using the Bonferroni correction.

Results

The CCBF values varied significantly over the study periods and were significantly lower at 48 h and day 7. Brain-death donor age and CCBF levels showed an inverse relationship (r: -0.62, p<0.001). Living donors showed higher mean CCBF levels than brain-death donors at each point in the study. These significant differences persisted at month 12 (54.5 ± 28.2 vs 33.7 ± 30 dB/sec, living vs brain-death donor, respectively, p = 0.004) despite similar serum creatinine levels (1.5 ± 0.3 and 1.5 ± 0.5 mg/dL). A sole rejection episode was associated with lower overall CCBF values over the first year. CCBF defined better than level of serum creatinine the graft function status at medium-term.

Conclusion

RT-CES is a non-invasive tool that can quantify and iteratively estimate cortical microcirculation. We have described the natural history of cortical capillary blood flow under regular clinical conditions.

Quantitative evaluation of contrast-enhanced ultrasound for differentiation of renal cell carcinoma subtypes and angiomyolipoma

PURPOSE

To investigate the value of quantitative parameters of contrast-enhanced ultrasound (CEUS) in the differentiation of subtypes of renal cell carcinoma (RCC) and angiomyolipoma (AML).

METHODS

The quantitative characteristics of 341 RCCs and 88 AMLs were analyzed with quantitative software (SonoLiver). Quantitative analysis was conducted in the whole tumor (ROItumor) and the maximum enhanced area of the tumor (ROImax), acquiring the parameters of maximum intensity (IMAX), rise time (RT), time to peak (TTP), mean transit time (mTT), and area under the curve (AUC), were derived and analyzed. The difference values between ROImax and normal renal cortex (ΔPar.s, including ΔIMAX, ΔRT, ΔTTP, ΔmTT, ΔAUC) were compared among renal histotypes.

RESULTS

All time-related parameters (including RT, TTP and mTT) of ROImax were shorter than the corresponding parameters of ROItumor in RCC subtypes (all p<0.05), but made no statistical difference in AMLs (all p>0.05). There were significant differences of all ΔPar.s among RCC subtypes and AML (all p<0.01). ΔIMAX and ΔAUC showed the trend that ccRCC>AML>pRCC=chRCC. ΔTTP showed AML=pRCC=chRCC>ccRCC, ΔRT and ΔmTT showed AML>pRCC=chRCC=ccRCC. ΔmTT could distinguish RCC from AML with the area under the ROC curve (AUC) of 0.86. The AUC of ΔIMAX and ΔAUC was 0.89 and 0.92 vs 0.85 and 0.85 for discriminating between pRCC (or chRCC) and AML vs ccRCC and AML.

CONCLUSIONS

Quantitative analysis of CEUS is a useful modality in AML and RCC subtypes' differentiation, by using ΔmTT, ΔIMAX and ΔAUC.

Papillary renal cell carcinoma and clear cell renal cell carcinoma: Differentiation of distinct histological types with contrast - enhanced ultrasonography

PURPOSE

Papillary renal cell carcinoma (pRCC) and clear cell renal cell carcinoma (ccRCC) have different biological behaviours and imaging features. The role of contrast-enhanced ultrasound (CEUS) in differentiating these two carcinoma subtypes has not been comprehensively studied.

MATERIALS AND METHODS

Forty-eight patients with 49 pRCC lesions and 153 patients with 156 ccRCC lesions underwent preoperative conventional ultrasound (US) and CEUS. Among them, 91 patients (25 pRCCs and 66 ccRCCs) also underwent preoperative contrast-enhanced computed tomography (CECT) in our hospital. The characteristics of CEUS and CECT images for each patient imaged were analysed by each of two blinded observers.

RESULTS

Images for five (5/25, 20%) pRCC patients demonstrated equivocal or no enhancement using CECT, while all lesions were enhanced using CEUS. From CEUS, images of pRCCs, when compared with ccRCC images, demonstrated significantly higher frequencies of slow wash-in (59.2% vs. 5.8%), fast wash-out (87.7% vs. 46.1%), and hypo-enhancement (57.1% vs. 7.1%) patterns, p<0.001, as well as the presence of pseudocapsule (42.9% vs. 23.1%), p=0.007. For lesions with large diameters (> 3 cm), a higher percentage of pRCC images demonstrated homogeneous enhancement compared with ccRCC images. Using the combination of slow wash-in, fast wash-out, and hypoenhancement patterns at peak as criteria to differentiate pRCC from ccRCC, positive and negative predictive value, and sensitivity and specificity were found to be 86.7%, 86.9%, 53.1%, and 97.4%, respectively.

CONCLUSIONS

CEUS imaging features of slow-in, fast-out, and hypo-enhancement patterns may be useful for differentiating pRCC and ccRCC. In addition, CEUS may be helpful for diagnosing hypovascular renal lesions that demonstrate equivocal or no enhancement by CECT and, thus, for improving diagnostic confidence.

Use of Contrast-Enhanced Ultrasound to Study Relationship between Serum Uric Acid and Renal Microvascular Perfusion in Diabetic Kidney Disease

Purpose. To investigate the relationship between uric acid and renal microvascular perfusion in diabetic kidney disease (DKD) using contrast-enhanced ultrasound (CEUS) method. Materials and Methods. 79 DKD patients and 26 healthy volunteers were enrolled. Renal function and urine protein markers were tested. DKD patients were subdivided into two groups including a normal serum uric acid (SUA) group and a high SUA group. Contrast-enhanced ultrasound (CEUS) was performed, and low acoustic power contrast-specific imaging was used for quantitative analysis. Results. Normal controls (NCs) had the highest levels of AUC, AUC1, and AUC2. Compared to the normal SUA DKD group, high SUA DKD patients had significantly higher IMAX, AUC, and AUC1 (P < 0.05). DKD patients with low urinary uric acid (UUA) excretion had significantly higher AUC2 compared to DKD patients with normal UUA (P < 0.05). Conclusion. Hyperuricemia in DKD patients was associated with a renal ultrasound image suggestive of microvascular hyperperfusion. The CEUS parameter AUC1 holds promise as an indicator for renal microvascular hyperperfusion, while AUC2 might be a useful indicator of declining glomerular filtration rate in DKD patients with decreased excretion of uric acid.

Diagnostic value of quantitative contrast-enhanced ultrasound (CEUS) for early detection of renal hyperperfusion in diabetic kidney disease

PURPOSE

To investigate the diagnostic value of quantitative contrast-enhanced ultrasound (CEUS) for early detection of renal hyperperfusion in diabetic kidney disease (DKD).

MATERIALS AND METHODS

55 DKD patients with estimated glomerular filtration rate (eGFR) >30 ml/min/1.73 m(2) and 26 normal controls (NCs) were enrolled. Clinical data was well documented. Blood samples were drawn for evaluation of renal function including blood urea nitrogen (BUN), serum creatinine (SCr) and serum uric acid (SUA), and urine samples were assayed for total protein quantification, and various microprotein markers. According to eGFR level, DKD patients were divided into early-stage DKD (eGFR ≥90 ml/min/1.73 m(2), n = 18) and middle-stage DKD (eGFR 30-90 ml/min/1.73 m(2), n = 37). Based on urinary microalbumin/creatinine ratio (MALB/UCR), early-stage DKD patients were further classified into two groups: MALB/UCR <10 g/mol (n = 11) and MALB/UCR ≥10 g/mol (n = 7). Then, CEUS was performed to observe the real-time renal perfusion, and low acoustic power contrast-specific imaging was used for quantitative analysis.

RESULTS

The renal perfusion images of CEUS were well developed successively. The corresponding perfusion curves based on echo-power signals in time series were constructed. Quantitative analysis showed that area under the descending curve (AUC2) was significantly increased in early-stage DKD compared to middle-stage DKD (p < 0.05), but AUC showed no significant difference. Further comparison between different MALB/UCR levels of early-stage DKD showed that patients with MALB/UCR ≥10 g/mol had significantly increased levels of AUC, AUC2 and proteinuria than patients with low MALB/UCR (p < 0.05). Also, high MALB/UCR DKD patients had increased proteinuria but similar eGFR compared to low MALB/UCR patients.

CONCLUSION

Renal microvascular hyperperfusion may be responsible for overt proteinuria until decline of renal filtration in DKD. AUC2 could be an early and sensitive marker for early renal injury and renal microvascular hyperperfusion in DKD.

Role of intra-operative contrast-enhanced ultrasound (CEUS) in robotic-assisted nephron-sparing surgery

This review examines studies of intra-operative contrast-enhanced ultrasound (CEUS) and its emerging role and advantages in robotic-assisted nephron-sparing surgery. Contrast-enhanced ultrasound is a technology that combines the use of second-generation contrast agents consisting of microbubbles with existent ultrasound techniques. Until now, this novel technology has aided surgeons with procedures involving the liver. However, with recent advances in the CEUS technique and the introduction of robotics in nephron-sparing surgery, CEUS has proven to be efficacious in answering several clinical questions with respect to the kidneys. In addition, the introduction of the microbubble-based contrast agents has increased the image quality and signal uptake by the ultrasound probe. This has led to better, enhanced scanning of the macro and microvasculature of the kidneys, making CEUS a powerful diagnostic modality. This imaging method is capable of further lowering the learning curve and warm ischemia time (WIT) during robotic-assisted nephron-sparing surgery, with its increased level of capillary perfusion and imaging. CEUS has the potential to increase the sensitivity and specificity of intra-operative images, and can significantly improve the outcome of robotic-assisted nephron-sparing surgery by increasing the precision and diagnostic insight of the surgeon. The purpose of this article is to review the practical and potential uses of CEUS as an intra-operative imaging technique during robotic-assisted nephron-sparing surgery.

Dynamic contrast-enhanced ultrasound for quantification of tissue perfusion

Dynamic contrast-enhanced ultrasound (US) imaging, a technique that uses microbubble contrast agents with diagnostic US, has recently been technically summarized and reviewed by a European Federation of Societies for Ultrasound in Medicine and Biology position paper. However, the practical applications of this imaging technique were not included. This article reviews and discusses the published literature on the clinical use of dynamic contrast-enhanced US. This review finds that dynamic contrast-enhanced US imaging is the most sensitive cross-sectional real-time method for measuring the perfusion of parenchymatous organs noninvasively. It can measure parenchymal perfusion and therefore can differentiate between benign and malignant tumors. The most important routine clinical role of dynamic contrast-enhanced US is the prediction of tumor responses to chemotherapy within a very short time, shorter than using Response Evaluation Criteria in Solid Tumors criteria. Other applications found include quantifying the hepatic transit time, diabetic kidneys, transplant grafts, and Crohn disease. In addition, the problems involved in using dynamic contrast-enhanced US are discussed.