Comparison of the effects of peritoneal dialysis and hemodialysis on spontaneous brain activity in CKD patients: an rs-fMRI study.

OBJECTIVE: To compare the effects of peritoneal dialysis and hemodialysis on spontaneous brain activity in patients with end-stage renal disease. METHODS: A total of 52 dialysis patients with end-stage renal disease, including 25 patients with chronic kidney disease undergoing hemodialysis (HD-CKD) and 27 patients with chronic kidney disease undergoing peritoneal dialysis (PD-CKD), and 49 healthy controls (normal control) were included. All participants underwent neuropsychological testing (Mini-Mental State Examination and Montreal cognitive assessment) and resting-state functional magnetic resonance imaging. Fractional amplitude of low frequency fluctuations and Regional Homogeneity algorithms were employed to evaluate spontaneous brain activity. Statistical analysis was performed to discern differences between the groups. RESULTS: When compared with the normal control group, the PD-CKD group exhibited significant alterations in fractional amplitude of low frequency fluctuations in various cerebellum regions and other brain areas, while the HD-CKD group showed decreased fractional amplitude of low frequency fluctuations in the bilateral pericalcarine cortex. The Regional Homogeneity values in the PD-CKD group were notably different than those in the normal control group, particularly in regions such as the bilateral caudate nucleus and the right putamen. CONCLUSION: Both peritoneal dialysis and hemodialysis modalities impact brain activity, but manifest differently in end-stage renal disease patients. Understanding these differences is crucial for optimizing patient care.

Diffusion tensor MRI is sensitive to fibrotic injury in a mouse model of oxalate-induced chronic kidney disease.

Chronic kidney disease (CKD) is characterized by inflammation and fibrosis in the kidney. Renal biopsies and estimated glomerular filtration rate (eGFR) remain the standard of care, but these endpoints have limitations in detecting the stage, progression, and spatial distribution of fibrotic pathology in the kidney. MRI diffusion tensor imaging (DTI) has emerged as a promising noninvasive technology to evaluate renal fibrosis in vivo both in clinical and preclinical studies. However, these imaging studies have not systematically identified fibrosis particularly deeper in the kidney where biopsy sampling is limited, or completed an extensive analysis of whole organ histology, blood biomarkers, and gene expression to evaluate the relative strengths and weaknesses of MRI for evaluating renal fibrosis. In this study, we performed DTI in the sodium oxalate mouse model of CKD. The DTI parameters fractional anisotropy, apparent diffusion coefficient, and axial diffusivity were compared between the control and oxalate groups with region of interest (ROI) analysis to determine changes in the cortex and medulla. In addition, voxel-based analysis (VBA) was implemented to systematically identify local regions of injury over the whole kidney. DTI parameters were found to be significantly different in the medulla by both ROI analysis and VBA, which also spatially matched with collagen III immunohistochemistry (IHC). The DTI parameters in this medullary region exhibited moderate to strong correlations with histology, blood biomarkers, hydroxyproline, and gene expression. Our results thus highlight the sensitivity of DTI to the heterogeneity of renal fibrosis and importance of whole kidney noninvasive imaging.NEW & NOTEWORTHY Chronic kidney disease (CKD) can be characterized by inflammation and fibrosis of the kidney. Although standard of care methods have been limited in scope, safety, and spatial distribution, MRI diffusion tensor imaging (DTI) has emerged as a promising noninvasive technology to evaluate renal fibrosis in vivo. In this study, we performed DTI in an oxalate mouse model of CKD to systematically identify local kidney injury. DTI parameters strongly correlated with histology, blood biomarkers, hydroxyproline, and gene expression.

Performance and Interpretation of Sonography in the Practice of Nephrology: Core Curriculum 2024.

Ultrasonography is increasingly being performed by clinicians at the point of care, and nephrologists are no exception. This Core Curriculum illustrates how ultrasonography can be incorporated into clinical decision making across the spectrum of kidney disease to optimize the care nephrologists provide to patients. Sonography is valuable in outpatient and inpatient settings for the diagnosis and management of acute and chronic kidney disease, evaluation of cystic disease, urinary obstruction, pain, hematuria, proteinuria, assessment of volume status, and in providing guidance for kidney biopsy. As kidney disease advances, ultrasound is useful in the placement and maintenance of temporary and permanent access for dialysis. After kidney transplantation, ultrasonography is critical for evaluation of allograft dysfunction and for biopsies. Sonography skills expedite patient care and enhance the practice of nephrology and are relatively easily acquired with training. It is our hope that this curriculum will encourage nephrologists to learn and apply this valuable skill.

Amide Proton Transfer-Weighted Magnetic Resonance Imaging for Application in Renal Fibrosis: A Radiological-Pathological-Based Analysis.

INTRODUCTION: Renal fibrosis (RF), being the most important pathological change in the progression of CKD, is currently assessed by the evaluation of a biopsy. This present study aimed to apply a novel functional MRI (fMRI) protocol named amide proton transfer (APT) weighting to evaluate RF noninvasively. METHODS: Male Sprague-Dawley (SD) rats were initially subjected to bilateral kidney ischemia/reperfusion injury (IRI), unilateral ureteral obstruction, and sham operation, respectively. All rats underwent APT mapping on the 7th and 14th days after operation. Besides, 26 patients underwent renal biopsy at the Nephrology Department of Shanghai Tongji Hospital between July 2022 and May 2023. Patients underwent APT and apparent diffusion coefficient (ADC) mappings within 1 week before biopsy. MRI results of both patients and rats were calculated by comparing with gold standard histology for fibrosis assessment. RESULTS: In animal models, the cortical APT (cAPT) and medullary APT (mAPT) values were positively correlated with the degree of RF. Compared to the sham group, IRI group showed significantly increased cAPT and mAPT values on the 7th and 14th days after surgery, but no group differences were found in ADC values. Similar results were found in human patients. Cortical/medullary APT values were significantly increased in patients with moderate-to-severe fibrosis than in patients with mild fibrosis. ROC curve analysis indicated that APT value displayed a better diagnostic value for RF. Furthermore, combination of cADC and cAPT improved fibrosis detection by imaging variables alone (p < 0.1). CONCLUSION: APT values had better diagnostic capability at early stage of RF compared to ADC values, and the addition of APT imaging to conventional ADC will significantly improve the diagnostic performance for predicting kidney fibrosis.

Histopathological correlations of CT-based radiomics imaging biomarkers in native kidney biopsy.

BACKGROUND: Kidney biopsy is the standard of care for the diagnosis of various kidney diseases. In particular, chronic histopathologic lesions, such as interstitial fibrosis and tubular atrophy, can provide prognostic information regarding chronic kidney disease progression. In this study, we aimed to evaluate historadiological correlations between CT-based radiomic features and chronic histologic changes in native kidney biopsies and to construct and validate a radiomics-based prediction model for chronicity grade. METHODS: We included patients aged ≥ 18 years who underwent kidney biopsy and abdominal CT scan within a week before kidney biopsy. Left kidneys were three-dimensionally segmented using a deep learning model based on the 3D Swin UNEt Transformers architecture. We additionally defined isovolumic cortical regions of interest near the lower pole of the left kidneys. Shape, first-order, and high-order texture features were extracted after resampling and kernel normalization. Correlations and diagnostic metrics between extracted features and chronic histologic lesions were examined. A machine learning-based radiomic prediction model for moderate chronicity was developed and compared according to the segmented regions of interest (ROI). RESULTS: Overall, moderate correlations with statistical significance (P < 0.05) were found between chronic histopathologic grade and top-ranked radiomic features. Total parenchymal features were more strongly correlated than cortical ROI features, and texture features were more highly ranked. However, conventional imaging markers, including kidney length, were poorly correlated. Top-ranked individual radiomic features had areas under receiver operating characteristic curves (AUCs) of 0.65 to 0.74. Developed radiomics models for moderate-to-severe chronicity achieved AUCs of 0.89 (95% confidence interval [CI] 0.75-0.99) and 0.74 (95% CI 0.52-0.93) for total parenchymal and cortical ROI features, respectively. CONCLUSION: Significant historadiological correlations were identified between CT-based radiomic features and chronic histologic changes in native kidney biopsies. Our findings underscore the potential of CT-based radiomic features and their prediction model for the non-invasive assessment of kidney fibrosis.

The value of tissue quantitative diffusion analysis of ultrasound elastography in the diagnosis of early-stage chronic kidney disease.

PURPOSE: To explore the value of tissue quantitative diffusion analysis of ultrasound elastography in the diagnosis of early-stage chronic kidney disease (CKD). METHODS: The observation group comprised 54 patients with early-stage CKD treated at Fuzhou No 7 Hospital, and the control group consisted of 40 healthy individuals who underwent physical examinations at the same hospital. The renal parenchyma of the participants were examined using ultrasonography, color Doppler ultrasonography, and tissue quantitative diffusion analysis of ultrasound elastography. Renal dimensions (diameter, thickness, and renal parenchyma thickness), interlobar artery blood flow parameters, and 11 elastic characteristic values were analyzed and compared between the two groups. The area under the receiver-operating characteristic (ROC) curve, cut-off values, sensitivity, and specificity were calculated using the ROC curve analysis. RESULTS: There were no significant differences in the blood flow parameters of the interlobar artery and the dimensions of renal meridians between the two groups. In the observation group, the mean (MEAN) decreased, while the blue area ratio and skewness, increased, compared to the control group (p < 0.05). In addition, the ROC curve revealed that the blue area ratio, MEAN, and skewness had significant diagnostic value (the area under the curve > 0.7). Notably, the best cut-off value of the MEAN was found to be 106, indicating that a MEAN value less than 106 represented early-stage CKD. Also, this cutoff value had a sensitivity of 80% and a specificity of 81%. CONCLUSION: Tissue quantitative diffusion analysis of ultrasound elastography can quantitatively evaluate renal parenchymal damage in early-stage CKD using quantitative diffusion parameters, with the MEAN parameter, having a cutoff of 106, being particularly effective. This parameter and cutoff value offer a valuable tool for the early detection and diagnosis of CKD, potentially improving patient outcomes through earlier intervention. CLINICAL TRIAL NUMBER: Not applicable.

Muscle ultrasound to diagnose sarcopenia in chronic kidney disease: a systematic review and bayesian bivariate meta-analysis.

OBJECTIVE: The aim of this systematic review was to assess the diagnostic test accuracy of muscle ultrasound for sarcopenia among chronic kidney disease (CKD) populations. BACKGROUND: Sarcopenia has become a worldwide health issue, especially for CKD patients. Conventional techniques of muscle mass assessment often prove limited, thus prompts increasing interest in ultrasound suitability. METHODS: We searched the Cochrane Library, PubMed and Embase for literature published up to June 2023. Ultrasound diagnosis of sarcopenia in CKD patients was included. Two independent investigators used the Quality Assessment Tool for Diagnosis Accuracy Studies (QUADAS-2) to assess the quality. We extracted valuable information from eligible studies. Using a Bayesian bivariate model, we pooled sensitivity and specificity values and summary receiver operating characteristic (SROC) curves. RESULTS: Five articles, involving 428 participants at various stages of CKD were included. Three studies diagnosed by the cross-sectional area (CSA) of the rectus femoris, while two others by muscle thickness (MT) and shear wave elastography (SWE) from the same muscle, separately. Overall, CSA or SWE had a pooled sensitivity of 0.95 (95% CrI, 0.80, 1.00), and the specificity was 0.73 (95% CrI, 0.55, 0.88) for diagnosing sarcopenia in CKD patients. CONCLUSIONS: Ultrasound measurements of CSA and SWE were more sensitive for diagnosing sarcopenia in the CKD population than in the general population. Ultrasound assessment from a single peripheral skeletal muscle site may serve as a rapid screening tool for identifying sarcopenic individuals within the CKD population, if a specific cut-off value could be determined.

Chronic kidney disease and its association with cerebral small vessel disease in the general older hypertensive population.

BACKGROUND: Cerebral small vessel disease can be identified using magnetic resonance imaging, and includes white matter hyperintensities, lacunar infarcts, cerebral microbleeds, and brain atrophy. Cerebral small vessel disease and chronic kidney disease share many risk factors, including hypertension. This study aims to explore an association between chronic kidney disease and cerebral small vessel disease, and also to explore the role of hypertension in this relationship. METHODS: With a cross sectional study design, data from 390 older adults was retrieved from the general population study Good Aging in Skåne. Chronic kidney disease was defined as glomerular filtration rate < 60 ml/min/1,73m2. Associations between chronic kidney disease and magnetic resonance imaging markers of cerebral small vessel disease were explored using logistic regression models adjusted for age and sex. In a secondary analysis, the same calculations were performed with the study sample stratified based on hypertension status. RESULTS: In the whole group, adjusted for age and sex, chronic kidney disease was not associated with any markers of cerebral small vessel disease. After stratification by hypertension status and adjusted for age and sex, we observed that chronic kidney disease was associated with cerebral microbleeds (OR 1.93, CI 1.04-3.59, p-value 0.037), as well as with cortical atrophy (OR 2.45, CI 1.34-4.48, p-value 0.004) only in the hypertensive group. In the non-hypertensive group, no associations were observed. CONCLUSIONS: In this exploratory cross-sectional study, we observed that chronic kidney disease was associated with markers of cerebral small vessel disease only in the hypertensive subgroup of a general population of older adults. This might indicate that hypertension is an important link between chronic kidney disease and cerebral small vessel disease. Further studies investigating the relationship between CKD, CSVD, and hypertension are warranted.

Chest CT radiomics is feasible in evaluating bone changes in chronic kidney diseases.

BACKGROUND: Non-invasive imaging methods are still lacking for evaluating bone changes in chronic kidney diseases (CKD). PURPOSE: To investigate the feasibility of chest CT radiomics in evaluating bone changes caused by CKD. MATERIAL AND METHODS: In total, 75 patients with stage 1 CKD (CKD1) and 75 with stage 5 CKD (CKD5) were assessed using the chest CT radiomics method. Radiomics features of bone were obtained using 3D Slicer software and were then compared between CKD1 and CKD5 cases. The methods of maximum correlation minimum redundancy (mRMR) and least absolute shrinkage and selection operator (LASSO) were used to establish a prediction model to determine CKD. The receiver operating characteristic (ROC) curve was used to determine the performance of the model. RESULTS: Cases of CKD1 and CKD5 differed in 40 radiomics features (P <0.05). Using the mRMR and LASSO methods, five features were finally selected to establish a predication model. The area under the receiver operating characteristic curve of the model in the determination of CKD1 and CKD5 was 0.903 and 0.854, respectively, for the training and validation cohorts. CONCLUSION: Chest CT radiomics is feasible in evaluating bone changes caused by CKD.

Skeletal Muscle Texture Assessment Using Ultrasonography: Comparison with Magnetic Resonance Imaging in Chronic Kidney Disease.

Skeletal muscle dysfunction is common in chronic kidney disease (CKD). Of interest is the concept of "muscle quality," of which measures include ultrasound-derived echo intensity (EI). Alternative parameters of muscle texture, for example, gray level of co-occurrence matrix (GCLM), are available and may circumvent limitations in EI. The validity of EI is limited in humans, particularly in chronic diseases. This study aimed to investigate the associations between ultrasound-derived parameters of muscle texture with MRI. Images of the thigh were acquired using a 3 Tesla MRI scanner. Quantification of muscle (contractile), fat (non-contractile), and miscellaneous (connective tissue, fascia) components were estimated. Anatomical rectus femoris cross-sectional area was measured using B-mode 2D ultrasonography. To assess muscle texture, first (i.e., EI)- and second (i.e., GLCM)-order statistical analyses were performed. Fourteen participants with CKD were included (age: 58.0 ± 11.9 years, 50% male, eGFR: 27.0 ± 7.4 ml/min/1.73m2, 55% Stage 4). Higher EI was associated with lower muscle % (quadriceps: ß = -.568, p = .034; hamstrings: ß = -.644, p = .010). Higher EI was associated with a higher fat % in the hamstrings (ß = -.626, p = .017). A higher angular second moment from GLCM analysis was associated with greater muscle % (ß = .570, p = .033) and lower fat % (ß = -.534, p = .049). A higher inverse difference moment was associated with greater muscle % (ß = .610, p = .021 and lower fat % (ß = -.599, p = .024). This is the first study to investigate the associations between ultrasound-derived parameters of muscle texture with MRI. Our preliminary findings suggest ultrasound-derived texture analysis provides a novel indicator of reduced skeletal muscle % and thus increased intramuscular fat.

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

BACKGROUND: This study aims to evaluate the clinical application value of ultrasound viscoelastic imaging in noninvasive quantitative assessment of chronic kidney disease (CKD). METHODS: A total of 332 patients with CKD and 190 healthy adults as a control group were prospectively enrolled. Before kidney biopsy, ultrasound viscoelastic imaging was performed to measure the mean stiffness value (Emean), mean viscosity coefficient (Vmean), and mean dispersion coefficient (Dmean) of the renal. CKD patients were divided into three groups based on estimated glomerular filtration rate. The differences in clinic, pathology, ultrasound image parameters between the control and patient groups, or among different CKD groups were compared. The correlation between viscoelastic parameters and pathology were analyzed. RESULTS: Emean, Vmean, and Dmean in the control group were less than the CKD group (p < 0.05). In the identification of CKD from control groups, the area under curve of Vmean, Dmean, Emean, and combining the three parameters is 0.90, 0.79, 0.69, 0.91, respectively. Dmean and Vmean were increased with the decline of renal function (p < 0.05). Vmean and Dmean were positively correlated with white blood cell, urea, serum creatinine, and uric acid (p < 0.05). Vmean is positively correlated with interstitial fibrosis and inflammatory cell infiltration grades (p < 0.001). CONCLUSIONS: Ultrasound viscoelastic imaging has advantages in noninvasive quantitative identification and evaluating renal function of CKD. Emean > 6.61 kPa, Vmean > 1.86 Pa·s, or Dmean > 7.51 m/s/kHz may suggest renal dysfunction. Combining Vmean, Dmean, and Emean can improve the efficiency of identifying CKD.

Renal stiffness measured by shear wave elastography and its relationship with perirenal fat in patients with chronic kidney disease.

PURPOSE: This study aimed to utilize shear wave elastography (SWE) to assess changes in renal stiffness and its influencing factors in patients with chronic kidney disease (CKD) across different estimated glomerular filtration rate (eGFR) categories. It also sought to determine the correlation between perirenal fat (PF) and renal stiffness at various stages of CKD. METHODS: A total of 190 CKD patients and 50 healthy controls were evaluated. Clinical parameters, conventional renal ultrasound measurements, PF, and renal stiffness trends were assessed separately. Factors independently associated with renal stiffness and PF were further analyzed. RESULTS: Renal parenchymal stiffness was significantly higher in the Albumin-CKD G1-2 (ALB-CKD G1-2) and CKD G3 groups than in the control group (p < 0.05). The parenchymal stiffness of the CKD G3 group was higher than that of the ALB-CKD G1-2 group (p < 0.05). The independent factors of renal parenchymal stiffness varied at different stages of disease development, with eGFR and PF being significant factors in the CKD G3 group. PF was elevated in the ALB-CKD G1-2 and CKD G3 groups compared to the control group, and the independent factors of PF varied across different stages, although waist circumference remained a common factor. CONCLUSION: Using SWE to detect renal elastic moduli can effectively assess changes in renal stiffness in patients with CKD with varying eGFRs. PF is an independent factor of renal stiffness in patients with CKD G3, providing a foundation for early diagnosis and clinical treatment.

Ultrasound localization microscopy of the human kidney allograft on a clinical ultrasound scanner.

Chronic kidney disease is a major medical problem, causing more than a million deaths each year worldwide. Peripheral kidney microvascular damage characterizes most chronic kidney diseases, yet noninvasive and quantitative diagnostic tools to measure this are lacking. Ultrasound Localization Microscopy (ULM) can assess tissue microvasculature with unprecedented resolution. Here, we optimized methods on 35 kidney transplants and studied the feasibility of ULM in seven human kidney allografts with a standard low frame rate ultrasound scanner to access microvascular damage. Interlobar, arcuate, cortical radial vessels, and part of the medullary organization were visible on ULM density maps. The medullary vasa recta can be seen but are not as clear as the cortical vessels. Acquisition parameters were derived from Contrast-Enhanced Ultrasound examinations by increasing the duration of the recorded clip at the same plane. ULM images were compared with Color Doppler, Advanced Dynamic Flow, and Superb Microvascular Imaging with a contrast agent. Despite some additional limitations due to movement and saturation artifacts, ULM identified vessels two to four times thinner compared with Doppler modes. The mean ULM smallest analyzable vessel cross section was 0.3 ± 0.2 mm in the seven patients. Additionally, ULM was able to provide quantitative information on blood velocities in the cortical area. Thus, this proof-of-concept study has shown ULM to be a promising imaging technique for qualitative and quantitative microvascular assessment. Imaging native kidneys in patients with kidney diseases will be needed to identify their ULM biomarkers.

Characterization of renal fibrosis in rats with chronic kidney disease by in vivo tomoelastography.

Chronic kidney disease (CKD) is characterized by structural changes, such as tubular atrophy, renal fibrosis, and glomerulosclerosis, all of which affect the viscoelastic properties of biological tissues. However, detection of renal viscoelasticity changes because diagnostic markers by in vivo elastography lack histopathological validation through animal models. Therefore, we investigated in vivo multiparametric magnetic resonance imaging (mp-MRI), including multifrequency magnetic resonance elastography-based tomoelastography, in the kidneys of 10 rats with adenine-induced CKD and eight healthy controls. Kidney volume (in mm3 ), water diffusivity (apparent diffusion coefficient [ADC] in mm2 /s), shear wave speed (SWS; in m/s; related to stiffness), and wave penetration rate (PR; in m/s; related to inverse viscosity) were quantified by mp-MRI and correlated with histopathologically determined renal fibrosis (collagen area fraction [CAF]; in %). Kidney volume (40% ± 29%, p = 0.009), SWS (11% ± 12%, p = 0.016), and PR (20% ± 15%, p = 0.004) were significantly increased in CKD, which was accompanied by ADC (-24% ± 27%, p = 0.02). SWS, PR, and ADC were correlated with CAF with R = 0.63, 0.75, and -0.5 (all p < 0.05), respectively. In the CKD rats, histopathology showed tubule dilation due to adenine crystal deposition. Collectively, our results suggest that collagen accumulation during CKD progression transforms soft-compliant renal tissue into a more rigid-solid state with reduced water mobility. We hypothesized that tubule dilation-a specific feature of our model-might lead to higher intraluminal pressure, which could also contribute to elevated renal stiffness. Tomoelastography is a promising tool for noninvasively assessing disease progression, detecting biomechanical properties that are sensitive to different pathologic features of CKD.

Fibrosis imaging with multiparametric proton and sodium MRI in pig injury models.

Chronic kidney disease (CKD) is common and has huge implications for health and mortality. It is aggravated by intrarenal fibrosis, but the assessment of fibrosis is limited to kidney biopsies, which carry a risk of complications and sampling errors. This calls for a noninvasive modality for diagnosing and staging intrarenal fibrosis. The current, exploratory study evaluates a multiparametric MRI protocol including sodium imaging (23 Na-MRI) to determine the opportunities within this modality to assess kidney injury as a surrogate endpoint of fibrosis. The study includes 43 pigs exposed to ischemia-reperfusion injury (IRI) or unilateral ureteral obstruction (UUO), or serving as healthy controls. Fibrosis was determined using gene expression analysis of collagen. The medulla/cortex ratio of 23 Na-MRI decreased in the injured kidney in the IRI pigs, but not in the UUO pigs (p = 0.0180, p = 0.0754). To assess the combination of MRI parameters in estimating fibrosis, we created a linear regression model consisting of the cortical apparent diffusion coefficient, ΔR2*, ΔT1, the 23 Na medulla/cortex ratio, and plasma creatinine (R2  = 0.8009, p = 0.0117). The 23 Na medulla/cortex ratio only slightly improved the fibrosis prediction model, leaving 23 Na-MRI in an ambiguous place for evaluation of intrarenal fibrosis. Use of multiparametric MRI in combination with plasma creatinine shows potential for the estimation of fibrosis in human kidney disease, but more translational and clinical work is warranted before MRI can contribute to earlier diagnosis and evaluation of treatment for acute kidney injury and CKD.

Exploration of Interstitial Fibrosis in Chronic Kidney Disease by Diffusion-Relaxation Correlation Spectrum MR Imaging: A Preliminary Study.

BACKGROUND: Renal interstitial fibrosis is one of the most common pathways in the progression of chronic kidney disease (CKD). Noninvasive evaluation of interstitial fibrosis would help monitoring CKD progression and prognosis prediction. PURPOSE: To evaluate the severity of renal interstitial fibrosis by diffusion-relaxation correlation spectrum imaging (DR-CSI). STUDY TYPE: Prospective. SUBJECTS: Forty patients with CKD and 10 healthy controls (average age 49.2 ± 14.8 years, 18 females). FIELD STRENGTH/SEQUENCE: 3-T, DR-CSI with 36 axial spin-echo echo-planar diffusion-weighted images (6 b-values, 6 echo times). ASSESSMENT: Interstitial fibrosis level (IFL) was assessed from biopsy results (IFL = 1, fibrosis percentage <25%, defined as mild; IFL = 2, 25%-50%, moderate; IFL = 3, >50%, severe). Estimated glomerular filtration rate (eGFR) was calculated using serum creatinine. The regions of interest included cortex for both kidneys. The diffusivity-T2 spectrum was assessed considering three compartments (threshold: T2 30-40 msec, diffusivity 5-9 µm2 /msec, according to visible peaks): A (low diffusivity, short T2), B (low diffusivity, long T2), and C (high diffusivity). Volume fractions Vi (i = A, B, C) were calculated. STATISTICAL TESTS: Intra-class coefficient (ICC, >0.6 as good) to assess inter-reader agreement of DR-CSI Vi . Spearman's correlation to assess relationship of Vi to IFL and eGFR. Receiver operating characteristic analyses with the area under the curve (AUC) to discriminate patients with moderate-severe fibrosis from mild ones. Statistical significance criteria: P-value <0.05. RESULTS: ICCs were good for all Vi . Correlations were found between IFL and VB (r = 0.424, significant) and VC (r = -0.400, significant), and between eGFR and VB (r = -0.303, P = 0.058) and VC (r = 0.487, significant). Regarding VB and VC , the AUCs were 0.903 and 0.824. DATA CONCLUSION: DR-CSI help distinguish patients with moderate or severe renal interstitial fibrosis from mild ones. EVIDENCE LEVEL: 2 Technical Efficacy: Stage 2.

Diagnostic accuracy of ultrasound-based multimodal radiomics modeling for fibrosis detection in chronic kidney disease.

OBJECTIVES: To predict kidney fibrosis in patients with chronic kidney disease using radiomics of two-dimensional ultrasound (B-mode) and Sound Touch Elastography (STE) images in combination with clinical features. METHODS: The Mindray Resona 7 ultrasonic diagnostic apparatus with SC5-1U convex array probe (bandwidth frequency of 1-5 MHz) was used to perform two-dimensional ultrasound and STE software. The severity of cortical tubulointerstitial fibrosis was divided into three grades: mild interstitial fibrosis and tubular atrophy (IFTA), fibrotic area < 25%; moderate IFTA, fibrotic area 26-50%; and severe IFTA, fibrotic area > 50%. After extracting radiomics from B-mode and STE images in these patients, we analyzed two classification schemes: mild versus moderate-to-severe IFTA, and mild-to-moderate versus severe IFTA. A nomogram was constructed based on multiple logistic regression analyses, combining clinical and radiomics. The performance of the nomogram for differentiation was evaluated using receiver operating characteristic (ROC), calibration, and decision curves. RESULTS: A total of 150 patients undergoing kidney biopsy were enrolled (mild IFTA: n = 74; moderate IFTA: n = 33; severe IFTA: n = 43) and randomized into training (n = 105) and validation cohorts (n = 45). To differentiate between mild and moderate-to-severe IFTA, a nomogram incorporating STE radiomics, albumin, and estimated glomerular filtration (eGFR) rate achieved an area under the ROC curve (AUC) of 0.91 (95% confidence interval [CI]: 0.85-0.97) and 0.85 (95% CI: 0.77-0.98) in the training and validation cohorts, respectively. Between mild-to-moderate and severe IFTA, the nomogram incorporating B-mode and STE radiomics features, age, and eGFR achieved an AUC of 0.93 (95% CI: 0.89-0.98) and 0.83 (95% CI: 0.70-0.95) in the training and validation cohorts, respectively. Finally, we performed a decision curve analysis and found that the nomogram using both radiomics and clinical features exhibited better predictability than any other model (DeLong test, p < 0.05 for the training and validation cohorts). CONCLUSION: A nomogram based on two-dimensional ultrasound and STE radiomics and clinical features served as a non-invasive tool capable of differentiating kidney fibrosis of different severities. KEY POINTS: • Radiomics calculated based on the ultrasound imaging may be used to predict the severities of kidney fibrosis. • Radiomics may be used to identify clinical features associated with the progression of tubulointerstitial fibrosis in patients with CKD. • Non-invasive ultrasound imaging-based radiomics method with accuracy aids in detecting renal fibrosis with different IFTA severities.

Utility of shear wave-based ultrasound elastography in chronic kidney disease and related pathological quantitative analysis.

OBJECTIVES: The purpose of this study was to investigate the effects of tissue fibrosis and microvessel density on shear wave-based ultrasound elastography (SWUE) of chronic kidney disease (CKD). In addition, we were looking to see whether SWUE could predict stage of CKD, correlating with the histology on kidney biopsy. METHODS: Renal tissue sections from 54 patients diagnosed with suspected CKD were subjected to immunohistochemistry (CD31 and CD34), and the degree of tissue fibrosis was assessed using Masson staining. Before renal puncture, both kidneys were examined using SWUE. Comparative analysis was used to assess the correlation between SWUE and microvessel density, and between SWUE and the degree of fibrosis. RESULTS: Fibrosis area according to Masson staining (p < 0.05) and integrated optical density (IOD) (p < 0.05) were positively correlated with CKD stage. The percentage of positive area (PPA) and IOD for CD31 and CD34 were not correlated with CKD stage (p > 0.05). When stage 1 CKD was removed, PPA and IOD for CD34 were negatively correlated with CKD stage (p < 0.05). Masson staining fibrosis area and IOD were not correlated with SWUE (p > 0.05), PPA and IOD for CD31 and CD34 were not correlated with SWUE (p > 0.05) and, finally, no correlation between SWUE and CKD stage was found (p > 0.05). CONCLUSION: The diagnostic value of SWUE for CKD staging was very low. The utility of SWUE in CKD was affected by many factors and its diagnostic value was limited. KEY POINTS: • There was no correlation between SWUE and the degree of fibrosis, or between SWUE and microvessel density among patients with CKD. • There was no correlation between SWUE and CKD stage and the diagnostic value of SWUE for CKD staging was very low. • The utility of SWUE in CKD is affected by many factors and its value was limited.

Capability of arterial spin labeling and intravoxel incoherent motion diffusion-weighted imaging to detect early kidney injury in chronic kidney disease.

OBJECTIVES: To prospectively investigate the capability of arterial spin labeling (ASL) and intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) for the identification of early kidney injury in chronic kidney disease (CKD) patients with normal estimated glomerular filtration rate (eGFR). METHODS: Fifty-four CKD patients confirmed by renal biopsy (normal eGFR group [eGFR ≥ 90 mL/min/1.73 m2]: n = 26; abnormal eGFR group [eGFR < 90 mL/min/1.73 m2]: n = 28) and 20 healthy volunteers (HV) were recruited. All subjects were examined by IVIM-DWI and ASL imaging. Renal blood flow (RBF) derived from ASL, true diffusion coefficient (D), pseudo-diffusion coefficient (D*), and perfusion fraction (f) derived from IVIM-DWI were measured from the renal cortex. One-way analysis of variance was used to compare MRI parameters among the three groups. The correlation between eGFR and MRI parameters was evaluated by Spearman correlation analysis. Diagnostic performances of MRI parameters for detecting kidney injury were assessed by receiver operating characteristic (ROC) curves. RESULTS: The renal cortical D, D*, f, and RBF values showed statistically significant differences among the three groups. eGFR was positively correlated with MRI parameters (D: r = 0.299, D*: r = 0.569, f: r = 0.733, RBF: r = 0.586). The areas under the curve (AUCs) for discriminating CKD patients from HV were 0.725, 0.752, 0.947, and 0.884 by D, D*, f, and RBF, respectively. D, D*, f, RBF, and eGFR identified CKD patients with normal eGFR with AUCs of 0.735, 0.612, 0.917, 0.827, and 0.733, respectively, and AUC of f value was significantly larger than that of eGFR. CONCLUSION: IVIM-DWI and ASL were useful for detecting underlying pathologic injury in early CKD patients with normal eGFR. KEY POINTS: • The renal cortical f and RBF values in the control group were significantly higher than those in the normal eGFR group. • A negative correlation was observed between the renal cortical D, D*, f, and RBF values and SCr and 24 h-UPRO, while eGFR was significantly positively correlated with renal cortical D, D*, f, and RBF values. • The AUC of renal cortical f values was statistically larger than that of eGFR for the discrimination between the CKD with normal eGFR group and the control group.

Evaluation of interstitial fibrosis in chronic kidney disease by multiparametric functional MRI and histopathologic analysis.

OBJECTIVES: To investigate the diagnostic value of functional MRI to assess renal interstitial fibrosis in patients with chronic kidney disease (CKD). METHODS: We prospectively recruited 80 CKD patients who underwent renal biopsies and 16 healthy volunteers to undergo multiparametric functional MRI examinations. The Oxford MEST-C classification was used to score the interstitial fibrosis. The diagnostic performance of functional MRI to discriminate interstitial fibrosis was evaluated by calculating the area under the receiver operating characteristic (ROC) curves. RESULTS: IgA nephropathy (60%) accounted for the majority of pathologic type in the CKD patients. Apparent diffusion coefficient (ADC) from diffusion-weighted imaging (DWI) was correlated with interstitial fibrosis (rho = -0.73). Decreased renal blood flow (RBF) derived from arterial spin labeling (rho = -0.78) and decreased perfusion fraction (f) derived from DWI (rho = -0.70) were accompanied by increased interstitial fibrosis. The T1 value from T1 mapping correlated with interstitial fibrosis (rho = 0.67) (all p < 0.01). The areas under the ROC curve for the discrimination of ≤ 25% vs. > 25% and ≤ 50% vs. > 50% interstitial fibrosis were 0.87 (95% confidence interval, 0.78 to 0.94) and 0.93 (0.86 to 0.98) by ADC, 0.84 (0.74 to 0.91) and 0.94 (0.86 to 0.98) by f, 0.93 (0.85 to 0.98) and 0.90 (0.82 to 0.96) by RBF, and 0.91 (0.83 to 0.96) and 0.77 (0.66 to 0.85) by T1, respectively. CONCLUSIONS: Functional MRI parameters were strongly correlated with the interstitial fibrosis of CKD. Therefore, it might a powerful tool to assess interstitial fibrosis of CKD noninvasively. KEY POINTS: • In CKD patients, the renal cortical ADC value decreased and T1 value increased significantly compared with healthy volunteers. • Functional MRI revealed significantly decreased renal perfusion in CKD patients compared with healthy volunteers. • The renal cortical ADC, f, RBF, and T1 values were strongly correlated with the interstitial fibrosis of CKD.