Renal Magnetic Resonance Imaging Research Articles

#2955 Incidental findings in a renal magnetic resonance imaging study for evaluation of chronic kidney disease in type 2 diabetes population

Abstract Background and Aims Novel Magnetic Resonance Imaging (MRI) techniques are potential methods to non-invasively assess and quantify functional, structural and pathophysiological changes in chronic kidney disease (CKD) that may improve diagnosis, prognosis and treatment of these patients. Advances in imaging techniques are also likely to result in the detection of unexpected and asymptomatic incidental findings. We retrospectively analyzed the overall prevalence of incidental findings in the participants of our previously reported study utilizing a non-contrast multiparametric MRI protocol in patients with type 2 DM (T2DM) as compared to healthy controls. Method The subjects of this sub-study were participants of our original prospective, single-center, observational study, in which several MRI biomarkers were evaluated to differentiate diabetic versus healthy kidneys, and various stages of CKD. A complete medical history and physical examination were performed. The inclusion criteria for the T2DM cohort were: Age 18-70 years, type II DM with CKD staged 3-4 (estimated glomerular filtration rate [eGFR] 15-60 ml/min/1.73 m2, body mass index (BMI) 18-35 and provision of written informed consent. The control group comprised of healthy volunteers who were age- and sex-matched and had the following inclusion criteria: Age 18-70 years, eGFR >80 ml/min/1.73 m2, UACR <30 mmol/g, BMI 18-35 and provision of written informed consent. Exclusion criteria for the diabetic group were any apparent cause/s of CKD other than diabetes, previous kidney transplantation, pregnancy, contraindication for MRI examination, heart failure (NYHA class III or IV), allergies to iodine-based contrast agents. Factors that excluded healthy participants were pregnancy, contraindication for MRI examination, allergy to iodine-based contrast agents and any active or chronic disease/diagnosis. Measured GFR (mGFR) was assessed in all participants using iohexol clearance. An MRI scan using a wide range of non-contrast techniques was performed at baseline. Total scan time for patients did not exceed 45 min per session and no gadolinium-based contrast agents were used in any of the MRI examinations. All patients with incidental findings on MRI were further evaluated and referred to appropriate specialists for management. Results A total of 38 T2DM patients with CKD and 20 age- and gender-matched healthy volunteers who completed the study were included in the analysis. Of the T2DM patients, 2 were found to have CKD stage 2 by mGFR and 36 CKD stages 3–4. Clinically significant incidental findings (excluding 4 cases of renal cysts requiring only follow-up without further intervention) were found in 13 of the 38 (34%) T2DM patients. The most frequent findings were intraductal papillary mucinous neoplasm (IPMN) in 7 patients, followed by 3 cancers (1 case of kidney cancer, 1 bladder cancer and 1 lymphoma) and 3 cases of adrenal gland mass later diagnosed to be benign adenoma on further investigation. In contrast, of the 20 healthy volunteers, 2 (10%) were found to have significant incidental findings, which were IPMN in both. The follow-up duration varied between 2-6 years. The patient with bladder cancer had metastatic disease and died shortly after the diagnosis, the one with kidney cancer is under observation and the one with lymphoma underwent adequate treatment and is under remission. The cases of IPMN are being followed up regularly at our surgical department. Conclusion Clinically important incidental findings on renal MRI appear to be more common in T2DM patients than in healthy volunteers, which would have been missed without MRI examination. Mechanisms for reporting and strategies for dealing with incidental findings need to be taken into account in such investigational imaging studies. The detection of incidental findings also poses various practical and ethical issues. Further larger studies with long-term follow-up are needed to delineate the clinical relevance, natural course and management of such incidental findings.

#1232 Integrating genotype and phenotype data is required for renal survival prediction in autosomal dominant polycystic kidney disease

Abstract Background and Aims Autosomal dominant polycystic kidney disease (ADPKD) is the cause for 5-10% of end stage kidney disease (ESKD) worldwide. Accurate renal prognosis is essential for effective disease management. Investigation of the prognostic value of combining genetic and phenotypic characteristics in a cohort of ADPKD patients is attempted. Method In 66 ADPKD patients (mean age 33 ± 12 years, 32 males) the genetic diagnosis (using targeted Next Generation, tNGS, or Sanger Sequencing or Multiplex ligation-dependent probe amplification, MLPA) and the Mayo Clinic Imaging Category (MCIC) (through Renal Magnetic Resonance Imaging, MRI, for Total Kidney Volume measurement) were assessed. The prediction of ESKD was performed using the Mayo Clinic formula (Irazabal MV et al JASN, 2015). The calculation incorporated variables such as sex, age, e-GFR, and the MCIC. The PROPKD score was derived by considering both phenotypic factors (sex, hypertension and urologic events before the age of 35 years) and genetic data (PKD1-truncating, PKD1-nontruncating and PKD2). Results Adjusted for age, the e-GFR was on average, 26 and 27 ml/min higher in PKD2 patients compared to ADPKD-PKD1-truncating and ADPKD-PKD1-non-truncating patients, respectively (p = 0.001). The median prediction of ESKD for ADPKD-PKD1-truncating, ADPKD-PKD1-non-truncating and PKD2 patients was 22 (11-31) years, 22 (11-34) years and 31 (21-59) years, respectively (NS). In patients categorized as high risk according to PROPKD (score 7-9) the predicted time to ESKD was 16 (9-30) years, for those at intermediate risk (score 4-6), 25 (13-34) years and for those at low risk (score 0-3), 28 (16-55) years (NS). Finally, the PROPKD score showed an inverse correlation to the years of ESKD prediction, as determined by the Mayo Clinic formula; a higher PROPKD score was associated with a shorter prediction period for ESKD (Spearman r = −0.3, p = 0.04). Conclusion Prognosis of renal survival in ADPKD patients requires not only a specific genetic diagnosis but also consideration of the phenotypic data, as incorporated in the PROPKD score, enhancing the accuracy of renal survival prediction.

#1040 Correlation of genotype to disease onset age and hypertension diagnosis in autosomal dominant polycystic kidney disease

Abstract Background and Aims Autosomal Dominant Polycystic Kidney Disease (ADPKD) is the predominant genetic disease leading to End Stage Kidney Disease (ESKD). Genetic identity could correlate to the disease profile. Correlations between genetic and phenotype characteristics in a cohort of ADPKD patients are investigated. Method Genetic analysis was conducted in 85 patients with an ADPKD phenotype, employing targeted Next Generation (tNGS) or Sanger Sequencing and Multiplex ligation-dependent probe amplification (MLPA). Medical history, clinical and laboratory data, including Renal Magnetic Resonance Imaging (MRI) for Total Kidney Volume (TKV) measurement (in 66 patients), were recorded and subsequently correlated to the respective genotypes. Results Eighty-five patients (43 females, 42 males, 33 ± 16 years old) were included in the study. The mean age at diagnosis of the disease was at 21.5 ± 13 (0.6-69) years. Fifty-eight out of 85 patients (68%) had a familial history of ADPKD. The mean age at which the affected parent reached ESKD was 53.0 ± 9 years. Hypertension was diagnosed in 60 individuals (71%) within the study cohort. The mean age at hypertension diagnosis was 31 ± 11 years. In the assessment based on height-adjusted TKV and age, the Mayo Clinic Imaging Categories revealed that 9% of patients were classified as 1A, 20% as 1B, 29% as 1C, 29% as 1D, and 13% as 1E. Mutations in PKD1 gene were detected in 70 patients (82%), with 61% exhibiting truncating mutations and 39% non-truncating mutations, while PKD2 mutations were identified in 15 patients (18%). The average age of ADPKD diagnosis differed among genetic subgroups. Patients carrying PKD1-truncating mutations were diagnosed at 17.6 ± 11 years, those with PKD1-non-truncating mutations at 24.5 ± 12 years, and those with PKD2 mutations at 27.3 ± 16 years (p = 0.01). Moreover, the mean age at which the affected parent reached ESKD was 50 ± 8 years, 55 ± 10 and 60 ± 7 years in PKD1-truncating, PKD1-non-truncating and PKD2 patients respectively (p = 0.04). Additionally, the mean age of hypertension diagnosis was 29 ± 12 years in PKD1-truncating, 30 ± 10 years in PKD1-non-truncating and 40 ± 7 years in PKD2 patients (p = 0.05). Conclusion Mutation type correlates with the age of ADPKD diagnosis, the renal survival within families and the hypertension onset. Patients with PKD1-truncating mutations manifest an earlier onset of both the disease and hypertension compared to those with PKD2 gene mutations.

#2242 mTORi: edging closer to targeted therapy in tuberous sclerosis complex

Abstract Background and Aims Tuberous sclerosis complex (TSC) is an autosomal dominant condition with an estimated incidence of 1 in 6000 births. TSC is caused mostly by mutations in either TSC1 or TSC2 genes, with 70–80% of cases resulting from sporadic mutations; however in 10-15% of cases no mutations are identified. A dysregulation of these genes that encode the hamartin and tuberin proteins, respectively, results in an aberrant signaling of the mammalian target of the rapamycin (mTOR) pathway and subsequent tumor growth. Indeed, the clinical features of TSC are characterized by the proliferation of different types of hamartomas in various organs, including brain, heart, skin, lungs, eyes, bone, kidneys and less frequently pancreas. TSC is mainly diagnosed clinically according to diagnostic criteria with genetic testing performed in cases of diagnostic uncertainty or/and to support the clinic diagnosis. Renal angiomyolipomas (AMLs), observed in more than 80% of patients with TSC, are benign, mostly bilateral tumors, composed of immature smooth muscle cells, abnormal blood vessels and fat cells in variable portions. Their size and the prevalence of their vascular component are directly associated with risk of acute bleeding that in 25% of cases may require embolization or nephrectomy. As a consequence, renal complications are the leading cause of death in adult TSC patients and AML-related surgery is performed in a high percentage of these patients. In the last decade, mTOR inhibitor (mTOR-i) therapy has demonstrated to be a potential alternative to embolization and nephrectomy for managing TSC-AML. The aim of this study was to evaluate over time, potential changes in the relative tissue composition of renal AMLs and their overall size following the initiation of mTOR-i therapy based on MRI measurements. Method From August 2011 to May 2023, 86 potentially eligible adult TSC patients with AML, across a great part of Italy were referred for assessment and monitoring at our center. 14 of these patients were eligible for mTOR-i therapy. An ethics committee approved its use as a compassionate therapy as mTOR-is are not approved as a conventional therapy for renal AMLs in Italy. These patients underwent baseline renal magnetic resonance imaging (MRI) assessment and a regular follow-up with MRI scan every 6-9 months after initiation of therapy. Dose titration was guided by trough levels, side effects and lesion radiological responsiveness on MRI. Results No AML bleeding events were documented during the study. None of the 14 patients on treatment discontinued therapy. Overall, 5 of them (35.7%) required dose adjustments during the course of treatment due to adverse events (40%), sub-optimal trough levels (40%) or minimal radiological response (20%). Radiologic assessment with MRI confirmed a halted growth trend in all treatment-naive cases (100%) and in 64% of them, a regression in AML volume and a reduction of their vascular component within the first year of treatment. Conclusion Our experience confirmed results that emerged from different clinical studies evaluating mTOR inhibition in TSC patients conducted in the last decade. For renal angiomyolipoma, mTOR-i treatment, carefully monitored, fundamentally changed the approach from preventive embolization or even partial nephrectomy to pharmacological treatment; drastically limiting the number of urgent interventional procedures that TSC patients often might undergo. In conclusion, mTOR-i therapy represents a valid and important therapeutic strategy to arrest the growth or regress of renal AMLs.

Differentiating mixed epithelial and stromal tumor family from predominantly cystic renal cell carcinoma using magnetic resonance imaging-based Bosniak classification system version 2019.

To differentiate mixed epithelial and stromal tumor family (MESTF) of the kidney from predominantly cystic renal cell carcinoma (RCC) using the magnetic resonance imaging (MRI)-based Bosniak classification system version 2019 (v2019). The study included 36 consecutive patients with MESTF and 77 with predominantly cystic RCC who underwent preoperative renal MRI. One radiologist evaluated and documented the clinical and MRI characteristics (age, sex, laterality, R.E.N.A.L. Nephrometry Score [RNS], surgical approach, the signal intensity on T2-weighted imaging, restricted diffusion and enhancement features in corticomedullary phase). Blinded to clinical and pathological information, another two radiologists independently evaluated Bosniak category of all masses. Interobserver agreement based on Bosniak classification system v2019 was measured by the weighted Cohen/Conger's Kappa coefficient. Furthermore, predominantly cystic RCCs and MESTFs were divided into low (categories I, II, and IIF) and high-class (categories III, and IV) tumors. The independent sample t test (Mann-Whitney U test) or Pearson Chi-square test (Fisher's exact probability test) was utilized to compare clinical and imaging characteristics between MESTFs and predominantly cystic RCCs. The performance of the Bosniak classification system v2019 in distinguishing MESTF from predominantly cystic RCC was investigated via receiver operating characteristic curve analysis. MESTF and predominantly cystic RCC groups significantly differed in terms of age, lesion size, RNS, restricted diffusion, and obvious enhancement in corticomedullary phase, but not sex, laterality, surgical approach, and the signal intensity on T2WI. Interobserver agreement was substantially based on the Bosniak classification system v2019. There were 24 low-class tumors and 12 high-class tumors in the MESTF group. Meanwhile, 13 low-class tumors and 64 high-class tumors were observed in the predominantly cystic RCC group. The distribution of low- or high-class tumors significantly differed between the MESTF and predominantly cystic RCC groups. Bosniak classification system v2019 had excellent discrimination (cutoff value = category III), and an area under curve value was 0.81; accuracy, 80.5%; sensitivity, 87.0%; and specificity, 66.7%. The MRI-based Bosniak classification system v2019 can effectively distinguish MESTF from predominantly cystic RCC if category III was used as a cutoff reference.

Magnetic resonance imaging as a noninvasive adjunct to conventional assessment of functional differences between kidneys in vivo and during ex vivo normothermic machine perfusion

Normothermic machine perfusion (NMP) is increasingly considered for pretransplant kidney quality assessment. However, fundamental questions about differences between in vivo and ex vivo renal function, as well as the impact of ischemic injury on ex vivo physiology, remain unanswered. This study utilized magnetic resonance imaging (MRI), alongside conventional parameters to explore differences between in vivo and ex vivo renal function and the impact of warm ischemia on a kidney’s behavior ex vivo. Renal MRI scans and samples were obtained from living pigs (n = 30) in vivo. Next, kidney pairs were procured and exposed to minimal, or 75 minutes of warm ischemia, followed by 6 hours of hypothermic machine perfusion. Both kidneys simultaneously underwent 6-hour ex vivo perfusion in MRI-compatible NMP circuits to obtain multiparametric MRI data. Ischemically injured ex vivo kidneys showed a significantly altered regional blood flow distribution compared to in vivo and minimally damaged organs. Both ex vivo groups showed diffusion restriction relative to in vivo. Our findings underscore the differences between in vivo and ex vivo MRI-based renal characteristics. Therefore, when assessing organ viability during NMP, it should be considered to incorporate parameters beyond the conventional functional markers that are common in vivo.

Socioeconomic deprivation and illness trajectory in the Scottish population after COVID-19 hospitalization

BackgroundThe associations between deprivation and illness trajectory after hospitalisation for coronavirus disease-19 (COVID-19) are uncertain.MethodsA prospective, multicentre cohort study was conducted on post-COVID-19 patients, enrolled either in-hospital or shortly post-discharge. Two evaluations were carried out: an initial assessment and a follow-up at 28–60 days post-discharge. The study encompassed research blood tests, patient-reported outcome measures, and multisystem imaging (including chest computed tomography (CT) with pulmonary and coronary angiography, cardiovascular and renal magnetic resonance imaging). Primary and secondary outcomes were analysed in relation to socioeconomic status, using the Scottish Index of Multiple Deprivation (SIMD). The EQ-5D-5L, Brief Illness Perception Questionnaire (BIPQ), Patient Health Questionnaire-4 (PHQ-4) for Anxiety and Depression, and the Duke Activity Status Index (DASI) were used to assess health status.ResultsOf the 252 enrolled patients (mean age 55.0 ± 12.0 years; 40% female; 23% with diabetes), deprivation status was linked with increased BMI and diabetes prevalence. 186 (74%) returned for the follow-up. Within this group, findings indicated associations between deprivation and lung abnormalities (p = 0.0085), coronary artery disease (p = 0.0128), and renal inflammation (p = 0.0421). Furthermore, patients with higher deprivation exhibited worse scores in health-related quality of life (EQ-5D-5L, p = 0.0084), illness perception (BIPQ, p = 0.0004), anxiety and depression levels (PHQ-4, p = 0.0038), and diminished physical activity (DASI, p = 0.002). At the 3-month mark, those with greater deprivation showed a higher frequency of referrals to secondary care due to ongoing COVID-19 symptoms (p = 0.0438). However, clinical outcomes were not influenced by deprivation.ConclusionsIn a post-hospital COVID-19 population, socioeconomic deprivation was associated with impaired health status and secondary care episodes. Deprivation influences illness trajectory after COVID-19.

Assessment of Acute Kidney Injury using MRI.

There has been growing interest in using quantitative magnetic resonance imaging (MRI) to describe and understand the pathophysiology of acute kidney injury (AKI). The ability to assess kidney blood flow, perfusion, oxygenation, and changes in tissue microstructure at repeated timepoints is hugely appealing, as this offers new possibilities to describe nature and severity of AKI, track the time-course to recovery or progression to chronic kidney disease (CKD), and may ultimately provide a method to noninvasively assess response to new therapies. This could have significant clinical implications considering that AKI is common (affecting more than 13 million people globally every year), harmful (associated with short and long-term morbidity and mortality), and currently lacks specific treatments. However, this is also a challenging area to study. After the kidney has been affected by an initial insult that leads to AKI, complex coexisting processes ensue, which may recover or can progress to CKD. There are various preclinical models of AKI (from which most of our current understanding derives), and these differ from each other but more importantly from clinical AKI. These aspects are fundamental to interpreting the results of the different AKI studies in which renal MRI has been used, which encompass different settings of AKI and a variety of MRI measures acquired at different timepoints. This review aims to provide a comprehensive description and interpretation of current studies (both preclinical and clinical) in which MRI has been used to assess AKI, and discuss future directions in the field. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY: Stage 3.

Multiparametric Renal Magnetic Resonance Imaging for Prediction and Annual Monitoring of the Progression of Chronic Kidney Disease over Two Years

Multiparametric Renal Magnetic Resonance Imaging for Prediction and Annual Monitoring of the Progression of Chronic Kidney Disease over Two Years

Socioeconomic status and post-covid illness trajectory

Abstract Background The associations between deprivation and illness trajectory after hospitalisation for coronavirus disease-19 (COVID-19) are uncertain. Methods A prospective, multicentre, longitudinal, cohort study involving post-COVID-19 patients enrolled in-hospital or early post-discharge (visit 1) and re-evaluated at 28-60 days post-discharge (visit 2) and in the longer term. Serial research blood tests (biomarkers), digital electrocardiography, and patient-reported outcome measures were obtained at both visits. Novel, multisystem imaging, including chest computed tomography (CT) with pulmonary and coronary angiography, cardiovascular and renal magnetic resonance imaging, was acquired at visit 2. The analysis of primary and secondary outcomes by socioeconomic status was prespecified. The Scottish Index of Multiple Deprivation (SIMD), a small-area measure of social deprivation based on domiciled post code reflecting seven factors including income, employment, education, health, access to services, crime, and housing, and categorized into general population quintiles, was used to measure social deprivation. The EQ-5D-5L, Brief Illness Perception Questionnaire (BIPQ), Patient Health Questionnaire-4 (PHQ-4) for Anxiety and Depression, and the Duke Activity Status Index (DASI) were used to assess health status. Follow-up of clinical outcomes was undertaken using electronic health records. Results Two hundred and fifty-two patients (mean±SD age 55.0 ±12.0 years, body mass index (BMI) 31.3 ±6.9 kg/m2,101 (40%) female, and 59 (23%) with diabetes) were enrolled and had follow-up completed at a median 428 (IQR 385, 538) days. Deprivation status was positively associated with BMI (p=0.0444) and diabetes (p=0.0239). One hundred and eighty-six (74%) patients reattended for investigation 28-60 days post-discharge. Lung ground glass opacity and/or consolidation (p=0.0085), obstructive coronary artery disease (p=0.0128) and renal inflammation (p=0.0421) were associated with deprivation. At 28-60 days post-discharge (n=184), health-related quality of life (EQ-5D-5L utility score, p=0.0084), illness perception, (BIPQ, p=0.0004), anxiety and depression (PHQ-4 score, p=0.0038), physical activity (DASI, p=0.002) and estimated peak oxygen consumption (ml/min/kg) (p=0.002) were worse with greater deprivation. At 3 months (n=252), deprivation status was associated with more referrals to secondary care because of ongoing COVID-19 symptoms (p=0.0438). Clinical outcomes did not associate with deprivation. Conclusion In a post-hospital COVID-19 population, socioeconomic deprivation was associated with impaired health status and secondary care episodes. Deprivation influences illness trajectory after COVID-19.

Application of DKI and IVIM imaging in evaluating histologic grades and clinical stages of clear cell renal cell carcinoma.

To evaluate the value of quantitative parameters derived from diffusion kurtosis imaging (DKI) and intravoxel incoherent motion (IVIM) in differentiating histologic grades and clinical stages of clear cell renal cell carcinoma (ccRCC). A total of 65 patients who were surgically and pathologically diagnosed as ccRCC were recruited in this study. In addition to routine renal magnetic resonance imaging examination, all patients underwent preoperative IVIM and DKI. The corresponding diffusion coefficient (D), pseudo-diffusion coefficient (D*), perfusion fraction (f), mean diffusivity (MD), kurtosis anisotropy (KA), and mean kurtosis (MK) values were obtained. Independent-samples t-test or Mann-Whitney U test was used for comparing the differences in IVIM and DKI parameters among different histologic grades and clinical stages. The diagnostic efficacy of IVIM and DKI parameters was evaluated using the receiver operating characteristic (ROC) curve. Spearman's correlation analysis was used to separately analyze the correlation of each parameter with histologic grades and stages of ccRCC. The D and MD values were significantly higher in low-grade ccRCC than high-grade ccRCC (all p < 0.001) and in low-stage than high-stage ccRCC (all p < 0.05), and the f value of high-stage ccRCC was lower than that of low-stage ccRCC (p = 0.007). The KA and MK values were significantly higher in low-grade than high-grade ccRCC (p = 0.000 and 0.000, respectively) and in low-stage than high-stage ccRCC (p = 0.000 and 0.000, respectively). The area under the curve (AUC) values of D, D*, f, MD, KA, MK, DKI, and IVIM+DKI values were 0.825, 0.598, 0.626, 0.792, 0.750, 0.754, 0.803, and 0.857, respectively, in grading ccRCC and 0.837, 0.719, 0.710, 0.787, 0.796, 0.784, 0.864, 0.823, and 0.916, respectively, in staging ccRCC. The AUC of IVIM was 0.913 in staging ccRCC. The D, D*, and MD values were negatively correlated with the histologic grades and clinical stages (all p < 0.05), and the KA and MK values showed a positive correlation with histologic grades and clinical stages (all p < 0.05). The f value was also negatively correlated with the ccRCC clinical stage (p = 0.008). Both the IVIM and DKI values can be used preoperatively to predict the degree of histologic grades and stages in ccRCC, and the D and MD values have better diagnostic performance in the grading and staging. Also, further slightly enhanced diagnostic efficacy was observed in the model with combined IVIM and DKI parameters.

Differentiation of Small Clear Renal Cell Carcinoma and Oncocytoma through Magnetic Resonance Imaging-Based Radiomics Analysis: Toward the End of Percutaneous Biopsy.

The aim of this study was to ascertain whether radiomics data can assist in differentiating small (<4 cm) clear cell renal cell carcinomas (ccRCCs) from small oncocytomas using T2-weighted magnetic resonance imaging (MRI). This retrospective study incorporated 48 tumors, 28 of which were ccRCCs and 20 were oncocytomas. All tumors were less than 4 cm in size and had undergone pre-biopsy or pre-surgery MRI. Following image pre-processing, 102 radiomics features were evaluated. A univariate analysis was performed using the Wilcoxon rank-sum test with Bonferroni correction. We compared multiple radiomics pipelines of normalization, feature selection, and machine learning (ML) algorithms, including random forest (RF), logistic regression (LR), AdaBoost, K-nearest neighbor, and support vector machine, using a supervised ML approach. No statistically significant features were identified via the univariate analysis with Bonferroni correction. The most effective algorithm was identified using a pipeline incorporating standard normalization, RF-based feature selection, and LR, which achieved an area under the curve (AUC) of 83%, accuracy of 73%, sensitivity of 79%, and specificity of 65%. Subsequently, the most significant features were identified from this algorithm, and two groups of uncorrelated features were established based on Pearson correlation scores. Using these features, an algorithm was established after a pipeline of standard normalization and LR, achieving an AUC of 90%, an accuracy of 77%, sensitivity of 83%, and specificity of 69% for distinguishing ccRCCs from oncocytomas. Radiomics analysis based on T2-weighted MRI can aid in distinguishing small ccRCCs from small oncocytomas. However, it is not superior to standard multiparameter renal MRI and does not yet allow us to dispense with percutaneous biopsy.

Noninvasive Assessment of Diabetic Kidney Disease With MRI: Hype or Hope?

Owing to the increasing prevalence of diabetic mellitus, diabetic kidney disease (DKD) is presently the leading cause of chronic kidney disease and end-stage renal disease worldwide. Early identification and disease interception is of paramount clinical importance for DKD management. However, current diagnostic, disease monitoring and prognostic tools are not satisfactory, due to their low sensitivity, low specificity, or invasiveness. Magnetic resonance imaging (MRI) is noninvasive and offers a host of contrast mechanisms that are sensitive to pathophysiological changes and risk factors associated with DKD. MRI tissue characterization involves structural and functional information including renal morphology (kidney volume (TKV) and parenchyma thickness using T1- or T2-weighted MRI), renal microstructure (diffusion weighted imaging, DWI), renal tissue oxygenation (blood oxygenation level dependent MRI, BOLD), renal hemodynamics (arterial spin labeling and phase contrast MRI), fibrosis (DWI) and abdominal or perirenal fat fraction (Dixon MRI). Recent (pre)clinical studies demonstrated the feasibility and potential value of DKD evaluation with MRI. Recognizing this opportunity, this review outlines key concepts and current trends in renal MRI technology for furthering our understanding of the mechanisms underlying DKD and for supplementing clinical decision-making in DKD. Progress in preclinical MRI of DKD is surveyed, and challenges for clinical translation of renal MRI are discussed. Future directions of DKD assessment and renal tissue characterization with (multi)parametric MRI are explored. Opportunities for discovery and clinical break-through are discussed including biological validation of the MRI findings, large-scale population studies, standardization of DKD protocols, the synergistic connection with data science to advance comprehensive texture analysis, and the development of smart and automatic data analysis and data visualization tools to further the concepts of virtual biopsy and personalized DKD precision medicine. We hope that this review will convey this vision and inspire the reader to become pioneers in noninvasive assessment and management of DKD with MRI. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY: Stage 2.

The Potentials of Contrast-Free Renal ASL MRI Perfusion in the Diagnosis and Dynamic Follow-Up of Renal Lesions in Patients with Diffuse Liver Diseases

Objective: to evaluate the potentials of contrast-free renal arterial spin labeling (ASL) perfusion during magnetic resonance imaging (MRI) for the diagnosis and dynamic follow-up of renal lesions in patients with diffuse liver diseases (DLD). Material and methods. The prospective study enrolled 82 patients with various DLD: alcoholic, viral, druginduced, autoimmune and mixed etiology. Ultrasound examination with Doppler abdominal and renal ultrasonography was conducted using Apogee 5300 (SIUI, China); abdominal MRI with contrast-free renal ASL-perfusion was performed using Vantage Titan 1.5 T (Toshiba, Japan). The parameters of renal perfusion (renal blood flow, RBF) were measured when the patients were admitted to the hospital, then during dynamic follow-up for 18 months. Results. Mathematical processing of results revealed normal RBF values (≥ 450 ml/100 g/min) and values associated with hepatorenal syndrome (HRS) (≤ 449 ml/100 g/min). High correlation between renal ASL-perfusion indicators and results of Doppler renal vessels ultrasonography was detected (r = 0,856). The diagnostic effectiveness parameters of contrast-free renal ASL-perfusion were: sensitivity 0.83, specificity 0.92, diagnostic accuracy 0.87. We created the algorithm of DLD patients examination for early HRS diagnosis and follow-up. Conclusion. Contrast-free renal ASL-perfusion is an informative method for predicting, diagnosis and dynamic follow-up of renal lesions in patients with various DLD.

Monoexponential, biexponential, stretched-exponential and kurtosis models of diffusion-weighted imaging in kidney assessment: comparison between patients with primary aldosteronism and healthy controls.

This study used various diffusion-weighted imaging (DWI) models (including monoexponential, biexponential, stretched-exponential and kurtosis models) in renal magnetic resonance imaging (MRI) to compare whether there were differences in each diffusion parameter between patients with primary aldosteronism (PA) and healthy volunteers. Twenty-two (female:male, 14:8; age, 48 ± 10years) patients with PA and 22 age- and sex-matched healthy controls (HCs) underwent MRI examinations of the kidneys. The independent-sample t test or the Mann‒Whitney U test was used to detect differences in the diffusion metrics of the kidneys between the two groups. Univariable and multivariable linear regression were applied to analyze the correlations between diffusion parameters and the clinical indicators. The mean diffusivity (MD, p < 0.001) and radial diffusivity (Dr, p < 0.001) values in the medulla were lower in the PA group than in the HC group. The medullary fractional anisotropy (FA, p < 0.001) was higher than that of HCs. The FA (p < 0.001) and axial diffusivity (Da, p < 0.001) values in the cortex were lower in the PA group. The cortical α (anomalous exponent term, p = 0.016) was higher in the PA patients than in the HCs. Linear regression analysis showed that log(plasma aldosterone concentration) and the estimated glomerular filtration rate (eGFR) were correlated with medullary FA. The stretched-exponential model (cortical α) and the kurtosis model (FA, MD and Dr in the medulla and FA and Da in the cortex) showed significant differences between PA patients and healthy volunteers and may have potential for noninvasive renal assessment in PA patients.

Multiparametric Magnetic Resonance Imaging of the Kidneys: Effects of Regional, Side, and Hydration Variations on Functional Quantifications.

To standardize renal functional magnetic resonance imaging (MRI), it is important to understand the influence of side-to-side variation, regional variation within the organ, and hydration states in MRI and to search for variables that are not affected by those variations. To assess MRI-based biomarkers for characterizing the kidney in healthy volunteers while considering variations in anatomic factors and hydration states. Prospective. Twenty-five healthy volunteers (15 females and 10 males, median age 25 years). 3.0 T intravoxel incoherent motion diffusion-weighted imaging, arterial spinning labeling imaging, blood oxygenation level dependent imaging, and three-dimensional MR elastography. Functional variables were measured before and after water challenge. Regions of interest were manually drawn by two investigators (JC and ZZ, with 8- and 5-year experiences in abdominal radiology) in the cortex, the medulla, and the entire kidney. The medulla/cortex ratio was calculated. Paired t-test or Wilcoxon signed rank test; interobserver correlation coefficient; repeatability coefficients; Spearman's correlation; significance level: P < 0.05. Diffusion parameters were only subject to regional variation. R2*, RBF, and renal stiffness (RS) showed regional variation, side variation, and dependence on hydration states. For each side and hydration state, the cortex showed significantly higher standard apparent diffusion coefficient (sADC), higher true diffusion (D), lower R2*, and lower RS than the medulla. For each region at baseline, the left kidney showed significantly higher R2*, higher RS, and lower renal blood flow (RBF) than the right kidney. For each region and side, RS and RBF increased significantly while R2* decreased significantly after water intake. After introducing the intrinsic regional difference, significantly higher medulla/cortex ratio of RS remained after water intake except for RS@90 Hz in the right kidney. Renal multiparametric MRI quantifications were affected by regional variation, side variation, and hydration states. 2 TECHNICAL EFFICACY: Stage 1.

Direct correlation of MRI with histopathology in pediatric renal tumors through the use of a patient-specific 3-D-printed cutting guide: a feasibility study

BackgroundPediatric renal tumors are often heterogeneous lesions with variable regions of distinct histopathology. Direct comparison between in vivo imaging and ex vivo histopathology might be useful for identification of discriminating imaging features.ObjectiveThis feasibility study explored the use of a patient-specific three-dimensional (3D)-printed cutting guide to ensure correct alignment (orientation and slice thickness) between magnetic resonance imaging (MRI) and histopathology.Materials and methodsBefore total nephrectomy, a patient-specific cutting guide based on each patient’s preoperative renal MRI was generated and 3-D printed, to enable consistent transverse orientation of the histological specimen slices with MRI slices. This was expected to result in macroscopic slices of 5 mm each. The feasibility of the technique was determined qualitatively, through questionnaires administered to involved experts, and quantitatively, based on structured measurements including overlap calculation using the dice similarity coefficient.ResultsThe cutting guide was used in eight Wilms tumor patients receiving a total nephrectomy, after preoperative chemotherapy. The median age at diagnosis was 50 months (range: 4–100 months). The positioning and slicing of the specimens were rated overall as easy and the median macroscopic slice thickness of each specimen ranged from 5 to 6 mm. Tumor consistency strongly influenced the practical application of the cutting guide. Digital correlation of a total of 32 slices resulted in a median dice similarity coefficient of 0.912 (range: 0.530–0.960).ConclusionWe report the feasibility of a patient-specific 3-D-printed MRI-based cutting guide for pediatric renal tumors, allowing improvement of the correlation of MRI and histopathology in future studies.

Magnetic Resonance Imaging to Diagnose and Predict the Outcome of Diabetic Kidney Disease—Where Do We Stand?

Diabetic kidney disease (DKD) is a major public health problem and its incidence is rising. The disease course is unpredictable with classic biomarkers, and the search for new tools to predict adverse renal outcomes is ongoing. Renal magnetic resonance imaging (MRI) now enables the quantification of metabolic and microscopic properties of the kidneys such as single-kidney, cortical and medullary blood flow, and renal tissue oxygenation and fibrosis, without the use of contrast media. A rapidly increasing number of studies show that these techniques can identify early kidney damage in patients with DKD, and possibly predict renal outcome. This review provides an overview of the currently most frequently used techniques, a summary of the results of some recent studies, and our view on their potential applications, as well as the hurdles to be overcome for the integration of these techniques into the clinical care of patients with DKD.

Assessment of Fasudil on Contrast-Associated Acute Kidney Injury Using Multiparametric Renal MRI.

Aims: To evaluate the utility of fasudil in a rat model of contrast-associated acute kidney injury (CA-AKI) and explore its underlying mechanism through multiparametric renal magnetic resonance imaging (mpMRI). Methods: Experimental rats (n = 72) were grouped as follows: controls (n = 24), CA-AKI (n = 24), or CA-AKI + Fasudil (n = 24). All animals underwent two mpMRI studies (arterial spin labeling, T1 and T2 mapping) at baseline and post iopromide/fasudil injection (Days 1, 3, 7, and 13 respectively). Relative change in renal blood flow (ΔRBF), T1 (ΔT1) and T2 (ΔT2) values were assessed at specified time points. Serum levels of cystatin C (CysC) and interleukin-1β (IL-1β), and urinary neutrophil gelatinase-associated lipocalin (NGAL) concentrations were tested as laboratory biomarkers, in addition to examining renal histology and expression levels of various proteins (Rho-kinase [ROCK], α-smooth muscle actin [α-SMA]), hypoxia-inducible factor-1α (HIF-1α), and transforming growth factor-β1 (TGF-β1) that regulate renal fibrosis and hypoxia. Results: Compared with the control group, serum levels of CysC and IL-1β, and urinary NGAL concentrations were clearly increased from Day 1 to Day 13 in the CA-AKI group (all p < 0.05). There were significant reductions in ΔT2 values on Days 1 and 3, and ΔT1 reductions were significantly more pronounced at all time points (Days 1–13) in the CA-AKI + Fasudil group (vs. CA-AKI) (all p < 0.05). Fasudil treatment lowered expression levels of ROCK-1, and p-MYPT1/MYPT1 proteins induced by iopromide, decreasing TGF-β1 expression and suppressing both extracellular matrix accumulation and α-SMA expression relative to untreated status (all p < 0.05). Fasudil also enhanced PHD2 transcription and inhibition of HIF-1α expression after CA-AKI. Conclusions: In the context of CA-AKI, fasudil appears to reduce renal hypoxia, fibrosis, and dysfunction by activating (Rho/ROCK) or inhibiting (TGF-β1, HIF-1α) certain signaling pathways and reducing α-SMA expression. Multiparametric MRI may be a viable noninvasive tool for monitoring CA-AKI pathophysiology during fasudil therapy.

Framework for estimating renal function using magnetic resonance imaging.

Purpose: Nephrologists have empirically predicted renal function from renal morphology. In diagnosing a case of renal dysfunction of unknown course, acute kidney injury and chronic kidney disease are diagnosed from blood tests and an imaging study including magnetic resonance imaging (MRI), and an examination/treatment policy is determined. A framework for the estimation of renal function from water images obtained using the Dixon method is proposed to provide information that helps clinicians reach a diagnosis by accurately estimating renal function on the basis of renal MRI. Approach: The proposed framework consists of four steps. First, the kidney area is extracted by MRI using the Dixon method with a U-net by deep learning. Second, the extracted renal region is registered with the target mask. Third, the kidney features are calculated based on the target mask classification information created by a specialist. Fourth, the estimated glomerular filtration rate (eGFR) representing the renal function is estimated using a regression support vector machine from the calculated features. Results: For the accuracy evaluation, we conducted an experiment to estimate the eGFR when MRI was performed and the eGFR slope, which is the annual rate of decline in eGFR. When the accuracy was evaluated for 165 subjects, the eGFR was estimated to have a root mean square error (RMSE) of 11.99 and a correlation coefficient of 0.83. Moreover, the eGFR slope was estimated to have an RMSE of 4.8 and a correlation coefficient of 0.5. Conclusions: Therefore, the proposed method shows the possibility of estimating the prognosis of renal function based on water images obtained by the Dixon method.