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Background Chronic allograft injury (CAI) is a significant reason for which many grafts were lost. The study was conducted to assess the usefulness of diffusional kurtosis imaging (DKI) technology in the non-invasive assessment of CAI. Methods Between February 2019 and October 2019, 110 renal allograft recipients were included to analyze relevant DKI parameters. According to estimated glomerular filtration rate (eGFR) (mL/min/ 1.73 m 2 ) level, they were divided to 3 groups: group 1, eGFR ≥ 60 (n = 10); group 2, eGFR 30–60 (n = 69); group 3, eGFR < 30 (n = 31). We performed DKI on a clinical 3T magnetic resonance imaging system. We measured the area of interest to determine the mean kurtosis (MK), mean diffusivity (MD), and apparent diffusion coefficient (ADC) of the renal cortex and medulla. We performed a Pearson correlation analysis to determine the relationship between eGFR and the DKI parameters. We used the receiver operating characteristic curve to estimate the predicted values of DKI parameters in the CAI evaluation. We randomly selected five patients from group 2 for biopsy to confirm CAI. Results With the increase of creatinine, ADC, and MD of the cortex and medulla decrease, MK of the cortex and medulla gradually increase. Among the three different eGFR groups, significant differences were found in cortical and medullary MK ( P  = 0.039, P  < 0.001, P  < 0.001, respectively). Cortical and medullary ADC and MD are negatively correlated with eGFR (r = − 0.49, − 0.44, − 0.57, − 0.57, respectively; P  < 0.001), while cortical and medullary MK are positively correlated with eGFR (r = 0.42, 0.38; P  < 0.001). When 0.491 was set as the cutoff value, MK's CAI assessment showed 87% sensitivity and 100% specificity. All five patients randomly selected for biopsy from the second group confirmed glomerulosclerosis and tubular atrophy/interstitial fibrosis. Conclusion The DKI technique is related to eGFR as allograft injury progresses and is expected to become a potential non-invasive method for evaluating CAI.

Most functional magnetic resonance research has primarily examined alterations in the affected kidney, often neglecting the contralateral kidney. Our study aims to investigate whether imaging parameters accurately depict changes in both the renal cortex and medulla in a unilateral ureteral obstruction rat model, thereby showcasing the utility of intravoxel incoherent motion (IVIM) in evaluating contralateral renal changes. Six rats underwent MR scans and were subsequently sacrificed for baseline histological examination. Following the induction of left ureteral obstruction, 48 rats were scanned, and the histopathological examinations were conducted on days 3, 7, 10, 14, 21, 28, 35, and 42. The apparent diffusion coefficient (ADC), pure molecular diffusion (D), pseudodiffusion (D*), and perfusion fraction (f) values were measured using IVIM. On the 10 day of obstruction, both cortical and medullary ADC values differed significantly between the UUO10 group and the sham group (  < 0.01). The cortical D values showed statistically significant differences between UUO3 group and sham group (  < 0.01) but not among UUO groups at other time point. Additionally, the cortical and medullary f values were statistically significant between the UUO21 group and the sham group (  < 0.01). Especially, the cortical f values exhibited significant differences between the UUO21 group and the UUO groups with shorter obstruction time (at time point of 3, 7, 10, 14 day) (  < 0.01). Significant hemodynamic alterations were observed in the contralateral kidney following renal obstruction. IVIM accurately captures changes in the unobstructed kidney. Particularly, the cortical f value exhibits the highest potential for assessing contralateral renal modifications.

Shear wave elastography (SWE) is increasingly used in renal imaging to assess cortical stiffness, potentially reflecting tissue alterations in conditions such as diabetic kidney disease. However, the reproducibility of SWE and traditional morphometric measurements remains a challenge. This is primarily due to factors such as operator dependency, variations in patient positioning, differences in breathing patterns during scanning, and the inherent technical limitations of ultrasound imaging. This pilot study aimed to assess the inter-observer agreement in ultrasound-based measurements of renal cortical stiffness, cortical thickness, length, and width in diabetic patients. In this prospective study, 30 adult diabetic patients underwent renal ultrasound performed by two independent observers. Parameters measured included cortical stiffness (kPa), cortical thickness (cm), kidney length (cm), and width (cm). Intraclass correlation coefficients (ICC), Bland–Altman plots, and Pearson’s correlation were used to evaluate inter-observer variability and bias. Cortical stiffness measurements demonstrated good inter-observer agreement (ICC = 0.824 for left kidney, 0.762 for right kidney). Morphometric measurements such as renal length and width showed excellent agreement (ICC > 0.9), although systematic and proportional biases were present. Cortical thickness exhibited poor agreement (ICC < 0.5), despite the absence of systematic bias. SWE has potential role in detecting early changes in renal tissue stiffness. Cortical stiffness shows reproducible between observers and can be considered reliable in diabetic patient. Morphometric parameters show high variability in certain aspects, particularly cortical thickness.

Renal hypoxia and ischemia significantly contribute to chronic kidney disease (CKD) progression, underscoring the need for noninvasive quantitative assessments. This study employs blood oxygenation level-dependent magnetic resonance imaging (BOLD-MRI) and arterial spin labeling (ASL) MRI to comprehensively evaluate renal oxygenation and blood flow in CKD patients. Forty-two CKD patients across stages 1-5 and ten healthy volunteers underwent simultaneous BOLD-MRI and ASL-MRI. We measured oxygenation (T2* values) and renal blood flow (RBF) in both the renal cortex and medulla, assessing their correlations with estimated glomerular filtration rate (eGFR) and other renal function indicators. BOLD and ASL revealed higher oxygenation and RBF in the renal cortex than in the medulla. Across CKD stages 2-5, both cortical and medullary oxygenation levels, as well as RBF, were lower than those in the control group and progressively decreased with CKD advancement. Additionally, renal oxygenation and blood flow levels positively correlated with serum creatinine (SCr), cystatin C (Cys C), and blood urea nitrogen (BUN), and negatively correlated with estimated glomerular filtration rate (eGFR) (  < 0.001). However, no significant correlation was observed with uric acid (UA) (  > 0.05). Notably, patients with CKD stages 1-3 exhibited strong correlations between renal oxygenation levels, RBF, and eGFR, while those with CKD stages 4-5 displayed weak correlations. BOLD-MRI and ASL-MRI effectively measure renal oxygenation and perfusion noninvasively, confirming their utility in tracking CKD progression. These modalities provide accurate assessments of renal function and hypoxic-ischemic injuries across CKD stages, particularly in the early stages.

The study aimed to discriminate renal allografts with impaired function by measuring cortical renal blood flow (cRBF) using magnetic resonance imaging arterial spin labelling (ASL-MRI) in paediatric and young adult patients. We included 18 subjects and performed ASL-MRI on 1.5 T MRI to calculate cRBF on parameter maps. cRBF was correlated to calculated glomerular filtration rate (GFR) and compared between patient groups with good (GFR ≥ 60 mL/min/1.73 m 2 ) and impaired allograft function (GFR < 60 mL/min/1.73 m 2 ). Mean cRBF in patients with good allograft function was significantly higher than in patients with impaired allograft function (219.89 ± 57.24 mL/min/100 g vs. 146.22 ± 41.84 mL/min/100 g, p  < 0.008), showing a highly significant correlation with GFR in all subjects (r = 0.75, p  < 0.0001). Also, the diffusion-weighted imaging (DWI-MRI) apparent diffusion coefficient (ADC) and Doppler measurements of peak-systolic and end-diastolic velocities and the resistive index (PS, ED, RI) were performed and both methods showed no significant difference between groups. ADC implied no correlation with GFR (r = 0.198, p  = 0.464), while PS indicated moderate correlation to GFR (r = 0.48, p  < 0.05), and PS and ED moderate correlation to cRBF (r = 0.58, p  < 0.05, r = 0.56, p  < 0.05, respectively). Cortical perfusion as non-invasively measured by ASL-MRI differs between patients with good and impaired allograft function and correlates significantly with its function.

This study explores alterations in renal cortical perfusion post-Early Goal-Directed Therapy (EGDT) in sepsis patients, to investigate its association with major adverse kidney events within 30 days (MAKE-30) and identify hemodynamic factors associated with renal cortical perfusion. Sepsis patients admitted to the ICU from Jan 2022 to Jul 2023 were prospectively enrolled. Contrast-enhanced ultrasound (CEUS) assessed renal cortical perfusion post-EGDT. Hemodynamic parameters and renal resistive index (RRI) were collected. Patients were categorized into MAKE-30 and non-MAKE-30 groups. The study examined the association between renal cortical perfusion and MAKE-30, explored the hemodynamic factors related to renal cortical perfusion. Of 94 sepsis patients, 46 (48.9 %) experienced MAKE-30. Distinctions in pulmonary (P = 0.012) and abdominal infection sites (P = 0.001) and significant SOFA (P < 0.001) and APACHE II scores (P = 0.003) differences were observed. No significant differences in baseline characteristics, vasopressor, or diuretic doses were noted (P > 0.05). Hemodynamic parameters in MAKE-30 and non-MAKE-30 patients showed no significant differences. RRI was higher in MAKE-30 patients (0.71 vs 0.66 P = 0.005). Renal microcirculation parameters, including AUC (p = 0.035), rBV (p = 0.021), and PI (p = 0.003), were lower in MAKE-30. Reduced cortical renal perfusion was associated with an increased risk of MAKE-30. Renal cortical perfusion RT was identified as an independent factor associated with this risk (HR 2.278, 95 % CI (1.152–4.507), P = 0.018). RRI correlated with renal cortical perfusion AUC (r = −0.220 p 0.033). Despite normal systemic hemodynamics post-sepsis EGDT, MAKE-30 patients show reduced renal cortical perfusion. CEUS-derived RT is an independent factor associated with this change. RRI correlates with renal cortical perfusion. •Investigated renal cortical perfusion changes post-EGDT in sepsis patients.•Analyzed link between renal cortical perfusion changes and MAKE-30.•Identified hemodynamic factors associated with renal cortical perfusion and MAKE-30 .•Enrolled ICU, utilizing CEUS to assess renal cortical perfusion post-EGDT.•Noted didderences in infection sites, SOFA, and APACHE II between MAKE-30 and non-MAKE-30 patients.•Lower renal microcirculation parameters observed in MAKE-30 patients, indicating reduced perfusion.•Reduced renal cortical perfusion associated with higher MAKE-30, Renal Transit Time is an independent risk factor.•Correlation of RRI with renal cortical perfusion AUC.•Conclusion: Despite normal systemic hemodynamics, MAKE-30 show lowerrenal cortical perfusion.

Objective To compare imaging findings with histopathology in AML without visible fat (AML wvf ). Material and methods With IRB approval, we identified 18 AML wvf that underwent CT between 2002-2014. A radiologist measured NECT-attenuation, corticomedullary (CM) and nephrographic (NG) enhancement, echogenicity relative to renal cortex (RC) ( N  = 5), T2W (T2 AML /T2 RC ) signal-intensity (SI), and chemical-shift SI ([SI IN-PHASE  − SI OPPOSED-PHASE ]/SI IN-PHASE ) indices ( N  = 6). A pathologist re-evaluated 15/18 AML wvf for 1) < or > 25 % adipocytes/high-power-field (HPF), 2) “many or few” blood vessels. Comparisons were performed using chi-square and independent t -tests. Results 73.3 %(11/15) of AML wvf had <25 % adipocytes/HPF and 86.7 %(13/15) had “many” blood vessels. NECT-attenuation was 41.8(±6.9) HU. 61.1 %(11/18) of AML wvf were hyper-attenuating and 38.9 %(7/18) iso-attenuating; attenuation was associated with %-adipocytes/HPF, ( p  = 0.01). CM/NG enhancement were 63.3(±20.8)/51.7(±15.5) HU. 72.2 %(13/18) of AML wvf had wash-out enhancement, with no association with amount of blood vessels at pathology, ( p  = 0.68). No difference in echogenicity was noted by histology ( p  > 0.05). All AML wvf were T2-hypointense (SI ratio = 0.61 [±0.1]). 2/6 AML wvf showed SI drop on chemical-shift MRI; both were iso-attenuating and were associated with >25 % adipocytes/HPF ( p  = 0.04). Conclusions AML wvf are typically T2-hypointense and hyper-attenuating with wash-out enhancement due to abundant smooth muscle and vessels respectively. Iso-attenuating AML wvf with microscopic fat on MRI contain more adipocytes/HPF. Key Points • Five percent of AML do not demonstrate detectable fat on imaging • These AML are hyperattenuating and T2-hypointense due to abundant smooth muscle • These AML show washout enhancement without association to vessel count at histopathology • Iso-attenuating AML with microscopic fat on MRI show >25 % adipocytes/HPF • The term “AML without visible fat” is proposed to reduce ambiguity

Purpose To investigate the effects of intrarenal pelvic pressure (IPP) on pyelo-tubular backflow and renal cortical blood perfusion during mini-percutaneous nephrolithotomy (MPCNL). Methods Dynamic changes in pyelo-tubular backflow and renal cortical blood perfusion were studied in six patients undergoing MPCNL using dynamic contrast-enhanced ultrasonography (CEUS) and IPP monitoring. Results CEUS of intrarenal pelvic perfusion revealed that renal tubules began to exhibit contrast agent reflux when IPP exceeded 34 mmHg during the MPCNL procedure. There was a positive correlation between renal tubule contrast agent reflux and IPP ( P  < 0.05). Intravenous CEUS of renal cortical blood flow demonstrated that both intrarenal pelvic perfusion time and IPP during MPCNL significantly affected renal cortical blood perfusion. Intrarenal pelvic perfusion time and pressure were negatively correlated with contrast agent peak intensity (PI) and area under the curve (AUC) ( P  < 0.05). Longer intrarenal pelvic perfusion times and higher pressures resulted in decreased renal cortical blood perfusion. Conclusion This study directly confirmed through dynamic CEUS and real-time IPP monitoring that an increase in IPP above the threshold of approximately 34 mmHg during MPCNL in patients leads to reflux through the renal tubules and a significant decrease in renal cortical blood perfusion. The safe upper limit for intrarenal pelvic perfusion pressure during MPCNL is approximately 34 mmHg.

Background Safety and survival during and after donor nephrectomy (DN) are one of the main concerns in living kidney donors (LKDs). Therefore, kidney (left/right) to be procured should be determined after considering the difficulty of DN, as well as the preservation of remnant renal function (RRF). In this prospective study, we investigated the roles of computed tomography volumetry (CTV) in split renal function (SRF) and established a predictive model for RRF in LKDs. Methods We assessed 103 LKDs who underwent DN at our institute. The Volume Analyzer SYNAPSE VINCENT image analysis system were used as CTV. RRF was defined as the estimated glomerular filtration rate (eGFR) 12 months after DN. The association between various factors measured by CTV and RRF were investigated, and a role of CTV on prediction for RRF was assessed. Results The median age and the preoperative eGFR were 58 years and 80.7 mL/min/1.73m 2 , respectively. Each factor measured by CTV showed an association with RRF. The ratio of remnant renal volume to body surface area (RRV/BSA) could predict RRF. In addition, RRV/BSA could predict RRF more accurately when used together with age and 24-h creatinine clearance (CrCl). Conclusions Our findings suggest that RRV/BSA measured by CTV can play an important role in predicting RRF, and a comprehensive assessment including age and CrCl is important to determine the kidney to be procured.