Early assessment of acute kidney injury in severe acute pancreatitis with multimodal DWI: an animal model.

OBJECTIVES: To evaluate the feasibility of multimodal diffusion-weighted imaging (DWI) for detecting the occurrence and severity of acute kidney injury (AKI) caused by severe acute pancreatitis (SAP) in rats. METHODS: SAP was induced in thirty rats by the retrograde injection of 5.0% sodium taurocholate through the biliopancreatic duct. Six rats underwent MRI of the kidneys 24 h before and 2, 4, 6, and 8 h after this AKI model was generated. Conventional and functional MRI sequences were used, including intravoxel incoherent motion imaging (IVIM), diffusion tensor imaging (DTI), and diffusion kurtosis imaging (DTI). The main DWI parameters and histological results were analyzed. RESULTS: The fast apparent diffusion coefficient (ADC) of the renal cortex was significantly reduced at 2 h, as was the fractional anisotropy (FA) value of the renal cortex on DTI. The mean kurtosis (MK) values for the renal cortex and medulla gradually increased after model generation. The renal histopathological score was negatively correlated with the medullary slow ADC, fast ADC, and perfusion scores for both the renal cortex and medulla, as were the ADC and FA values of the renal medulla in DTI, whereas the MK values of the cortex and medulla were positively correlated (r = 0.733, 0.812). Thus, the cortical fast ADC, medullary MK, FADTI, and slow ADC were optimal parameters for diagnosing AKI. Of these parameters, cortical fast ADC had the highest diagnostic efficacy (AUC = 0.950). CONCLUSIONS: The fast ADC of the renal cortex is the core indicator of early AKI, and the medullary MK value might serve as a sensitive biomarker for grading renal injury in SAP rats. CLINICAL RELEVANCE STATEMENT: The multimodal parameters of renal IVIM, DTI, and DKI are potential beneficial for the early diagnosis and severity grading of renal injury in SAP patients. KEY POINTS: • The multimodal parameters of renal DWI, including IVIM, DTI, and DKI, may be valuable for the noninvasive detection of early AKI and the severity grading of renal injury in SAP rats. • Cortical fast ADC, medullary MK, FA, and slow ADC are optimal parameters for early diagnosis of AKI, and cortical fast ADC has the highest diagnostic efficacy. • Medullary fast ADC, MK, and FA as well as cortical MK are useful for predicting the severity grade of AKI, and the renal medullary MK value exhibits the strongest correlation with pathological scores.

Acute kidney injury in critically ill children: predictive value of renal arterial Doppler assessment.

BACKGROUND: Renal resistive index (RRI) and renal pulsatility index (RPI) are Doppler-based variables proposed to assess renal perfusion at the bedside in critically ill patients. This study aimed to assess the accuracy of such variables to predict acute kidney injury (AKI) in mechanically ventilated children. METHODS: Consecutive children aged <14 years underwent kidney Doppler ultrasound examination within 24 h of invasive mechanical ventilation. Renal resistive index (RRI) and renal pulsatility index (RPI) were measured. The primary outcome was severe AKI (KDIGO stage 2 or 3) on day 3. RESULTS: On day 3, 22 patients were classified as having AKI, of which 12 were severe. RRI could effectively predict severe AKI (area under the ROC curve [AUC] = 0.94) as well as RPI (AUC = 0.86). The optimal cut-off for RRI was 0.85 (sensitivity, 91.7%; specificity, 84.7%; PPV, 50.0%; and NPV, 98.4%). Similar results were obtained when the accuracy to predict AKI on day 5 was assessed. Significant correlations were observed between RRI and estimated glomerular filtration rate at enrollment (ρ = -0.495) and on day 3 (ρ = -0.467). CONCLUSIONS: Renal Doppler ultrasound may be a promising tool to predict AKI in critically ill children under invasive mechanical ventilation. IMPACT: Early recognition of acute kidney injury (AKI) is essential to promptly initiate supportive care aimed at restoring renal perfusion, which may prevent or attenuate acute tubular necrosis. Renal arterial Doppler-based parameters are rapid, noninvasive, and repeatable variables that may be promising for the prediction of AKI in children. To the best of our knowledge, this is the first study to evaluate the use of renal Doppler-based variables to predict AKI in critically ill children. The present study found that Doppler-based variables could accurately predict the occurrence of severe AKI and were correlated with urinary output and diuretic use.

Monitoring kidney size to interpret MRI-based assessment of renal oxygenation in acute pathophysiological scenarios.

AIM: Tissue hypoxia is an early key feature of acute kidney injury. Assessment of renal oxygenation using magnetic resonance imaging (MRI) markers T2 and T2 * enables insights into renal pathophysiology. This assessment can be confounded by changes in the blood and tubular volume fractions, occurring upon pathological insults. These changes are mirrored by changes in kidney size (KS). Here, we used dynamic MRI to monitor KS for physiological interpretation of T2 * and T2 changes in acute pathophysiological scenarios. METHODS: KS was determined from T2 *, T2 mapping in rats. Six interventions that acutely alter renal tissue oxygenation were performed directly within the scanner, including interventions that change the blood and/or tubular volume. A biophysical model was used to estimate changes in O2 saturation of hemoglobin from changes in T2 * and KS. RESULTS: Upon aortic occlusion KS decreased; this correlated with a decrease in T2 *, T2 . Upon renal vein occlusion KS increased; this negatively correlated with a decrease in T2 *, T2 . Upon simultaneous occlusion of both vessels KS remained unchanged; there was no correlation with decreased T2 *, T2 . Hypoxemia induced mild reductions in KS and T2 *, T2 . Administration of an X-ray contrast medium induced sustained KS increase, with an initial increase in T2 *, T2 followed by a decrease. Furosemide caused T2 *, T2 elevation and a minor increase in KS. Model calculations yielded physiologically plausible calibration ratios for T2 *. CONCLUSION: Monitoring KS allows physiological interpretation of acute renal oxygenation changes obtained by T2 *, T2 . KS monitoring should accompany MRI-oximetry, for new insights into renal pathophysiology and swift translation into human studies.

Doppler ultrasound in the assessment of renal perfusion before and during continuous kidney replacement therapy in the pediatric intensive care unit.

BACKGROUND: This study aimed to assess observer variability and describe renal resistive index (RRI) and pulsatility index (PI) before and after onset of continuous kidney replacement therapy (CKRT). A secondary objective was to correlate Doppler ultrasound findings with those from direct measurement of renal blood flow (RBF). METHODS: This is a prospective observational study in hemodynamically stable Maryland piglets with and without acute kidney injury (AKI) and in hemodynamically unstable critically ill children requiring CKRT. Doppler-based RRI and PI were assessed for each subject. Measurements were made by two different operators (pediatric intensivists) before and after CKRT onset. RESULTS: Observer variability assessment in the measurement of RRI and PI rendered a moderate correlation for both RRI (ICC 0.65, IQR 0.51-0.76) and PI (ICC 0.63, IQR 0.47-0.75). RRI and PI showed no correlation with RBF or urine output. Baseline RRI and PI were normal in control piglets [RRI 0.68 (SD 0.02), PI 1.25 (SD 0.09)] and those with AKI [RRI 0.68 (SD 0.03), PI 1.20 (SD 0.13)]. Baseline RRI and PI were elevated in critically ill children (RRI 0.85, PI 2.0). PI and RRI did not change with CKRT in any study group. CONCLUSIONS: Observer variability between inexperienced pediatric intensivists was comparable with that between senior and junior operators. Doppler-based calculations did not correlate with invasive measurements of RBF. RRI and PI were normal in hemodynamically stable piglets with and without AKI. RRI and PI were high in hemodynamically unstable patients requiring CKRT. RRI and PI did not change after CKRT onset, despite changes in hemodynamic status. A higher resolution version of the Graphical abstract is available as Supplementary information.

A Novel Risk Assessment Model Using Urinary System Contrast Blush Grading to Predict Contrast-Induced Acute Kidney Injury in Low-Risk Profile Patients.

Contrast-induced acute kidney injury (CI-AKI) can occur after coronary interventions despite protective measures. We evaluated the effect of urinary system contrast blush grading for predicting post-procedure CI-AKI in 486 patients with chronic coronary artery disease. Patient characteristics and blood samples were collected. Urinary system contrast blush grade was recorded during the coronary angiography and interventions. Post-procedure third to fourth day blood samples were collected for diagnosis of CI-AKI. The median age of the patients was 61 years (53-70, interquartile range), and 194 (39.9%) participants were female. Contrast-induced acute kidney injury occurred in 78 (16%) patients. By comparing full and reduced models with the likelihood ratio test, it was observed that in the reduced model, factors such as age, diabetes mellitus, body weight-adapted contrast media (CM), hemoglobin, and urinary system blush were associated with CI-AKI presence. The probability of CI-AKI presence increased slightly from grade 0 to 1 blush, but it increased sharply grade from 1 to 2 blush. According to our results, an increase in body weight-adapted CM and urinary blush grading were the main predictors of CI-AKI. These findings suggest that when body weight-adapted CM ratio exceeds 3.5 mL/kg and urinary contrast blush reaches grade 2, the patients should be followed up more carefully for the development of CI-AKI.

Assessment of Gadobutrol Safety in Combination with Ionizing Radiation Using a Preclinical MRI-Guided Radiotherapy Model.

MR-linac technology enhances the precision of therapeutic radiation by clarifying the tumor-normal tissue interface and provides the potential for adaptive treatment planning. Accurate delineation of tumors on diagnostic magnetic resonance imaging (MRI) frequently requires gadolinium-based contrast agents (GBCAs). Despite generally being considered safe, previous literature suggests that GBCAs are capable of contrast-induced acute kidney injury (AKI). It is unclear if the risk for AKI is enhanced when GBCAs are administered concurrently with ionizing radiotherapy. During irradiation, gadolinium may be liberated from its chelator which may induce AKI. The goal of this work was to determine if radiation combined with GBCAs increased the incidence of AKI. Using a preclinical MRI-guided irradiation system, where MRI acquisitions and radiation delivery are performed in rapid succession, tumor-bearing mice with normal kidney function were injected with GBCA and treated with 2, 8 or 18 Gy irradiation. Renal function was assessed on days three and seven postirradiation to assess for AKI. No clinically relevant changes in blood urea nitrogen and creatinine were observed in any combination of GBCA and radiation dose. From these data, we conclude that GBCA in combination with radiation does not increase the risk for AKI in mice. Additional investigation of multiple doses of GBCA administered concurrently with irradiation is warranted to evaluate the risk of chronic kidney injury.

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

PURPOSE OF REVIEW: Many forms of acute and chronic disease are linked to changes in renal blood flow, perfusion, vascular density and hypoxia, but there are no readily available methods to assess these parameters in clinical practice. Dynamic contrast enhanced ultrasound (DCE-US) is a method that provides quantitative assessments of organ perfusion without ionising radiation or risk of nephrotoxicity. It can be performed at the bedside and is suitable for repeated measurements. The purpose of this review is to provide updates from recent publications on the utility of DCE-US in the diagnosis or assessment of renal disease, excluding the evaluation of benign or malignant renal masses. RECENT FINDINGS: DCE-US has been applied in clinical studies of acute kidney injury (AKI), renal transplantation, chronic kidney disease (CKD), diabetic kidney disease and to determine acute effects of pharmacological agents on renal haemodynamics. DCE-US can detect changes in renal perfusion across these clinical scenarios and can differentiate healthy controls from those with CKD. In sepsis, reduced DCE-US measures of perfusion may indicate those at increased risk of developing AKI, but this requires confirmation in larger studies as there can be wide individual variation in perfusion measures in acutely unwell patients. Recent studies in transplantation have not provided robust evidence to show that DCE-US can differentiate between different causes of graft dysfunction, although it may show more promise as a prognostic indicator of graft function 1 year after transplant. DCE-US can detect acute haemodynamic changes in response to medication that correlate with changes in renal plasma flow as measured by para-aminohippurate clearance. SUMMARY: DCE-US shows promise and has a number of advantages that make it suitable for the assessment of patients with various forms of kidney disease. However, further research is required to evidence its reproducibility and utility before clinical use can be advocated.

Application of MR diffusion imaging for non-invasive assessment of acute kidney injury after lung transplantation.

To assess whether MR diffusion imaging may be applied for non-invasive detection of renal changes correlating with clinical diagnosis of acute kidney injury (AKI) in patients after lung transplantation (lutx).Fifty-four patients (mean age 49.6, range 26-64 years) after lutx were enrolled in a prospective clinical study and underwent functional MR imaging of the kidneys in the early postoperative period. Baseline s-creatinine ranged from 39 to 112 µmol/L. For comparison, 14 healthy volunteers (mean age 42.1, range 24-59 years) underwent magnetic resonance imaging (MRI) using the same protocol. Renal tissue injury was evaluated using quantification of diffusion and diffusion anisotropy with diffusion-weighted (DWI) and diffusion-tensor imaging (DTI). Renal function was monitored and AKI was defined according to Acute-Kidney-Injury-Network criteria. Statistical analysis comprised one-way ANOVA and Pearson correlation.67% of lutx patients (36/54) developed AKI, 47% (17/36) had AKI stage 1, 42% (15/36) AKI stage 2, and 8% (3/36) severe AKI stage 3. Renal apparent diffusion coefficients (ADCs) were reduced in patients with AKI, but preserved in transplant patients without AKI and healthy volunteers (2.07 ±â€Š0.02 vs 2.18 ±â€Š0.05 vs 2.21 ±â€Š0.03 × 10 mm/s, P < .05). Diffusion anisotropy was reduced in all lutx recipients compared with healthy volunteers (AKI: 0.27 ±â€Š0.01 vs no AKI: 0.28 ±â€Š0.01 vs healthy: 0.33 ±â€Š0.02; P < .01). Reduction of renal ADC correlated significantly with acute loss of renal function after lutx (decrease of renal function in the postoperative period and glomerular filtration rate on the day of MRI).MR diffusion imaging enables non-invasive assessment of renal changes correlating with AKI early after lutx. Reduction of diffusion anisotropy was present in all patients after lutx, whereas marked reduction of renal ADC was observed only in the group of lutx recipients with AKI and correlated with renal function impairment.

Ultrasound super-resolution imaging provides a noninvasive assessment of renal microvasculature changes during mouse acute kidney injury.

Acute kidney injury (AKI) is a risk factor for the development of chronic kidney disease (CKD). One mechanism for this phenomenon is renal microvascular rarefaction and subsequent chronic impairment in perfusion. However, diagnostic tools to monitor the renal microvasculature in a noninvasive and quantitative manner are still lacking. Ultrasound super-resolution imaging is an emerging technology that can identify microvessels with unprecedented resolution. Here, we applied this imaging technique to identify microvessels in the unilateral ischemia-reperfusion injury mouse model of AKI-to-CKD progression in vivo. Kidneys from 21 and 42 day post- ischemia-reperfusion injury, the contralateral uninjured kidneys, and kidneys from sham-operated mice were examined by ultrasound super-resolution and histology. Renal microvessels were successfully identified by this imaging modality with a resolution down to 32 µm. Renal fibrosis was observed in all kidneys with ischemia-reperfusion injury and was associated with a significant reduction in kidney size, cortical thickness, relative blood volume, and microvascular density as assessed by this imaging. Tortuosity of the cortical microvasculature was also significantly increased at 42 days compared to sham. These vessel density measurements correlated significantly with CD31 immunohistochemistry (R2=0.77). Thus, ultrasound super-resolution imaging provides unprecedented resolution and is capable of noninvasive quantification of renal vasculature changes associated with AKI-to-CKD progression in mice. Hence, this technique could be a promising diagnostic tool for monitoring progressive kidney disease.

Diagnostic accuracy of arterial and venous renal Doppler assessment for acute kidney injury in critically ill patients: A prospective study.

BACKGROUND AND PURPOSE: Renal Resistive Index (RRI) and Venous Impedance Index (VII) might be of additional value for diagnosing Acute Kidney Injury (AKI). The purpose of this study was to assess the diagnostic accuracy of RRI and VII for AKI. MATERIALS AND METHODS: In the prospective Simple Intensive Care Studies-II (NCT03577405), we measured RRI and VII in acutely admitted adult intensive care patients within 24 h of admission. AKI was defined by the Kidney Disease Improving Global Outcome (KDIGO) criteria. The primary outcome was persistent AKI, defined as non-resolved AKI on day three. We tested specificity, sensitivity and diagnostic accuracy of both RRI and VII for persistent AKI. RESULTS: In total, 371 patients were included of whom 123 patients (33%) had persistent AKI. RRI and VII did not differ between patients with and those without persistent AKI (p = .08 and p = .59). RRI had a moderate specificity (72%, 95%CI 66-78%) and low sensitivity (32%, 95%CI 24-41%) and VII had high sensitivity (93%, 95%CI 85-98%) and low specificity (11%, 95%CI 6-16%) for persistent AKI. Overall diagnostic accuracy of RRI and VII was moderate. CONCLUSIONS: In acutely admitted critically ill patients, measures of renal perfusion by renal ultrasound were not different between patients with and without AKI, and show limited diagnostic accuracy for AKI. Registered:NCT03577405.

Need for Objective Assessment of Volume Status in Critically Ill Patients with COVID-19: The Tri-POCUS Approach.

As the coronavirus disease 2019 (COVID-19) continues to spread across the globe, the knowledge of its epidemiology, clinical features, and management is rapidly evolving. Nevertheless, the data on optimal fluid management strategies for those who develop critical illness remain sparse. Adding to the challenge, the fluid volume status of these patients has been found to be dynamic. Some present with several days of malaise, gastrointestinal symptoms, and consequent hypovolemia requiring aggressive fluid resuscitation, while a subset develop acute respiratory distress syndrome with renal dysfunction and lingering congestion necessitating restrictive fluid management. Accurate objective assessment of volume status allows physicians to tailor the fluid management goals throughout this wide spectrum of critical illness. Conventional point-of-care ultrasonography (POCUS) enables the reliable assessment of fluid status and reducing the staff exposure. However, due to specific characteristics of COVID-19 (e.g., rapidly expanding lung lesions), a single imaging method such as lung POCUS will have significant limitations. Herein, we suggest a Tri-POCUS approach that represents concurrent bedside assessment of the lungs, heart, and the venous system. This combinational approach is likely to overcome the limitations of the individual methods and provide a more precise evaluation of the volume status in critically ill patients with COVID-19.

A feasibility study of using noninvasive renal oxygenation imaging for the early assessment of ischemic acute kidney injury in an embolization model.

PURPOSE: To investigate the feasibility of using MRI based oxygenation imaging for early assessment of ischemic acute kidney injury (AKI) in an embolization model. METHODS: Ischemic AKI model was induced in 40 rabbits by injection of microspheres into the right renal arteries. Animals were grouped according to the dose of microspheres: Severe AKI group, 2.0 mg (N = 10); Moderate AKI group, 1.0 mg (N = 10); Mild AKI group, 0.5 mg (N = 10); Control group, saline without microspheres (N = 10). A serial MRI examination was performed at intervals of 1 h, 1 day, 1 week and 4 weeks to evaluate the deterioration of renal function. A multi-echo ASE sequence was implemented for renal oxygenation measurement 1 h after surgery. Pathological examinations were performed 4 weeks after the surgery. RESULTS: In renal cortex, renal oxygen extraction fraction (OEF) raised significantly after embolization procedures in all experimental groups (severe AKI: 0.39 ±â€¯0.05, P < 0.05; moderate AKI: 0.36 ±â€¯0.03, P < 0.05; mild AKI: 0.34 ±â€¯0.02, P < 0.05) compared to the control group (0.29 ±â€¯0.02). In outer medulla, significant difference was observed between control group (0.29 ±â€¯0.03) and severe AKI group (0.35 ±â€¯0.03, P < 0.05), and between control group and moderate AKI group (0.34 ±â€¯0.04, P < 0.05). Corresponding lesions were found in pathological examinations 4 weeks after the procedure. CONCLUSION: This study demonstrates the feasibility of using oxygenation imaging to assess the embolization induced ischemic AKI at an early stage.

Duplex Ultrasound Assessment and Outcomes of Renal Malperfusion Syndromes after Acute Aortic Dissection.

BACKGROUND: We investigated the feasibility of renal duplex ultrasound in the identification of renal malperfusion in acute aortic dissection and evaluated whether intervention for renal malperfusion improved outcomes over best medical management alone. METHODS: All patients with acute aortic dissections involving the renovisceral aorta who underwent a duplex ultrasound were included (2004-2016). We assessed duplex findings among patients who developed acute kidney injury (AKI; 50% increase in serum creatinine) and compared AKI, 30-day mortality, and overall survival among patients who underwent a procedure to treat malperfusion versus those who did not. RESULTS: Of 37 patients with acute dissection involving the renovisceral aorta (73% were male, 59% had type B dissection, mean follow-up 4.6 ± 0.6 years), 70% developed AKI, 11% required dialysis, and 5% developed permanent dialysis dependence. AKI was correlated with higher peak creatinine levels (4.2 vs. 2.2 mg/dL, P < 0.001), although 30-day mortality and overall survival were similar (both, P ≥ 0.24). Progression to AKI was associated with significantly lower end-diastolic velocity (EDV) measurements on renal duplex (17 vs. 27 cm/sec, P = 0.03); an EDV threshold of 23 cm/sec had a positive predictive value of 85% for AKI. Operative intervention (n = 10) was associated with lower follow-up creatinine (0.9 vs. 2.1 mg/dL, P = 0.002), although there was no difference in progression to dialysis dependence, 30-day mortality, or overall survival (all, P ≥ 0.34). CONCLUSIONS: Patients who developed AKI demonstrated characteristic renal duplex ultrasound findings with lower EDV measurements in the distal renal arteries bilaterally. Performing a renal malperfusion procedure was associated with normalization of postoperative creatinine without affecting 30-day mortality or overall survival.

Risk-benefit Assessment of Systematic Thoracoabdominal-pelvic Computed Tomography in Infective Endocarditis.

BACKGROUND: In the management of infective endocarditis (IE), the presence of extracardiac complications has an influence on both diagnosis and treatment. Current guidelines suggest that systematic thoracoabdominal-pelvic computed tomography (TAP-CT) may be helpful. Our objective was to describe how systematic TAP-CT affects the diagnosis and the management of IE. METHODS: In this multicenter cohort study, between January 2013 and July 2016 we included consecutive patients who had definite or possible IE according to the Duke modified criteria, validated by endocarditis teams. We analyzed whether the Duke classification and therapeutic management were modified regarding the presence or the absence of IE-related lesion on CT and investigated the tolerance of this examination. RESULTS: Of the 522 patients included in this study, 217 (41.6%) had 1 or more IE-related lesions. On the basis of CT results in asymptomatic patients, diagnostic classification was upgraded from possible endocarditis to definite endocarditis for only 4 cases (0.8%). The presence of IE-related lesions on CT did not modify the duration of antibiotic treatment (P = .55), nor the decision of surgical treatment (P = .39). Specific treatment of the lesion was necessary in 42 patients (8.0%), but only 9 of these lesions (1.9%) were asymptomatic and diagnosed only on the TAP-CT. Acute kidney injury (AKI) within 5 days of CT was observed in 78 patients (14.9%). CONCLUSIONS: The TAP-CT findings slightly affected diagnosis and treatment of IE in a very small proportion of asymptomatic patients. Furthermore, contrast media should be used with caution because of the high risk of AKI.

Ultrasound Assessment of Acute Kidney Injury.

Ultrasound assessment of the kidneys in patients with renal impairment has been described in various ways in the critical care, nephrology, and radiology literature, resulting in a somewhat heterogeneous picture of the gray-scale and Doppler ultrasound manifestation of acute kidney injury (AKI). Given that ultrasound assessment can potentially identify reversible causes of AKI or identify underlying chronic kidney disease, it is important for radiologists to be aware of the common etiologies of AKI and the spectrum of ultrasound findings. We review the definition and etiologies of renal injury and introduce the ultrasound SERVeillance framework-assessment of renal size, echogenicity, renal hilum, and vascularity-for the imaging assessment of AKI.

Early assessment of acute kidney injury using targeted field of view diffusion-weighted imaging: An in vivo study.

Acute kidney injury (AKI) is a common complication in various clinical settings. In recent years, AKI diagnostics have been investigated intensively showing the emerging need for early characterization of this disease. To verify whether targeted field-of-view diffusion-weighted imaging (tFOV-DWI) is feasible to significantly improve the performance of traditional full field-of-view diffusion-weighted imaging (fFOV-DWI) in the early assessment of AKI. 14 rabbits with unilateral AKI were induced by injection of microspheres under the guidance of digital subtraction angiography (DSA). All rabbits underwent tFOV-DWI and fFOV-DWI immediately after the surgery. Artifacts, distortion and lesion identification were graded by two experienced radiologists, and the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured. Apparent diffusion coefficient (ADC) maps were then derived. Blood samples were collected pre- and post-surgery and serum creatinine weres measured. Renal specimen and biopsy were performed as the reference standard. Student t-test was used to ascertain statistical significance between the above parameters for tFOV-DWI and fFOV-DWI. The interobserver agreement and ADC measurements agreement were assessed. A higher percentage of renal lesions (17 out of 19) were detected in tFOV-DWI compared with fFOV-DWI (14 out of 19). Significant differences were observed in ADC value for both techniques between the lesion regions and normal tissues (p < 0.001). Histological findings were inversely correlated with ADC values of tFOV-DWI (r = -0.97, P < 0.001 for cortex; r = -0.98, P < 0.001 for medulla) and fFOV-DWI sequences (r = -0.95, P < 0.001 for cortex; r = -0.98, P < 0.001 for medulla). Those tFOV-DW images rated by the radiologists exhibit superior performance in terms of all assessed measures (P < 0.05), and interobserver agreement was excellent (ICC, 0.78 to 0.92). Besides, the ADC values derived from tFOV-DWI had a satisfactory agreement with those estimated by fFOV-DWI. The animal study demonstrates that the tFOV-DWI strategy provided visually better image quality and lesion depiction than conventional fFOV-DWI for early assessment of AKI.

Duplex scan and histologic assessment of acute renal injury in a kidney-kidney crosstalk swine experimental model.

OBJECTIVE: The objective of this study was to identify the effect of two left renal vasculature occlusion strategies on the duplex ultrasound-assessed rheology and histology of the contralateral kidney. METHODS: Pigs were randomly assigned to one of two groups: left renal artery-only clamping (A group, n = 8) or left renal artery and vein clamping (AV group, n = 9). Bilateral renal parenchymal biopsy specimens were taken every 10 minutes for 90 minutes. Duplex ultrasound resistive index (RI) and pulsatility index (PI) were measured. Mixed models with normal distribution and first-order autoregressive correlation structure and generalized estimating equation models were used. Results are presented as adjusted means with standard errors, estimated proportions with standard errors, and line plots with 95% confidence intervals. RESULTS: RI and PI increased in the nonischemic kidney. In A group animals, RI values increased significantly (P < .01) after 30 minutes of ischemia and PI increased significantly (P < .04) from 30 to 60 minutes of ischemia. The number of histologic abnormalities was higher in A group than in AV group biopsy specimens. The percentage of lesions increased significantly after 10 minutes in A group nonischemic kidneys (P < .02) and between 50 and 80 minutes in AV group nonischemic kidneys (P < .01). CONCLUSIONS: Nonischemic kidneys were acutely affected by contralateral ischemia. Their function was more adversely affected by unilateral renal artery occlusion with preserved renal vein patency (A group).

Fast simultaneous assessment of renal and liver function using polymethine dyes in animal models of chronic and acute organ injury.

Simultaneous assessment of excretory liver and kidney function is still an unmet need in experimental stress models as well as in critical care. The aim of the study was to characterize two polymethine-dyes potentially suitable for this purpose in vivo. Plasma disappearance rate and elimination measurements of simultaneously injected fluorescent dyes DY-780 (hepato-biliary elimination) and DY-654(renal elimination) were conducted using catheter techniques and intravital microscopy in animals subjected to different organ injuries, i.e. polymicrobial sepsis by peritoneal contamination and infection, ischemia-reperfusion-injury and glycerol-induced acute kidney-injury. DY-780 and DY-654 showed organ specific and determined elimination routes in both healthy and diseased animals. They can be measured simultaneously using near-infrared imaging and spectrophotometry. Plasma-disappearance rates of DY-780 and DY-654 are superior to conventional biomarkers in indicating hepatic or kidney dysfunction in different animal models. Greatest impact on liver function was found in animals with polymicrobial sepsis whereas glomerular damage due to glycerol-induced kidney-injury had strongest impact on DY-654 elimination. We therefore conclude that hepatic elimination and renal filtration can be assessed in rodents measuring plasma-disappearance rates of both dyes. Further, assessment of organ dysfunction by polymethine dyes correlates with, but outperforms conventional biomarkers regarding sensitivity and the option of spatial resolution if biophotonic strategies are applied. Polymethine-dye clearance thereby allows sensitive point-of-care assessment of both organ functions simultaneously.

Renal ischemia and reperfusion assessment with three-dimensional hyperpolarized 13 C,15 N2-urea.

PURPOSE: The aim of this work was to investigate whether hyperpolarized 13 C,15 N2 -urea can be used as an imaging marker of renal injury in renal unilateral ischemic reperfusion injury (IRI), given that urea is correlated with the renal osmotic gradient, which describes the renal function. METHODS: Hyperpolarized three-dimensional balanced steady-state 13 C magnetic resonance imaging (MRI) experiments alongside kidney function parameters and quantitative polymerase chain reaction measurements were performed in rats subjected to unilateral renal ischemia for 60-minute and 24-hour reperfusion. RESULTS: We revealed a significant reduction in the intrarenal gradient in the ischemic kidney in agreement with cortical injury markers neutrophil gelatinase-associated lipocalin and kidney injury molecule 1, as well as functional kidney parameters. CONCLUSION: Hyperpolarized functional 13 C,15 N2 urea MRI can be used to successfully detect changes in the intrarenal urea gradient post-IRI, thereby enabling in vivo monitoring of the intrarenal functional status in the rat kidney. Magn Reson Med 76:1524-1530, 2016. © 2016 International Society for Magnetic Resonance in Medicine.