Contrast-Enhanced Ultrasound: A Viable Diagnostic Tool in Predicting Treatment Failure after Non-union Revision Surgery for Upper- and Lower-Limb Non-unions

Non-unions remain a major complication in the treatment of long-bone fractures and affect quality of life considerably. Both early detection and treatment of non-unions are essential to secure subsequent fracture union. Sufficient vascularization plays a key role in the healing process. The aim of this prospective study was to quantify the microperfusion within non-unions by means of contrast-enhanced ultrasound (CEUS) as early as 12 wk after non-union surgery and to examine the prognostic capability of CEUS in predicting treatment failure. Among 112 patients who had undergone non-union surgery, consolidation within 36 mo was achieved in 89 patients (“responders”), whereas 23 patients showed persistent non-unions (“non-responders”) and required further surgery. CEUS quantification parameters such as peak enhancement, wash-in area under the curve and wash-in perfusion index revealed significantly higher perfusion levels in “responders” compared with “non-responders” (p < 0.05). Receiver operator characteristic curve analysis revealed that persistent fracture non-unions could be predicted with a sensitivity/specificity of 88.7%/72.2% in lower-limb non-unions and a sensitivity/specificity of 66.7%/100.0% in upper-limb non-unions. CEUS is a suitable diagnostic tool in predicting treatment failure as early as 12 wk after non-union surgery and should be integrated into the clinical routine when deciding on revision surgery at an early stage.     

The AMANDUS Project—Advanced Microperfusion Assessed Non-Union Diagnostics With Contrast-Enhanced Ultrasound (CEUS) for the Detection of Infected Lower Extremity Non-Unions

The pre-operative determination of infection plays a decisive role in non-union treatment. This study investigated in a large cohort the diagnostic potential of contrast-enhanced ultrasound (CEUS) as stand-alone method for the differentiation between aseptic and infected non-unions. Of 109 patients with lower extremity non-unions (tibia n = 78, femur n = 31) osseous perfusion with CEUS was prospectively assessed before revision surgery. The perfusion was quantified via time-intensity curves and peak enhancement (PE) (arbitrary unit [au]). Significant perfusion differences between aseptic and infected non-unions were evident (PE, p < 0.001). The sensitivity and specificity for the detection of infected tibial and femoral non-unions could be determined with 85.1% and 88.7% (cutoff PE: 81.2 au). CEUS illustrates tibial and femoral non-union perfusion in real time and discriminates reliably between aseptic and infected non-unions. Consequently, when CEUS is integrated into the diagnostic routine algorithm, non-union revision surgery can be planned more accurately as a single or multistep procedure.     

The AMANDUS Project PART II—Advanced Microperfusion Assessed Non-Union Diagnostics with Contrast-Enhanced Ultrasound (CEUS): A Reliable Diagnostic Tool for the Management and Pre-operative Detection of Infected Upper-Limb Non-unions

The management of upper-limb non-unions can be challenging, especially when infection is existent. Thus, pre-operative detection of infection plays a relevant role in non-union treatment. This study investigated in a large cohort the diagnostic potential of contrast-enhanced ultrasound (CEUS) as stand-alone method for differentiating between aseptic and infected upper-limb non-unions. Osseous perfusion of 50 upper-extremity non-unions (radius/ulna, n = 20; humerus, n = 22; clavicle, n = 8) was prospectively assessed with CEUS before revision surgery. The perfusion was quantified via time-intensity curves and peak enhancement (in arbitrary units). Significant perfusion differences between aseptic and infected non-unions could be detected (peak enhancement, p < 0.001). The sensitivity and specificity for the detection of infected upper-limb non-unions were 80% and 94.3% (cutoff peak enhancement: 130.8 arbitrary units). CEUS reliably differentiates between aseptic and infected upper-limb non-unions. Consequently, CEUS should be integrated into the daily diagnostic routine algorithm to plan non-union revision surgery more precisely as a single- or multi-step procedure.     

Utilizing Contrast-Enhanced Ultrasound Imaging for Evaluating Fatty Liver Disease Progression in Pre-clinical Mouse Models

We developed a protocol to investigate and optimize the application of contrast-enhanced ultrasound (CEUS) to non-invasive diagnosis of progressing fatty liver disease in mouse models. Eighteen 4-wk-old male C57 L/J mice were randomly assigned to one of the three groups and placed on a control diet, high-fat diet or non-alcoholic steatohepatitis diet for the next 10 wk. After 14 wk, B-mode imaging and CEUS imaging using a VisualSonics Vevo2100 system were performed. CEUS imaging and data analysis using three different parameters—peak enhancement, wash-in rate and wash-in perfusion index—revealed a significant decrease in representative blood flow in the high-fat diet group versus controls and a further significant decrease in the non-alcoholic steatohepatitis group (p < 0.001; n?=?6/group). In conclusion, compared with B-mode imaging, non-targeted CEUS imaging was more sensitive in diagnosing early-stage fatty infiltration-mediated vascularity changes in liver parenchyma and provided a more accurate steatohepatitis diagnosis in mouse models.     

肾肿瘤的超声造影研究

目的探讨各种不同肾肿瘤的超声造影表现。方法124例肾肿瘤（平均直径3.4cm）,应用超声造影观察肿块回声增强时间和造影剂消退时间（皮质相与延迟相）,观察肿块的假包膜（与二维声像图对比）,所有患者均行手术和病理证实。结果透明细胞癌和乳头状癌98例,移行细胞癌5例,肾盂鳞癌6例,血管平滑肌脂肪瘤7例,肾盂上皮细胞癌1例,肾母细胞瘤5例,嗜酸细胞瘤2例（潜在恶性）。透明细胞癌98中超声造影有58例出现假包膜（58/98,73.3%）,而二维声像图显示假包膜31例（31/98,17%）;造影剂呈快进快退76例,快进慢退11例,慢进慢退7例,肿块局部回声增强4例。而血管平滑肌脂肪瘤回声增强程度明显低于肾细胞癌。结论超声造影有助于鉴别肾肿瘤,有助于显示出肾细胞癌的假包膜。     

Contrast-enhanced Doppler perfusion index: clinical and experimental evaluation.

OBJECTIVE: To assess the potential of the power Doppler signal intensity rate of enhancement due to contrast agent wash-in for assessment of hepatic hemodynamics. METHODS: With the use of standardized settings, power Doppler sonography was performed before and after administration of a contrast agent. Video-recorded examinations were digitized for offline analysis on a personal computer. The temporal changes of the power Doppler signal intensity were quantified to provide contrast agent wash-in curves. The contrast-enhanced Doppler perfusion index was defined by the ratio of the wash-in gradient of the hepatic artery and portal vein as contrast-enhanced Doppler perfusion index = hepatic artery gradient/(hepatic artery gradient + portal vein gradient). The contrast-enhanced Doppler perfusion index was evaluated at 4 contrast agent doses in each of 14 patients with liver metastases and 3 patients with hemangiomas. An in vitro flow model was used to determine the relationships between the power Doppler rate of enhancement and flow in vessels of 4, 8, and 12 mm in diameter. RESULTS: In vivo, there was a significantly higher (P < .0001) mean contrast enhanced Doppler perfusion index in patients with liver metastases (mean, 0.59; 95% confidence interval, 0.54-0.63), compared with patients with hemangiomas (mean, 0.33; 95% confidence interval, 0.24-0.41). The corresponding coefficients of variations were 25% for patients with liver metastases and 31% for patients with hemangiomas. In vitro, the power Doppler rate of enhancement was proportional to flow speed and independent of vessel diameter. CONCLUSIONS: Measurement of the contrast-enhanced Doppler perfusion index may have potential in assessment of hepatic hemodynamics and focal liver disease.     

A Study on Correlation between Contrast-Enhanced Ultrasound Parameters and Pathological Features of Diabetic Nephropathy

The objective of this study was to evaluate the correlation between contrast-enhanced ultrasound (CEUS) parameters and histopathological features in patients with diabetic nephropathy (DN). Sixty-two patients with DN (44 men, mean age: 52.61 ± 10.63 y) were enrolled. They underwent renal biopsy for DN at the Department of Ultrasound, PLA Hospital, between May 2017 and February 2020. Renal tissue was obtained by ultrasound-guided percutaneous needle biopsy. CEUS was performed, and time–intensity curves (TICs) and renal perfusion parameters were analyzed. Differences in CEUS parameters were analyzed according to the glomerular classification and interstitial fibrosis–tubular atrophy (IFTA) score. Continuous variables were evaluated using the analysis of variance or Mann–Whitney U-test. Discontinuous variables were compared with the χ²-test. Spearman correlation analyses evaluated associations among quantitative ultrasound perfusion parameters and histopathological characteristics. Peak enhancement (PE), wash-in rate (WiR), wash-in perfusion index (WiPI) and wash-out rate (WoR) of the cortex, and their cortex/medulla ratios, decreased with increasing glomerular classification grade (p < 0.05). The fall time (FT) of the cortex, and their cortex/medulla ratios, increased with increasing glomerular classification grade (p < 0.05). There were no significant differences in the CEUS parameters for different IFTA scores. The perfusion volume-relevant parameters (such as PE, WiR and WiPI) had a negative correlation (p < 0.05), while the perfusion time-relevant parameters (such as RT and FT) had a positive correlation (p < 0.05), with the severity of glomerular lesions, glomerulosclerosis rate and number of Kimmelstiel–Wilson lesions. The CEUS parameters of the cortex could reflect pathological characteristics, especially changes in glomerular lesions.     

Potential Application Value of Contrast-Enhanced Ultrasound In Neoadjuvant Chemotherapy of Breast Cancer

The purpose of this study was to investigate the value of contrast-enhanced ultrasound (CEUS) in evaluating the response of breast cancer to neoadjuvant chemotherapy (NAC). The study included 31 breast cancer patients who were treated with NAC between August 2010 and October 2011. All patients were evaluated by both conventional ultrasound (US) and CEUS. The tumor sizes measured by CEUS were larger and more accurately imaged than those evaluated by US. Necrosis at the tumor center could be detected by CEUS, which showed a local blood perfusion defect in 26 cases (83.9%) before NAC and 27 cases (87.1%) after NAC, whereas US did not show liquefaction in any patient. The CEUS time-intensity curve displayed quantitatively the tumors' blood-perfusion changes; after NAC, blood perfusion reduced, enhancement intensity decreased, time to peak increased, peak intensity reduced, and the wash-in slope reduced (p < 0.05). Overall, the CEUS is a promising tool for evaluating the response of breast cancer to NAC.     

Contrast-Enhanced Ultrasound Characteristics of Breast Cancer: Correlation with Prognostic Factors

The purpose of the work described here was to investigate the correlation of contrast-enhanced ultrasound (CEUS) characteristics with prognostic factors in breast cancer. Forty-five consecutive breast cancer patients were studied with CEUS. All patients were diagnosed with invasive ductal carcinoma on the basis of biopsy or surgery results. Lack of blood perfusion of the tumor was identified in 2 cases; blood perfusion was observed in 43 cases. Enhancement was heterogeneous in 25 cases, and centripetal in 25 cases. A blood perfusion defect was present in 27 cases. Enhancement shape was irregular in 37 cases, margins were poorly defined in 34 cases, and penetrating vessels were present in 32 cases. Compared with the surrounding normal tissue, tumor tissue had faster rising times and times to peak and higher peak intensities and wash-in slopes; the differences between the two groups were statistically significant (p < 0.05). Compared with the interior of the tumor, the periphery had faster times to peak and higher peak intensities and wash-in slopes (p < 0.05). Heterogeneous enhancement, perfusion defect, centripetal enhancement and penetrating vessels were correlated with prognosis (p < 0.05). Overall, some CEUS characteristics of breast cancer were associated with prognostic factors that can predict breast cancer prognosis in vivo.     

超声造影鉴别诊断子宫内膜良恶性病变

目的 探讨CEUS时相及时间-强度曲线(TIC)鉴别诊断子宫内膜良恶性病变的价值。 方法 回顾性分析47例阴道不规则出血或排液患者,其中23例为子宫内膜癌(恶性组),24例为良性病变(良性组),分析其CEUS表现及TIC参数,并进行统计学比较。 结果 灌注时相:恶性组中52.17%(12/23)早于肌层灌注,47.83%(11/23)同步或晚于肌层灌注;良性组中16.67%(4/24)早于肌层灌注,83.33%(20/24)同步或晚于肌层灌注,二者差异具有统计学意义(P=0.028)。洗出时相:恶性组中82.61%(19/23)早于肌层洗出,良性组62.50%(15/24)早于肌层洗出,差异具有统计学意义(P=0.037)。良性组与恶性组子宫内膜的造影剂到达时间(AT)差异无统计学意义(P >0.05),达峰时间(TTP)及达峰强度(PI)的差异有统计学意义(P均<0.05)。 结论 子宫内膜良恶性病变的CEUS时相与TIC参数具有一定特征性,联合应用二者能够为临床提供丰富的信息,有助于鉴别良恶性子宫内膜病变。     

Revised Value of Contrast-Enhanced Ultrasound for Solid Hypo-Echoic Thyroid Nodules Graded with the Thyroid Imaging Reporting and Data System

The use of ultrasound in differentiation of benign and malignant solid hypo-echoic thyroid nodules is a dilemma in clinical practice. The aim of this study was to investigate the revised value of contrast-enhanced ultrasound (CEUS) for differentiating solid hypo-echoic thyroid nodules using the Thyroid Imaging Reporting and Data System (TI-RADS).The study included 135 patients with 135 nodules confirmed by fine-needle aspiration and/or surgery. Every nodule underwent both conventional US and CEUS. Binary logistic regression analysis for conventional US features revealed that irregular shape, microcalcification and height greater than width were significant malignant predictive features. Binary logistic analysis for CEUS features indicated that hetero-enhancement, slow wash-in, an ill-defined enhancement border and fast wash-out were significantly associated with malignancy. The areas under the curve of the TI-RADS, CEUS and the combination were 0.806, 0.934 and 0.950, respectively. CEUS is a potentially useful tool in the differentiation of solid hypo-echoic thyroid nodules.     

The feasibility of low mechanical index contrast enhanced ultrasound (CEUS) in distinguishing malignant from benign thoracic lesions

We proposed to assess the feasibility of low mechanical index (MI) contrast enhanced ultrasound (CEUS) in the characterisation of thoracic lesions. Fifty patients were prospectively examined by CEUS and images acquired on a low MI (0.17–0.24) setting following injection of SonoVue. From region-of-interest (ROI) generated signal intensity (SI) time curves, the maximum SI, bolus arrival time (BAT), time to peak intensity (TTP), wash-in slope and mean transit time (MTT) were calculated. Using the Wilcoxon rank test; parameters and threshold values for positive differentiation were determined. In addition, for the parameters that allowed positive differentiation between malignant and benign lesions receiver operator curves (ROC) were obtained. The wash-in slope, TTP and MTT (p = 0.0003, <0.0001, 0.02) allowed positive differentiation. The sensitivity and specificity was 93% and 78%, with 6.87 s⁻¹ threshold value for the wash-in slope, 78% and 89% with 11.84 s threshold for the TTP and 48% and 89% with 78.6 s threshold for the MTT. CEUS is a useful tool for differentiating malignant and benign thoracic lesions.     

小肾癌的超声造影诊断和鉴别诊断

目的探讨超声造影对直径≤3cm小肾癌的诊断价值。方法回顾性分析85例经手术病理证实的小肾癌病例超声造影资料。结果 85例小肾癌中,5例囊性肾癌超声造影时可见分隔状强化,80例实性小肾癌中超声造影呈"快进快退"52例,"快进慢出"20例,"慢进快出"4例,"慢进慢出"4例。小肾癌超声造影时多呈富血供表现,其坏死灶和假包膜造影后更易显示。结论超声造影对常规超声诊断有困难或结果不一致的肾脏小占位病变有重要的诊断和鉴别价值。     

Contrast-Enhanced Ultrasound Findings and Differential Diagnosis of Hepatic Epithelioid Angiomyolipoma Compared with Hepatocellular Carcinoma

Hepatic epithelioid angiomyolipoma (EAML) has malignant potential that can easily be misdiagnosed as hepatocellular carcinoma (HCC), but the treatment options of these conditions are different. This retrospective study investigated whether contrast-enhanced ultrasound (CEUS) can differentiate EAML from HCC. We included 24 patients with pathologically confirmed EAML and 36 patients with HCC who underwent pre-operative conventional ultrasound and CEUS. The conventional ultrasound and CEUS features of the two groups were analyzed. Time intensity curves (TICs) were analyzed for all lesions using quantitative perfusion analysis software. This study found that significant differences existed between the EAML and HCC groups in terms of clinical features such as sex, age, symptoms, alpha-fetoprotein and history of hepatitis B virus infection (p < 0.05). Tumor size, number, border and echogenicity on conventional ultrasound were significantly different between EAML and HCC (p < 0.05). Regarding CEUS, EAML was more likely to have a centripetal enhancement pattern than HCC (p < 0.05). The tumor enhancement degree in the delayed phase in CEUS was significantly different between EAML and HCC (p < 0.05). Quantitative analysis of CEUS parameters revealed that the wash-in area under the curve (AUC) was larger in EAML than in HCC (p < 0.05). Time to peak was significantly shorter in EAML than in HCC (p < 0.05). The peak intensity was significantly stronger in EAML than in HCC (p < 0.05). Regarding the diagnostic performance of CEUS parameters that showed statistical significance on univariate analysis, the sensitivity and specificity for distinguishing EAML from HCC was 66.7%–100.0% and 55.6%–91.7%, respectively. Overall, CEUS could be valuable in differentiating EAML from HCC. Specific features such as the centripetal filling and prolonged enhancement patterns on CEUS, higher peak intensity, bigger wash-in AUC and shorter time to peak on TICs may contribute to a more confirmative differential diagnosis of EAML.     

超声造影在膀胱占位性病变中的诊断价值

目的 探讨超声造影在膀胱占位性病变中的诊断价值.方法 157例膀胱可疑占位性病变患者,共169个病灶结节,超声造影观测其造影剂灌注模式,病变造影时间-强度曲线的上升时间(RT)、达峰时间(TTP)和峰值强度(IMAX).结果 116个膀胱癌病灶,96个表现为“快进慢退”,呈高增强;16个表现为“快进快退”,呈高增强;4个呈等增强.23个腺性膀胱炎病灶中,18个与周围正常膀胱壁同步增强和消退,5个表现为“快进慢退”.22个膀胱内血块和3个膀胱前壁混响伪像在造影过程中始终无增强.5个前列腺增生组织突入膀胱内,与前列腺组织同步增强和消退,无明显分界线.与自身膀胱壁比较,膀胱恶性肿瘤RT、TTP缩短,IMAX增强(P＜0.05).对膀胱占位性病变诊断准确率,常规超声为85.8％,超声造影为97.0％.结论 超声造影可为膀胱占位性病变的鉴别诊断提供强有力的依据.     

Value of Contrast-Enhanced Ultrasound in Differentiating Clinically Atypical Subacute Thyroiditis from Papillary Thyroid Carcinomas

Our objective was to provide the various sonographic characteristics of clinically atypical subacute thyroiditis (CAST) in distinguishing CAST from papillary thyroid carcinomas (PTCs) by using conventional ultrasound (US) and contrast-enhanced ultrasound (CEUS). Forty-six CAST patients and 50 PTC patients were enrolled in this study. We evaluated the size, shape, margin, echogenicity, calcification, vascularity and CEUS parameters for each nodule. The final diagnosis of CAST was confirmed via fine-needle aspiration (FNA) or surgery. Of the 46 CASTs, 13 (28.3%) were confirmed by surgery to be benign, and 33 (71.7%) were proven by FNA to be benign. Univariate analysis indicated that compared with PTCs, CAST lesions more frequently had wider-than-taller shapes, blurred margins, the absence of microcalcifications, peripheral high echogenicity, the absence of internal vascularity, hypo-enhancement, centrifugal perfusion and a peak intensity index <1 and area under the curve index <1 on pre-operative US and CEUS. A multivariate analysis revealed that clear margins, microcalcifications and centripetal perfusion were independent characteristics related to PTCs for their differentiation from CAST (all p values <0.05). Our study indicated that the pre-operative multiparameter US characteristics may serve as a useful tool for distinguishing CAST from malignant thyroid nodules to avoid surgical excisions or unnecessary FNAs.     

实时超声造影在正常移植肝血流动力学研究中的应用

目的：应用实时超声造影定量研究正常移植肝的灌注，并与正常人肝脏灌注特点比较，总结移植肝的血流动力学特征。方法：选取原位肝移植术后临床指标正常的患者30例，健康志愿者35例，分别对肝脏行实时造影及声学定量分析，比较肝实质的灌注及血流动力学特点。结果：实时超声造影可动态显示肝实质内造影剂的增强过程，其时间一信号强度曲线客观反映造影剂的渡越过程。正常移植肝组与健康人组肝动脉显影时间、门静脉显影时间、肝静脉显影时间、肝动静脉渡越时间，肝动脉－门静脉渡越时间、肝实质开始显影时间、增强峰值时间、峰值强度等与健康人组均无显著差异。结论：本研究初步结果显示移植肝的灌注特征与正常肝脏一致，利用超声造影肝脏灌注显像对移植肝并发症的诊断时，可以考虑采用正常肝脏的指数。     

Contrast-Enhanced Ultrasound Assisted Surgery of Intramedullary Spinal Cord Tumors: Analysis of Technical Benefits and Intra-operative Microbubble Distribution Characteristics

Intra-operative contrast-enhanced ultrasound (CEUS) is a relatively standardized procedure in brain neurosurgery, but it is still underused in spinal cord and intramedullary tumor evaluation. We reviewed and analyzed the intra-operative data from a surgical series of patients harboring intramedullary spinal cord tumors who underwent surgery under CEUS guidance. CEUS was performed in 12 patients (age range: 13–55 y); all lesions had ill-defined boundaries or peritumoral cysts at preliminary intra-operative B-mode ultrasound. CEUS highlighted the tumors in all cases. The contrast agent's spinal distribution revealed different phases (arterial, peak, washout), as observed in the brain, but these appeared to be slower and less intense. In our experience, intra-operative CEUS allows surgeons to assess spinal cord perfusion and highlight intramedullary tumors in real time. As for other imaging modalities, ultrasound contrast agents add valuable information over baseline imaging, and their use should be fostered to better understand microbubble distribution dynamics.     

Contrast-enhanced ultrasound to evaluate changes in renal cortical perfusion around cardiac surgery: a pilot study

Introduction

Contrast-enhanced ultrasound (CEUS) is a new technique that might enable portable and non-invasive organ perfusion quantification at the bedside. However, it has not yet been tested in critically ill patients. We sought to establish CEUS''s feasibility, safety, reproducibility and potential diagnostic value in the assessment of renal cortical perfusion in the peri-operative period in cardiac surgery patients.

Methods

We recruited twelve patients deemed at risk of acute kidney injury (AKI) planned for elective cardiac surgery. We performed renal CEUS with destruction-replenishment sequences before the operation, on ICU arrival and the day following the admission. Enhancement was obtained with Sonovue^® (Bracco, Milano, Italy) at an infusion rate of 1 ml/min. We collected hemodynamic parameters before, during and after contrast agent infusion. At each study time, we obtained five video sequences, which were analysed using dedicated software by two independent radiologists blinded to patient and time. The main output was a perfusion index (PI), corresponding to the ratio of relative blood volume (RBV) over mean transit time (mTT).

Results

All 36 renal CEUS studies, including 24 in the immediate post-operative period could be performed and were well tolerated. Correlation between readers for PI was excellent (R² = 0.96, P < 0.0001). Compared with baseline, there was no overall difference in median PI''s on ICU admission. However, the day after surgery, median PI''s had decreased by 50% (P < 0.01) (22% decrease in RBV (P = 0.09); 48% increase in mTT (P = 0.04), both suggestive of decreased perfusion). These differences persisted after correction for haemoglobin; vasopressors use and mean arterial pressure. Four patients developed AKI in the post-operative period.

Conclusions

CEUS appears feasible and well-tolerated in patients undergoing cardiac surgery even immediately after ICU admission. CEUS derived-parameters suggest a decrease in renal perfusion occurring within 24 hours of surgery.     

Contrast-enhanced ultrasound: a new vision of microcirculation in the intensive care unit

To gain new insights into renal perfusion and pathogenesis of acute kidney injury in intensive care unit (ICU) patients, we need new techniques to evaluate renal microcirculation. In addition, a bedside technique applicable in the ICU could be extremely useful for physicians to adjust the optimal therapeutic/preventive modalities for kidney perfusion in each patient. Contrast-enhanced ultrasound (CEUS) has been validated to assess and quantify the microcirculation up to capillary perfusion in several organs. In a recent issue, Schneider and colleagues suggest that CEUS is feasible, well tolerated and able to quantify cortical renal microcirculation in patients undergoing cardiac surgery. In addition, CEUS derived-parameters suggest a decrease in renal perfusion occurring within 24 hours of surgery in patients at risk of acute kidney injury. This study opens up new possibilities for the assessment of cortical renal microcirculation in ICU patients.