Ultrasound Contrast Agents in the Study of Kidney Function in Health and Disease

B-mode and contrast-enhanced ultrasonography for intestinal assessment in dogs: A review

Ultrasound (USG) is a valuable diagnostic tool for evaluating the gastrointestinal tract of small animals, providing noninvasive and dynamic information. This review discusses intestinal evaluation in dogs using B-mode ultrasound and advanced contrast-enhanced ultrasound (CEUS) with microbubbles. B-mode USG allows the examination of the thickness and stratification of the intestinal wall, motility, and adjacent structures, such as lymph nodes and peritoneum to be examined. Reference values for intestinal wall thickness in dogs are based on body weight. The duodenum, jejunum, and ileum can be differentiated sonographically by location wall stratification, and relationship to other intestinal segments. Intestinal motility is assessed by counting peristaltic waves, and abnormalities indicate various diseases. CEUS uses microbubble-based contrast agents, such as sulfur hexafluoride, which remain stable in the vascular system and are eliminated by the lungs. This technique improves the perception of ultrasound echoes, making it possible to quantify tissue perfusion using parameters such as entry time, peak enhancement, and exit time. In human medicine, CEUS is used to assess intestinal perfusion in conditions such as Crohn's disease and ischemia. In veterinary medicine, this technique has been used to assess duodenal perfusion in healthy dogs and those with chronic enteropathies or alimentary lymphoma. Although CEUS shows potential in differentiating dogs with chronic enteropathies from healthy controls, more research is needed to standardize the methodology, establish reference values, and define clinical applications in various canine intestinal diseases. The combination of B-mode USG and CEUS provides a noninvasive assessment of intestinal morphology and function, contributing to the understanding of the pathophysiology of enteropathies in dogs.

Theranostics in the vasculature: bioeffects of ultrasound and microbubbles to induce vascular shutdown

Ultrasound-triggered microbubbles destruction leading to vascular shutdown have resulted in preclinical studies in tumor growth delay or inhibition, lesion formation, radio-sensitization and modulation of the immune micro-environment. Antivascular ultrasound aims to be developed as a focal, targeted, non-invasive, mechanical and non-thermal treatment, alone or in combination with other treatments, and this review positions these treatments among the wider therapeutic ultrasound domain. Antivascular effects have been reported for a wide range of ultrasound exposure conditions, and evidence points to a prominent role of cavitation as the main mechanism. At relatively low peak negative acoustic pressure, predominantly non-inertial cavitation is most likely induced, while higher peak negative pressures lead to inertial cavitation and bubbles collapse. Resulting bioeffects start with inflammation and/or loose opening of the endothelial lining of the vessel. The latter causes vascular access of tissue factor, leading to platelet aggregation, and consequent clotting. Alternatively, endothelium damage exposes subendothelial collagen layer, leading to rapid adhesion and aggregation of platelets and clotting. In a pilot clinical trial, a prevalence of tumor response was observed in patients receiving ultrasound-triggered microbubble destruction along with transarterial radioembolization. Two ongoing clinical trials are assessing the effectiveness of ultrasound-stimulated microbubble treatment to enhance radiation effects in cancer patients. Clinical translation of antivascular ultrasound/microbubble approach may thus be forthcoming.

Evaluation of Contrast-Enhanced Ultrasound in Diagnosis of Acute Kidney Injury of Patients in Intensive Care Unit

Background

Ultrasound can assess renal perfusion, but its role in the evaluation of acute kidney injury (AKI) is still unclear. This prospective cohort study was to investigate the value of contrast-enhanced ultrasound (CEUS) in the evaluation of AKI in intensive care unit (ICU) patients.

Methods

Fifty-eight patients were recruited from ICU between October 2019 and October 2020, and CEUS was used to monitor the renal microcirculation perfusion within 24h after admission. Parameters included rise time (RT), time to peak intensity (TTP), amplitude of peak intensity (PI), area under the curve (AUC), time from peak to one half (TP1/2) of renal cortex and medulla. Ultrasonographical findings, demographics, laboratory, etc were collected for further analysis.

Results

There were 30 patients in the AKI group and 28 patients in the non-AKI group. The TTP, PI, TP1/2 of the cortex and the RT, TTP, TP1/2 of the medulla in the AKI group were significantly longer than in the non-AKI group (P < 0.05);. The TTP (OR = 1.261, 95% CI: 1.083-1.468, P = 0.003) (AUCs 0.733, Sen% 83.3, Spe%57.1), TP1/2 (OR = 1.079, 95% CI: 1.009-1.155, P = 0.027) (AUCs 0.658, Sen% 76.7, Spe%50.0) of the cortex and RT (OR = 1.453, 95% CI: 1.051-2.011, P = 0.024) (AUCs 0.686, Sen% 43.3, Spe%92.9) of the medulla were related to the AKI. Eight new-onset AKI cases occurred in the non-AKI group within 7 days, the RT, TTP, TP1/2 of the cortex and medulla were significantly longer in the new-onset AKI group than in the non-AKI group (P < 0.05), but serum creatinine and blood urea nitrogen were no differences between groups (P > 0.05).

Conclusion

This study indicates CEUS can assess the renal perfusion in AKI. TTP and TP1/2 of the cortex and RT of the medulla can aid the diagnosis of AKI in ICU patients.

[Contrast-enhanced ultrasound: history, application and perspectives]

The article discusses the stages of formation and development of ultrasound diagnostics, including those with contrast enhancement. The main types of contrast agents and their mechanism of action are presented. Examples of the use of contrast-enhanced ultrasound in various fields of medicine are given. The prospects of the method and its place in clinical practice are discussed.

Artifacts and Technical Considerations at Contrast-enhanced US

Contrast-enhanced US (CEUS), similar to other radiologic modalities, requires specific technical considerations and is subject to image artifacts. These artifacts may affect examination quality, negatively impact diagnostic accuracy, and decrease user comfort when using this emerging technique. Some artifacts are related to commonly known gray-scale US artifacts that can also appear on the contrast-only image (tissue-subtracted image obtained with the linear responses from background tissues nulled). These may include acoustic shadowing and enhancement; reverberation, refraction, and reflection; and poor penetration. Other artifacts are exclusive to CEUS owing to the techniques used for contrast mode image generation and the unique properties of the microbubbles that constitute ultrasound-specific contrast agents (UCAs). UCA-related artifacts may appear on the contrast-only image, the gray-scale image, or various Doppler mode images. Artifacts related to CEUS may include nonlinear artifacts and unintentional microbubble destruction resulting in pseudowashout. The microbubbles themselves may result in specific artifacts such as pseudoenhancement, signal saturation, and attenuation and shadowing and can confound the use of color and spectral Doppler US. Identifying and understanding these artifacts and knowing how to mitigate them may improve the quality of the imaging study, increase user confidence, and improve patient care. The authors review the principles of UCAs and the sound-microbubble interaction, as well as the technical aspects of image generation. Technical considerations, including patient positioning, depth, acoustic window, and contrast agent dose, also are discussed. Specific artifacts are described, with tips on how to identify and, if necessary, apply corrective measures, with the goal of improving examination quality. ^© RSNA, 2022 Online supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article.

Quantitative assessment of renal obstruction in multi-phase CTU using automatic 3D segmentation of the renal parenchyma and renal pelvis: A proof of concept

Purpose

Quantitative evaluation of renal obstruction is crucial for preventing renal atrophy. This study presents a novel method for diagnosing renal obstruction by automatically extracting objective indicators from routine multi-phase CT Urography (CTU).

Material and methods

The study included multi-phase CTU examinations of 6 hydronephrotic kidneys and 24 non-hydronephrotic kidneys (23,164 slices). The developed algorithm segmented the renal parenchyma and the renal pelvis of each kidney in each CTU slice. Following a 3D reconstruction of the parenchyma and renal pelvis, the algorithm evaluated the amount of the contrast media in both components in each phase. Finally, the algorithm evaluated two indicators for assessing renal obstruction: the change in the total amount of contrast media in both components during the CTU phases, and the drainage time, "T1/2", from the renal parenchyma.

Results

The algorithm segmented the parenchyma and renal pelvis with an average dice coefficient of 0.97 and 0.92 respectively. In all the hydronephrotic kidneys the total amount of contrast media did not decrease during the CTU examination and the T1/2 value was longer than 20 min. Both indicators yielded a statistically significant difference (p < 0.001) between hydronephrotic and normal kidneys, and combining both indicators yielded 100% accuracy.

Conclusions

The novel algorithm enables accurate 3D segmentation of the renal parenchyma and pelvis and estimates the amount of contrast media in multi-phase CTU examinations. This serves as a proof-of-concept for the ability to extract from routine CTU indicators that alert to the presence of renal obstruction and estimate its severity.

Dual-Mode Fluorescence/Ultrasound Imaging with Biocompatible Metal-Doped Graphene Quantum Dots

Sonography offers many advantages over standard methods of diagnostic imaging due to its non-invasiveness, substantial tissue penetration depth, and low cost. The benefits of ultrasound imaging call for the development of ultrasound-trackable drug delivery vehicles that can address a variety of therapeutic targets. One disadvantage of the technique is the lack of high-precision imaging, which can be circumvented by complementing ultrasound contrast agents with visible and, especially, near-infrared (NIR) fluorophores. In this work, we, for the first time, develop a variety of lightly metal-doped (iron oxide, silver, thulium, neodymium, cerium oxide, cerium chloride, and molybdenum disulfide) nitrogen-containing graphene quantum dots (NGQDs) that demonstrate high-contrast properties in the ultrasound brightness mode and exhibit visible and/or near-infrared fluorescence imaging capabilities. NGQDs synthesized from glucosamine precursors with only a few percent metal doping do not introduce additional toxicity in vitro, yielding over 80% cell viability up to 2 mg/mL doses. Their small (<50 nm) sizes warrant effective cell internalization, while oxygen-containing surface functional groups decorating their surfaces render NGQDs water soluble and allow for the attachment of therapeutics and targeting agents. Utilizing visible and/or NIR fluorescence, we demonstrate that metal-doped NGQDs experience maximum accumulation within the HEK-293 cells 6-12 h after treatment. The successful 10-fold ultrasound signal enhancement is observed at 0.5-1.6 mg/mL for most metal-doped NGQDs in the vascular phantom, agarose gel, and animal tissue. A combination of non-invasive ultrasound imaging with capabilities of high-precision fluorescence tracking makes these metal-doped NGQDs a viable agent for a variety of theragnostic applications.

Applications of Contrast-Enhanced Ultrasound in Splenic Studies of Dogs and Cats

Simple Summary

Contrast-enhanced ultrasound (CEUS) is a noninvasive imaging technique that has become a reliable tool for identifying and monitoring lesions in both human and animals. In the last decade, its use in veterinary diagnostic imaging has gained increasing importance, and it can be reliable in everyday clinical practice. However, there is a lack of reviews describing existing CEUS results in the study of splenic lesions, which is of particular importance in dogs and cats. This information is important for validating its efficacy, to facilitate decision making related to sampling procedures and diagnosis, or even as a means to select CEUS as an alternative diagnostic tool in specific cases. Our goal was to review the existing studies of CEUS applications for splenic ultrasound studies in cats and dogs, present these results in a systematic manner, and combine this information into practical guidelines that can be used to help diagnosis and interpretation in both clinical cases and research.

Abstract

Contrast-enhanced ultrasound (CEUS) is an emerging technology in veterinary medicine involving the administration of intravenous contrast agents, and it is increasingly recognized for its high potential as a diagnostic imaging tool for small animals. This exam is easy and quick to perform, safe and reliable, and allows for the differentiation of lesions. It permits the identification of lesions that may require more invasive procedures, from those that can be safely dismissed to those that can be followed-up with ultrasound imaging. Although it has been extensively reviewed for use in human medicine, there is an overall lack of information about the application of this technique for cats and dogs, particularly in splenic studies, which can be particularly important for small animals. The present review describes and summarizes the CEUS applications used for splenic analysis in cats and dogs, providing a basic overview of CEUS technology with examples of common and uncommon features of focal splenic lesions. It also systematically gathers the results obtained for benign and malignant splenic lesions described in the literature, whilst providing guidelines for their interpretation. Furthermore, it presents the advantages of using CEUS for splenic analysis in cats and dogs and the main factors that may influence the quality of the imaging and the accuracy of the diagnosis. This type of knowledge can be used to provide a framework to help veterinarians make informed decisions regarding the use of this emerging technique for splenic lesions, guiding their interpretation of CEUS findings in the splenic ultrasounds of cats and dogs.

Imaging of Benign and Malignant Breast Lesions Using Contrast-Enhanced Ultrasound: A Pictorial Essay

ABSTRACT

Contrast-enhanced ultrasound is a promising noninvasive imaging technique for evaluating benign and malignant breast lesions, as contrast provides information about perfusion and microvasculature. Contrast-enhanced ultrasound is currently off-label use in the breast in the United States, but its clinical and investigational use in breast imaging is gaining popularity. It is important for radiologists to be familiar with the imaging appearances of benign and malignant breast masses using contrast-enhanced ultrasound. This pictorial essay illustrates enhancement patterns of various breast masses from our own experience. Pathologies include subtypes of invasive breast cancer, fibroadenomas, papillary lesions, fibrocystic change, and inflammatory processes. Contrast-enhanced ultrasound pitfalls and limitations are discussed.

Predicting the Risk of Acute Kidney Injury in Patients After Percutaneous Coronary Intervention (PCI) or Cardiopulmonary Bypass (CPB) Surgery: Development and Assessment of a Nomogram Prediction Model

Background

We sought to create a model that incorporated ultrasound examinations to predict the risk of acute kidney injury (AKI) after percutaneous coronary intervention (PCI) or cardiopulmonary bypass (CPB) surgery.

Material/Methods

A total of 292 patients with AKI after PCI or CPB surgery were enrolled for the study. Afterwards, treatment-related information, including data pertaining to ultrasound examination, was collected. A random forest model and multivariate logistic regression analysis were then used to establish a predictive model for the risk of AKI. Finally, the predictive quality and clinical utility of the model were assessed using calibration plots, receiver-operating characteristic curve, C-index, and decision curve analysis.

Results

Predictive factors were screened and the model was established with a C-index of 0.955 in the overall sample set. Additionally, an area under the curve of 0.967 was obtained in the training group. Moreover, decision curve analysis also revealed that the prediction model had good clinical applicability.

Conclusions

The prediction model was efficient in predicting the risk of AKI by incorporating ultrasound examinations and a number of factors. Such included operation methods, age, congestive heart failure, body mass index, heart rate, white blood cell count, platelet count, hemoglobin, uric acid, and peak intensity (kidney cortex as well as kidney medulla).

Time-intensity curve analysis of contrast-enhanced ultrasound is unable to differentiate renal dysfunction in the early post-transplant period - a prospective study

Background

Contrast enhanced ultrasonography (CEUS) assessment of kidney allografts mainly focuses on graft rejection. However, studies on delayed graft function (DGF) without acute rejection are still lacking. The aim of this study was to build a time-intensity curve (TIC) using CEUS in non-immunological DGF to understand the utility of CEUS in early transplantation.

Methods

Twenty-eight patients in the short-term postoperative period (<14 days) were divided according to the need for dialysis (early graft function [EGF] and [DGF]) and 37 subjects with longer than 90 days follow-up were divided into creatinine tertiles. Time to peak [TTP] and rising time [RT were compared between groups.

Results

EGF and DGF were similar, except for creatinine. In comparison to the late group, medullary TTP and RT were shorter in the early group as well as the delay regarding contrast arrival in the medulla (in relation to cortex) and reaching the medullary peak (in relation to artery and cortex). In the late group, patients with renal dysfunction showed shorter temporal difference to reach medullary peak in relation to artery and cortex.

Conclusions

Although it was not possible to differentiate EGF and DGF using TIC, differences between early and late groups point to blood shunting in renal dysfunction.

Contrast-enhanced ultrasonography in chronic glomerulonephritides: correlation with histological parameters of disease activity

PURPOSE

To compare contrast-enhanced ultrasonography (CEUS)-derived time-intensity (TI) curves with histological findings in kidneys of patients affected by chronic glomerulonephritides (GN) in the early stage of disease.

METHODS

Research ethics committee approval and patient written informed consent were obtained. Thirty-one patients who showed clinical and laboratory signs of GN, with preserved renal function, were consecutively enrolled. They underwent kidney CEUS, from which TI curves were obtained, and kidney biopsy. TI curves were compared with clinical data, ultrasound (US) Doppler, and histological parameters.

RESULTS

The persistence of contrast agent signal during the wash-out phase was found to be correlated with the degree of disease activity (p = 0.016) and in particular with the presence of mesangial hyperplasia (p = 0.008). No correlation was observed between TI curves and clinical or Doppler US-derived parameters.

CONCLUSIONS

The persistence of contrast agent signal in the wash-out phase of CEUS appears to reflect a disturbance of perfusion in glomerular capillaries in the early stages of GN. We found that the histological element directly correlated with the prolonged wash-out was mesangial hyperplasia.

Diagnostic accuracy of contrast-enhanced ultrasound for characterization of kidney lesions in patients with and without chronic kidney disease

BACKGROUND

Patients with chronic kidney disease are at increased risk of cystic kidney disease that requires imaging monitoring in many cases. However, these same patients often have contraindications to contrast-enhanced computed tomography and magnetic resonance imaging. This study evaluates the accuracy of contrast-enhanced ultrasound (CEUS), which is safe for patients with chronic kidney disease, for the characterization of kidney lesions in patients with and without chronic kidney disease.

METHODS

We performed CEUS on 44 patients, both with and without chronic kidney disease, with indeterminate or suspicious kidney lesions (both cystic and solid). Two masked radiologists categorized lesions using CEUS images according to contrast-enhanced ultrasound adapted criteria. CEUS designation was compared to histology or follow-up imaging in cases without available tissue in all patients and the subset with chronic kidney disease to determine sensitivity, specificity and overall accuracy.

RESULTS

Across all patients, CEUS had a sensitivity of 96% (95% CI: 84%, 99%) and specificity of 50% (95% CI: 32%, 68%) for detecting malignancy. Among patients with chronic kidney disease, CEUS sensitivity was 90% (95% CI: 56%, 98%), and specificity was 55% (95% CI: 36%, 73%).

CONCLUSIONS

CEUS has high sensitivity for identifying malignancy of kidney lesions. However, because specificity is low, modifications to the classification scheme for contrast-enhanced ultrasound could be considered as a way to improve contrast-enhanced ultrasound specificity and thus overall performance. Due to its sensitivity, among patients with chronic kidney disease or other contrast contraindications, CEUS has potential as an imaging test to rule out malignancy.

TRIAL REGISTRATION

This trial was registered in clinicaltrials.gov, NCT01751529 .

Contrast-enhanced ultrasound for differentiating benign from malignant solid small renal masses: comparison with contrast-enhanced CT

PURPOSE

The study aimed to compare the diagnostic efficiency of contrast-enhanced ultrasound (CEUS) with that of contrast-enhanced computed tomography (CECT) in the evaluation of benign and malignant small renal masses (SRMs) (<4 cm) confirmed by pathology.

METHODS

A total of 118 patients with 118 renal masses smaller than 4 cm diagnosed by both CEUS and CECT were enrolled in this study, including 25 benign lesions and 93 malignant lesions. All lesions were confirmed by histopathologic diagnosis after surgical resection. The diagnostic imaging studies of the patients were retrospectively reviewed by two independent ultrasonologists and two independent radiologists blinded to the CT or ultrasound findings and final histological results. All lesions on both CEUS and CECT were independently scored on a 3-point scale (1: benign, 2: equivocal, and 3: malignant). The concordance between interobserver agreement was interpreted using a weighted kappa statistic. The diagnostic efficiency of the evaluation of benign and malignant lesions was compared between CEUS and CECT.

RESULTS

All the 118 included lesions were detected by both CEUS and CECT. In CEUS and CECT imaging evaluation of the 118 lesions, the weighted kappa value interpreting the concordance between interobserver agreement was 0.89 (95% CI 0.79-0.98) and 0.93 (95% CI 0.87-0.99), respectively. Both CEUS and CECT demonstrated good diagnostic performance in differential diagnosis of benign and malignant SRMs with sensitivity of 93.5% and 89.2%, specificity of 68% and 76%, PPV of 91.6% and 93.3%, NPV of 73.9% and 65.5%, and AUC of 0.808 and 0.826, respectively. There was no statistically significant difference in any of the diagnostic performance indices between these two methods (P > 0.05). However, the qualitative diagnosis of small papillary renal cell carcinoma (RCC) by CEUS was significantly better than that by CECT (P < 0.05), while there was no significant difference in qualitative diagnostic accuracy on other histotypes of SRMs between CEUS and CECT (P > 0.05).

CONCLUSIONS

Both CEUS and CECT imaging modalities are effective for the differential diagnosis of benign and malignant SRMs. Furthermore, CEUS may be more effective than CECT for the qualitative diagnosis of small papillary RCC.

How to Develop a Contrast-Enhanced Ultrasound Program

With the recent Food and Drug Administration approval of Lumason (sulfur hexafluoride lipid-type A microsphere, Bracco Diagnostics Inc, Monroe Township, NJ) for contrast-enhanced ultrasound (CEUS) to characterize focal liver lesions in both adult and pediatric patients, widespread use of CEUS is expected in the United States. This paper provides guidance in setting up a CEUS program, and reviews the practical details that will need to be instituted in a standard ultrasound department to provide both safe and efficient use of CEUS. A review of the indications, contraindications, adverse events, instructions for performing the exam, and image interpretation are discussed.

Contrast-Enhanced Ultrasound Reveals Exercise-Induced Perfusion Deficits in Claudicants

Background

Contrast-Enhanced Ultrasonography (CEUS) is an imaging modality allowing perfusion quantification in targeted regions of interest of the lower extremity that has not been possible with color-flow imaging or with measurement of ankle brachial indices. We developed a protocol to quantify lower extremity muscle perfusion impairment in PAD patients in response to exercise.

Methods and findings

Thirteen patients with Rutherford Class I-III Peripheral Arterial Disease (PAD) and no prior revascularization procedures were recruited from the Baltimore Veterans Affairs Medical Center and compared with eight control patients without PAD. CEUS interrogation of the index limb gastrocnemius muscle was performed using an intravenous bolus of lipid-stabilized microsphere contrast before and after a standardized treadmill protocol. Peak perfusion (PEAK) and time to peak perfusion (TTP) were measured before and after exercise. Between and within group differences were assessed. Control subjects demonstrated a more rapid TTP (p<0.01) and an increase in peak perfusion (PEAK, p=0.02) after exercise, when compared to their baseline measures. Patients with PAD demonstrated TTP and PEAK measures equivalent to controls at baseline (p=0.39, p=0.71, respectively). However, they exhibited no significant exercise-induced changes in perfusion (TTP p=0.49 and PEAK 0.67, respectively compared to baseline). After exercise, normal subjects had significantly shorter TTP (p=0.04) and greater PEAK (p=0.02) than PAD patients.

Conclusion

Consistent with their lack of ischemic symptoms at rest, class I to III claudicant PAD patients showed similar perfusion measures (TTP and PEAK) at rest. PAD patients, however, were unable to increase perfusion in response to exercise, whereas controls increased perfusion significantly. This corresponds with claudication and limited walking capacity observed in PAD. CEUS with bolus injection offers a convenient, objective, quantitative and visual physiologic assessment of perfusion limitation in specific muscle groups of PAD patients. This has the potential for substantial clinical and research utility.

Contrast-enhanced ultrasound of both kidneys in healthy, non-anaesthetized cats

Background

Changes in perfusion are considered to play a key role in the pathophysiology of renal disease. Contrast-enhanced ultrasound (CEUS) has shown a promising diagnostic imaging technique to non-invasively and repetitively quantify tissue perfusion. Examination protocols have varied between studies regarding US equipment, quantification software, the use of sedation or anaesthesia, and animals. The purpose of the present study was, to assess the feasibility of a standardized CEUS protocol for perfusion analysis of both kidneys in nine healthy, non-anaesthetized cats.

Results

CEUS was fairly tolerable for all but one cat. In 6/18 kidneys (2 left, 4 right), a second contrast medium injection was needed due to motion artifacts. Perfusion variables such as peak intensity (PI), wash-in slope (WI_S), wash-out slope (WO_S) and mean transit time (MTT) did not significantly differ between left and right renal cortex and medulla nor between the cranial and caudal renal cortex within each kidney. In contrast, for all kidneys, mean PI, WI_S, and MTT were significantly higher in the cortex than in the medulla (P = 0.001, 0.012 and <0.001, respectively).

Conclusions

The herein reported CEUS protocol and the perfusion measurements may serve as a baseline protocol and normal reference values for the evaluation of feline patients. However, the protocol and results may be of limited value in uncooperative animals.

Inflammation in AKI: Current Understanding, Key Questions, and Knowledge Gaps

Inflammation is a complex biologic response that is essential for eliminating microbial pathogens and repairing tissue after injury. AKI associates with intrarenal and systemic inflammation; thus, improved understanding of the cellular and molecular mechanisms underlying the inflammatory response has high potential for identifying effective therapies to prevent or ameliorate AKI. In the past decade, much knowledge has been generated about the fundamental mechanisms of inflammation. Experimental work in small animal models has revealed many details of the inflammatory response that occurs within the kidney after typical causes of AKI, including insights into the molecular signals released by dying cells, the role of pattern recognition receptors, the diverse subtypes of resident and recruited immune cells, and the phased transition from destructive to reparative inflammation. Although this expansion of the basic knowledge base has increased the number of mechanistically relevant targets of intervention, progress in developing therapies that improve AKI outcomes by modulation of inflammation remains slow. In this article, we summarize the most important recent developments in understanding the inflammatory mechanisms of AKI, highlight key limitations of the commonly used animal models and clinical trial designs that may prevent successful clinical application, and suggest priority approaches for research toward clinical translation in this area.

Contrast-enhanced ultrasound (CEUS): an excellent tool in the follow-up of small renal masses treated with cryoablation

Strict imaging follow-up is mandatory after cryoablation of small renal masses (SRMs). Although it uses ionizing radiation and nephrotoxic iodinated contrast, computed tomography (CT) is still the gold standard test. Contrast-enhanced ultrasound (CEUS) is a novel technique that informs in real time about renal perfusion avoiding radiation and nephrotoxicity. The objective of this study is to compare outcomes between CEUS and CT in the follow-up of SRMs treated with cryoablation, as well as to assess degree of agreement between them. This is a prospective observational study (May 2012 to December 2013) comparing CEUS and CT in 16 patients with SRMs cryoablated. The on-going protocol of the study includes a CT and CEUS 3 months after treatment and then every 6 months during 5 years. Local relapse was defined as the presence of contrast enhancement in the mass. All the CEUS were performed by a single experienced observer (E.S.). Degree of agreement was measured with kappa index. CEUS detected contrast enhancement in three patients (3/16, 18.8%) and CT in two patients (2/16, 12.5%). Degree of agreement between CEUS and CT, according to Landis-Koch classification, was 0.76 (CI 0.33-1.19; p = 0.0165), which is excellent and higher than expected by random. Sensitivity of the test is 93.75% (15/16). Median time of follow-up after cryoablation is 22 months (15.5-36.5). CEUS has an excellent agreement with CT and a high sensitivity in the follow-up of SRMs treated with cryosurgery, demonstrating its usefulness. Due to these encouraging results, it could become a reference test in the near future for monitoring SRMs after ablative treatment.

Contrast echocardiography for analysis of heart anatomy in tortoises

OBJECTIVE

The cardiac anatomy in tortoises depicted on B-mode and color-Doppler should be better differentiated by additional contrast-echocardiography.

MATERIAL AND METHODS

An intravenous contrast agent (INN-sulphur hexafluoride [SonoVue®]) was injected in four tortoises (three Testudo hermanni, one Agrionemys horsfieldii), via the coccygeal vein, with parallel B-mode echocardiographic examination. The results of the contrast-enhanced echocardiography were compared with the contrast-free B-mode recordings and color-Doppler ultrasound.

RESULTS

The use of SonoVue® enabled clearer distinction of the cardiac structures, differentiation of the arising major arteries, identification of wash-out-shunts, and visualization of blood flow patterns throughout the tortoise heart.

CONCLUSION AND CLINICAL RELEVANCE

This study enables the accurate depiction and differentiation of cardiac anatomy in tortoises through the use of a combination of B-mode, color-Doppler and contrast-echocardiography. Basic knowledge of blood flow in the reptile heart is essential to understand echocardiographic anatomy. Blood-flow-patterns and anatomy of the tortoise heart as found in this study will help to establish a basis for further echocardiographic examinations of these animals.

Use of quantitative contrast-enhanced ultrasonography to detect diffuse renal changes in Beagles with iatrogenic hypercortisolism

OBJECTIVE

To determine the feasibility of quantitative contrast-enhanced ultrasonography (CEUS) for detection of changes in renal blood flow in dogs before and after hydrocortisone administration.

ANIMALS

11 Beagles.

PROCEDURE

Dogs were randomly assigned to 2 treatment groups: oral administration of hydrocortisone (9.6 mg/kg; n = 6) or a placebo (5; control group) twice a day for 4 months, after which the dose was tapered until treatment cessation at 6 months. Before treatment began and at 1, 4, and 6 months after, CEUS of the left kidney was performed by IV injection of ultrasonography microbubbles. Images were digitized, and time-intensity curves were generated from regions of interest in the renal cortex and medulla. Changes in blood flow were determined as measured via contrast agent (baseline [background] intensity, peak intensity, area under the curve, arrival time of contrast agent, time-to-peak intensity, and speed of contrast agent transport).

RESULTS

Significant increases in peak intensity, compared with that in control dogs, were observed in the renal cortex and medulla of hydrocortisone-treated dogs 1 and 4 months after treatment began. Baseline intensity changed similarly. A significant increase from control values was also apparent in area under the curve for the renal cortex 4 months after hydrocortisone treatment began and in the renal medulla 1 and 4 months after treatment began. A significant time effect with typical time course was observed, corresponding with the period during which hydrocortisone was administered. No difference was evident in the other variables between treated and control dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

Quantitative CEUS allowed detection of differences in certain markers of renal blood flow between dogs treated orally with and without hydrocortisone. Additional studies are needed to investigate the usefulness of quantitative CEUS in the diagnosis of diffuse renal lesions.

Contrast-enhanced ultrasound reveals real-time spatial changes in vascular perfusion during early implantation in the macaque uterus

OBJECTIVE

To use contrast-enhanced ultrasound (CEU) to quantify blood flow in the macaque uterus during early pregnancy.

DESIGN

Prospective nonhuman primate study.

SETTING

Oregon National Primate Research Center.

ANIMALS

Naturally cycling female rhesus macaques (Macaca mulatta).

INTERVENTION(S)

Female macaques were mated on days 11-14 of the cycle. Females were then imaged by CEU and Doppler ultrasound once every 3 days from day 21 through day 39 of the fertile cycle.

MAIN OUTCOME MEASURE(S)

Visualization and quantification of uterine vascular perfusion.

RESULT(S)

CEU identified the primary placental disc and underlying vessels approximately 2 days earlier than Doppler ultrasound was able to observe endometrial thickening. CEU revealed spatial differences in vascular perfusion between the endometrium, myometrium, and endometrial-myometrial (junctional) zone. Myometrium displayed the highest rate of blood flow (>10 mL/min/g tissue). There was less blood flow in the endometrium and junctional zone (<3 mL/min/g). A brief fall in progesterone was observed during early implantation, which was correlated with reduced blood flow to all three uterine compartments, but did not reduce flow to the placenta.

CONCLUSIONS

CEU provides a sensitive, noninvasive method to assess vascular perfusion of the uterus during embryo implantation in macaques. We propose CEU as a new diagnostic tool to monitor vascular changes associated with early pregnancy in women.

Systematic method to assess microvascular recruitment using contrast-enhanced ultrasound. Application to insulin-induced capillary recruitment in subjects with T1DM

Contrast-enhanced ultrasound (CEU) is an ultrasound imaging technique used to assess tissue perfusion. Analysis of microvascular recruitment necessitates the definition of a region of interest (ROI) containing exclusively the tissues to be studied. Conventional ROI selection requires examining the images and drawing the ROI by hand, making the analysis of CEU images non-reproducible and analyst-dependent. We have designed a systematic ROI selection method that is both reproducible and analyst-independent. Microvascular blood volume (MBV) assessed in 21 sequences of images was used to correlate the systematic ROI selection method with the conventional method performed by two independent analysts (correlation of 0.88 and 0.87 respectively) and the MBV sample distribution from the systematic method was not significantly different from those obtained from the conventional one. Using the systematic method, we found no significant insulin-induced capillary recruitment in subjects with type 1 diabetes mellitus, which might be related to the observed low glucose uptake during the hyperinsulinemic euglycemic clamp compared to healthy patients.