Contrast-enhanced ultrasonography for bedside imaging in subclinical acute kidney injury

Intravenous administration of ultrasound contrast to critically ill pediatric patients

BACKGROUND

The off-label use of contrast-enhanced ultrasound has been increasingly used for pediatric patients.

OBJECTIVE

The purpose of this retrospective study is to report any observed clinical changes associated with the intravenous (IV) administration of ultrasound contrast to critically ill neonates, infants, children, and adolescents.

MATERIALS AND METHODS

All critically ill patients who had 1 or more contrast-enhanced ultrasound scans while being closely monitored in the neonatal, pediatric, or pediatric cardiac intensive care units were identified. Subjective and objective data concerning cardiopulmonary, neurological, and hemodynamic monitoring were extracted from the patient's electronic medical records. Vital signs and laboratory values before, during, and after administration of ultrasound contrast were obtained. Statistical analyses were performed using JMP Pro, version 15. Results were accepted as statistically significant for P-value<0.05.

RESULTS

Forty-seven contrast-enhanced ultrasound scans were performed on 38 critically ill patients, 2 days to 17 years old, 19 of which were female (50%), and 19 had history of prematurity (50%). At the time of the contrast-enhanced ultrasound scans, 15 patients had cardiac shunts or a patent ductus arteriosus, 25 had respiratory failure requiring invasive mechanical oxygenation and ventilation, 19 were hemodynamically unstable requiring continual vasoactive infusions, and 8 were receiving inhaled nitric oxide. In all cases, no significant respiratory, neurologic, cardiac, perfusion, or vital sign changes associated with IV ultrasound contrast were identified.

CONCLUSION

This study did not retrospectively identify any adverse clinical effects associated with the IV administration of ultrasound contrast to critically ill neonates, infants, children, and adolescents.

Advances of Contrast-Enhanced Ultrasonography and Elastography in Kidney Transplantation: From Microscopic to Microcosmic

Kidney transplantation is the best choice for patients with end-stage renal disease. To date, allograft biopsy remains the gold standard for revealing pathologic changes and predicting long-term outcomes. However, the invasive nature of transplant biopsy greatly limits its application. Ultrasound has been a first-line examination for evaluating kidney allografts for a long time. Advances in ultrasound in recent years, especially the growing number of studies in elastography and contrast-enhanced ultrasonography (CEUS), have shed new light on its application in kidney transplantation. Elastography, including strain elastography and shear wave elastography, is used mainly to assess allograft stiffness and, thus, predict renal fibrosis. CEUS has been used extensively in evaluating blood microperfusion, assessing acute kidney injury and detecting different complications after transplantation. Requiring the use of microbubbles also makes CEUS a novel method of gene transfer and drug delivery, enabling promising targeted diagnosis and therapy. In this review, we summarize the advances of elastography and CEUS in kidney transplantation and evaluate their potential efficiency in becoming a better complement to or even substitute for transplant biopsy in the future.

Molecular Ultrasound Imaging of Tissue Inflammation Using an Animal Model of Acute Kidney Injury

PURPOSE

The objective of this study was to evaluate the use of molecular ultrasound (US) imaging for monitoring the early inflammatory effects following acute kidney injury.

PROCEDURES

A population of rats underwent 30 min of renal ischemia (acute kidney injury, N = 6) or sham injury (N = 4) using established surgical methods. Animals were divided and molecular US imaging was performed during the bolus injection of a targeted microbubble (MB) contrast agent to either P-selectin or vascular cell adhesion molecule 1 (VCAM-1). Imaging was performed before surgery and 4 and 24 h thereafter. After manual segmentation of renal tissue space, the molecular US signal was calculated as the difference between time-intensity curve data before MB injection and after reaching steady-state US image enhancement. All animals were terminated after the 24 h imaging time point and kidneys excised for immunohistochemical (IHC) analysis.

RESULTS

Renal inflammation was analyzed using molecular US imaging. While results using the P-selectin and VCAM-1 targeted MBs were comparable, it appears that the former was more sensitive to biomarker expression. All molecular US imaging measures had a positive correlation with IHC findings.

CONCLUSIONS

Acute kidney injury is a serious disease in need of improved noninvasive methods to help diagnose the extent of injury and monitor the tissue throughout disease progression. Molecular US imaging appears well suited to address this challenge and more research is warranted.

Targeting Endogenous Repair Pathways after AKI

AKI remains a highly prevalent disease associated with poor short- and long-term outcomes and high costs. Although significant advances in our understanding of repair after AKI have been made over the last 5 years, this knowledge has not yet been translated into new AKI therapies. A consensus conference held by the Acute Dialysis Quality Initiative was convened in April of 2014 and reviewed new evidence on successful kidney repair to identify the most promising pathways that could be translated into new treatments. In this paper, we provide a summary of current knowledge regarding successful kidney repair and offer a framework for conceptualizing the therapeutic targeting that may facilitate this process. We outline gaps in knowledge and suggest a research agenda to more efficiently bring new discoveries regarding repair after AKI to the clinic.