Contrast-Enhanced Ultrasound Examination for the Assessment of Renal Perfusion in Cats with Chronic Kidney Disease

Assessment of pharmacologically induced changes in canine kidney function by multiparametric magnetic resonance imaging and contrast enhanced ultrasound

Introduction

Dynamic contrast-enhanced (DCE) MRI and arterial spin labeling (ASL) MRI enable non-invasive measurement of renal blood flow (RBF), whereas blood oxygenation level-dependent (BOLD) MRI enables non-invasive measurement of the apparent relaxation rate (R2*), an indicator of oxygenation. This study was conducted to evaluate the potential role of these MRI modalities in assessing RBF and oxygenation in dogs. The correlation between contrast-enhanced ultrasound (CEUS) and the MRI modalities was examined and also the ability of the MRI modalities to detect pharmacologically induced changes.

Methods

RBF, using CEUS, ASL- and DCE-MRI, as well as renal oxygenation, using BOLD-MRI of eight adult beagles were assessed at two time-points, 2–3 weeks apart. During each time point, the anesthetized dogs received either a control (0.9% sodium chloride) or a dopamine treatment. For each time point, measurements were carried out over 2 days. An MRI scan at 3 T was performed on day one, followed by CEUS on day two.

Results

Using the model-free model with caudal placement of the arterial input function (AIF) region of interest (ROI) in the aorta, the DCE results showed a significant correlation with ASL measured RBF and detected significant changes in blood flow during dopamine infusion. Additionally, R2* negatively correlated with ASL measured RBF at the cortex and medulla, as well as with medullary wash-in rate (WiR) and peak intensity (PI). ASL measured RBF, in its turn, showed a positive correlation with cortical WiR, PI, area under the curve (AUC) and fall time (FT), and with medullary WiR and PI, but a negative correlation with medullary rise time (RT). During dopamine infusion, BOLD-MRI observed a significant decrease in R2* at the medulla and entire kidney, while ASL-MRI demonstrated a significant increase in RBF at the cortex, medulla and the entire kidney.

Conclusion

ASL- and BOLD-MRI can measure pharmacologically induced changes in renal blood flow and renal oxygenation in dogs and might allow detection of changes that cannot be observed with CEUS. However, further research is needed to confirm the potential of ASL- and BOLD-MRI in dogs and to clarify which analysis method is most suitable for DCE-MRI in dogs.

Classifying Kidney Disease in a Vervet Model Using Spatially Encoded Contrast-Enhanced Ultrasound Perfusion Parameters

Early stages of diabetic kidney disease (DKD) are difficult to diagnose in patients with type 2 diabetes. This work was aimed at identifying contrast-enhanced ultrasound (CEUS) perfusion parameters, a microcirculatory biomarker indicative of early DKD progression. CEUS kidney flash-replenishment data were acquired in control, insulin resistant and diabetic vervet monkeys (N = 16). By use of a mono-exponential model, time-intensity curve parameters related to blood volume (A), velocity (β) and flow rate (perfusion index [PI]) were extracted from 10 concentric kidney layers to study spatial perfusion patterns that could serve as strong indicators of disease. Mean squared error (MSE) was used to assess model performance. Features calculated from the perfusion parameters were inputs for the linear regression models to determine which features could distinguish between cohorts. The mono-exponential model performed well, with average MSEs (±standard deviation) of 0.0254 (±0.0210), 0.0321 (±0.0242) and 0.0287 (±0.0130) for the control, insulin resistant and diabetic cohorts, respectively. Perfusion index features, with blood pressure, were the best classifiers between cohorts (p < 0.05). CEUS has the potential to detect early microvascular changes, providing insight into disease-related structural changes in the kidney. The sensitivity of this technique should be explored further by assessing various stages of DKD.

Intra- and Inter-Observer Variability of Quantitative Parameters Used in Contrast-Enhanced Ultrasound of Kidneys of Healthy Cats

Contrast-enhanced ultrasound (CEUS) is a non-invasive imaging technique which allows qualitative and quantitative assessment of tissue perfusion. Although CEUS offers numerous advantages, a major challenge remains the variability in tissue perfusion quantification. This study aimed to assess intra- and inter-observer variability for quantification of renal perfusion. Two observers with different levels of expertise performed a quantitative analysis of 36 renal CEUS studies, twice. The CEUS data were collected from 12 healthy cats at 3 different time points with a 7-day interval. The inter- and intra-observer agreement was assessed by the intraclass correlation coefficient. Within and between observers, a good agreement was demonstrated for intensity-related parameters in the cortex, medulla, and interlobular artery. For some parameters, ICC_inter was considerably lower than ICC_intra, mostly when the ROI encompassed the entire kidney or medulla. With the exception of time to peak (TTP) and mean transit time (mTTI), time-related and slope-related parameters showed poor agreement among observers. In conclusion, it may be advised against having the quantitative assessment of renal perfusion performed by different observers, especially if their experience levels differ. The cortical mTTI seemed to be the most appropriate parameter as it showed a favorable inter-observer agreement and inter-period agreement.

Factors influencing the time-intensity curve analysis of contrast-enhanced ultrasound in kidney transplanted patients: Toward a standardized contrast-enhanced ultrasound examination

Background

Time-intensity curve analysis (TIC analysis) based on contrast-enhanced ultrasound (CEUS) provides quantifiable information about the microcirculation of different tissues. TIC analysis of kidney transplantations is still a field of research, and standardized study protocols are missing though being mandatory for the interpretation of TIC parameters in the clinical context. The aim of this study was to evaluate the impact of different sizes and forms of regions of interest (ROIs) on the variance of different TIC parameters and the level of interoperator variance between the different ROI methods in kidney transplantations.

Methods

In 25 renal transplanted patients, 33 CEUS of the transplanted kidney were performed, and TIC analysis with ROIs sized 5 mm2 (ROI5), 10 mm2 (ROI10), and ROIs circumscribing the outlines of anatomical regions (ROI Anat ) were analyzed based on CEUS examination. The TIC analysis was repeated by a second independent operator for ROI5 and ROI Anat .

Results

Statistical analysis revealed significant differences between TIC parameters of different ROI methods, and overall, the interoperator variance was low. But a greater ROI surface (ROI10) led to higher values of the intensity parameters A and AUC compared with ROI5 (p < 0.05). The difference in the ROI form led to high variation of certain TIC parameters between ROI5 and ROI Anat in the myelon [intraclass correlation coefficient (A, ICC = 0.578 (0.139-0.793); TIC parameter (TTP); and ICC = 0.679 (0.344-0.842) (p < 0.05)]. A mean variation of 1 cm of the depth of ROI5 in the cortex did not show significant differences in the TIC parameters, though there was an impact of depth of ROI Anat on the values of TIC parameters. The interoperator variance in the cortex was low and equal for ROI5 and ROI Anat , but increased in the myelon, especially for ROI Anat . Furthermore, the analysis revealed a strong correlation between the parameter AUC and the time interval applied for the TIC analysis in the cortex and myelon (r = 0.710, 0.674, p < 0.000).

Conclusion

Our findings suggest the application of multiple ROIs of 5 mm2 in the cortex and medulla to perform TIC analysis of kidney transplants. For clinical interpretation of AUC, a standardized time interval for TIC analysis should be developed. After the standardization of the TIC analysis, the clinical predictive value could be investigated in further studies.

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.

Dynamic changes of renal cortical blood perfusion before and after percutaneous transluminal renal artery stenting in patients with severe atherosclerotic renal artery stenosis

BACKGROUND

This study aims to observe the dynamic changes of renal artery (RA) disease and cortical blood perfusion (CBP) evaluated by contrast-enhanced ultrasound (CEUS) after percutaneous transluminal renal artery stenting (PTRAS) in patients with severe atherosclerotic renal artery stenosis (ARAS) and to analyze the relationship between CBP and prognosis.

METHODS

This was a single-center retrospective cohort study. A total of 98 patients with unilateral severe ARAS after successful PTRAS in Beijing Hospital from September 2017 to September 2020 were included. According to renal glomerular filtration rate (GFR) detected by radionuclide imaging at 12 months after PTRAS, all patients were divided into the poor prognosis group (n = 21, GFR decreased by ≥20% compared with baseline) and the control group (n = 77, GFR decreased by < 20% or improved compared with baseline). Renal artery stenosis was diagnosed by digital subtraction angiography, and renal CBP was evaluated by CEUS using TomTec Imaging Systems (Germany) before PTRAS, at 6 months and 12 months after discharge. The receiver operating characteristic (ROC) curve with area under the curve (AUC) was used to analyze the predictive value of CBP parameters, including area under ascending curve (AUC1), area under the descending curve (AUC2), rising time (RT), time to peak intensity (TTP), maximum intensity (IMAX), and mean transit time (MTT) for poor prognosis.

RESULTS

Among the 98 patients, there were 52 males (53.1%), aged 55-74 years old, with an average age of 62.1 ± 8.7 years, and an average artery stenosis of 82.3 ± 12.9%. The poor prognosis group was associated with significantly increased incidence of diabetes (76.2% vs. 41.6%), and lower levels of GFR of the stenotic kidney (21.8 mL/min vs. 25.0 mL/min) and total GFR (57.6 mL/min vs. 63.7 mL/min) (all P < 0.05), compared with the control group (P < 0.05). In addition, the rate of RA restenosis was significantly higher in the poor prognosis group than in the control group (9.5% vs. 0, χ2 = 9.462, P = 0.002). Compared with the control group, the poor prognosis group was associated with significantly decreased baseline AUC1 and AUC2, and extended duration of TTP and MTT (P < 0.05). At 6 months and 12 months of follow-up, patients in the control group were associated with markedly increased AUC1, AUC2, and IMAX, and shorter duration of RT and MTT (P < 0.05). The ROC curve showed that the predictive values of AUC1, AUC2, RT, TTP, IMAX, and MTT for poor prognosis were 0.812 (95% CI: 0.698-0.945), 0.752 (95% CI: 0.591-0.957), 0.724 (95% CI: 0.569-0.961), 0.720 (95% CI: 0.522-0.993), 0.693 (95% CI: 0.507-0.947), and 0.786 (95% CI: 0.631-0.979), respectively.

CONCLUSIONS

Preoperative renal CBP in severe ARAS patients with poor prognosis is significantly reduced, and does not show significant improvement after stent treatment over the first year of follow-up. The parameter AUC1 may be a good predictor for renal dysfunction after PTRAS in severe ARAS patients. Trial Registration: ChiCTR.org.cn, ChiCTR1800016252.

Resistivity and pulsatility indexes in feline kidney disease: a systematic review

Doppler ultrasonography is used in the evaluation of hemodynamics, and the resistivity (RI) and pulsatility (PI) indexes provide information about resistance to blood flow within a vessel. This systematic review was carried out to evaluate renal RI and PI in clinically healthy and nonsedated cats and as well as their usefulness in the evaluation of kidney disease in cats. An electronic search in the PubMed, Scopus, and Web of Science databases was carried out using the terms "resistive index" or "resistivity index" or "pulsatility index;" "Doppler;" "renal" or "kidney;" and "cat" or "feline" in titles, abstracts, and keywords. Variables of interest related to experimental model features, research methods, and technical resources were extracted from the studies. The methodological quality was assessed with SYRCLE's risk of bias tool. Thus, 14 studies involving healthy and sick cats were selected. Interestingly, the upper limits estimated for both RI and PI varied among studies. The upper limits of renal RI for healthy cats varied between 0.64 and 0.72, while for PI, the values varied from 1.06 to 1.29. A limited number of studies evaluated cats with kidney disease. In most studies, RI values of kidneys with different conditions were significantly different from kidneys of healthy animals, indicating that RI values increase with kidney disease. The parameters body weight, heart rate, and age seem to influence the RI values. Standardized studies regarding its realization and description are still necessary to define normal values and analyze its applicability in the clinical diagnostic routine.

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.

Quantitative assessment of renal perfusion in children with UPJO by contrast enhanced ultrasound: A pilot study

BACKGROUND

Contrast-enhanced ultrasound (CEUS) is a new potential modality for the quantitative evaluation of the microvascular perfusion of a parenchymal organ.

OBJECTIVE

To prospectively and quantitatively analyse the role of CEUS in evaluating renal perfusion for assessing renal function in children with ureteropelvic junction obstruction (UPJO).

METHODS

The study protocol was approved by the local ethics committee, and written informed consent was obtained from the patients' parents or guardians. Ultrasonography, CEUS, and radioisotope renography were performed for 51 children (42 boys, 9 girls; mean age, 6.75 ± 4.14 years) with unilateral UPJO. The slope of the ascending curve (A), time to peak (TTP), peak intensity (PI), and area under the curve (AUC) were recorded during CEUS; quantitative data were calculated by QLab system (semiautomated border tracking, Philips Healthcare) software. Sensitivity and specificity values were determined for CEUS with respect to radioisotope renography.

RESULTS

CEUS was used to evaluate 102 kidneys in 51 patients, for which the perfusion time-intensity curve (TIC) was determined. The TIC of renal cortical perfusion in all groups showed an asymmetrical single-peak curve, which could be clearly distinguished between the experimental group and the control group. Compared with the control group, the experimental group showed a markedly prolonged TTP but a significantly decreased A (P < 0.05). There was no significant correlation between the AUC, PI and differential renal function (DRF), but the correlation coefficient between TTP, A and DRF remained significant (p < 0.001).The receiver operating characteristic (ROC) curves drawn to differentiate DRF using the TTP value yielded an area under the ROC curve (AUROC) of 0.86. For a quantitative assessment of DRF less than 40% by CEUS, the sensitivity and specificity values were 92.86% and 76.14%, respectively.

DISCUSSION

Unlike in previous studies, no significant difference in the AUC or PI was found between the control group and the experimental group in this study (P > 0.05). Renal blood perfusion could not be evaluated overall by CEUS. Parenchymal thinning may be considered a limitation to CEUS.

CONCLUSIONS

This preliminary experience represents the first report of evaluating the diagnostic value of CEUS in assessing renal function in children with UPJO. CEUS is a highly sensitive, rapid, and cost-effective diagnostic imaging modality for detecting and monitoring renal function noninvasively.

Ultrasonographic study of hemodynamics and CEUS in the rhesus monkey kidney

Nonhuman primates share many developmental similarities with humans. As the world has recognized the rhesus monkey as a standard experimental monkey, studies of rhesus monkey are very important and essential. The purpose of this study was to use gray-scale ultrasound, color Doppler flow imaging (CDFI), and contrast-enhanced ultrasound (CEUS) to study the ultrasound appearance of adult healthy rhesus monkey kidneys and to investigate the relationship between renal ultrasound manifestations and body weight, gender, and the left and right kidneys. Thirty adult healthy rhesus monkeys were studied in the experiments. The size of the kidney and the length and diameter of the renal artery were measured. The peak systolic velocity (PSV), end diastolic velocity (EDV), and resistance index (RI) of the renal artery and intrarenal arteries were measured by CDFI. In CEUS, the time-intensity curve (TIC) was used to obtain microvascular perfusion parameters. There were significant differences in renal size, diameter and length of the renal artery, and hemodynamics of the renal arteries between the different weight groups. In CEUS, there were significant differences in area under curve (AUC), time from peak to one half (THP), intensity peak (PI), time to peak (TTP), mean transit time (MTT), and wash-in-slope (WIS) between the different weight groups. There were no statistical differences between genders or the left and right kidneys. Our study provides valuable reference data for the studies of the kidney and indicates that CEUS can be used to evaluate renal perfusion in rhesus monkeys.

Quantitative contrast-enhanced ultrasound for the differentiation of kidney allografts with significant histopathological injury

OBJECTIVE

To identify specific quantitative contrast-enhanced ultrasound (CEUS) parameters that could distinguish kidney transplants with significant histopathological injury.

METHODS

Sixty-four patients were enrolled in this prospective observational study. Biopsies were performed following CEUS and blood examination.

RESULTS

28 biopsy specimens had minimal changes (MC group), while 36 had significant injury (SI group). Of these, 12 had rejection (RI group) and 24 non-rejection injury (NRI group). In RI and NRI groups, temporal difference in time to peak (TTP) between medulla and cortex (ΔTTPm-c) was significantly shorter compared to the MC group (5.77, 5.92, and 7.94 s, P = 0.048 and 0.026, respectively). Additionally, RI group had significantly shorter medullary TTP compared to the MC group (27.75 vs. 32.26 s; P = 0.03). In a subset of 41 patients with protocol biopsy at 1-year post-transplant, ΔTTPm-c was significantly shorter in the SI compared to the MC group (5.67 vs. 7.67 s; P = 0.024). Area under receiver operating characteristic curves (AUROCs) for ΔTTPm-c was 0.69 in all patients and 0.71 in patients with protocol biopsy.

CONCLUSIONS

RI and NRI groups had shorter ΔTTPm-c compared to the MC group. AUROCs for both patient groups were good, making ΔTTPm-c a promising CEUS parameter for distinguishing patients with significant histopathological injury.

Liver-type fatty acid-binding protein and neutrophil gelatinase-associated lipocalin in cats with chronic kidney disease and hyperthyroidism

BACKGROUND

Liver-type fatty acid-binding protein (L-FABP) and neutrophil gelatinase-associated lipocalin (NGAL) are candidate biomarkers for the detection of early chronic kidney disease (CKD) in cats.

OBJECTIVE

To evaluate urinary and serum L-FABP and NGAL concentrations in CKD cats and in hyperthyroid cats before and after radioiodine (¹³¹ I) treatment.

ANIMALS

Nine CKD cats, 45 healthy cats and hyperthyroid cats at 3 time points including before (T0, n = 49), 1 month (T1, n = 49), and 11 to 29 months after (T2, n = 26) ¹³¹ I treatment.

METHODS

Cross-sectional and longitudinal study. Serum L-FABP (sL-FABP), serum NGAL (sNGAL), urinary L-FABP (uL-FABP), and urinary NGAL (uNGAL) were compared between the 3 groups and between hyperthyroid cats before and after treatment. Data are reported as median (min-max).

RESULTS

CKD cats had significantly higher sL-FABP (13.50 [3.40-75.60] ng/ml) and uL-FABP/Cr (4.90 [0.97-2139.44] µg/g) than healthy cats (4.25 [1.34-23.25] ng/ml; P = .01 and 0.46 [0.18-9.13] µg/g; P < .001, respectively). Hyperthyroid cats at T0 had significantly higher uL-FABP/Cr (0.94 [0.15-896.00] µg/g) than healthy cats (P < .001), thereafter uL-FABP/Cr significantly decreased at T2 (0.54 [0.10-76.41] µg/g, P = .002). For the detection of CKD, uL-FABP/Cr had 100% (95% confidence interval [CI], 66.4-100.0) sensitivity and 93.2% (95% CI, 81.3-98.6) specificity. There were no significant differences in sNGAL and uNGAL/Cr between the 3 groups.

CONCLUSIONS AND CLINICAL IMPORTANCE

L-FABP, but not NGAL, is a potential biomarker for the detection of early CKD in cats. Utility of uL-FABP to predict azotemia after treatment in hyperthyroid cats remains unknown.

Quantitative evaluation of dexamethasone treatment effects in renal ischemia-reperfusion injury using contrast enhanced ultrasonography in rats

BACKGROUND

Renal ischemia-reperfusion (I/R) injury often occurs in various clinical events, and its incidence and mortality have been increasing.

OBJECTIVE

To investigate the value of contrast enhanced ultrasonography (CEUS) in the monitoring of dexamethasone in the improvement of renal I/R injury in rats.

METHODS

Eighteen healthy male Sprague-Dawley rats were randomly divided into sham-operated, I/R, and I/R surgery plus dexamethasone treatment (Dexa) groups. In the I/R group 45-minute renal ischemia with 24 h reperfusion period was monitored. Time-intensity curve (TIC)-derived parameters, which included peak value, time to peak (TP), area under the curve (AUC), and mean transit time (MTT) were compared to the blood creatinine, urea, Caspase-1, and NLRP3 levels.

RESULTS

The I/R group showed an increased peak value, prolonged TP and MTT, and greater AUC (P < 0.05). The Dexa group showed shorter TP and MTT, and smaller AUC (P < 0.05). Results show that the associations between (i) TP, AUC, and MTT and (ii) creatinine, urea, Caspase-1, and NLRP3 levels were significant (P < 0.05).

CONCLUSION

Dexamethasone can alleviate renal I/R injury in rats, which may be related to the inhibition of NLRP3 and caspase-1. CEUS can quantitatively measure this change, in which the changes in TP, AUC and MMT values have considerable reference values.

Comparison of Renal Blood Flow Using Maximum Slope-Based Computed Tomography Perfusion and Ultrasound Flow Probe in Healthy Dogs

Computed tomography (CT) perfusion can analyze tissue perfusion and quantitative parameters, including blood flow, blood volume, and transit time. CT perfusion has been used for evaluating split renal function. However, its applicability in veterinary medicine was not validated. This study aimed to evaluate the correlation of renal blood flow (RBF) derived by maximum slope-based CT perfusion and an ultrasonic flow probe and assess the effect of the presence of a pre-existing contrast medium on CT perfusion in the kidneys. In five healthy purpose-bred beagles, CT perfusion was performed at the level of the left renal hila after injection of 1 mg/kg iohexol, during measuring RBF with an ultrasonic flow probe placed on the left renal artery. After post-contrast CT scan with injection of 2 mg/kg iohexol, CT perfusion scan was repeated with the same protocol used in the first perfusion study. The CT perfusion derived RBF was analyzed based on the maximum slope and was compared with the true RBF obtained using an ultrasonic flow probe. Results indicated that CT perfusion derived RBF was significantly correlated with true RBF, although CT perfusion derived RBF did not match the absolute value of the true RBF. It was correlated with the true RBF, even in the presence of a pre-existing contrast medium in the kidney. CT perfusion can estimate the change in individual renal perfusion non-invasively, and this method can be used supplementary to the conventional CT protocol in clinic.

Novel contrast agent Visphere™ is feasible for contrast-enhanced ultrasonography in dogs

Contrast-enhanced ultrasonography provides a more functional diagnostic image than conventional ultrasonography. This prospective exploratory study compared the novel contrast agent, Visphere^™ , with commercial contrast agents in five healthy Beagle dogs. Visphere^™ has the smallest diameter and highest concentration compared with Sonazoid^® and SonoVue^® . Each dog received an intravenous injection of Visphere^™ , Sonazoid^® , or SonoVue^® . Images were recorded for 300, 600, and 60 s in the heart, liver, and left kidney, respectively. The mean pixel values of the regions of interest for each organ were expressed as time intensity curves (TIC). The agents all improved the visualization of left ventricular endocardial border delineation in the heart, and had similar TICs and clinical useful durations. In contrast, Visphere^™ expressed the highest mean pixel value in the liver parenchyma at an early observation time and maintained the intensity until 600 s, like Sonazoid^® . The renal evaluation results indicated there were no statistically significant differences in time-to-peak for the renal cortex or medulla among the agents. Compared with the other two agents, SonoVue^® had the lowest peak enhancement for the renal cortex and medulla. No dogs had any adverse reactions during or after the study. All three agents provided adequate results for left ventricular endocardial border delineation, and Visphere^™ may have the same potential as Sonazoid^® to detect and characterize hepatic lesions. Visphere^™ and Sonazoid^® may offer better visualization quality to evaluate renal function. In conclusion, the novel contrast agent, Visphere^™ , is comparable with commercial agents and could be applied in different major organs in dogs.

Value of early diagnosis of sepsis complicated with acute kidney injury by renal contrast-enhanced ultrasound

BACKGROUND

The incidence of acute kidney injury (AKI) in patients with sepsis is high, and the prognosis of patients with septic AKI is poor. The early diagnosis and treatment of septic AKI is of great significance in improving the prognosis of patients with sepsis.

AIM

To explore the value of contrast-enhanced ultrasound (CEUS), serum creatinine (Scr), and other indicators in the early diagnosis of septic AKI.

METHODS

Ninety patients with sepsis during hospitalization at Tongji Hospital of Tongji University were recruited as subjects. Each patient was recorded with relevant basic data, clinical indicators, and CEUS results. The patients were divided into AKI group and non-AKI group according to the results of renal function diagnosis after 48 h. On the 7th day, the renal function of the non-AKI group was re-evaluated and the patients were further divided into AKI subgroup and non-AKI subgroup. The differences of the indicators in different groups were compared, and the diagnostic value of each indicator and their combination for septic AKI was analyzed.

RESULTS

Systemic inflammatory response score (2.58 ± 0.75), blood lactic acid (3.01 ± 1.33 mmol/L), Scr (141.82 ± 27.19 μmol/L), blood urea nitrogen (4.41 ± 0.81mmol/L), and rise time (10.23 ± 2.63 s) in the AKI group were higher than those in the non-AKI group. Peak intensity (PI) (10.78 ± 3.98 dB) and wash in slope (WIS) (1.07 ± 0.53 dB/s) were lower than those in the non-AKI group. The differences were statistically significant (P < 0.05). The PI (12.83 ± 3.77 dB) and WIS (1.22 ± 0.68 dB/s) in the AKI subgroup were lower than those in the non-AKI subgroup, and the differences were statistically significant (P < 0.05). The area under curve (AUC) of Scr for the diagnosis of septic AKI was 0.825 with a sensitivity of 56.76% and a specificity of 100%. The AUCs of WIS and PI (0.928 and 0.912) were higher than those of Scr. Their sensitivities were 100%, but the specificities were 71.70% and 75.47%. The AUC of the combination of three indicators for the diagnosis of septic AKI was 0.943, which was significantly higher than the AUC diagnosed by each single indicator. The sensitivity was 94.59%, and the specificity was 81.13%.

CONCLUSION

The combination of Scr, PI, and WIS can improve the diagnostic accuracy of septic AKI. PI and WIS are expected to predict the occurrence of early septic AKI.

Effect of catheter diameter and injection rate of flush solution on renal contrast-enhanced ultrasonography with perfluorobutane in dogs

OBJECTIVE

To assess effects of catheter diameter and injection rate of flush solution (saline [0.9% NaCl] solution) on renal contrast-enhanced ultrasonography (CEUS) with perfluorobutane in dogs.

ANIMALS

5 healthy Beagles.

PROCEDURES

CEUS of the kidneys was performed by IV injection of contrast medium (0.0125 mL/kg) followed by injection of 5 mL of saline solution at rates of 1, 3, and 5 mL/s through a 20-gauge or 24-gauge catheter; thus, CEUS was repeated 3 times for each catheter diameter. Time-intensity curves were created for regions of interest drawn in the renal cortex and medulla. Repeatability was determined by calculating the coefficient of variation (CV). Statistical analysis was used to assess whether perfusion variables or CV of the perfusion variables was associated with catheter diameter or injection rate.

RESULTS

Perfusion variables did not differ significantly between catheter diameters. Time to peak enhancement (TTP) in the renal cortex was affected by injection rate, and there were significantly lower values for TTP at higher injection rates. The CEUS variables with the lowest CVs among injection rates were TTP for the renal cortex; the CV for TTP of the renal cortex was the lowest at an injection rate of 5 mL/s.

CONCLUSIONS AND CLINICAL RELEVANCE

Use of a 24-gauge catheter did not alter CEUS with perfluorobutane; therefore, such catheters could be used for CEUS of the kidneys of small dogs. Moreover, a rate of 5 mL/s is recommended for injection of flush solution to obtain greater accuracy for renal CEUS in Beagles.

Renal shear wave elastography and urinary procollagen type III amino-terminal propeptide (uPIIINP) in feline chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is one of the most common diseases occurring in cats. It is characterized by renal fibrosis, which is strongly correlated with impairment of renal function. Since renal biopsy is not performed routinely in clinical practice, the non-invasive method of ultrasonographic shear-wave elastography (SWE) was used to determine renal parenchymal stiffness. Currently, urinary procollagen type III amino-terminal propeptide (uPIIINP) is a renal fibrosis biomarker in humans. Moreover, PIIINP is increasingly applied for identification of fibrosis in various organs in animals.

RESULTS

The Young's modulus (E) value on SWE, uPIIINP, and renal function were evaluated in 23 CKD cats and 25 healthy cats (HC). The renal cortical E values were significantly higher than those of the renal medulla in both groups (P < 0.001). The E values of the renal cortex and medulla were significantly higher in CKD cats than in HC (P < 0.001 and P < 0.01, respectively). The E values, especially of the cortex, showed a significant positive correlation with concentrations of plasma creatinine (P < 0.001), blood urea nitrogen (P < 0.05), while they had a negative correlation with urine specific gravity (P < 0.001) and urine osmolality per plasma osmolality ratio (P < 0.01). The uPIIINP to creatinine ratios (uPIIINP/Cr) were significantly higher in CKD cats than in HC (P < 0.01) and were highly correlated with renal cortical E values (P < 0.001).

CONCLUSIONS

SWE might be an additively useful and non-invasive diagnostic imaging tool to evaluate renal parenchymal stiffness, which correlates with renal functional impairment in CKD cats. Moreover, the uPIIINP/Cr might be a promissing biomarker for adjunctive assessing the renal fibrosis in feline CKD.

Renal perfusion parameters measured by contrast-enhanced ultrasound in healthy dogs demonstrate a wide range of variability in the long-term

Contrast-enhanced ultrasound may be helpful for detecting early renal microvascular damage and dysfunction in dogs. However, before this noninvasive imaging method can be tested as an early-stage screening tool in clinical patients, an improved understanding of long-term variation in healthy animals is needed. In this prospective, secondary, longitudinal, serial measurements study, variability of contrast-enhanced ultrasound renal perfusion parameters was described for eight healthy dogs, using seven time points and a period of 83 weeks. Dogs were sedated with butorphanol (0.4 mg/kg), and contrast-enhanced ultrasound of each kidney was performed after an intravenous bolus injection of a microbubble contrast agent (0.04 mL/kg). Time-intensity curves were created from regions-of-interest drawn in the renal cortex and medulla. Intensity-related parameters representing blood volume and time-related parameters representing blood velocity were determined. A random-effects model using restricted maximum likelihood was used to estimate variance components. Within-dog coefficient of variation was defined as the ratio of the standard deviation over the mean. Time-related parameters such as time-to-peak, rise and fall time had lowest within-dog variability. Intensity-related parameters such as peak enhancement, wash-in and wash-out area under the curve, total area under the curve, and wash-in and washout rates had high within-dog variability (coefficient of variation > 45%). Authors therefore recommend the use of time-related parameters for future studies of renal perfusion. Within-dog variability for bilateral kidney measurements was extremely low, therefore contrast-enhanced ultrasound may be particularly useful for detecting unilateral changes in renal perfusion. Future studies are needed to compare contrast-enhanced ultrasound findings in healthy dogs versus dogs with renal disease.