Doppler angle correction in the measurement of intrarenal parameters

Effect of Hydration on Doppler Velocity of Renal Arteries

CONTEXT

Doppler sonography is a noninvasive method to evaluate the hemodynamic status of the kidney, and its parameters are used as direct and indirect predictors of certain parenchyma and renovascular diseases. However, the effect of hydration on kidney hemodynamics has not been explored via Doppler sonography.

OBJECTIVE

To examine differences in arterial Doppler velocities of normal adult kidney before and after hydration.

METHODS

A total of 60 native kidneys in 30 normal adult participants (mean age, 26 years) were assessed using Doppler sonography. Quantitative ultrasound Doppler parameters of peak systolic velocity (PSV), end diastolic velocity (EDV), and resistive index (RI) of the main renal artery and the intrarenal (interlobar) arteries were measured immediately before and 1 hour after ingestion of 500 mL of water. We tested differences in Doppler parameters before and after hydration using a paired t test, analyzed the correlation of the increase in PSV to the increase in EDV after hydration using Pearson correlation coefficient (PCC), and examined intraobserver reliability using intraclass correlation coefficient (ICC).

RESULTS

Statistical analyses revealed that the differences in PSV and EDV values before and after hydration at the main renal artery and interlobar arteries of the kidney were significant (P<.001), whereas the RI at the main renal artery and interlobar arteries were not (P>.05). PCC for the correlation of the increase in PSV to the increase in EDV was greater than 0.80. ICC for intraobserver repeatability in performing kidney Doppler sonography was 0.92.

CONCLUSION

Our results suggest that Doppler sonography is able to demonstrate changes in kidney hemodynamics within 1 hour after hydration. The normal kidney reflects proportional increases in PSV and EDV at the main renal artery and interlobar arteries, while maintaining vascular resistance. Doppler flow velocities of renal arteries can be considered as noninvasive quantitative markers for evaluating the response of kidney hemodynamics to hydration.

A rat model of acute kidney injury through systemic hypoperfusion evaluated by micro-US, color and PW-Doppler

AIM

To create an animal model of acute renal ischemia induced by systemic hypoperfusion, controllable and reproducible to study, in real time, hemorrhagic shock changes with micro-imaging.

ANIMALS AND METHODS

Hemorrhagic shock was induced in rats activating a syringe pump setup to remove 1 mL/min of blood, through the femoral artery catheter. The withdrawal was continued until the mean arterial pressure (MAP) dropped to 25-30 mmHg. For the next 60 min, the MAP was maintained at a constant pressure value, by automatic pump infusion and withdrawal. Micro-ultrasound imaging was performed using the Vevo 2100 system with the MS250 transducer (13-24 MHz). Renal size, morphology and echogenicity were evaluated in B-mode. Renal blood flow was evaluated using color and PW-Doppler.

RESULTS

After 1 h of ischemia, B-mode images documented slight changes in kidney echogenicity. Color and PW-Doppler analysis showed a reduction in renal blood flow in kidneys during the hypoperfusion with a progressive and significant change from baseline values of resistive index (RI). At the histological evaluation, 60 min of hypoperfusion resulted in ischemic changes in the kidneys.

CONCLUSIONS

The results of this experimental study encourage the use of the described model to study acute renal ischemia trough severe hypoperfusion. The histological data confirmed that the model was able to produce injury in renal parenchyma. It can be used to assess acute ischemic damage not only in the kidney but also in other organs by using all available dedicated small animals imaging techniques.

Optimizing renal transplant Doppler ultrasound

Doppler ultrasound is routinely used for the post-operative evaluation of renal transplant patients. Knowledge of the surgical anatomy and application of a robust technique are important for appropriate evaluation of a transplanted kidney. In this review article, we discuss the surgical anatomy of renal transplantation, techniques to optimize image acquisition, as well as commonly associated pitfalls with Doppler ultrasound evaluation of renal grafts.

Utility of Angle Correction for Hemodynamic Measurements with Doppler Echocardiography

OBJECTIVES

The routine application angle correction (AnC) in hemodynamic measurements with transesophageal echocardiography currently is not recommended but potentially could be beneficial. The authors hypothesized that AnC can be applied reliably and may change grading of aortic stenosis (AS).

DESIGN

Retrospective analysis.

SETTING

Single institution, university hospital.

PARTICIPANTS

During phase I, use of AnC was assessed in 60 consecutive patients with intraoperative transesophageal echocardiography. During phase II, 129 images from a retrospective cohort of 117 cases were used to quantify AS by mean pressure gradient.

INTERVENTIONS

A panel of observers used custom-written software in Java to measure intra-individual and inter-individual correlation in AnC application, correlation with preoperative transthoracic echocardiography gradients, and regrading of AS after AnC.

MEASUREMENTS AND MAIN RESULTS

For phase I, the median AnC was 21 (16-35) degrees, and 17% of patients required no AnC. For phase II, the median AnC was 7 (0-15) degrees, and 37% of assessed images required no AnC. The mean inter-individual and intra-individual correlation for AnC was 0.50 (95% confidence interval [CI] 0.49-0.52) and 0.87 (95% CI 0.82-0.92), respectively. AnC did not improve agreement with the transthoracic echocardiography mean pressure gradient. The mean inter-rater and intra-rater agreement for grading AS severity was 0.82 (95% CI 0.81-0.83) and 0.95 (95% CI 0.91-0.95), respectively. A total of 241 (7%) AS gradings were reclassified after AnC was applied, mostly when the uncorrected mean gradient was within 5 mmHg of the severity classification cutoff.

CONCLUSIONS

AnC can be performed with a modest inter-rater and intra-rater correlation and high degree of inter-rater and intra-rater agreement for AS severity grading.

Multiparametric Quantitative Ultrasound Imaging in Assessment of Chronic Kidney Disease

OBJECTIVES

To evaluate the value of multiparametric quantitative ultrasound imaging in assessing chronic kidney disease (CKD) using kidney biopsy pathologic findings as reference standards.

METHODS

We prospectively measured multiparametric quantitative ultrasound markers with grayscale, spectral Doppler, and acoustic radiation force impulse imaging in 25 patients with CKD before kidney biopsy and 10 healthy volunteers. Based on all pathologic (glomerulosclerosis, interstitial fibrosis/tubular atrophy, arteriosclerosis, and edema) scores, the patients with CKD were classified into mild (no grade 3 and <2 of grade 2) and moderate to severe (at least 2 of grade 2 or 1 of grade 3) CKD groups. Multiparametric quantitative ultrasound parameters included kidney length, cortical thickness, pixel intensity, parenchymal shear wave velocity, intrarenal artery peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistive index. We tested the difference in quantitative ultrasound parameters among mild CKD, moderate to severe CKD, and healthy controls using analysis of variance, analyzed correlations of quantitative ultrasound parameters with pathologic scores and the estimated glomerular filtration rate (GFR) using Pearson correlation coefficients, and examined the diagnostic performance of quantitative ultrasound parameters in determining moderate CKD and an estimated GFR of less than 60 mL/min/1.73 m² using receiver operating characteristic curve analysis.

RESULTS

There were significant differences in cortical thickness, pixel intensity, PSV, and EDV among the 3 groups (all P < .01). Among quantitative ultrasound parameters, the top areas under the receiver operating characteristic curves for PSV and EDV were 0.88 and 0.97, respectively, for determining pathologic moderate to severe CKD, and 0.76 and 0.86 for estimated GFR of less than 60 mL/min/1.73 m² . Moderate to good correlations were found for PSV, EDV, and pixel intensity with pathologic scores and estimated GFR.

CONCLUSIONS

The PSV, EDV, and pixel intensity are valuable in determining moderate to severe CKD. The value of shear wave velocity in assessing CKD needs further investigation.

Novel Transoesophageal Echocardiographic Views Attain Superior Incident Angles for Tricuspid, but not Pulmonary, Valvular Doppler Interrogation

For accurate spectral Doppler valvular evaluation, intraoperative sonographers must use transoesophageal echocardiographic (TOE) views that offer optimal incident angles. We hypothesised that views added to the 2013 American Society of Echocardiography/Society of Cardiovascular Anesthesiologists (ASE/SCA) standard views and other novel views we have described of the tricuspid (TV) and pulmonary valves (PV) offered superior incident angles to those included in the origina 1999 ASE/SCA recommendations for comprehensive intraoperative TOE examination. We compared the acquisition feasibility and incident angles obtained by these views in 62 patients undergoing elective cardiac surgery, who received TOE monitoring as standard care. Overall, the 2013 ASE/SCA standard and novel views provided superior incident angles for the TV (28% and 66% of patients) whereas the 1999 ASE/SCA standard views provided superior incident angles for the PV (79% of patients, P <0.0001). The novel 90° mid-oesophageal modified bicaval view (90°MEMBC) and the 1999 ASE/SCA standard aortic arch short-axis view (AoArSAX) obtained best incident angles for the TV (mean [95% confidence interval] 13° [10°-16°]) and PV (5° [3°-7°]) respectively. PV view acquisition feasibility between the 1999 ASE/SCA standard, 2013 ASE/SCA standard and novel views was not significantly different (acquisition rate difference 11%, P >0.11). We conclude that the 2013 ASE/SCA TV standard and novel views obtained superior incident angles for the tricuspid, but not pulmonary valves. We recommend that ntraoperative sonographers consider the use of these views, particularly when incident angles obtained with standard views are suboptimal.

Correlation of ultrasonographic measurement of intrarenal arterial resistance index with microalbuminuria in nonhypertensive, nondiabetic obese patients

PURPOSE

To determine whether intrarenal arterial resistance index (RI) value is related to increased urinary albumin excretion and whether RI value is an independent good indicator to evaluate early renal damage in nonhypertensive, nondiabetic obese subjects.

METHODS

Sixty-four nonhypertensive, nondiabetic obese patients (OB) and 35 age- and sex-matched normal healthy subjects were involved in this study. Clinical characteristics and blood biochemistry of all the subjects were measured. Urinary albumin/creatinine ratio (ACR) and sonographic evaluation of renal blood flow were determined.

RESULTS

ACR and interlobar arterial RI were significantly higher in obese patients than those of normal healthy subjects. Interlobar arterial RI value was higher in patients with microalbuminuria than those with normoalbuminuria. Correlation analysis showed interlobar artery RI value had a positive correlation with ACR (r = 0.615, p < 0.01) and plasma free fatty acids (FFAs, r = 0.407, p < 0.01). ACR had a positive correlation with BMI (r = 0.380, p < 0.01), waist circumference (r = 0.414, p < 0.01), plasma FFAs (r = 0.537, p < 0.01). Multivariate regression analyses showed that ACR was best predicted by interlobar artery RI value even when body mass index, waist circumference, FFAs, and high-sensitive C reaction protein were added in the statistical analysis.

CONCLUSIONS

Interlobar arterial RI may be an independent predictor of microalbuminuria in nonhypertensive, nondiabetic obese patients, and interlobar arterial RI could be a useful tool for assessment early renal damage in obese patients.