Assessment Of Renal Blood Flow Research Articles

Methods for Assessing Renal Нemodynamics after Minimally lnvasive Treatment of Urolithiasis

The purpose of research. Urolithiasis occupies a leading place among all urological diseases after infectious and inflammatory ones. /n addition, it does not lose its relevance due to the fact that the number of patients with this disease is steadily increasing. Тhe aim of the study is to study the peculiarities of changes in renal hemodynamics after minimally invasive methods of treatment of urolithiasis remote shock wave lithotripsy (DLТ) and percutaneous nephrolithotripsy (РNL) to improve the quality of medical care for urological patients.Methods. Numerous studies have shown in detail the effectiveness of using remote shock wave lithotripsy and percutaneous nephrolithotorypsy in the treatment of kidney stones. Тhese methods are minimally invasive, well tolerated by patients, and reduce the risks of complications, but they are accompanied by kidney injury, in particular, microcirculation disorders. Тhe use of the Dopplerographic method of investigation allows for a highly informative assessment of the degree of impaired renal microcirculation for the diagnosis of urolithiasis, including for the assessment of hemodynamics after minimally invasive treatment methods.Results. Тhe work shows that when using dopplerography of renal vessels after remote shock wave lithotripsy and percutaneous nephrolithotorypsy, a violation of hemodynamics after DLТ is noted in dynamics already on the first day. In addition, the terms of normalization of indicators are longer in comparison with hemodynamics after РNL. Аlso, with РNL, there is a gradual increase in blood flow indicators in the dynamics of the postoperative period.Conclusion. Тhe work shows that ultrasound Dopplerography is an effective method of dynamic assessment of renal blood flow, and the indicator of renal damage is the resistance index, mainly in the interlobular arteries.

Evaluation of Renal Perfusion: A Comparative Study between Intravoxel Incoherent Motion (IVIM) Imaging and Arterial Spin Labeling (ASL) to Assess Renal Blood Flow in Rodents.

To compare diagnostic reliability between an intravoxel incoherent motion (IVIM) imaging and an arterial spin labeling (ASL) in assessment of renal blood flow in rodents. We first evaluated 3 different fitting methods on 5 datasets of diffusion-weighted imaging (DWI) with 10 b-values (0-1000 s/mm2) for bi-exponential analysis in IVIM imaging to calculate pseudo-diffusion parameters. Coefficient of variation (CV) for each parameter and correlation among the parameters was assessed to test the robustness of the 3 fitting methods. Subsequently, DWI and ASL methods were performed before and 14 days after onset of acute kidney injury (AKI) in a rat model. Temporal change before and after AKI onset in the pseudo-diffusion parameters in 3 fitting methods was compared with that in the renal blood flow (RBF) derived in the ASL method. The CVs in all IVIM parameters were the lowest in the fitting method that estimated pseudo-diffusion parameters after a fixed true-diffusion was determined where the pseudo- and true-diffusion coefficients had no correlation. The RBF substantially reduced (~50%, P < 0.001) due to the AKI onset; however, no pseudo-diffusion parameters in any of 3 fitting methods could not detect the change. Further, any pseudo-diffusion parameters showed no correlation with the RBF. Pseudo-diffusion parameters in the IVIM concept were not reliable to estimate RBF in the study. Since the kidney has a unique profile in the "tissue flow", our data indicate that study design and interpretation of results needs to be carefully considered when IVIM imaging is used for evaluation of blood flow in tissue, especially in the kidney.

Assessment of Kidney Dysfunction in Patients with Chronic Heart Failure

BACKGROUND: Heart failure and kidney disease share common pathophysiological pathways which can lead to mutual dysfunction, known as cardiorenal syndrome. The formation of cardiorenal syndrome in patients with chronic heart failure (CHF) is a natural manifestation of a functionally interconnected process at the organ level. Renal dysfunction is a common and independent factor in the progression of the disease, a high incidence of cardiovascular events, and death in the population. AIM: The aim of the study of the relationship between kidney dysfunction and the clinical course of the disease, quality of life, and indicators of the left ventricular systolic function in patients with CHF. MATERIALS AND METHODS: The study involved 150 patients with CHF I–III functional class according to the New York Heart Association. Exercise tolerance (6 min walk test) was assessed, the clinical condition was assessed using the clinical assessment scale, and the quality of life of patients with CHF (QoL) was assessed according to the Minnesota QOL questionnaire. An assessment of the functional state of the kidneys was carried out: The level of serum creatinine was determined; glomerular filtration rate (GFR) was calculated using the calculation formulas CKD-EPI. The assessment of renal blood flow was carried out using the ultrasound apparatus “SONOACEX6” (Korea). The structural and functional state of the myocardium and the process of left ventricle (LV) remodeling were assessed using the “MEDISON ACCUVIX V20” echocardiograph (Korea), using a 3.25 MHz transducer in standard echocardiographic positions, by the transthoracic method in accordance with the recommendations of the American Association of Echocardiography. RESULTS: The results of the study of physical performance according to 6 min walk test in patients of Group I with CHF GFR &gt;60 ml/min/1.73 m2 were 363.59 ± 7.6 m, respectively. The decrease in the distance traveled according to the 6 min walk test data in Group II of patients with eGFR ≤60 ml/min/1.73 m2, exercise tolerance was more pronounced than in patients of Group I and this figure was 248.7 ± 11.0 m, which was 46.2% lower than the results of Group I of the study (p &lt; 0.001). Analysis of the parameters of clinical manifestations according to the data of the clinical assessment scale showed that in patients of Group I, the total score was 5.5 ± 0.13 points. In CHF patients with renal dysfunction, changes were also noted at the level of the lobar and segmental renal arteries, characterized by a significant increase in pulsatility index and resistance index, there was a decrease in speed indicators during diastole, systole, and the average blood flow velocity. Further analysis of the parameters of LV systolic function ejection fraction (EF), as well as fractional shortening of the LV in systole (Fs%), showed that in Group II, these indicators had significant differences with Group I. There was a significant difference in EF by 10.5% and 25.4% and Fs% by 11.2% (p &lt; 0.001). CONCLUSION: In CHF patients with impaired renal function, changes in renal blood flow were characterized by a significant increase in pulsatile and resistive indices, a decrease in the rate of renal blood flow at the level of the lobar and segmental renal arteries.

Feasibility of intracardiac echocardiography for assessment of renal blood flow in humans

Abstract Background Intracardiac echocardiography (ICE) is routinely used for guiding cardiac ablation procedures. However, the potential of ICE for measurement of renal artery (RA) blood flow (RABF) has not been fully exploited. Aims To investigate the feasibility of ICE for the assessment of RABF and to evaluate its reproducibility in humans. Methods The study included 15 patients undergoing catheter ablation of atrial fibrillation guided by ICE (age: 61±14 years, body mass index: 30±5 kg/m2, left ventricular ejection fraction: 57±6%, serum creatinine: 80±29 μmol/l). During sinus rhythm, the ICE probe was withdrawn from the right atrium to the inferior vena cava until the right RA with its ostium became visible. Blood flow in the RA was visualized by colour flow mapping. The RA diameter was measured at 10 mm from the ostium. RABF at this location was measured by pulse wave Doppler. Velocity-time integral (VTI) was delineated manually and averaged over five consecutive beats. RABF was calculated by the formula: RABF = (RA radius)2 x π x VTI x heart rate. To assess reproducibility of the method, the ICE probe was repositioned in the right atrium and the measurement of RABF was repeated by the same operator. Results The right RA was visualized in all 15 patients. No procedure-related clinical complications occurred. The mean RA radius was 2.5±0.4 mm. In all cases, the angle of incidence during the measurement of VTI was &amp;lt;5°. The mean RABF was 403±163 and 399±156 ml/min during the first and the second measurement, respectively (p=0.7 by a paired t-test, coefficient of variation 5,3±3,8%; see Figure for Bland-Altman plot). Conclusions This study demonstrated that measurement of RABF by ICE is feasible and has reasonable intra-observer reproducibility. The method can be used to study RABF during various interventions and hemodynamic conditions. Figure 1. Intra-individual reproducibility Funding Acknowledgement Type of funding source: None

Inter-study reproducibility of interleaved spiral phase velocity mapping of renal artery haemodynamics.

BackgroundQualitative and quantitative assessment of renal blood flow is valuable in the evaluation of patients with renal and renovascular diseases as well as in patients with heart failure. The temporal pattern of renal flow velocity through the cardiac cycle provides important information about renal haemodynamics. High temporal resolution interleaved spiral phase velocity mapping could potentially be used to study temporal patterns of flow and measure resistive and pulsatility indices which are measures of downstream resistance.MethodsA retrospectively gated breath-hold spiral phase velocity mapping sequence (TR 19 ms) was developed at 3 Tesla. Phase velocity maps were acquired in the proximal right and left arteries of 10 healthy subjects in each of two separate scanning sessions. Each acquisition was analysed by two independent observers who calculated the resistive index (RI), the pulsatility index (PI), the mean flow velocity and the renal artery blood flow (RABF). Inter-study and inter-observer reproducibility of each variable was determined as the mean +/− standard deviation of the differences between paired values. The effect of background phase errors on each parameter was investigated.ResultsRI, PI, mean velocity and RABF per kidney were 0.71+/− 0.06, 1.47 +/− 0.29, 253.5 +/− 65.2 mm/s and 413 +/− 122 ml/min respectively. The inter-study reproducibilities were: RI −0.00 +/− 0.04 , PI −0.03 +/− 0.17, mean velocity −6.7 +/− 31.1 mm/s and RABF per kidney 17.9 +/− 44.8 ml/min. The effect of background phase errors was negligible (<2% for each parameter).ConclusionsHigh temporal resolution breath-hold spiral phase velocity mapping allows reproducible assessment of renal pulsatility indices and RABF.

Renal embolic protection devices improve blood flow after stenting for atherosclerotic renal artery stenosis

We sought to measure angiographic renal frame counts (RFC), as a quantitative angiographic assessment of renal blood flow, to evaluate microvascular compromise due to atheroembolism associated with RAS. Atheroembolism associated with renal artery stenting (RAS) has been implicated as a cause for worsening renal function following successful intervention. Use of a distal embolic protection device (EPD) during RAS has been shown to be safe with debris capture in a high percentage of cases. However, objective benefit for renal function with EPD has been difficult to demonstrate. A control group of 30 consecutive patients (33 kidneys) who underwent RAS without EPD were compared with 33 consecutive patients (33 kidneys) who underwent RAS with EPD using RFC measurement. The prestent and poststent mean RFC for the control group was 30.4 ± 12.1 vs. 23.7 ± 9.9 (P = 0.002) and for the EPD group it was 42.6 ± 12.6 vs. 28.3 ± 9.2 (P < 0.0001). The EPD group had a greater improvement in renal blood flow, manifested by a greater reduction of the RFC (Δ RFC) 14.2 ± 15.2 vs. 6.7 ± 11.7 (P = 0.03) compared with the control group. The use of an EPD was associated with a much larger improvement in renal blood flow (lower RFC) following RAS. This suggests that EPD's may be effective in preventing renal atheroembolic injury and that a controlled trial measuring the impact of EPD's on renal blood flow following RAS should be performed.

Renal Viability Evaluated by the Multiprobe Assembly: A Unique Tool for the Assessment of Renal Ischemic Injury

Background: One of the major causes of transplanted organs’ dysfunction is ischemia-reperfusion injury, where mitochondrial dysfunction is the primary contributor to cell damage. Mitochondrial NADH fluorescence reliably describes intracellular oxygen deficiency and mitochondrial function. Therefore, its monitoring at the tissue level, together with other physiological parameters, can serve to evaluate tissue vitality. Methods: The multiprobe assembly (MPA) enabled the assessment of renal blood flow (RBF) using laser Doppler flowmetry, mitochondrial NADH redox state using the fluorometric technique, and ionic homeostasis using specific mini-electrodes (K⁺ and H⁺). The MPA was utilized in two rat groups in which ischemia was induced for a period of 25–30 min (group 1) or for 60 min (group 2), and RBF and NADH were also monitored in a group of rats that underwent a complete kidney ischemia 24 h before the monitoring – a well-known model of acute renal failure. Results: During ischemia, the RBF was completely abolished, NADH and extracellular potassium levels increased, and extracellular pH decreased. Immediately after the reperfusion, full recovery was observed; however, in the rats undergoing 60-min ischemia followed by 24-hour reperfusion, the tissue hemodynamic and mitochondrial functions were significantly impaired. Conclusion: This study demonstrates the advantage of using the MPA for real-time evaluation of kidney physiological state, which may serve as a practical instrument for the evaluation of graft viability during transplantation procedures.

Parametric renal blood flow imaging using [15O]H2O and PET

The quantitative assessment of renal blood flow (RBF) may help to understand the physiological basis of kidney function and allow an evaluation of pathophysiological events leading to vascular damage, such as renal arterial stenosis and chronic allograft nephropathy. The RBF may be quantified using PET with H(2)(15)O, although RBF studies that have been performed without theoretical evaluation have assumed the partition coefficient of water (p, ml/g) to be uniform over the whole region of renal tissue, and/or radioactivity from the vascular space (V(A). ml/ml) to be negligible. The aim of this study was to develop a method for calculating parametric images of RBF (K(1), k(2)) as well as V(A) without fixing the partition coefficient by the basis function method (BFM). The feasibility was tested in healthy subjects. A simulation study was performed to evaluate error sensitivities for possible error sources. The experimental study showed that the quantitative accuracy of the present method was consistent with nonlinear least-squares fitting, i.e. K(1,BFM)=0.93K(1,NLF)-0.11 ml/min/g (r=0.80, p<0.001), k(2,BFM)=0.96k(2,NLF)-0.13 ml/min/g (r=0.77, p<0.001), and V(A,BFM)=0.92V(A,NLF)-0.00 ml/ml (r=0.97, p<0.001). Values of the Akaike information criterion from this fitting were the smallest for all subjects except two. The quality of parametric images obtained was acceptable. The simulation study suggested that delay and dispersion time constants should be estimated within an accuracy of 2 s. V(A) and p cannot be neglected or fixed, and reliable measurement of even relative RBF values requires that V(A) is fitted. This study showed the feasibility of measurement of RBF using PET with H(2)(15)O.

Intra-aortic balloon pumping increases renal blood flow in patients with low left ventricular ejection fraction

Intra-aortic balloon pumping (IABP) has, for decades, been one of the key treatment modalities following impaired cardiac function after cardiac surgery. IABP increases cardiac output, decreases oxygen consumption of the heart and relieves the left ventricle. However, a number of complications have been reported in connection with IABP treatment. Only a few studies have evaluated renal blood flow and the purpose of this prospective study was to evaluate whether renal blood flow was affected by IABP treatment in high-risk patients. After approval from the county ethical committee and informed consent, seven consecutive patients with low left ventricular ejection fraction and scheduled for preoperative IABP treatment were allocated to the study. Assessment of renal blood flow was based on ultrasound spectral Doppler estimation of the flow velocity profiles in the interlobar kidney arteries. The result was described as balloon index (BI), which is maximal systolic velocity divided by the temporal mean velocity. Typical velocity profiles were demonstrated in all patients before, during and after IABP. BI measurement changed with time (p <0.05). BI was lower during IABP compared to both pre-IABP and post-IABP (p <0.025), indicating a higher renal blood flow. No statistically significant changes were seen in s-creatinine or creatinine clearance. Assuming unchanged diameter of kidney arteries and no considerable decrease in renal resistance and/or compliance, we conclude that the interlobar renal blood flow was significantly increased during IABP treatment, measured by ultrasound Doppler technique, but without a simultaneously significant change in creatinine clearance.

Methods of renal blood flow measurement.

Variations in regional renal blood flow have been implicated in a variety of disease states. Many techniques have been developed in an attempt to accurately assess these changes. The microsphere technique is the most widely used method at the present time. This technique allows focal measurements to be performed, but there is a conflict between the resolution of the method and the number of microspheres necessary in each sample. New imaging techniques such as tomography and autoradiography enable visual assessment of renal blood flow. Though there is no ideal method, these techniques have opened up new possibilities in the quantification of regional renal blood flow.

Color Doppler Ultrasonography for the Assessment of Renal Blood Flow in Heart Failure

To validate color Doppler ultrasonography of renal arteries for the assessment of renal blood flow (RBF), we compared left and right RBF estimates and their sum (total RBF) by echo-Doppler with data obtained by iodine 123-123I-p-aminohippuric acid (PAH) scintigraphy in 19 patients with heart failure and 7 normal control subjects. Single-side and total RBF estimates by echo-Doppler ranged, respectively, between 179 and 428 mL/min/m2 and from 378 to 835 mL/min/m2 in patients with heart failure and between 265 and 601 mL/min/m2 and from 564 to 1,182 mL/min/m2 in normal control subjects. Single-side and total RBF estimates by echo-Doppler correlated well with measurements obtained by scintigraphy (r = 0.74 and 0.76, respectively, in patients with heart failure; both: p < 0.001). At Bland and Altman's analysis of correspondence between the 2 techniques, there were 17 disagreements (33.7%) for single-side RBF and 8 disagreements (31.8%) for total RBF. However, the two techniques disagreed markedly in only two single-side and one total RBF estimates. Thus, in patients with heart failure, RBF assessed noninvasively by color Doppler ultrasonography has a good correlation with 123I-PAH renal scintigraphy data over a wide range of blood flow.

Noninvasive assessment of renal blood flow in patients with liver cirrhosis by duplex sonography: [formula omitted], E. Treher, V. Gross, J. Schölmerich, Department of Internal Medicine I, University of Regensburg, 93042 Regensburg, Germany

Noninvasive assessment of renal blood flow in patients with liver cirrhosis by duplex sonography: [formula omitted], E. Treher, V. Gross, J. Schölmerich, Department of Internal Medicine I, University of Regensburg, 93042 Regensburg, Germany

Ultrafast Contrast Enhanced Magnetic Resonance Imaging of Congenital Hydronephrosis in a Rat Model

Since new ultrafast magnetic resonance imaging (MRI) might offer unique advantages for evaluating renal blood flow, anatomy and urinary excretion, we used this technique to characterize a rat model with congenital partial ureteropelvic junction obstruction. MRI of 9 rats from an inbred colony with unilateral congenital (nonsurgical) hydronephrosis was compared with the contralateral nonhydronephrotic kidney serving as control. Our new imaging technique consisted of a 1-minute ultrafast gradient recalled imaging sequence during the first minute (64 images per imaging time 960 milliseconds) after contrast bolus injection with gadolinium-diethylenetri-aminepentaacetic acid for assessment of renal blood flow followed by a 30-minute period with image acquisition every 30seconds to study contrast distribution and excretion. Signal intensities were analyzed continuously over selected, different regions of interest. Anatomic analysis of MRI noncontrast studies showed precise delineation of the hydronephrotic pelvis and cortico-medullary junction. After contrast gadolinium-diethylenetriaminepentaacetic acid injection signal intensity from the region of interest from hydronephrotic kidneys differed from nonhydronephrotic kidneys by showing less cortical decrease, suggesting decreased blood flow, less medullary decrease and delayed contrast excretion. Clear contrast distribution among the cortex, medulla and collecting system allowed selective estimation of different regions of interest and excellent anatomic evaluation. Renal anatomy and renal pelvic pressures were confirmed after scans were completed.Ultrafast contrast enhanced MRI allows simultaneous assessment of renal morphology, blood flow and function. In hydronephrotic partially obstructed kidneys distinct flow and excretion patterns measured with contrast enhanced MRI allow differentiation between the obstructed and nonobstructed kidney on physiological rather than purely anatomic means. This imaging technique may provide a useful method of evaluating congenital hydronephrosis obviating the need for multiple different diagnostic procedures.

Assessment of renal blood flow with contrast ultrasonography.

Sonicated albumin microspheres, a digitalizing ultrasound system, and a mathematical model for flow were used to determine whether blood flow in the canine kidney could be assessed with contrast ultrasound. Albunex ultrasound contrast microspheres were injected into the aorta while ultrasound images of the kidney and aorta were recorded simultaneously. Ultrasound data were obtained during contrast injections at 93 different renal blood flow rates in nine dogs. Contrast dose was calibrated to ultrasound system response for both aortic and renal images. A linear relationship between microbubble concentration used and pixel intensity was established (r = 0.89 for aortic images and r = 0.91 for renal images). Renal blood flow was manipulated from baseline by means of a hydraulic renal artery occluder and by intravenous dopamine or fenoldopam infusion. Blood flow calculated with contrast ultrasonography was compared with direct measurement obtained with an electromagnetic flow probe at each flow rate. Direct measurement correlated with rates calculated with contrast ultrasonography (r = 0.84, 95% confidence limits from 0.75 to 0.90). Overall, calculations tended to overestimate absolute flow measurements, and overestimation of flow tended to be greater during pharmacologically manipulated flow rates. We conclude the changes and trends in renal blood flow can be serially assessed in vivo with contrast ultrasonography, but technical limitations of present commercial ultrasounds systems preclude absolute quantification at this time.

Validation of bedside measurements of absolute human renal blood flow by a continuous thermodilution technique.

There is a clinical need for a system that would allow rapid assessment of renal blood flow in patients with oliguric circulatory shock. A local, continuous thermodilution technique for the measurement of renal venous blood flow, using readily available equipment, was developed. To test the hypothesis that this system would allow measurement of renal blood flow in clinical situations, we compared simultaneous measurements made by the continuous thermodilution technique with measurements of: a) absolute flow measured by volumetric collection in an in vitro flow model; b) renal arterial blood flow measured by electromagnetic flow probe under changing hemodynamic conditions in nine pigs; and c) calculated renal blood flow derived from a clearance technique in 16 patients after cardiac catheterization. The technique utilizes a short-duration, constant infusion of room temperature normal saline into the renal vein via a retrograde thermodilution catheter, with measurement of flow at a thermistor 1 cm back from the tip of the catheter. The method measured absolute blood flow in an in vitro model, with a correlation coefficient of .99 over blood flows ranging from 55 to 885 mL/min (r2 = .98). There was a .92 correlation coefficient with renal arterial blood flow measured by electromagnetic flow probe in a pig model (r2 = .85), and a .8 correlation with simultaneous measurement of renal blood flow by corrected iodohippurate clearance in humans (r2 = .64). Compared with electromagnetic flow probe measurements, a single measurement by the thermodilution technique would be accurate to within 80 mL/min in 95% of cases. Variability between individual measurements, expressed as the mean of the coefficient of variance for each patient, was 5.5 +/- 3.7%. This technique is simple to use, requires only venous cannulation and injection of normal saline, and allows rapidly repeatable, immediately available measurements of renal blood flow in a wide range of clinical circumstances, including severe renal impairment or anuria.

Assessment of Renal Blood Flow by Colour Flow Doppler Ultrasound during Dopamine Infusion in Normal Subjects

Assessment of Renal Blood Flow by Colour Flow Doppler Ultrasound during Dopamine Infusion in Normal Subjects

Assessment of renal blood flow in dogs: analysis of I-hippuran blood clearance in healthy dogs and in dogs with proteinuria

In 30 clinically healthy dogs (weights 7.5 to 57 kg) and in 41 proteinuric dogs the 131I-hippuran blood disappearance curve after single injection was determined (0 to 90 minutes), described by a bi-exponential function and analysed according to a two compartment model. The dependence of the blood clearance (C), representing an effective renal blood flow, on the bodyweight (W) (kg) could be described with both a linear function (C = 61 + 13.2 W ml min-1) and a power function (C = 30.56 W0.79 ml min-1) in the healthy dogs. The results of the regression between blood clearance and bodyweight were reproducible (r = 0.92, n = 10 residual error 12 per cent, P less than 0.01).

In vivo autoradiography of xenon 133 distribution in the cystic human kidney.

The radiologic assessment of renal blood flow leaves much to be desired. The orthoiodohippurate renogram measures an integration of many variables including blood flow, tubular enzymatic function, tubular transport, and renal pelvic storage. The mercury renogram is even more complex. These technics are therefore useful only as an index of total renal function and not as a measure of renal blood flow. With the use of nonisotopic methods, the mean transit time of radiopaque contrast material affords an index of renal blood flow but is also limited by the fact that in addition to blood flow, renal function plays an important part in the changing kidney density. In 1963 Thorburn et al. (1) applied the Kety-Schmidt washout technic of inert radioactive gases to the assessment of renal blood flow, affording the opportunity to quantitate the intrarenal distribution and renal blood flow in cubic centimeters per 100 g perfused tissue per minute. The radioactive gas washout technic requires intra-arterial injection ...