Renal Artery Flow Research Articles

Flujo sanguíneo de las arterias renales fetales en preeclámpticas graves y embarazadas normotensas sanas

Objective To compare the blood flow in fetal renal arteries in severe preeclamptic and healthy normotensive pregnant women. Method The sample consisted of 30 women with severe preeclampsia (group A) and 30 healthy normotensive pregnant women (group B) with single pregnancies of more than 30 weeks. The pulsatility and resistance indexes of the uterine, umbilical, fetal middle cerebral and fetal renal arteries were measured. Results There were no significant differences in maternal age, gestational age or newborn weight (p = ns). Pulsatility and resistance index values in the uterine and umbilical arteries were significantly higher and both measurements for the fetal middle cerebral artery were significantly lower in group A than in group B (p = 0.0001). Pulsatility and resistance index values in the fetal renal artery were significantly higher in group A than in group B (p = 0.0001). The fetal renal artery pulsatility index was significantly correlated with the pulsatility index of the uterine artery (p = 0.011) and the fetal middle cerebral artery (p < 0.007). The fetal renal artery resistance index was correlated with the resistance index of the three vessels (p < 0.05). Conclusion Women with severe preeclampsia show blood flow alterations in the fetal renal arteries compared with healthy normotensive pregnant women.

Non-invasive investigation of kidney disease in type 1 diabetes by magnetic resonance imaging

Pathophysiological abnormalities in early diabetic nephropathy are poorly understood. We employed MRI to characterise renal perfusion, tissue oxygenation and kidney size in non-diabetic volunteers and type 1 diabetic patients without and with early renal disease. We studied ten control participants (C; age 40.0 [range 31-54] years), nine longstanding normotensive type 1 diabetic patients (T1Normo; age 40.1 [31-50] years, estimated glomerular filtration rate [eGFR] 83.4 ± 10.6 ml min(-1) 1.73 m(-2)) and eight microalbuminuric type 1 diabetic patients (T1Micro; age 42.4 [33-52] years, eGFR 71.6 ± 13.7 ml min(-1) 1.73 m(-2)). Six microalbuminuric patients were restudied after 4 weeks without renin-angiotensin-aldosterone system inhibitors. Phase contrast angiography and kidney blood oxygen level dependent (BOLD) (R(2)(*)) MRI were performed, before and during water diuresis. Contrast-enhanced MRI was performed at baseline urine flow rate. Renal artery flow, renal vascular resistance (RVR), cortical and medullary volumes, and R(2)(*) were determined. Renal cortical and medullary volumes were similar in all groups (cortex: C 108 ± 16, T1Normo 112 ± 21, T1Micro 111 ± 10 cm(3)/1.73 m(2); medulla: C 35 ± 14, T1Normo 29 ± 10, 33 ± 6 cm(3)/1.73 m(2)). RVR increased from control to normoalbuminuric to microalbuminuric type 1 diabetic patients (C 0.061 ± 0.018, T1Normo 0.077 ± 0.014, T1Micro 0.093 ± 0.024 mmHg ml(-1) min(-1) 1.73 m(-2), ANOVA p = 0.012). RVR correlated inversely with eGFR in normoalbuminuric, but not in microalbuminuric diabetic patients. Renal artery flow was lower in the whole diabetes cohort (control 740 ± 205 vs diabetes 591 ± 128 ml min(-1) 1.73 m(-2), p = 0.035). Cortical and medullary volumes remain normal in early diabetic nephropathy. Decreased renal flow in longstanding normoalbuminuric type 1 diabetic patients may reflect intrarenal vascular stiffening, whereas in the microalbuminuric patients it may also reflect increased intraglomerular pressure.

Predictors of Diagnostic Success With Renal Artery Duplex Ultrasonography

Renal artery duplex ultrasonography (RA-DUS) is commonly used for the evaluation and follow-up of renal artery atherosclerotic disease. In a complete study, renal artery flow is evaluated from the vessel origin to the intraparenchymal branches. The quality of RA-DUS is in part technologist-dependent, but many factors may affect the ability to complete a diagnostic examination. This study evaluated the clinical and technical factors that predict the ability to obtain a complete RA-DUS examination. A prospective evaluation of all patients undergoing RA-DUS between July 2008 and February 2009 was performed. Factors such as patient age, gender, body mass index, technologists' years of experience, patient care setting (inpatient vs. outpatient), bedside examination, smoking before the examination, fasting status, and recent abdominal surgery were all recorded. Multivariate logistic regression analysis was performed. A p value of ≤ 0.05 was considered significant. During the study period, 250 patients underwent RA-DUS (mean age: 59.9 ± 17.8 years, 57% [143] female). A total of 87 (35%) examinations were incomplete. This included nondiagnostic examinations which did not exhibit any segment of the renal artery. Factors that were associated with an incomplete examination included technologists' years of experience (OR = 0.92, p = 0.042), bedside examination (OR = 4.17, p = 0.016), and recent abdominal surgery (OR = 3.45, p = 0.047). Body mass index, fasting status, and smoking before the examination did not affect the ability to obtain a complete study. One-third of the RA-DUS studies were classified as incomplete by the strict criteria used in this prospective study. An experienced ultrasound technologist is more likely to obtain a complete RA-DUS examination. Recent abdominal surgery and bedside examinations were predictive of a limited examination as well. Vascular laboratories should consider these factors when scheduling examinations so as to obtain complete RA-DUS studies, as well as improve the cost-effectiveness of resource utilization.

Effects of chronic sympatho-inhibition on renal excretory function in renovascular hypertension

Treatment of renovascular hypertension with drugs that directly target the renin-angiotensin system may compromise glomerular filtration and renal excretory function, leading to renal failure. Centrally acting sympathoinhibitory agents also inhibit the renin-angiotensin system, so we determined whether this treatment modality alters renal excretory function in rabbits with renovascular hypertension. Rabbits were equipped with bilateral renal artery flow probes and a renal nerve electrode. Hypertension was induced with a renal artery clip (2K1C) or rabbits were sham-clipped. After 2 weeks, a subcutaneous minipump was implanted to deliver rilmenidine (2.5 mg/kg per day) or vehicle for 3 weeks. Haemodynamic variables and renal function were studied under control conditions and during intravenous infusion of isotonic saline (154 mmol/l NaCl) at increasing rates of 4, 12 and 36 ml/kg per hour. Mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA) were greater in 2K1C rabbits than sham-clipped rabbits, but total urine flow, sodium excretion and glomerular filtration rate were similar in the two groups. In 2K1C rabbits, rilmenidine reduced MAP to close to control levels and reduced RSNA (40%), but did not significantly alter basal renal blood flow, glomerular filtration rate, urine flow or sodium excretion. The natriuretic response to isotonic saline load in 2K1C rabbits was not significantly altered by rilmenidine. These observations show that chronic treatment of rabbits with renal artery stenosis with a centrally acting sympathoinhibitory agent, despite normalizing MAP, does not compromise renal excretory function. Thus, this treatment modality may be particularly useful in renovascular hypertension.

Time-Dependent Doppler Ultrasonographic Findings in Transplanted Kidneys From Living Donors: A 5-Year Follow-Up Study

Introduction Ultrasonography and color Doppler have been used extensively to evaluate transplanted kidneys. Several recent studies have suggested its value to assess renal transplant dysfunction, particularly in the early postoperative period. The aim of the present study was to evaluate the time-dependent changes in color Doppler ultrasonography (DUS) findings during the first 5 years after renal transplantation. Methods Among a prospective cohort we evaluated the results of collar Doppler findings in renal allograft recipients over 5 years after transplantation. For this purpose we compared the DUS findings of kidney size, pulsatile index (PI), resistive index (RI) and renal artery flow before transplantation in living donor kidneys versus 6–12 months as well as 5 years after transplantation in 23 patients. The statistical analysis was performed using SPSS version 16. P value was set at .05. Results The mean length of the transplanted kidney was 110.60 ± 7.92 mm before transplantation in the living donors body versus 120.29 ± 9.01 mm and 119.36 +/− 9.9 mm at 6–12 months versus more than 5 years after transplantation, respectively. Mean PI and RI were 1.00 +/− 0.14 and 0.60 +/− 0.05 before transplantation and 1.00 +/− 0.22 and 0.61 +/− 0.08 and 1.07 +/− 0.26 and 0.63 +/− 0.07 at 6–12 months versus more than 5 years after transplantation, respectively. There was no significant difference in mean PI and RI during the 5 years of the follow-up study. Mean length and anteroposterior diameter increased significantly at 6–12 months and 5 years after transplantation when compared with the results before transplantation ( P < .05). No significant difference was present in Doppler findings of transplanted kidneys between 6–12 months and 5 years after transplantation. In conclusion we observed increasing kidney size after transplantation that remained constant during 5 year follow-up among renal allograft recipients.

Infrarenal aortic‐clamping after renal ischaemia aggravates acute renal failure

Renal failure is a frequent complication of juxtarenal abdominal aortic aneurysm (JAA)-repair. During this operation, suprarenal aortic-clamping is followed by infrarenal aortic-clamping (below renal arteries) to restore renal flow, while performing the distal anastomosis. We hypothesized that infrarenal aortic-clamping, despite restoring renal perfusion provokes additional renal damage. We studied three groups of rats. After 45min of suprarenal aortic-clamping, group 1 had renal reperfusion for 90min without aortic-clamps (n=7). In group 2, 45min of suprarenal aortic-clamping with a distal clamp on the aortic-bifurcation was followed by 20min of infrarenal aortic-clamping. Renal reperfusion was continued for 70min without aortic-clamps (i.e. 90 min of renal reperfusion; n=8). The sham-group had no clamps (n=7). We measured renal haemodynamics, functional parameters and tissue damage. On suprarenal aortic-clamp removal, renal artery flow, cortical flow and arterial pressures were higher in group 2 than in group 1. We detected increased tubular brush border damage, luminal lipocalin-2 and 30-60% higher renal protein nitrosylation in group 2 when compared to group 1 (P<0·05). Group 2 showed more release of asymmetrical dimethylarginine (ADMA) from the kidneys in the renal vein, therefore indicating diminished clearing capacity (P<0·001). Arginine/ADMA-ratio, which defines the bio-availability of nitric oxide, tended to be lower in group 2 and correlated with renal flow. Furthermore, there were no significant differences found in creatinine levels and renal leucocyte accumulation between group 1 and 2. Additional infrarenal aortic-clamping leads to increased renal damage and oxidative stress, despite adequate perfusion of kidneys after suprarenal aortic-clamping. This study indicates that the clamping sequence used in JAA-repair causes more than simple renal I/R-injury.

28 Milrinone is Preferred to Levosimendan for Mesenteric Perfusion in Hypoxia-Reoxygenated Newborn Piglets on Dopamine

Objectives: To determine the effect on systemic and regional perfusion of adding milrinone or levosimendan to a background infusion of dopamine in newborn piglets following hypoxia-reoxygenation (H-R).Methods: Piglets (1-4d) were instrumented for continuous monitoring of systemic and pulmonary arterial pressures, cardiac output (CI) and common carotid, superior mesenteric and renal arterial flows. Sham piglets (n=6) had no H-R. H-R piglets underwent 2h of hypoxia followed by reoxygenation with 100% (0.5h) and 21% oxygen (3.5h). H-R piglets were blindly randomized (n=6/group) to saline control or dopamine (10 mcg/kg/min) with milrinone (D+M - 50 mcg/kg bolus then 0.5 mcg/kg/min) or levosimendan (D+L - 24 mcg/kg bolus then 0.2 mcg/kg/min). Tissue was collected for biochemical and histological analysis. Data were analyzed using ANOVA.Results: Following 2h of hypoxia, H-R piglets were in cardiogenic shock with depressed CI and hypotension. D+M and D+L treatments increased heart rate, CI and systemic oxygen delivery (all p< 0.05 vs. controls) without significant effects on pressures. Both treatments improved common carotid flow, oxygen delivery and vascular resistance (p< 0.05 vs. controls). D+M additionally improved superior mesenteric flow and oxygen delivery (p< 0.05 vs. controls). No disparate effect was appreciated on renal perfusion. D+M piglets had lower myocardial oxidized-to-total glutathione ratio than controls (p=0.05). No differences were appreciated in plasma lactate, myocardial lactate or histologic indices of H-R injury.Conclusions: In H-R newborn piglets, either milrinone or levosimendan addition to dopamine similarly improves systemic hemodynamics. Milrinone addition, in particular, improves mesenteric perfusion and attenuates myocardial oxidative stress.

333 Cyclosporine and Regional Hemodynamics of Newborn Piglets Following Asphyxia-Reoxygenation: A Dose-Response Study

Introduction: Asphyxiated neonates commonly have multi-organ failure. Cyclosporine has recently been shown to improve systemic hemodynamics, however, its effects on the regional circulation have not yet been studied. We hypothesize that cyclosporine in asphyxiated newborn piglets will dose-dependently improve regional hemodynamics and oxygen metabolism. Methods: Piglets (1-4 days-old) were acutely instrumented for continuous monitoring of common carotid (CA), superior mesenteric (SMA) and renal (RA) arterial flows. After stabilization, normocapnic alveolar hypoxia (10-15% oxygen) was instituted for 2h followed by reoxygenation with 100% oxygen for 0.5h, then 21% for 3.5h. Piglets were blockrandomized to receive one of three cyclosporine intravenous boluses (2.5, 10 or 25 mg/kg) or placebo (normal saline, control) after 5 minutes of 100% reoxygenation (n=8/group). Blood samples were collected for co-oximetry analysis and oxygen transport calculation. Statistical analysis was performed using ANOVA. Results: All piglets had decreased regional blood flow (CA 52-64%, SMA 34-56%, RA 25-35% compared to respective baseline), hypotension (mean arterial pressure 30mmHg) and acidosis (pH 7.04) at 2h of hypoxia. Cyclosporine (2.5 and 10 mg/ kg) treatment at reoxygenation caused dose-related improvements in SMA flow and oxygen delivery. Cyclosporine (10 mg/kg) significantly increased RA flow and oxygen delivery (P< 0.05 vs. controls). While CA flows were not different among groups, cyclosporine (25 mg/kg) had significantly higher CA oxygen delivery than controls. Conclusion: In newborn piglets following asphyxiareoxygenation, post-resuscitation administration of cyclosporine caused differential and dose-related improvements of regional perfusion.

E0457 Establishment of contrast induced nephropathy model in rats intervention

ObjectivesThe purpose of this study was to establish a rat model of CIN and to evaluate its efficacy.MethodsTotally 24 SD rats were randomly allocated into experimental group (group A, n=12)...

E0644 Establishment of contrast induced nephropathy model in rats

ObjectivesThe purpose of this study was to establish an rat model of CIN and to evaluate its efficacy.MethodsTotally 24 SD rats were randomly allocated into experimental group (group A, n=12)...

Development of a Range of Anatomically Realistic Renal Artery Flow Phantoms

Computer-aided modelling techniques were used to generate a range of anatomically realistic phantoms of the renal artery from medical images of a 64-slice CT data set acquired from a healthy volunteer. From these data, models of a normal healthy renal artery and diseased renal arteries with 30%, 50%, 70% and 85% stenoses were generated. Investment casting techniques and a low melting point alloy were used to create the vessels with varying degrees of stenosis. The use of novel inserts significantly reduced the time, materials and cost required in the fabrication of these anatomically realistic phantoms. To prevent residual metal remaining in the final phantom lumens a technique employing clingfilm was used to remove all molten metal from the lumen. These novel flow phantoms developed using efficient methods for producing vessels with various degrees of stenosis can provide a means of evaluation of current and emerging ultrasound technology. (E-mail: king.deirdre@mayo.edu)

Carbon Dioxide–Enhanced CT-Guided Placement of Aortic Stent-Grafts: Feasibility in an Animal Model

To test the feasibility of carbon dioxide (CO(2))-enhanced computed tomography (CT)-guided placement of infrarenal abdominal aortic stent-grafts in an animal model. Appearance of a stent-graft mounted on its deployment system and the feasibility of CT fluoroscopy-guided placement were analyzed in an in vitro setting. Five domestic pigs weighing 70 to 80 kg underwent CO(2)-enhanced 64-slice CT arteriography (CTA). After surgical exposure of the right iliac artery, an 18-mm stent-graft was advanced into the abdominal aorta. Infrarenal position of the graft was monitored using CT fluoroscopy with CO(2) administered intermittently in a flow-regulated manner using a computer-controlled injection system. After the final position of the stent-graft was determined, the graft was deployed under CT fluoroscopy guidance. Graft position was confirmed by contrast enhanced 64-slice CTA and conventional catheter angiography. To quantitatively assess the position of the stent-graft, the distance between the proximal stent struts and the radiopaque marker was determined using an electronic caliper. CT-guided placement of infrarenal aortic stent-grafts was feasible in all animals without complications. CO(2)-enhanced CTA allowed for the identification of the renal arteries in all animals. CT fluoroscopy permitted the continuous online monitoring of stent deployment. In all animals, the grafts were placed without impairment of renal artery flow or stent-graft dislocation. The mean distance between the stent-graft and origin of the more caudal renal artery was 0.9+/-0.3 mm. CO(2)-enhanced CT fluoroscopy permits the precise placement of infrarenal aortic stent-grafts in an animal model.

The renal artery ostium flow diverter: Structure and potential role in atherosclerosis

Initiation of renal atherosclerosis occurs primarily at the caudal region of the renal artery ostium. To date, no mechanism for initiation of atherosclerosis at this site has been substantiated. Herein, we identify a renal artery flow diverter on the caudal wall of the renal artery ostium that directs flow into the renal artery and selectively retains LDL, an initial step in atherosclerosis. High-resolution ultrasound revealed the generation of flow eddies by the caudal diverter in vivo, consistent with a role in directing aortic flow to the renal artery. Two-photon excitation en face microscopy of the diverter revealed a substantial reduction in the elastic lamina exposing potential retention sites for LDL. Fluorescent LDL was selectively retained by the renal artery diverter, consistent with its molecular structure. We propose that the rigid macromolecular structure of the renal artery ostium diverter is required for its vascular function and contributes to the initiation of renal atherosclerosis by the retention of LDL.

Thrombosis in renal artery in a newborn. Presentation a review of a case

This report describes a newborn who presents high pressure values and absence of pulses in inferior extremities in his 4th day of life. Posterior to placement of umbilical arterial catheter, confirming diagnostic of thrombosis in aorta and left renal artery. A gamagraphy with MAG 3 was performed that gave evidence of left renal exclusion and aorta and left renal angioresonance. A management with no fractional heparin and streptokinase during 6 hours was initiated. The compromise in lower extremities was totally recovered, improving presure values in a few days. Following studies of renal function and growth give evidence of left renal artery flow and some function. This report describes an improvement with anticoagulant and thrombolitic treatment of a newborn kidney depite of a prolonged ischemia.

Hypothermic Circulatory Arrest: Renal Protection by Atrial Natriuretic Peptide

Moderate hypothermic circulatory arrest with selective cerebral perfusion has been developed for cerebral protection during thoracic aortic surgery. However, visceral organs, particularly the kidneys, suffer greater tissue damage under moderate hypothermic circulatory arrest, and acute renal failure after hypothermic circulatory arrest is an independent risk factor for early and late mortality. This study investigated whether atrial natriuretic peptide could prevent the reduction in renal perfusion and protect renal function after moderate hypothermic circulatory arrest. Twelve pigs cooled to 30 degrees C during cardiopulmonary bypass were randomly assigned to a peptide-treated group of 6 and a control group of 6. Moderate hypothermic circulatory arrest was induced for 60 min. Systemic arterial mean pressure and renal artery flow did not differ between groups during the study. However, renal medullary blood flow increased significantly in the peptide-treated group after hypothermic circulatory arrest. Myeloperoxidase activity was significantly reduced in the medulla of the peptide-treated group. Renal medullary ischemia after hypothermic circulatory arrest was ameliorated by atrial natriuretic peptide which increased medullary blood flow and reduced sodium reabsorption in the medulla. Atrial natriuretic peptide also reduced the release of an inflammatory marker after ischemia in renal tissue.

1405: Development of a Vessel Mimicking Material for Use in Anatomical Flow Phantoms

A vessel mimicking material for use in an anatomically realistic renal artery flow phantom was developed. Currently available commercial flow phantoms consist of a straight silicone vessel embedded in a tissue mimicking material (TMM) through which a blood mimicking fluid is pumped. These phantoms are useful for determining the accuracy of the ultrasound scanners for example, maximum velocity estimation. However, they cannot be used to obtain realistic haemodynamic flow information as is the case for anatomically realistic flow phantoms. Polyvinyl alcohol (PVA) cyrogel was used to mimic the renal arteries. Using this vessel mimicking material it was possible to achieve acoustic properties that closely matched those of the normal and abnormal renal artery. Both the acoustic and mechanical properties of the vessel mimicking material were varied by adjusting the number of freeze/thaw (F/T) cycle, the concentration of PVA and the concentration of various additives (e.g. silicone carbide, aluminium oxide). The acoustic and mechanical properties were determined using an acoustic macroscope and a Uniaxial Tensile testing machine (Zwick Z010), respectively. Speed of sound values varied from 1510 1560m/s at 3.5MHz at 22°C, and Young's modulus from 18-165kPa, for 1-6 F/T cycles and a 10% PVA concentration. The effect of other additives on both the acoustic and mechanical properties of PVA taking into account the materials non-linear and viscoelastic characteristics such as Stress Softening, Stress Relaxation and Set will also be presented. In conclusion, a suitable vessel mimicking material for use in anatomical renal flow phantoms was developed.

1403: Development of Anatomically Realistic Renal Artery Flow Phantoms with Varying Degrees of Stenosis

1403: Development of Anatomically Realistic Renal Artery Flow Phantoms with Varying Degrees of Stenosis

Standardizing resistive indices in healthy pediatric transplant recipients of adult-sized kidneys

Small pediatric recipients of an adult-sized kidney have insufficient renal blood flow early after transplantation, with secondary chronic hypoperfusion and irreversible histological damage of the tubulo-interstitial compartment. It is unknown whether this is reflected by renal resistive indices. We measured renal graft resistive indices and volumes of 47 healthy pediatric kidney transplant recipients of an adult-sized kidney in a prospective study for six months post-transplant. A total of 205 measurements were performed. The smallest recipients (BSA <or=0.75 m(2)) had higher resistive indices compared to recipients with a BSA between 0.75 and 1.5 m(2) (p < 0.0001) and to recipients with a BSA >or= 1.5 m(2) (p < 0.0001). Resistive indices increased during the first six months in the smallest recipients (p = 0.02), but not in the two larger recipient groups (BSA 0.75-1.5 m(2) and >or=1.5 m(2)). All three BSA groups showed a reduction in renal volume after transplantation, with the greatest reduction occurring in the smallest recipients. In conclusion, renal transplant resistive indices reflect pediatric recipient BSA dependency. The higher resistance to intra-renal vascular flow and significant decrease in renal volume in the smallest group likely reflect accommodation of the size discrepant transplanted adult-sized kidney to the smaller pediatric recipient vasculature with associated lower renal artery flow.

Pathophysiology of Renal Hemodynamics and Renal Cortical Microcirculation in a Porcine Model of Elevated Intra-abdominal Pressure

Elevated intra-abdominal pressure (IAP) has been shown to impair renal perfusion and renal function. This study was designed to further investigate the effects of elevated IAP on renal venous hemodynamics and renal perfusion pressure (RPP). Another aim was to evaluate the renal cortical microcirculation by sidestream dark field (SDF) imaging in a porcine model of elevated IAP. In 11 pigs, IAP was increased stepwise while renal hemodynamics and urinary output were recorded. RPP (RPP = mean arterial pressure minus IAP) and renal filtration gradient (RFG = mean arterial pressure minus 2xIAP) were calculated. Renal cortical microcirculatory perfusion was assessed by calculating the microvascular flow index (MFI) based on SDF data. With IAP elevated to 30 mm Hg, renal arterial and venous flow decreased in parallel by 34% (p < 0.05) and RPP decreased by 12% (p < 0.05). With increasing IAP, renal vascular resistance increased and MFI decreased significantly. RFG showed a moderate correlation with renal blood flow (r = 0.39, p < 0.05) and MFI (r = 0.46, p < 0.005), whereas RPP did not. In a porcine model of IAP-induced renal impairment, we observed a parallel decrease in renal venous and arterial blood flow together with blood flow redistribution away from the kidney. SDF imaging was used for the first time to assess renal cortical microcirculation and MFI was found to decrease with increasing IAP. RFG, as a clinical estimator of renal perfusion, correlated moderately with renal blood flow and microcirculatory perfusion, whereas RPP did not. Increased renal vascular resistance with elevated IAP might account for this.

Acoustic droplet vaporization for enhancement of thermal therapies.

Vaporization of superheated microdroplets of perfluorocarbon can be triggered by transcutaneous ultrasound for the local production of gas bubbles. Acoustic droplet vaporization (ADV) was performed in the canine renal artery or segmental artery for blood flow control by capillary occlusion to accelerate rf ablation exclusively in the target vascular bed and for future trapping of released drugs. Occlusions of 82% were obtained for >20 min in the two best exteriorized canine kidneys with intracardiac droplet injections. Intravenous injection studies avoided induced cardiac arrhythmias. In four of the six IV studies, mean achieved renal artery flow reduction was 75% for 3 min. Perfusion by colored microspheres showed larger regional reductions in some cases. Droplets that administered IV or intra‐arterially were vaporized by transcutaneous ultrasound in five studies with 3.5–5.5‐cm tissue paths to produce increased kidney cortex echogenicity, but not substantial occlusion. Improved occlusion is expected by enhanced bubble coalescence and creation of a narrower droplet size distribution at diameters close to the transpulmonary limit. Achieved ADV bubble concentrations also appear adequate for enhancement of HIFU therapy by reflection of acoustic energy exiting the focus, increasing absorption exclusively therein, and revealing targeted tissues. [Work supported in part by NIH Grants R01‐EB000281 and S10‐RR022425.]