Doppler ultrasound and renal artery stenosis: An overview

Influence of hyperthermic intraperitoneal chemotherapy on renal blood perfusion

PURPOSE

Hyperthermic intraperitoneal chemotherapy (HIPEC) is accompanied with an increased risk of acute kidney injury (AKI). Whether AKI is induced by chemotoxicity or hyperthermia-related changes in renal perfusion remains controversial. The influence of HIPEC on renal perfusion has not been evaluated in patients yet.

METHODS

Renal blood perfusion was assessed in ten patients treated with HIPEC by intraoperative renal Doppler pulse-wave ultrasound. Ultrasound (US) examinations were performed pre-, intra-, and postoperative with analyses of time-velocity curves. Patient demographics, surgical details, and data regarding renal function were recorded perioperatively. For evaluation of renal Doppler US to predict AKI, patients were divided in two groups with (AKI +) and without (AKI -) kidney injury.

RESULTS

Throughout HIPEC perfusion, neither significant nor consistent changes in renal perfusion could be observed. Postoperative AKI occurred in 6 of 10 participating patients. Intraoperative renal resistive index (RRI) values > 0.8 were observed in one patient developing stage 3 AKI according KDIGO criteria. At 30 min in perfusion, RRI values were significantly higher in AKI + patients.

CONCLUSION

AKI is a common and frequent complication after HIPEC, but underlying pathophysiology remains elusive. High intraoperative RRI values may indicate an increased risk of postoperative AKI. Present data challenges the relevance of hyperthermia-derived hypothesis of renal hypoperfusion with prerenal injury during HIPEC. More attention should be drawn towards chemotoxic-induced hypothesis of HIPEC-induced AKI and caution applying regimens containing nephrotoxic agents in patients. Further confirmatory and complementary studies on renal perfusion as well as pharmacokinetic HIPEC studies are required.

Canagliflozin on top of dual renin-angiotensin system blockade in a woman with partial acquired lipodystrophy, type 2 diabetes and severely proteinuric chronic kidney disease: a case report

Sodium glucose cotransporter 2 inhibitors have proven strong efficacy in reducing end-stage renal disease in patients with type 2 diabetes. We are presenting here the case of a 40-year-old woman with acquired partial lipodystrophy, type 2 diabetes and essential hypertension complicated by chronic kidney disease and proteinuria in the nephrotic range. She first came to our attention in 2012; estimated glomerular filtration rate (eGFR) was 41.5 ml/min/1.73 m² and total proteinuria was 375 mg/24h; she was treated with dual renin angiotensin system blocking. Proteinuria significantly increased during the following years, reaching a nephrotic range (>5 g/day). A kidney biopsy revealed a tubule-interstitial involvement compatible with type 2 diabetes. Leptin replacement therapy, started in 2018, improved glycaemic control and lipid profile, also determining a reduction in insulin total daily dose. In 2019, after the publication of the CREDENCE study, canagliflozin was started on top of losartan and ramipril. After an initial, expected eGFR drop, kidney function stabilized, and albuminuria significantly reduced (from 4120 to 984 mg/24h), while serum potassium showed only minimal increase. At last follow-up (2022) total proteinuria was still reducing (510 mg/24h), while kidney function was substantially unchanged (eGFR 40 ml/min/1.73 m²). This case report suggests that, despite not recommended in international guidelines, the use of SGLT2i in combination with dual renin angiotensin system blockade should be considered in specific conditions and under close clinical monitoring.

Multimodal imaging approach in hyponatremic hypertensive syndrome. A rare case of pediatric unilateral hypoplasia of the main renal artery combined itself with stenosis and review of literature

Renal artery stenosis (RAS) accounts for approximately 5%-10% of secondary renovascular hypertension in the pediatric population. It can occur as an isolated entity, or as a hypoplasia combined itself with stenosis. Hypoplasia, or long-segment developmental narrowing, is a rare cause of renovascular hypertension. Hyponatremic hypertensive syndrome (HHS) is a malignant complication of unilateral RAS and/or renal artery hypoplasia. Hyponatremia, hypokalemic hypochloremic metabolic alkalosis, nephrotic range proteinuria, polyuria, polydipsia, and weight loss are the most common findings. In particular, hypertension remains refractory despite aggressive antihypertensive therapy. Laboratory findings of elevated plasma levels of renin in most case suggest that the stimulation of renin release from the ischemic kidney plays an important pathophysiologic role. HHS is a diagnostic and therapeutic challenge in children. We report a case of a unilateral right renal artery hypoplasia, complicated by a segmental narrowing, in a 17-month-old male, clinically symptomatic for hypertension. We emphasize the role of ultrasound, computed tomography, and digital subtraction angiography that should be planned as reliable and non-invasive multimodal imaging approach.

Phasicity and resistance of the arterial spectral Doppler waveform in a canine femoral focal artery stenosis model

INTRODUCTION

This study aims to evaluate changes in the arterial spectral Doppler waveform in a canine artery stenosis model.

METHODS

Canine femoral artery stenosis models were established in 12 beagle dogs. Doppler waveforms were recorded in the femoral artery preoperatively and postoperatively in the femoral artery and at the ankle after formation of a 50%, 70%, and 90% stenosis or occlusion. Major descriptors for arterial Doppler waveform were used to analyse waveforms.

RESULTS

The proportion of multiphasic waveforms proximal to a moderate stenosis decreased compared to normal baseline, although the difference was not statistically significant, whereas the decreases at the stenosis, distal to the stenosis, and at the ankle were significant (p < 0.05). The decreases in arteries with a more severe stenosis or occlusion were significant at all locations (p < 0.05). The proportion of high resistive waveforms decreased significantly at the ankle in the arteries with a moderate stenosis (50%) (p = 0.002), but the decreases proximal to, at, and distal to the stenosis were not significant. The decreases were significant at all locations in the arteries with a more severe stenosis (p < 0.05). The decrease was significant at the ankle in the arteries with an occlusion (p < 0.001) but not significant pre, at, and post an occlusion.

CONCLUSIONS

Phasicity and resistance of Doppler waveforms alter in canine femoral arteries with a stenosis. Phasicity change seems more sensitive in response to an arterial stenosis than resistance change. Additional information on arterial resistance could be obtained using end-diastolic ratios, resistive indices, and potentially end-systolic notch velocity measurements.

Therapy for Renal Artery Stenosis: A Call for Change

CLINICAL IMPACT

We present a brief case description of a patient who benefitted from stenting in ARAS and provide a comprehensive review of ARAS; its prevalence, pathophysiology, clinical manifestations, diagnosis and treatment. We review the evidence for and against stenting in ARAS as well as consensus guidelines for stenting. Our review is valuable as we argue that stenting in ARAS is underutilized and the randomized control data for stenting in those patients who may benefit most is lacking. Our review will provide an important perspective for clinicians faced with decisions of how to treat ARAS.

Gray-Scale, Color Doppler, Spectral Doppler, and Contrast-Enhanced Renal Artery Ultrasound: Imaging Techniques and Features

Renal artery stenosis (RAS) is increasingly being detected in elderly patients as life expectancy increases. RAS induces hypertension or reduces renal function. Computed tomography or magnetic resonance angiography are objective in detecting RAS but may cause iodine-induced nephrotoxicity or nephrogenic systemic fibrosis in patients with RAS. Ultrasound (US) is, by contrast, a noninvasive and real-time imaging modality useful in patients with reduced renal function. Renal US is not as sensitive for detecting RAS because this technique indirectly assesses the renal artery by analyzing intrarenal hemodynamic changes. Although, ideally, US would be used to directly evaluate the renal artery, its current utility for RAS detection remains unclear. The purpose of this review is to introduce how to assess renal artery with US, to describe imaging features of renal artery US, to compare renal artery US and renal US, and to show how to perform work-up in patients in whom RAS is suspected.

Endovascular interventions in main renal artery pathologies: an overview and update

Renal arteries are involved in a wide spectrum of pathologies including atherosclerosis, fibromuscular dysplasia, Takayasu arteritis, aneurysms, and aortic type B dissections extending into main renal arteries. They manifest as renovascular hypertension, renal ischemia, and cardiovascular dysfunction. The location of the renal arteries in relation to the abdominal aortic aneurysm is a critical determinant of interventional options and long-term prognosis. This article provides a comprehensive review of the role of interventional radiologists in transcatheter interventions in various pathologies involving the main renal arteries with analysis of epidemiology, pathophysiology, newer interventional techniques, and management options.

Long-term clinical outcomes of patients with nonsignificant transplanted renal artery stenosis

Background

Transplant renal artery stenosis (TRAS) is the main vascular complication of kidney transplantation. For research and treatment purposes, several authors consider critical renal artery stenosis to be greater than 50%, and percutaneous intervention is indicated in this scenario. However, there are no reports in the current literature on the evolution of patients with less than 50% stenosis.

Method

This retrospective study included data from all patients who underwent kidney transplantation and were suspected of having TRAS after transplantation with stenosis under 50% independent of age and were referred for angiography at a single centre between January 2007 and December 2014.

Results

During this period, 6,829 kidney transplants were performed at Hospital do Rim, 313 of whom had a clinical suspicion of TRAS, and 54 of whom presented no significant stenosis. The average age was 35.93 years old, the predominant sex was male, and most individuals (94.4%) underwent dialysis before transplantation. In most cases in this group, transplants occurred from a deceased donor (66.7%). The time between transplantation and angiography was less than one year in 79.6% of patients, and all presented nonsignificant TRAS. Creatinine levels, systolic blood pressure, diastolic blood pressure and glomerular filtration rate improved over the long term. The outcomes found were death and allograft loss.

Conclusion

Age, sex and ethnic group of patients were factors that did not interfere with the frequency of renal artery stenosis. The outcomes showed that in the long term, most patients evolve well and have improved quality of life and kidney function, although there are cases of death and kidney loss.

Endovascular stenting with a drug-eluting stent of transplanted renal artery stenosis in a dual kidney transplanted patient

Renal transplant remains the preferred therapy for end-stage renal disease (ESRD). Given the shortage of suitable donor kidneys, use of an expanded criteria donor (ECD) allows marginal kidneys to be transplanted; albeit at risk of increased graft failure due to lower nephron mass. To reduce the risk of graft failure, double kidney transplant (DKT) is advocated, with favorable outcomes. Transplant renal artery stenosis (TRAS) is one of the most common vascular complications following renal transplant. Unlike single kidney transplants, where TRAS usually presents with fluid overload, uncontrolled hypertension, and worsening kidney functions; it may be clinically silent in DKT patients since they have two functional transplanted kidneys. We hereby report a case of TRAS in a DKT patient who had 2 years of favorable clinical outcomes following successful endovascular stenting. He however recently died of COVID-19 associated pneumonitis.

Elevated renal resistive index is independently predicted by older age, but not by the presence of chronic kidney disease: A retrospective cohort study

PURPOSE

Renal resistive index (RRI), which reflects intra-renal arterial impedance is routinely measured when undertaking renal Doppler ultrasonography (RDU). We investigated the relationship between elevated RRI and presence of chronic kidney disease (CKD), and examined whether elevated RRI at baseline is associated with decline in estimated glomerular filtration rate (eGFR) on follow-up.

METHODS

This retrospective observational study examined the association of elevated RRI (>0.7) with the presence of CKD (eGFR <60 mL/min for >3 months), demographic and clinical factors in multivariable models. We also examined the effect of elevated RRI on eGFR decline on follow-up using mixed models.

RESULTS

Of the 346 patients undergoing RDU (median age 69.7 years, 46.2% male), 180 had elevated RRI. There was a strong inverse association between RRI and eGFR at baseline, 1 and 2 years (rho = -0.53, -0.51, -0.53, all p < 001). Elevated RRI was independently predicted by older age (Odds Ratio 3.29, 95% CI: 2.25-4.8, p < 0.001) and diabetes (Odds Ratio 2.65, 95% CI: 1.21-5.80, p = 0.015) but not CKD using multivariate logistic regression. Decline of eGFR was not different between RRI categories on follow-up.

CONCLUSION

Elevated RRI was predicted by older age and diabetes, but not by the presence of CKD. Baseline RRI was not associated with eGFR decline. This article is protected by copyright. All rights reserved.

Cardiovascular Risk Factors in Children with Obesity, Preventive Diagnostics and Possible Interventions

The increasing burden of obesity plays an essential role in increased cardiovascular morbidity and mortality. The effects of obesity on the cardiovascular system have also been demonstrated in childhood, where prevention is even more important. Obesity is associated with hormonal changes and vascular dysfunction, which eventually lead to hypertension, hyperinsulinemia, chronic kidney disease, dyslipidemia and cardiac dysfunction—all associated with increased cardiovascular risk, leading to potential cardiovascular events in early adulthood. Several preventive strategies are being implemented to reduce the cardiovascular burden in children. This paper presents a comprehensive review of obesity-associated cardiovascular morbidity with the preventive diagnostic workup at our hospital and possible interventions in children.

The Renal Vasculature: What the Radiologist Needs to Know

The physiologic role of the kidneys is dependent on the normal structure and functioning of the renal vasculature. Knowledge and understanding of the embryologic basis of the renal vasculature are necessary for the radiologist. Common anatomic variants involving the renal artery (supernumerary arteries and prehilar branching) and renal vein (supernumerary veins, delayed venous confluence, retroaortic or circumaortic vein) may affect procedures like renal transplantation, percutaneous biopsy, and aortic aneurysm repair. Venous compression syndromes (anterior and posterior nutcracker syndrome) can be symptomatic and can be diagnosed with a combination of radiologic features. Renal artery stenosis is commonly atherosclerotic and is diagnosed with Doppler US, CT angiography, or MR angiography. Fibromuscular dysplasia, the second most common cause of renal artery narrowing, has a characteristic string-of-beads appearance resulting from multifocal stenoses and dilatations. Manifestations of renal vasculitis differ depending on whether the affected vessels are large, medium, or small. Renal vascular injury is graded according to the American Association for the Surgery of Trauma (AAST) renal injury scale, which defines vascular injury and active bleeding in renal injuries. Both renal arteries and veins are affected by primary neoplasms or secondarily by neoplasms from adjacent structures. Differentiation between bland thrombus and tumor thrombus and the extent of involvement dictate management in malignancies, especially renal cell carcinoma. Aneurysms, pseudoaneurysms, arteriovenous malformations, and arteriovenous fistulas can affect renal vessels and can be diagnosed with specific imaging features. The radiologist has a critical role in identification of specific imaging characteristics and establishing the diagnosis in the varied pathologic conditions affecting the renal vasculature, which is critical for directing management. Thus, the renal vasculature should be an integral part of radiologists' checklist. ^©RSNA, 2021.

Analysis of the Peak Systolic Velocity in the Transplant Renal Artery Anastomosis to Determine Normal Values in Patients Without Graft Dysfunction

Objective:

The primary purpose is to define the mean renal artery anastomosis peak systolic velocity (RAA PSV) and the renal artery anastomosis to external iliac artery ratio (RAA-to-EIA) of renal transplant recipients without graft dysfunction. Moreover, to determine associations with type of vascular anastomosis and type of graft.

Materials and Methods:

This is a single-center retrospective analysis of kidney transplant recipients. Recorded variables included recipient age, type of vascular anastomosis, type of graft, RAA PSV, and external iliac artery PSV (EIA PSV). Such variables were evaluated on different postoperative follow-up periods.

Results:

There was a high degree of reliability between the RAA PSV and EIA PSV ( P < .001). The mean RAA PSV was 174 cm/s ± 72.9 cm/s with 95% confidence interval (CI) (162.2 cm/s-185.5 cm/s].

Conclusion:

This study highlights the importance of determining the normal range of RAA PSV and showed that a high PSV does not necessarily indicate dysfunction.

Renal arterial resistance index among subjects with liver cirrhosis in a Nigerian population

PURPOSE

To describe the relationship between renal artery resistance index (RARI) and liver function based on Child-Pugh system among patients with liver cirrhosis (LC) in Southwest Nigeria.

METHODS

About 50 patients with LC and 50 controls were consecutively recruited into this prospective comparative case control study. Each LC patient was classed based on Child-Turcotte-Pugh (CTP) system after relevant tests. Subjects underwent abdominal ultrasonography with triplex Doppler examination of the right kidney to obtain RARI.

RESULTS

About 50 cirrhotic and 50 controls completed the study. Age range of cirrhotic subjects was 19-69 years (mean ± SD = 47.5 ± 13.3) while that of controls was 18-69 years (46.9 ± 15.0). RARI was higher (P = <.001) in patients with LC (0.68) than in controls (0.57). RARI was also significantly higher (P = <.001) in cirrhotic subjects in CTP class C (0.72) than in those in classes B (0.66) and A (0.58). Additionally, RARI showed significant correlation with CTP total score (r = .662; P = <.001), serum bilirubin (r = .297; P = .036), serum albumin (r = -.494; P = <.001), serum sodium (r = -.369; P = .008), Model for End Stage Liver Disease (MELD) score (r = .316; P = .026) and MELD-Na score (r = .470; P = .001). RARI showed no significant relationship with serum creatinine (r = .110; P = .445) and blood urea nitrogen (r = .112; P = .437).

CONCLUSION

Liver cirrhosis is associated with renovascular changes which manifest as increased resistance in the renal arteries. RARI is a useful noninvasive tool for the assessment of these changes and should be done routinely in the evaluation of patients with LC.

Imaging strategies for safety surveillance after renal artery denervation

Renal denervation has emerged as a safe and effective therapy to lower blood pressure in hypertensive patients. In addition to the main renal arteries, branch vessels are also denervated in more contemporary studies. Accurate and reliable imaging in renal denervation patients is critical for long-term safety surveillance due to the small risk of renal artery stenosis that may occur after the procedure. This review summarizes three common non-invasive imaging modalities: Doppler ultrasound (DUS), computed tomography angiography (CTA), and magnetic resonance angiography (MRA). DUS is the most widely used owing to cost considerations, ease of use, and the fact that it is less invasive, avoids ionizing radiation exposure, and requires no contrast media use. Renal angiography is used to determine if renal artery stenosis is present when non-invasive imaging suggests renal artery stenosis. We compiled data from prior renal denervation studies as well as the more recent SPYRAL-HTN OFF MED Study and show that DUS demonstrates both high sensitivity and specificity for detecting renal stenosis de novo and in longitudinal assessment of renal artery patency after interventions. In the context of clinical trials DUS has been shown, together with the use of the baseline angiogram, to be effective in identifying stenosis in branch and accessory arteries and merits consideration as the main screening imaging modality to detect clinically significant renal artery stenosis after renal denervation and this is consistent with guidelines from the recent European Consensus Statement on Renal Denervation.

Flow Complexity Estimation in Dysfunctional Arteriovenous Dialysis Fistulas using Vector Flow Imaging

Non-invasive assessment is preferred for monitoring arteriovenous dialysis fistulas (AVFs). Vector concentration assesses flow complexity, which may correlate with stenosis severity. We determined whether vector concentration could assess stenosis severity in dysfunctional AVFs. Vector concentration was estimated in four stenotic phantoms at different pulse repetition frequencies. Spectral Doppler peak velocity and vector concentration were measured in 12 patients with dysfunctional AVFs. Additionally, 5 patients underwent digital subtraction angiography (DSA). In phantoms, vector concentration exhibited an inverse relationship with stenosis severity and was less affected by aliasing in severe stenoses. In nine stenoses of 5 patients undergoing DSA, vector concentration correlated strongly with stenosis severity (first stenosis: r = -0.73, p = 0.04; other stenoses; r = -0.69, p = 0.02) and mid-stenotic diameter (first stenosis: r = 0.87, p = 0.006; other stenoses: r = 0.70, p = 0.02) as opposed to peak velocities (p > 0.05). Vector concentration is less affected by aliasing in severe stenoses and correlates with DSA in patients with dysfunctional AVF.

Contrast-Enhanced Ultrasound Evaluation of Renal Blood Perfusion Changes After Percutaneous Transluminal Renal Angioplasty and Stenting for Severe Atherosclerotic Renal Artery Stenosis

This study used contrast-enhanced ultrasound (CEUS) to evaluate changes in renal cortical blood perfusion after percutaneous transluminal renal angioplasty and stenting (PTRAS) for severe renal artery stenosis (RAS) (≥70%). CEUS was performed in 21 patients with 24 severe RASs that underwent PTRAS. Renal cortical perfusion was quantitatively evaluated by comparing time intensity curve (TIC) parameters for SonoVue (Bracco, Milan, Italy) contrast enhancement, including peak intensity (PI), time to peak (TTP), mean transmit time (MTT), curve ascending slope (S), area under the curve (AUC), AUC-wash-in and AUC-wash-out. The parameters PI, TTP, MTT and S differed significantly between the pre-intervention and post-intervention TIC analysis (p < 0.05). Of the 24 pre-intervention curve appearances, 58.3% (14/24) improved after operation. The PI difference correlated positively with the estimated glomerular filtration rate difference (r = 0.433, p < 0.05). In conclusion, changes in some ultrasound perfusion parameters on CEUS and the shape of the TIC can be used to quantitatively and intuitively evaluate renal cortical blood perfusion change after PTRAS.

Interpretation of peripheral arterial and venous Doppler waveforms: A consensus statement from the Society for Vascular Medicine and Society for Vascular Ultrasound

This expert consensus statement on the interpretation of peripheral arterial and venous spectral Doppler waveforms was jointly commissioned by the Society for Vascular Medicine (SVM) and the Society for Vascular Ultrasound (SVU). The consensus statement proposes a standardized nomenclature for arterial and venous spectral Doppler waveforms using a framework of key major descriptors and additional modifier terms. These key major descriptors and additional modifier terms are presented alongside representative Doppler waveforms, and nomenclature tables provide context by listing previous alternate terms to be replaced by the new major descriptors and modifiers. Finally, the document reviews Doppler waveform alterations with physiologic changes and disease states, provides optimization techniques for waveform acquisition and display, and provides practical guidance for incorporating the proposed nomenclature into the final interpretation report.

Renal arteriography with endovascular ultrasound for the management of renal infarction patients

Background

Renal infarction (RI) is a rare disease with poor prognosis. Appropriate secondary prevention treatment is essential and requires an exhaustive etiological assessment. We aimed to determine whether invasive endovascular explorations may improve the diagnostic process and change the secondary prevention treatment strategy in RI patients.

Methods

We report a retrospective observational study of 25 RI patients referred to Tours University Hospital between 2011 and 2018 for etiological investigation including renal arteriography and intravascular ultrasonography (IVUS). We sought for antithrombotic treatment regimen, vital status, bleeding and ischemic outcomes during the median follow-up of 59 months.

Results

Invasive explorations showed local arterial disease in 14 patients (56%). This led to a diagnosis or change in diagnosis in 9 patients (36%) and to a change in antithrombotic strategy in 56% of cases, with an increased prescription of antiplatelet therapy. No patient died, only two patients (8%) had persistent mild renal insufficiency. One IVUS complication was reported and treated without any significant long-term consequences.

Conclusion

Invasive endovascular investigations of RI may modify the secondary prevention treatment through a better assessment of the aetiology of RI. Multicentric randomized studies are necessary to advocate the hypothesis that invasive exploration of renal artery can improve long-term prognosis.

Ratio of diastolic to systolic blood pressure represents renal resistive index

Increased intrarenal vascular resistance is suggested to accompany chronic kidney diseases (CKD), which is known to be closely associated with hypertension. However, there are few studies that have examined the relationship between blood pressure and intrarenal vascular resistance. Renal color Doppler ultrasonography is one method that can non-invasively evaluate intrarenal vascular resistance. In this study, we comprehensively studied the correlations between ultrasonic parameters and blood pressure indices to elucidate their relationships. In total, 162 patients with suspected CKD were enrolled for this study. Demographics, blood pressure, blood test, urine test, and renal color Doppler ultrasonography data were obtained. The ratio of diastolic to systolic blood pressure (D/S ratio) and pulse pressure were calculated. Our results indicated strong negative correlations between the renal resistive index (RI) values in all four of the studied kidney regions and the D/S ratio. The RI values also showed significant correlations with diastolic pressure and pulse pressure, but they were weaker. Partial correlation coefficients between pulse pressure, mean arterial pressure, D/S ratio, and RI showed that D/S ratio significantly correlated with RI, but pulse pressure or mean arterial pressure did not. Systolic blood pressure did not correlate with any of the studied ultrasonic values. The negative correlation between RI values and the D/S ratio was still observed in subjects without renal dysfunction or any medications. In conclusion, D/S ratio, rather than pulse pressure or mean arterial pressure, would be the most appropriate index to estimate/calculate/judge intrarenal vascular resistance.

Impact of different conditions of breath-holding on the results of renal artery Doppler sonography: A pilot study

PURPOSE

To investigate the impact of different breath-holding conditions on the results of renal artery Doppler ultrasonography (RADS).

METHODS

In 45 healthy volunteers, we performed RADS examination during breath-holding while breathing naturally and after a deep inspiration. We measured and compared peak systolic flow velocity (PSV), end diastolic velocity (EDV), and resistance index (RI) of the right (RRA) and left (LRA) renal artery, and PSV, EDV, RI, acceleration time and acceleration index (AI) of the right and left interlobar arteries.

RESULTS

The RRA and LRA PSV were, respectively, 76 ± 13 cm/s and 77 ± 15 cm/s under natural breathing and 93 ± 18 cm/s and 89 ± 24 cm/s after deep inspiration (P ≤ .001). The RRA and LRA EDV were also greater at deep inspiration (P < .001 and P = .019, respectively). There was no significant difference in RRA or LRA RI. The PSV, RI, and AI of the right and left interlobar arteries were greater after deep inspiration (P ≤ .001), without difference in AI.

CONCLUSION

Breath-holding conditions may influence Doppler measurements of renal artery flow velocity and should be reported and taken into account.

How should we define appropriate patients for percutaneous transluminal renal angioplasty treatment?

Renovascular hypertension (RVH) is one of the most common causes of secondary hypertension and can result in resistant hypertension. RVH is associated with an increased risk for progressive decline in renal function, cardiac destabilization syndromes including "flash" pulmonary edema, recurrent congestive heart failure, and cerebrocardiovascular disease. The most common cause of renal artery stenosis (RAS) is atherosclerotic lesions, followed by fibromuscular dysplasia. The endovascular technique of percutaneous transluminal renal angioplasty (PTRA) with or without stenting is one of the standard treatments for RAS. Randomized controlled trials comparing medical therapy with PTRA to medical therapy alone have failed to show a benefit of PTRA; however, the subjects of these randomized clinical trials were limited to atherosclerotic RAS patients, and patients with the most severe RAS, who would be more likely to benefit from PTRA, might not have been enrolled in these trials. This review compares international guidelines related to PTRA, reevaluates the effects of PTRA treatment on blood pressure and renal and cardiac function, discusses strategies for the management of RVH patients, and identifies factors that may predict which patients are most likely to benefit from PTRA.

REACT - A novel flow-independent non-gated non-contrast MR angiography technique using magnetization-prepared 3D non-balanced dual-echo dixon method: Preliminary clinical experience

Flow-independent relaxation-based non-contrast MR angiography techniques yield good signal-to-noise ratio and high blood-tissue contrast, complementing non-contrast flow-dependent and contrast-enhanced MR angiography techniques in the assessment of vascular disorders. However, these techniques often suffer from imaging artifacts at high magnetic field strengths or across large fields-of-view. Relaxation-Enhanced Angiography without Contrast and Triggering (REACT) is a recently introduced flow-independent non-gated non-contrast three-dimensional MR angiography technique that has been developed to mitigate some of these issues. We present our initial experience with the clinical applications of REACT in imaging disorders of the central and peripheral vascular systems.

Pattern of Renal Blood Flow and Renovascular Parameters in Adult Patients With Sickle Cell Disease

OBJECTIVES

To evaluate renal blood flow patterns and renovascular parameters in adult patients with sickle cell disease (SCD) without laboratory evidence of renal impairment.

METHODS

Sixty-five steady-state adult patients with SCD (50 hemoglobin SS [HbSS], 12 HbSβ⁰ , and 3 HbSD) and 30 age- and sex-matched healthy controls were studied. The kidney length, echo pattern, peak systolic velocity (PSV), end-diastolic velocity, renal-to-aortic ratio, resistive index (RI), acceleration time (AT), and renal vein velocity were acquired, recorded, and analyzed with a 1-5-MHz curvilinear transducer through the abdomen.

RESULTS

The mean age ± SD of the patients with SCD was 32.89 ± 13.89 years. The highest means for the ultrasound-measured renal length and cortical thickness in the SCD and control groups were 11.78 ± 1.30 and 11.27 ± 0.77 cm and 1.86 ± 0.41 and 1.78 ± 0.28 cm, respectively. The figures were significantly higher in the SCD group than the control group (P < .05). Fifty-nine (90.8%) patients had a mild diffuse increase in cortical echogenicity with preserved renal cortical thickness. The highest mean extrarenal PSVs in the SCD and control groups were 138.46 ± 56.32 and 101.75 ± 31.48 cm/s (P < .05). However, the highest intrarenal RI and AT in SCD and control groups were 0.69 ± 0.07 and 0.06 ± 0.02 seconds and 0.63 ± 0.05 and 0.04 ± 0.01 seconds (P < .05). There was no significant correlation between the RI, AT, and PSV among the patients with SCD (P > .05).

CONCLUSIONS

Increased renal length and cortical echogenicity with elevated PSV, RI, and AT values can serve as early ultrasound changes in adult patients with SCD without renal impairment.

Ureteroscopic Doppler Ultrasonography: Mapping Renal Blood Flow from Within the Collecting System

Introduction: Herein we provide the first report regarding in vivo porcine renal forniceal, papillary, and infundibular blood flow at the urothelial level using a novel ureteroscopic Doppler transducer. Materials and Methods: Nephroureteroscopy was performed on 11 female Yorkshire pigs to map the forniceal, papillary, and infundibular blood flow. A Doppler transducer was mounted to a 3F 120 cm catheter; the probe was passed through the working channel of a flexible ureteroscope. Blood flow was categorized from 0 (no flow) to 3 (highest flow) based on auditory intensity. At each site, a holmium laser probe was activated until it penetrated ∼1 cm into each of the examined areas; bleeding times were recorded. Results: The frequency of the Doppler transducer signal was proportional to the blood velocity within the vessel with expected increased bleeding times confirmed after puncture with a holmium laser. Analysis demonstrated that the 6 o'clock position of the fornix had significantly greater blood flow than any other forniceal location (p < 0.001). The center of each papilla had the least blood flow (p < 0.001). Blood flow was significantly higher at the infundibular level compared with the caliceal fornices at all locations (anterior, posterior, upper pole, midkidney, and lower pole) (p < 0.001). Conclusions: In a porcine model, a miniaturized Doppler ultrasound probe used during ureteroscopy demonstrated that the renal papilla had the least amount of blood flow whereas the infundibula had the highest blood flow. These data may serve to inform site selection during percutaneous nephrostomy placement.

Influence of resting before sonographic examination on Doppler measurements of renal blood flow

Renal artery stenosis (RAS) is the most common cause of secondary hypertension, via increases in plasma renin-angiotensin-aldosterone levels. Renal artery stenosis is diagnosed from blood examinations such as renin activity and from imaging examinations such as sonography. Patients are required to lie on the bed for 30 min before and during phlebotomy, since plasma renin activity is easily altered by posture. However, no such pre-examination rest is required for sonography. The present study therefore investigated the possible influence of resting before examination on Doppler parameters used for the diagnosis of RAS. Subjects comprised 55 healthy young adults (24 males, 31 females; mean age, 22 ± 1 years). Sonographic measurements were made shortly after subjects entered the examination room and again after 30 min of rest lying on a bed. Median peak systolic velocity in the renal artery was significantly decreased after rest (106 cm/s, interquartile range (IQR) 96-121 cm/s) compared with before rest (120 cm/s, IQR 107-135 cm/s; p < .001). Median acceleration time in the intra-renal segmental artery was also significantly shorter after rest (49 ms, IQR 38-54 ms) compared to before rest (50 ms, IQR 38-59 ms; p = .039). The present results suggest that serious consideration should be given regarding whether pre-examination resting is needed to accurately interpret Doppler measurements of renal blood flow when diagnosing RAS from sonography.

Efficacy of Antihypertensive Therapy in a Child with Unilateral Focal Fibromuscular Dysplasia of the Renal Artery: A Case Study and Review of Literature

Background: Fibromuscular dysplasia (FMD) is one of the important etiologies of renovascular hypertension in children. It is usually resistant to multiple antihypertensive agents and can cause extreme elevation in blood pressures, which can lead to end organ damage if not promptly diagnosed and treated. Treatment options include medical management with antihypertensive agents, balloon or stent angioplasties, surgical revascularization, and nephrectomy. The aim of the study was to review the efficacy of antihypertensive therapy only in the management of FMD in a very young child. Methods: This is a retrospective chart study with review of literature. Results: Here, we report a 22-month-old toddler who presented with severe resistant hypertension and cardiomyopathy who was found to have focal FMD of the right renal artery. She also presented with proteinuria, hyponatremia that was probably secondary to pressure natriuresis, hypokalemia, hyperaldosteronism, and elevated plasma renin activity. The stabilization of blood pressures was done medically with the usage of antihypertensive medications only, without the need for angioplasty or surgical revascularization. Conclusions: We demonstrate that surgical intervention may not always be necessary in the treatment of all cases of FMD, especially in a small child where such intervention may be technically challenging and lead to potential complications. Hence, medical management alone may be sufficient, at least for the short-term, in small children with controlled hypertension and normal renal function, with surgical intervention reserved for FMD with medication-refractory hypertension and/or compromised renal function.

Reliability and agreement of human renal and segmental artery hemodynamics measured using Doppler ultrasound

To optimize study design and data interpretation, there is a need to understand the reliability of Doppler ultrasound-derived measures of blood velocity (BV) measured in the renal and segmental arteries. Thus, this study tested the following two hypotheses: 1) renal and segmental artery BV measured over the current standard of three cardiac cycles have good agreement with measurements over nine cardiac cycles (study 1); and 2) renal and segmental artery BV measurements have relatively poor day-to-day reliability (study 2). In study 1, there was excellent agreement between measurements over three and nine cardiac cycles for BV in both the renal and segmental arteries, as evidenced by BV measurements that were not statistically different (P ≥ 0.68), were highly consistent (r ≥ 0.99, P < 0.01), had a coefficient of variation ≤2.5 ± 1.8%, and 97% (renal artery) and 92% (segmental artery) of the individual differences fell within the 95% limits of agreement. In study 2, there was relatively good day-to-day reliability in renal artery BV as evidenced by no differences between three separate days (P ≥ 0.30), an intraclass correlation coefficient (ICC) of 0.92 (0.78, 0.98), and 7.4 ± 5.5% coefficient of variation. The day-to-day reliability was relatively poor in the segmental artery with an ICC of 0.77 (0.41, 0.93) and 9.0 ± 5.6% coefficient of variation. These findings support measuring renal and segmental artery hemodynamics over three cardiac cycles and the utility in reporting renal BV across days. However, because of the variation across days, hemodynamic responses in the segmental arteries should be reported as changes from baseline when making comparisons across multiple days.NEW & NOTEWORTHY The present study indicates that Doppler ultrasound-derived measures of renal and segmental artery hemodynamics over three cardiac cycles have excellent agreement with those over nine cardiac cycles. These findings support the current practice of measuring renal and segmental artery blood velocity over three cardiac cycles. This study also demonstrates that there is excellent day-to-day reliability for measures of renal artery blood velocity, which supports reporting absolute values of renal artery blood velocity across days. However, it was also found that the day-to-day reliability of segmental artery measurements is relatively poor. Thus, to account for this variability, we suggest that segmental artery hemodynamics be compared as relative changes from baseline across separate days.

Ultrasonographic measurement of the renal resistive index in the cynomolgus monkey (Macaca fascicularis) under conscious and ketamine-immobilized conditions

Measurement of the renal resistive index (RRI) is one of the standard diagnostic procedures for assessing kidney disability clinically. This method is expected to be used for the same purpose in many kinds of animals, including monkeys utilized in conventional toxicology studies. To establish a practical RRI measurement procedure in cynomolgus monkeys (Macaca fascicularis), RRI was measured by ultrasonography in the spine position in conscious and ketamine-immobilized monkeys. The RRI of conscious monkeys and ketamine-immobilized monkeys could be measured consistently without excessive abdominal or thoracic movement. Consequently, the variability of the RRI in conscious monkeys was comparable to that in ketamine-anesthetized monkeys. No sex difference in RRI was noted between the two conditions. The mean values and SD of the RRI of 48 healthy monkeys (n=24/sex) were 0.55 ± 0.07 and 0.50 ± 0.05, under conscious and ketamine-immobilized conditions, respectively. The RRI of ketamine-immobilized monkeys was significantly lower than that of conscious monkeys, correlating with the decreased blood pressure and heart rate. In a monkey model of cisplatin-induced acute renal injury, which was characterized histopathologically by minimal to mild renal tubular necrosis and regeneration, the RRI was increased beyond the cut off value (mean + 2SD, 0.68) associated with the progression of renal pathogenesis. The present results suggest that ultrasonographic measurement of the RRI in conscious monkeys would be a useful tool in conventional toxicology studies evaluating drug-induced renal injury.

Doppler sonography of uterine blood flow at mid-oestrus during different degree of clinical endometritis in dairy cows

The present study was aimed at analysing the mid-oestrous uterine blood flow parameters during varying degree of endometritis in dairy cows. Degree of clinical endometritis was adjudged on the basis of visual examination of uterine discharge collected from cows at mid-oestrus, that is mild (slightly turbid; n = 13), moderate (turbid with pus flakes; n = 14) and severe (milky; n = 13). Pulsatility and resistance indices (PI and RI), time average mean velocity (TAMEAN), time average maximum velocity (TAMAX), diameter of the artery, volume of blood flow, Doppler pulse duration (DPD) and systolic upstroke/acceleration time (AT) were measured to study the spectral waveforms at mid-oestrus. Significantly higher (p < .01) PI and RI were found in cows diagnosed with mild degree in comparison with cows diagnosed with moderate and severe degrees of clinical endometritis. There was significantly higher (p < .01) velocity (TAMEAN and TAMAX), volume of blood flow (BFV-TAMEAN, BFV-TAMAX) and DPD in both the middle uterine arteries during moderate and severe degrees of clinical endometritis as compared to mild endometritis. However, significantly higher (p < .01) AT was recorded in cows diagnosed with mild degree as compared to moderate and severe degrees of clinical endometritis. Pearson's correlation analysis has shown that RI was positively correlated with PI and AT in all the groups under study (mild degree, r = .72 and .49; moderate degree, r = .54 and .38; severe degree, r = .90 and .42; p < .05). However, there found significantly negative correlation (p < .05) with other parameters in all the cows irrespective of degree of inflammation. Therefore, it may be deducted that assessment of uterine inflammation can be done with a non-invasive technique known as Doppler sonography which can be useful in adjudging the hemodynamic changes inside uterus and future fertility of dairy cows.

The short-term effects of intravitreal aflibercept injections and dexamethasone implant on ocular hemodynamics in retinal vein occlusions

Purpose

To determine the early effects of intravitreal anti-VEGF and dexamethasone application on blood flow velocities in patients with retinal vein occlusions.

Methods

The ophthalmic (OA) and the central retinal arteries (CRAs) of the affected and unaffected eyes of 21 patients with central retinal vein occlusion (CRVO), and 26 patients with branch retinal vein occlusion (BRVO) were investigated by Color Doppler imaging (CDI). Peak systolic volume (PSV), end diastolic volume (EDV), and average blood velocity (Vmean) of the CRA and OA were measured and resistive indexes (RI) were calculated at pre-injection and the 1st week and 1st month post-injection.

Results

There was no statistically significant difference between the OA values for affected and unaffected eyes in the CRVO group before treatment. The CRA, EDV, and Vmean values were significantly lower in affected eyes. Blood flow velocities of both CRA and OA were not significantly different than in the fellow unaffected eyes in the BRVO group. The differences between PSV, EDV, and Vmean measurements of OA and CRA at different times pre- and post-injection in response to anti-VEGF and dexamethasone treatment in the CRVO group were significant; but there was no difference in RI value. OA blood flow velocity measurements were not statistically different post-injection in the BRVO group; however, the values of PSV and EDV of CRA decreased post-injection.

Conclusion

Intravitreal anti-VEGF and dexamethasone implant may induce retinal arteriolar vasoconstriction in patients with retinal vein occlusion.

An investigation of the detection capability of pulsed wave duplex Doppler of low grade stenosis using ultrasound contrast agent microbubbles - An in-vitro study

OBJECTIVE

The objective of the study was to investigate whether clinically used ultrasonic contrast agents improved the accuracy of spectral Doppler ultrasound in the detection of low grade (<50%) renal artery stenosis. Low grade stenoses in the renal artery are notoriously difficult to reliably detect using Doppler ultrasound due to difficulties such as overlying fat and bowel gas.

METHODS

A range of anatomically-realistic renal artery phantoms with varying low degrees of stenosis (0, 30 and 50%) were constructed and peak velocity data was measured from within the pre-stenotic and mid-stenotic regions in each phantom, for both unenhanced and contrast-enhanced spectral Doppler data acquisitions. The effect of a 20 mm overlying fat layer on the ultrasound beam distortion and phase aberration, and hence on the measured peak velocity data, was also investigated.

RESULTS

The overlying fat layer produced a statistically significant underestimation (p < 0.01) in both the peak velocity and peak velocity ratio [Stenotic Region(Vmax)/Pre-stenotic Region(Vmax)] for the 0% and 30% stenosis models, but not the 50% model. A statistically significant increase (p < 0.01) in the peak velocity was found in the contrast-enhanced Doppler spectra; however, no significant difference was found between the unenhanced and contrast enhanced peak velocity ratio data, which suggests that the ratio metric has better diagnostic accuracy. The peak velocity ratios determined for each of the contrast-enhanced phantoms correctly predicted if the phantom had a stenosis and furthermore correctly classified the degree of stenosis.

CONCLUSION

Contrast-enhanced Doppler ultrasound could significantly assist in the early detection of renal artery disease.

Point of care renal ultrasonography for the busy nephrologist: A pictorial review

The application of bedside ultrasonography in routine clinical practice has dramatically evolved over the last few decades and will likely continue to grow as technological advances lead to enhanced portability and affordability of the equipment. Despite mounting interest, most nephrology fellowship training programs do not offer formal training in renal ultrasonography and there is inertia among practicing nephrologists to adopt this skill as a practice-changing advancement. Lack of familiarity with the topic is considered a key reason for this inertia. Understanding of basic ultrasound physics, instrumentation, principles of optimal image acquisition and interpretation is critical for enhanced efficiency and patient safety while using this tool. Herein, we provide a brief overview of the basic principles of diagnostic renal ultrasonography as well as introduction to common sonographic pathologies encountered in day-to-day nephrology practice with illustrative images.

Renal haemodynamics and coronary atherosclerotic burden are associated in patients with hypertension and mild coronary artery disease

Intrarenal hemodynamic alterations are independent predictors of cardiovascular events in different populations. It has been hypothesized that there is an association between renal hemodynamics and coronary atherosclerotic burden in patients with hypertension. Therefore, the present study examined the associations between renal hemodynamics, coronary atherosclerotic burden and carotid atherosclerotic disease. A total of 130 patients with hypertension aged between 30-80 years who had been referred for an elective coronary angiography were enrolled in the present study. A duplex ultrasound of the intrarenal vasculature was performed to evaluate the resistive index (RI), pulsatility index (PI) and acceleration time (AT). The carotid intima-media thickness was additionally assessed. A coronary angiography was performed to detect the atherosclerotic burden using the Gensini Score (GS). Based on the GS values, subjects were divided into quintiles (I: ≤9; II: 9-17; III: 17-30; IV: 30-44; and V: GS >44) as well as in subjects with mild (GS ≤30) or severe coronary disease (GS >30). A weak significant difference in PI was identified among quintiles (P=0.041), whereas, RI and AT did not differ significantly. PI was associated with GS in the group with low coronary atherosclerotic burden (GS ≤30; P=0.047), whereas, no association was detected in subjects with GS >30. This association remained following adjustment for age and left ventricular ejection fraction (P=0.025). In conclusion, renal vascular alterations were associated with coronary atherosclerotic burden in patients with hypertension with mild coronary disease.

Prevention of Possible Toxic Effects on the Kidney Graft with Parvus Tardus Waveform

The aim of this study was to present a patient (acute allograft dysfunction after a kidney transplantation) with previously detected minimum plaque on both iliac arteries by scintigram and afterward a pathological Color Doppler Ultrasound (CDU) record and to point on possibility of avoiding toxic computed tomography (CT) angiography in certain renal graft recipients. Ultrasound (US) findings showed normal graft size, whereas Doppler signals detected parvus-tardus waveforms pointing to arterial stenosis. Isotope perfusion scintigraphy registered a slow flow on both iliac arteries and normal graft perfusion. CT angiography has not been performed because of the possible toxic effects to the graft. We believe that favorable clinical and biochemical findings along with US and isotope ratio monitoring are sufficient to avoid CT contrast angiography.

Renal resistive index and aortic knob width relationship as a predictor of renal prognosis in essential hypertension

The scientific studies that have been conducted so far highlight that renal resistive index (RI) and aortic knob width (AKW) indicate poor prognosis regarding renal and cardiovascular mortality. But the existence of a direct relationship RI and AKW is unclear. This study aims investigating the relationship between RI and the measured AKW in chest radiography of the patients with hypertensive nephropathy who do not require renal replacement therapy.This prospective study included 268 consecutive patients with essential hypertension. Patients were divided into 2 groups as RI ≥0.7 and RI <0.7. The ROC curve, sensitivity, and specificity ratios were evaluated to determine which AKW value is the best predictive one for the RI ≥0.7.The cutoff point of AKW was evaluated as ≥36 for the cases with RI ≥0.7: sensitivity was 71.22%; specificity was 71.32%; the positive predictive value (PPV) was 72.79; the negative predictive value (NPV) was 69.70, and the accuracy was 71.27. Area under the ROC curve ± standard error (AUC ± SE) = 0.729 ± 0.031 (P < .001).AKW can provide important predictive information about the subclinical renal dysfunction in hypertensive patients with RI ≥0.7. Moreover; AKW is a predictive factor for both the diagnostic and prognostic evaluation of renal pathologies.

Ultrasound and color Doppler applications in chronic kidney disease

Chronic kidney disease (CKD) includes all clinical features and complications during the progression of various kidney conditions towards end-stage renal disease (ESRD). These conditions include immune and inflammatory disease such as: primary and hepatitis C virus (HCV)-related glomerulonephritis; infectious disease such as pyelonephritis with or without reflux and tuberculosis; vascular disease such as chronic ischemic nephropathy; hereditary and congenital disease such as polycystic disease and congenital cystic dysplasia; metabolic disease including diabetes and hyperuricemia; and systemic disease (collagen disease, vasculitis, myeloma). During the progression of CKD, ultrasound imaging and color Doppler imaging (US-CDI) can differentiate the etiology of the renal damage in only 50-70% of cases. Indeed, the end-stage kidney appears shrunken, reduced in volume (Ø < 9 cm), unstructured, amorphous, and with acquired cystic degeneration (small and multiple cysts involving the cortex and medulla) or nephrocalcinosis, but there are rare exceptions, such as polycystic kidney disease, diabetic nephropathy, and secondary inflammatory nephropathies. The main difficulties in the differential diagnosis are encountered in multifactorial CKD, which is commonly presented to the nephrologist at stage 4-5, when the kidney is shrunken, unstructured and amorphous. As in acute renal injury and despite the lack of sensitivity, US-CDI is essential for assessing the progression of renal damage and related complications, and for evaluating all conditions that increase the risk of CKD, such as lithiasis, recurrent urinary tract infections, vesicoureteral reflux, polycystic kidney disease and obstructive nephropathy. The timing and frequency of ultrasound scans in CKD patients should be evaluated case by case. In this review, we will consider the morpho-functional features of the kidney in all nephropathies that may lead to progressive CKD.

Meal Ingestion and Hemodynamic Interactions Regarding Renal Blood Flow on Duplex Sonography: Potential Diagnostic Implications

Splanchnic blood flow changes dramatically after meal ingestion. The present study evaluated physiologic interactions between meal ingestion and hemodynamics with respect to renal blood flow on duplex sonography, assessing the possible influence on Doppler parameters used as diagnostic criteria for renal artery stenosis. Subjects comprised 26 healthy young men (mean age: 22 ± 2 y). Sonographic measurements were made shortly after breakfast and every 1 h thereafter and were compared with values measured before the meal. Peak systolic velocity in the renal artery was elevated post-prandially, peaking at 1 h (90 ± 12 cm/s), compared with pre-prandially (73 ± 10 cm/s, p < 0.01). Similarly, acceleration time at the intra-renal segmental artery shortened to a minimum at 1 h (45 ± 5 ms) compared with baseline (51 ± 6 ms, p < 0.01). The present study indicates that renal blood flow is altered for a few hours after meal ingestion. Attention should be paid to the interpretation of data measured after meals on duplex sonography for diagnosis of renal artery stenosis.

Computational Fluid Dynamic Accuracy in Mimicking Changes in Blood Hemodynamics in Patients with Acute Type IIIb Aortic Dissection Treated with TEVAR

Background: We aimed to verify the accuracy of the Computational Fluid Dynamics (CFD) algorithm for blood flow reconstruction for type IIIb aortic dissection (TBAD) before and after thoracic endovascular aortic repair (TEVAR). Methods: We made 3D models of the aorta and its branches using pre- and post-operative CT data from five patients treated for TBAD. The CFD technique was used to quantify the displacement forces acting on the aortic wall in the areas of endograft, mass flow rate/velocity and wall shear stress (WSS). Calculated results were verified with ultrasonography (USG-Doppler) data. Results: CFD results indicated that the TEVAR procedure caused a 7-fold improvement in overall blood flow through the aorta (p = 0.0001), which is in line with USG-Doppler data. A comparison of CFD results and USG-Doppler data indicated no significant change in blood flow through the analysed arteries. CFD also showed a significant increase in flow rate for thoracic trunk and renal arteries, which was in accordance with USG-Doppler data (accuracy 90% and 99.9%). Moreover, we observed a significant decrease in WSS values within the whole aorta after TEVAR compared to pre-TEVAR (1.34 ± 0.20 Pa vs. 3.80 ± 0.59 Pa, respectively, p = 0.0001). This decrease was shown by a significant reduction in WSS and WSS contours in the thoracic aorta (from 3.10 ± 0.27 Pa to 1.34 ± 0.11Pa, p = 0.043) and renal arteries (from 4.40 ± 0.25 Pa to 1.50 ± 0.22 Pa p = 0.043). Conclusions: Post-operative remodelling of the aorta after TEVAR for TBAD improved hemodynamic patterns reflected by flow, velocity and WSS with an accuracy of 99%.

Diagnosis and management of systemic hypertension due to renovascular and aortic stenosis in patients with Williams-Beuren syndrome

SUMMARY AIM To describe the incidence, diagnosis, and management of systemic arterial hypertension related to renal artery stenosis in patients with Williams-Beuren syndrome. METHODS Sixty-five patients with Williams-Beuren syndrome were evaluated for hypertension. Enrolled patients underwent Doppler sonography of the renal arteries and Doppler echocardiography. Those with Doppler sonography-detected lesions or with normal Doppler sonography but severe hypertension underwent computed tomography or gadolinium-enhanced magnetic resonance angiography of the aorta and renal vessels. Patients needing vascular therapeutic intervention underwent conventional angiography. RESULTS Systemic arterial hypertension was diagnosed in 21/65 patients with Williams-Beuren syndrome (32%; 13 male) with a mean age of 13.9 years (5mo-20yrs). In 8/21 patients renovascular hypertension was detected. Angioplasty was unsuccessful in five patients with renal artery stenosis, requiring additional treatment. Doppler echocardiography showed cardiac abnormalities in 16/21 (76%) hypertensive patients. CONCLUSION Cardiac abnormalities and hypertension in patients with Williams-Beuren syndrome are common. Thus, thorough evaluation and follow-up are necessary to reduce cardiovascular risks and mortality of these patients

Simulation of phase contrast angiography for renal arterial models

BACKGROUND

With the development of versatile magnetic resonance acquisition techniques there arises a need for more advanced imaging simulation tools to enable adequate image appearance prediction, measurement sequence design and testing thereof. Recently, there is a growing interest in phase contrast angiography (PCA) sequence due to the capabilities of blood flow quantification that it offers. Moreover, as it is a non-contrast enhanced protocol, it has become an attractive option in areas, where usage of invasive contrast agents is not indifferent for the imaged tissue. Monitoring of the kidney function is an example of such an application.

RESULTS

We present a computer framework for simulation of the PCA protocol, both conventional and accelerated with echo-planar imaging (EPI) readout, and its application to the numerical models of kidney vasculatures. Eight patient-specific renal arterial trees were reconstructed following vessel segmentation in real computed tomography angiograms. In addition, a synthetic model was designed using a vascular tree growth simulation algorithm. The results embrace a series of synthetic PCA images of the renal arterial trees giving insight into the image formation and quantification of kidney hemodynamics.

CONCLUSIONS

The designed simulation framework enables quantification of the PCA measurement error in relation to ground-truth flow velocity data. The mean velocity measurement error for the reconstructed renal arterial trees range from 1.5 to 12.8% of the aliasing velocity value, depending on image resolution and flip angle. No statistically significant difference was observed between measurements obtained using EPI with a number of echos (NETL) = 4 and conventional PCA. In case of higher NETL factors peak velocity values can be underestimated up to 34%.

Cerebral Haemodynamics: Effects of Systemic Arterial Pulsatile Function and Hypertension

PURPOSE OF REVIEW

Concepts of pulsatile arterial haemodynamics, including relationships between oscillatory blood pressure and flow in systemic arteries, arterial stiffness and wave propagation phenomena have provided basic understanding of underlying haemodynamic mechanisms associated with elevated arterial blood pressure as a major factor of cardiovascular risk, particularly the deleterious effects of isolated systolic hypertension in the elderly. This topical review assesses the effects of pulsatility of blood pressure and flow in the systemic arteries on the brain. The review builds on the emerging notion of the "pulsating brain", taking into account the high throughput of blood flow in the cerebral circulation in the presence of mechanisms involved in ensuring efficient and regulated cerebral perfusion.

RECENT FINDINGS

Recent studies have provided evidence of the relevance of pulsatility and hypertension in the following areas: (i) pressure and flow pulsatility and regulation of cerebral blood flow, (ii) cerebral and systemic haemodynamics, hypertension and brain pathologies (cognitive impairment, dementia, Alzheimer's disease), (iii) stroke and cerebral small vessel disease, (iv) cerebral haemodynamics and noninvasive estimation of cerebral vascular impedance, (v) cerebral and systemic pulsatile haemodynamics and intracranial pressure, (iv) response of brain endothelial cells to cyclic mechanical stretch and increase in amyloid burden. Studies to date, producing increasing epidemiological, clinical and experimental evidence, suggest a potentially significant role of systemic haemodynamic pulsatility on structure and function of the brain.

RENAL ARTERIAL DOPPLER VELOCIMETRIC INDICES AMONG HEALTHY SUBJCTS IN NORTH WEST NIGERIA

BACKGROUND

Doppler sonography is a non-invasive modality for evaluation of renal vascular anatomy and flow dynamics, causes of secondary hypertension and renal diseases.

AIM

To determine the normal reference values for the renal arterial Doppler velocimetric indices in healthy adults and correlate them with gender and age.

METHODOLOGY

The subjects consist of 36 males and 44 females. They were scanned using 3.5MHz transducer. After parenchymal assessment, the renal arteries were identified using colour mapping, followed by measurement of velocimetric indices on spectral Doppler tracings on each side.

RESULTS

The mean peak systolic velocity (PSV) was highest on the left side in males measuring 65.75 ± 28.41cm/sec and 60.7 ± 24.20cm/sec on the right. In females, it measured 61.83 ± 22.50cm/sec and 60.04 ± 24.67cm/sec on the right and left sides. The mean end diastolic velocity (EDV) was higher on the right side, measuring 23.59 ± 11.45cm/sec and 22.50 ± 8.37cm/sec in males and 25.19 ± 10.72cm/sec and 22.33 ± 8.47cm/sec in females. There was age related dependency on the mean resistive index (RI).

CONCLUSION

This study has shown that there was a statistical significant correlation between RI and systolic-diastolic ratio (S/D) with age. However, gender did not show significant correlation with these indices.

Pilot study to evaluate the potential use of the renal resistive index as a preliminary diagnostic tool for chronic kidney disease in cats

Objectives Chronic kidney disease (CKD) is the most common renal pathology diagnosed in geriatric cats, and its prevalence increases with age. The arterial resistive index (RI) is important when evaluating vascular resistance and compliance, and can be applied in the kidney (renal RI [RRI]), allowing the evaluation of its vascular haemodynamics. The present study aimed to: (1) investigate in cats with CKD the relationships between the RRI and the following parameters: age, sex, body weight, plasmatic creatinine, blood urea nitrogen, potassium, urine specific gravity, urine protein:creatinine ratio and systolic arterial pressure; and (2) evaluate the potential use of the RRI as a preliminary diagnostic tool in cats with CKD. Methods The present study involved 24 cats of both sexes. Six were healthy cats (control group [CG]) and 18 had CKD, but did not have any concomitant diseases and were not being treated with any medications (study group [SG]). For RRI measurement we used colour Doppler ultrasound (CDUS). Results RRI differed significantly between the CG and SG ( P <0.01) and was higher in the SG. A statistically significant correlation was only achieved between the RRI and the body weight of the patients and it was negative. A strong and positive correlation was noted between the mean RRI of both kidneys (r = 0.66). Receiver-operating curve analysis allowed us to establish an admissible cut-off for the RRI value of 0.639 for a preliminary diagnosis of CKD for both kidneys. Conclusions and relevance No differences were found for the RRI between the left and right kidneys, suggesting that evaluation of only one kidney is sufficient to provide an estimate of the RRI value for both organs. RRI measurement, which can be achieved with CDUS, is an easy-to-use diagnostic tool that, with a cut-off value of 0.639 for both kidneys, is useful in establishing a preliminary diagnosis of CKD.

Ultrasound imaging of renin-mediated hypertension

The incidence of primary (i.e. essential) hypertension in children and adolescents is increasing; however, secondary hypertension, with an identifiable cause, remains relatively common and might be treatable or even curable. Renovascular hypertension is an uncommon but important secondary cause of hypertension in the pediatric population that can be associated with substantial morbidity. In this article we discuss renin-mediated causes of hypertension in children and related complications, review renal Doppler ultrasound techniques for the evaluation of renin-mediated hypertension (including both direct and indirect assessments), and briefly appraise the literature pertaining to renal Doppler ultrasound and the assessment of pediatric hypertension. Finally, we describe a proposed role for renal Doppler ultrasound in the workup of suspected renin-mediated hypertension in children and adolescents.