Is it necessary to study accessory arteries when screening the renal arteries for renovascular hypertension?

Doppler Ultrasound of the Renal Vasculature

Ultrasound is the first-line imaging modality used in patients with suspected renovascular disease. Common indications include renovascular hypertension and unexplained renal dysfunction. We review the ultrasound imaging findings of various pathologies involving the renal vessels, including the renal arteries (atherosclerotic stenosis, fibromuscular dysplasia, dissection, arteriovenous fistula, and aneurysm) and veins (tumor and bland thrombus as well as vascular compression syndromes). The current role of renal artery stent placement for atherosclerotic stenosis is also discussed.

Mesenteric and renal arterial duplex ultrasound: A review

Duplex ultrasound examinations of the mesenteric and renal circulations are commonly used to detect disease as well as to follow up patients after open surgery or endovascular intervention. The aims of this review were to present essential elements of these duplex ultrasound examinations as well as conduct a literature review of diagnostic criteria. Documentation of appropriate images and data will aid in an accurate interpretation. Spectral Doppler waveforms from various segments of these arterial systems can contribute both direct and indirect evidence of the presence of disease. Various studies have validated the duplex ultrasound diagnostic criteria which more recently have expanded to include specific criteria for stented vessels. This review presents a summary of the fundamental exam components and diagnostic criteria utilized for mesenteric and renal duplex ultrasound.

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.

Frequency of Acccessory Renal Arteries Diagnosed by Computerized Tomography

INTRODUCTION

Accessory renal arteries play a significant role in kidney and abdominal aorta surgery, and renovascular hypertension. In the published literature, the frequency varies considerably, depending on the size of the sample, the method of examination and the ethnic group.

MATERIALS AND METHODS

The aim of this study is to determine the general frequency of accessory renal arteries, their frequency in relation to gender, the origin and the vascularization area, and to determine the differences in left-right and bilateral distribution.

RESULTS AND DISCUSSION

CT scans of 1357 patients were retrospectively analyzed. Accessory renal arteries were recorded in 35.5% of patients, with a statistically significant difference in male and female incidence (p<0.05) with a ratio of 1.4 : 1. Accessory arteries occur more commonly unilaterally (p<0.05) than bilaterally with a ratio of 4 : 1. Unilateral accessory renal arteries occur at approximately the same frequency at right and left side 1.1 : 1, without statistically significant differences in frequencies (p>0.05). Of the total number of noticed accessory renal arteries 76.7% was originated from abdominal aorta (AA), 23% from renal artery and 0.3% from CIA, with a ratio of 3.3: 1 : 0.0005.

CONCLUSIONS

The study showed a relatively high frequency of accessory arteries and described their anatomy in detail, which can be of great importance in surgical interventions on abdominal aorta, kidneys, and in case of kidney transplantation.

Spontaneously Resolving Hyperreninemic Hypertension Caused by Accessory Renal Artery Stenosis in a 13-Year-Old Girl: A Case Report

The authors describe the clinical investigation and progress of a 13-year-old girl diagnosed with hypertension 4 years prior to her admission. A thorough history was taken and physical examination performed. Laboratory analysis and relevant radiological evaluation were obtained in order to determine the etiology for suspected secondary hypertension, and later to differentiate between the possible causes of hyperreninemic hypertension. The patient had an accessory left renal artery, presumptively leading to renin secretion by the underperfused kidney. The patient was treated medically with spontaneous resolution of her hypertension and near normalization of plasma renin activity. On repeat imaging, the artery was not demonstrated. The authors concluded that the diagnosis of hyperreninemic hypertension in young ages should prompt investigation for the etiology. However, cautious observation is a valid option that might lead to spontaneous resolution.

Renal denervation in a patient with unilateral ectopic kidney in the pelvis and refractory hypertension

Ectopic kidney and inherent vascular abnormalities may result in renovascular hypertension. The case we report is peculiar as a left ectopic iliac kidney supplied by a superior and an inferior polar renal arteries was detected in a treatment-resistant hypertensive man. In conclusion, percutaneous renal artery denervation was successfully performed in the right renal artery and in both left accessory renal arteries, obtaining excellent blood pressure decrease at follow-up.

Prevalence of renal artery stenosis in subjects with moderate hypertension. A population-based study

AIM

To examine the prevalence of significant renal artery stenosis (RAS) in subjects with moderate to severe hypertension.

MATERIALS AND METHODS

Subjects aged 50-66 years with blood pressure >160/100 mmHg or receiving antihypertensive treatment were selected from the population study Inter99. We examined 332 subjects (209 men, 123 women) for RAS >50% of diameter with Doppler-US. Subjects with RAS were re-examined 2 years later. Furthermore, we report sensitivity and specificity of the screening method based on consecutive examinations of 100 patients before referral to renal angiography.

RESULTS

The sensitivity and specificity of the Doppler US examination for the detection of RAS was 98% and 96%, respectively. Unilateral RAS was found in 11 subjects. Nine were women. The prevalence of RAS in the examined population was 3.3% (men: 0.9%, women: 7.3%). One patient was referred to balloon angioplasty. Two patients had reduced size and function of the affected kidney. Among the non-invasively treated patients, one showed stenosis progression at the 2-year follow-up examination.

CONCLUSION

In subjects aged 50-66 years with hypertension grade II-III, RAS is rare among men, but not among women. These women may suffer from fibromuscular dysplasia. They are at risk of losing kidney function and developing severe hypertension, but they would not have been considered for screening according to present criteria.

Vascular anomaly in bilateral ectopic kidney: a case report

Ectopic kidney occurs as a result of a halt in migration of kidneys to their normal locations during embryonal period. While kidneys ascend through pelvis, they receive new branches from vessels (iliac and aorta) close to them. When they reach the highest point, they receive new branches from aorta and the former branches degenerate. Renal vessels do not degenerate in the ectopic caudal kidney, more than one accessory and polar arteries may arise. In various studies, a possibility of association between presence of multiple renal arteries and hypertension, has been reported. We aimed to present a case with bilateral ectopic kidney and vascular anomaly associated with hypertension and renal dysfunction.

Doppler ultrasound and renal artery stenosis: An overview

Renovascular disease is a complex disorder, most commonly caused by fibromuscular dysplasia and atherosclerotic diseases. It can be found in one of three forms: asymptomatic renal artery stenosis (RAS), renovascular hypertension, and ischemic nephropathy. Particularly, the atherosclerotic form is a progressive disease that may lead to gradual and silent loss of renal function. Thus, early diagnosis of RAS is an important clinical objective since interventional therapy may improve or cure hypertension and preserve renal function. Screening for RAS is indicated in suspected renovascular hypertension or ischemic nephropathy, in order to identify patients in whom an endoluminal or surgical revascularization is advisable. Screening tests for RAS have improved considerably over the last decade. While captopril renography was widely used in the past, Doppler ultrasound (US) of the renal arteries (RAs), angio-CT, or magnetic resonance angiography (MRA) have replaced other modalities and they are now considered the screening tests of choice. An arteriogram is rarely needed for diagnostic purposes only. Color-Doppler US (CDUS) is a noninvasive, repeatable, relatively inexpensive diagnostic procedure which can accurately screen for renovascular diseases if performed by an expert. Moreover, the evaluation of the resistive index (RI) at Doppler US may be very useful in RAS affected patients for predicting the response to revascularization. However, when a discrepancy exists between clinical data and the results of Doppler US, additional tests are mandatory.

Frequency of renal artery stenosis and variants of renal vascularization in hypertensive patients: analysis of 1550 angiographies in one centre

Renal artery stenosis (RAS) is an important cause of arterial hypertension and chronic kidney disease. The aims of our study were to assess the prevalence of RAS and to examine the frequency of variants of renal vasculature, that is, multiple and/or accessory renal arteries in hypertensive patients referred to renal angiography. We evaluated retrospectively 1554 arteriographies of hypertensive patients. Angiograms were evaluated to find RAS, significant RAS (>60% stenosis of the lumen), radiological signs of atherosclerosis, aneurysms of the renal arteries or aorta and variants of kidney vascularization. The frequency of RAS including occlusions was 15.1% (21.3% of them were significant and suitable for revascularization). Variants of renal arterial vascularization were found in 26.5% of patients (multiple renal arteries-11.2% and accessory renal arteries-15.3%). Significant RAS was found more frequently in patients older than 60 years-OR 4.76 (2.08-10.86). Coronary artery disease, history of myocardial infarction or stroke significantly increased the chance of RAS detection. The frequency of renal accessory arteries was lower in patients older than 60 years and in patients with the radiological signs of atherosclerosis. Results of this study indicate that haemodynamically important RAS is found more frequently in hypertensive patients older than 60 years. Symptomatic atherosclerotic disease found in the peripheral and/or coronary arteries and diabetes mellitus increases the chance of RAS detection. Decreased occurrence of renal accessory arteries was found in hypertensive patients with radiological signs of atherosclerosis.

Advances in contrast-enhanced MR angiography of the renal arteries

Renal artery stenosis (RAS) is a potentially curable cause of renovascular hypertension (RVH) and is caused by either atherosclerosis or fibromuscular dysplasia in the vast majority of patients. Although intra-arterial digital subtraction angiography is still considered the standard of reference test for the anatomic diagnosis of RAS, MR angiography and functional renal MR imaging are promising alternatives that also allow for functional characterization of RAS. This article provides an overview of these techniques and discusses their relative merits and shortcomings. Because missing RVH may have serious consequences the most important requirement for an alternative test is that it has high sensitivity. An unresolved issue is the prediction of functional recovery after therapy.

Imaging modalities for renal artery stenosis in suspected renovascular hypertension: prospective intraindividual comparison of color Doppler US, CT angiography, GD-enhanced MR angiography, and digital substraction angiography

The aim of the study was to evaluate the diagnostic accuracy of Color Doppler US, CT Angiography (CTA), and GD-enhanced MR Angiography (MRA) compared with digital subtraction angiography (DSA) for the detection of renal artery stenosis in patients with clinically suspected renovascular hypertension. Fifty-eight patients with suspected renovascular hypertension were enrolled in the study. All patients underwent Color Doppler US, CTA and GD-enhanced MRA. DSA was the gold standard method for the number of renal arteries, existence and degree of stenosis, or evidence of fibromuscular dysplasia. DSA depicted 132 renal arteries, 16 stenoses, and 4 arteries with fibromuscular dysplasia. Color Doppler US failed to detect 1 main and 14 polar arteries. CTA depicted all main renal arteries and 7/16 polar arteries, but failed to detect stenosis in two accessory vessels. Likewise, MRA did not detect stenotic accessory renal arteries, depicted 9/16 polar renal arteries, but missed two main renal arteries. All methods depicted the four main renal arteries with fibromuscular dysplasia. The overall sensitivity, specificity, and positive and negative predictive accuracy were 75%, 89.6%, 60% and 94.6%, respectively, for color Doppler US; 94%, 93%, 71%, and 99%, respectively, for CTA; and 90%, 94.1%, 75%, and 98%, respectively, for GD-enhanced MRA. CTA and GD-enhanced MRA have comparable and satisfactory results with respect to the negative predictive accuracy of the suspected renal artery stenosis. The concept of an imaging algorithm including US as screening test when appropriate and CTA or MRA as the second step-procedure is suggested. Therefore, DSA may be reserved for cases with major discrepancies or therapeutic interventions.

Potential Pitfalls of Renal Angiography: A Case of Atypical Fibromuscular Dysplasia

Although angiography remains the gold standard for the diagnosis of renal artery stenosis, renovascular disease can at times present with unusual patterns that may be difficult to detect. The authors present a case in which an initial renal angiogram failed to identify the presence of severe disease involving both a main and accessory renal artery. Repeat angiography coupled with the use of adjunctive catheter-based techniques including translesional pressure gradient determination and intravascular ultrasound with virtual histology imaging revealed the presence of atypical fibromuscular dysplasia that was treated with good clinical results. The case highlights the importance of performing careful and complete renal angiography, including imaging of smaller accessory renal arteries, and describes several readily available catheter-based techniques that can be useful in elucidating the physiological significance and etiology of renal artery stenosis.

Renal artery stenosis evaluation: diagnostic performance of gadobenate dimeglumine-enhanced MR angiography--comparison with DSA

PURPOSE

To prospectively determine diagnostic performance and safety of contrast material-enhanced (CE) magnetic resonance (MR) angiography with 0.1 mmol per kilogram of body weight gadobenate dimeglumine for depiction of significant steno-occlusive disease (> or =51% stenosis) of renal arteries, with digital subtraction angiography (DSA) as reference standard.

MATERIALS AND METHODS

This multicenter study was approved by local institutional review boards; all patients provided written informed consent. Patient enrollment and examination at centers in the United States complied with HIPAA. Two hundred ninety-three patients (154 men, 139 women; mean age, 61.0 years) with severe hypertension (82.2%), progressive renal failure (11.3%), and suspected renal artery stenosis (6.5%) underwent CE MR angiography with three-dimensional spoiled gradient-echo sequences after administration of 0.1 mmol/kg gadobenate dimeglumine at 2 mL/sec. Anteroposterior and oblique DSA was performed in 268 (91.5%) patients. Three independent blinded reviewers evaluated CE MR angiographic images. Sensitivity, specificity, and accuracy of CE MR angiography for detection of significant steno-occlusive disease (> or =51% vessel lumen narrowing) were determined at segment (main renal artery) and patient levels. Positive and negative predictive values and positive and negative likelihood ratios were determined. Interobserver agreement was analyzed with generalized kappa statistics. A safety evaluation (clinical examination, electrocardiogram, blood and urine analysis, monitoring for adverse events) was performed.

RESULTS

Of 268 patients, 178 who were evaluated with MR angiography and DSA had significant steno-occlusive disease of renal arteries at DSA. Sensitivity, specificity, and accuracy of CE MR angiography for detection of 51% or greater stenosis or occlusion were 60.1%-84.1%, 89.4%-94.7%, and 80.4%-86.9%, respectively, at segment level. Similar values were obtained for predictive values and for patient-level analyses. Few CE MR angiographic examinations (1.9%-2.8%) were technically inadequate. Interobserver agreement for detection of significant steno-occlusive disease was good (79.9% agreement; kappa = 0.69). No safety concerns were noted.

CONCLUSION

CE MR angiography performed with 0.1 mmol/kg gadobenate dimeglumine, compared with DSA, is safe and provides good sensitivity, specificity, and accuracy for detection of significant renal artery steno-occlusive disease.

Renal vascular imaging: ultrasound and other modalities

Sonographic evaluation of the genitourinary system is a fast, safe, and effective means to detect renal disease. In conjunction with other modalities, Doppler can depict a variety of abnormalities. However, optimization of Doppler techniques and a solid understanding of Doppler threshold criteria are critical for success, whether in the native or transplanted kidney.

Renovascular disease among patients referred for renal duplex ultrasonography

OBJECTIVE

This study was conducted to determine the prevalence of renal artery stenosis (RAS) among patients referred to a vascular laboratory in a university hospital, to identify those who are possible candidates for revascularization, and to determine the prevalence of other pathologies incidentally detected.

METHODS

Consecutive patients referred to our laboratory for exclusion of RAS were included. Color duplex ultrasound (DU) imaging of the abdominal aorta, renal vasculature, and kidney parenchyma was performed. The resistivity index of the kidney (RI) was measured, and 0.8 was used as a cutoff to identify those with severe kidney disease that could be excluded from an intervention. Incidental findings were also noted.

RESULTS

A total of 324 patients were included from September 1998 to August 2003. Unilateral RAS was found in 14% and bilateral in 7%. Unilateral (1.5%) and bilateral (0.6%) renal artery occlusions were rare. The main reason for referral was uncontrolled (43%) and controlled hypertension (34%). Most patients (63%) were taking two or more antihypertensive drugs. The diagnostic yield was 22% among those using two drugs and 55% among those using three or more. In 46 patients (64%), the RI was <0.8. Seven cases of fibromuscular dysplasia were found (10% of RAS patients or 2% overall). Incidental findings were detected in 24% and were significant enough to alter management in 26% among those with such findings.

CONCLUSIONS

Our study identified a RAS prevalence of 22% and a renal artery occlusion prevalence of 4%. There was a high yield for RAS in patients receiving three or more drugs; however, the yield was also significant among those receiving two or more. About two thirds of patients diagnosed with RAS were potential revascularization candidates, evidenced by a low RI. DU imaging is also very useful in detecting pathology that is significant to alter patients' management.

Modeling of the aorta artery aneurysms and renal artery stenosis using cardiovascular electronic system

Background

The aortic aneurysm is a dilatation of the aortic wall which occurs in the saccular and fusiform types. The aortic aneurysms can rupture, if left untreated. The renal stenosis occurs when the flow of blood from the arteries leading to the kidneys is constricted by atherosclerotic plaque. This narrowing may lead to the renal failure. Previous works have shown that, modelling is a useful tool for understanding of cardiovascular system functioning and pathophysiology of the system. The present study is concerned with the modelling of aortic aneurysms and renal artery stenosis using the cardiovascular electronic system.

Methods

The geometrical models of the aortic aneurysms and renal artery stenosis, with different rates, were constructed based on the original anatomical data. The pressure drop of each section due to the aneurysms or stenosis was computed by means of computational fluid dynamics method. The compliance of each section with the aneurysms or stenosis is also calculated using the mathematical method. An electrical system representing the cardiovascular circulation was used to study the effects of these pressure drops and the compliance variations on this system.

Results

The results showed the decreasing of pressure along the aorta and renal arteries lengths, due to the aneurysms and stenosis, at the peak systole. The mathematical method demonstrated that compliances of the aorta sections and renal increased with the expansion rate of the aneurysms and stenosis. The results of the modelling, such as electrical pressure graphs, exhibited the features of the pathologies such as hypertension and were compared with the relevant experimental data.

Conclusion

We conclude from the study that the aortic aneurysms as well as renal artery stenosis may be the most important determinant of the arteries rupture and failure. Furthermore, these pathologies play important rules in increase of the cardiovascular pulse pressure which leads to the hypertension.

Navigator-Gated MR Angiography of the Renal Arteries: A Potential Screening Tool for Renal Artery Stenosis

OBJECTIVE

The purpose of our study was to determine how well unenhanced navigator-gated steady-state free precession (Nav SSFP) MR angiography (MRA) performs as a screening test for the detection of renal artery stenosis.

SUBJECTS AND METHODS

Forty patients referred to rule out renal artery stenosis were imaged using an optimized Nav SSFP MRA sequence before conventional contrast-enhanced MRA (CE-MRA). Two radiologists evaluated Nav SSFP for maximum stenosis measurement, and comparison was made with CE-MRA results.

RESULTS

Fifteen of the 40 patients had greater than 50% renal artery stenosis as determined on CE-MRA. Sensitivity for detecting renal artery stenosis with Nav SSFP was 100%; specificity, 84%; negative predictive value, 100%; and positive predictive value, 79%. The average mean stenosis difference between Nav SSFP and CE-MRA was 10% +/- 9%.

CONCLUSION

Sensitivity and negative predictive value for the detection of renal artery stenosis using Nav SSFP were perfect, with an acceptable specificity of 84%. This suggests Nav SSFP is a promising technique for simple unenhanced screening for the detection of renal artery stenosis.

Fibromuscular Dysplasia of the Main Renal Arteries: Comparison of Contrast-enhanced MR Angiography with Digital Subtraction Angiography

PURPOSE

To retrospectively evaluate the sensitivity and specificity of contrast material-enhanced magnetic resonance (MR) angiography by using digital subtraction angiography as the reference standard in patients with hypertension and renal artery fibromuscular dysplasia (FMD).

MATERIALS AND METHODS

Institutional review board approval was obtained, with waiver of informed consent. The results of renal contrast-enhanced MR angiography were retrospectively analyzed in 25 patients with hypertension (24 women, one man; mean age, 48 years +/- 19 [standard deviation]; age range, 18-72 years) who had FMD diagnosed on the basis of clinical and angiographic features. All examinations were performed at 1.5 T. Results were analyzed by two readers, and a third reader established a consensus in case of discrepancy. Sensitivity, specificity, and 95% confidence intervals (CIs) were calculated for FMD and for each possible type of FMD lesion ("string of pearls" appearance, stenosis, and aneurysm). A linear-weighted kappa statistic was calculated to determine agreement between digital subtraction angiography and contrast-enhanced MR angiography for the diagnosis of FMD and to determine inter- and intraobserver agreement regarding FMD diagnosis.

RESULTS

Fifty main renal arteries were analyzed, 35 of which demonstrated abnormal arteriographic features of FMD (stenosis, 22 arteries; string of pearls, 21 arteries; and aneurysm, four arteries). The sensitivity and specificity of contrast-enhanced MR angiography for the diagnosis of FMD were 97% (95% CI: 83%, 100%) and 93% (95% CI: 66%, 100%), respectively. Sensitivity was 68% (95% CI: 83%, 100%), 95% (95% CI: 74%, 100%), and 100% (95% CI: 40%, 100%) for the diagnosis of stenosis, string of pearls, and aneurysm, respectively. Linear-weighted kappa statistics for inter- and intraobserver agreement regarding FMD diagnosis were 0.63 and 0.92, respectively.

CONCLUSION

In patients with renal FMD, contrast-enhanced MR angiography can reliably facilitate diagnosis by demonstrating characteristic lesions.

Magnetic resonance angiography of abdominal and lower extremity vasculature

Magnetic resonance angiography (MRA) has evolved over the past years from an experimental imaging modality to a technique that is now widely applied in clinical practice. This article reviews the fundamentals of the different magnetic resonance angiographic techniques and how they can be applied for abdominal and peripheral arterial imaging. Currently, contrast-enhanced magnetic resonance angiography (CE-MRA), whereby a luminogram is obtained during initial arterial passage of contrast material, is the most widely used technique. With current hardware and software, high-spatial resolution images of the abdominal aorta and proximal visceral branches can be obtained that are equivalent to intra-arterial digital subtraction angiography (IA-DSA). High-quality imaging of the renal arteries demands isotropic voxels and reformations orthogonal to the vessel axis for evaluation. Contrast-enhanced magnetic resonance angiography of the peripheral vascular tree is now a highly accurate technique and has replaced diagnostic intra-arterial digital subtraction angiography and duplex ultrasonography in many hospitals.

New intrarenal echo-Doppler velocimetric indices for the diagnosis of renal artery stenosis

We aimed at comparing the positive and negative predictive values (PPV, NPV) of several intrarenal velocimetric indices for revealing the presence of renal artery stenosis (RAS) among hypertensive patients who underwent a renal angiography for the clinical suspicion of renovascular hypertension. In 106 patients (200 kidneys), the pulsatility index (PI) and resistive index (RI), the acceleration time (AT), and the mean systolic acceleration (ACC(sys)) were evaluated. In addition, the maximal systolic acceleration (ACC(max)), that is, the maximal slope of the acceleration phase, and the maximal acceleration index (AI(max)), that is, the ratio between ACC(max) and the relative peak systolic velocity, were calculated. On angiography, we found that 56 (28%) of the 200 arteries had a greater than 60% RAS. PI and RI had an NPV below 75%, whereas AT, ACC(sys), ACC(max), and AI(max) had an NPV always above 95%. However, ACC(max), and AI(max), at their best cutoff limits, had higher PPV than ACC(sys) and AT (60 and 70% vs 45 and 51%, respectively). Thus, in a cohort of patients with a high prevalence of RAS, PI and RI failed to reach an NPV adequate for a screening test. In contrast, all the acceleration indices we tested had a sufficiently high NPV but AI(max) appears superior to the others because of higher PPV. We propose the evaluation of AI(max) as an additional screening test in patients with hypertension and the clinical suspicion of RAS.

Contemporary imaging techniques for the diagnosis of renal artery stenosis

Renal artery stenosis (RAS) is a potentially curable cause of renovascular hypertension (RVH) and is caused by either atherosclerosis or fibromuscular dysplasia (FMD) in the vast majority of patients. Although intra-arterial digital subtraction angiography (IA-DSA) is still considered the standard of reference test for the anatomical diagnosis of RAS, noninvasive techniques such as MR angiography, CT angiography, and color-aided duplex ultrasonography are promising alternatives that also allow functional characterization of RAS. We provide an overview of these techniques and discuss their relative merits and shortcomings. Analysis of high-quality studies shows that both MR and CT angiography are significantly more accurate for the diagnosis of at least 50% atherosclerotic RAS than ultrasonographic techniques. The primary strength of ultrasonography at present is its suggested ability to predict functional recovery based on preinterventional resistance index measurements. A still unresolved issue is the detection of FMD. Because missing RVH may have serious consequences the most important requirement for a screening test is that it has high sensitivity.

Pediatric applications of abdominal vascular Doppler: Part II

Ultrasound is a remarkably powerful and versatile modality for pediatric imaging, without requiring exposure to radiation or sedatives. By providing information on blood flow, Doppler sonography can reveal details about normal physiology and disease processes not discernable from gray-scale anatomic images alone. In part I, the basics of hemodynamics and effects on the Doppler waveform were discussed, along with clinical applications in hepatic disease. In part II, the application of Doppler in renal disease and in conditions affecting the deep abdominal vessels are discussed. The role of ultrasound contrast agents in pediatric Doppler imaging is briefly reviewed.

Accessory Renal Arteries Are Not Related to Hypertension Risk:A Review of MR Angiography Data

OBJECTIVE

It has been hypothesized that accessory renal arteries are related to the risk of hypertension. Our goal was to determine the prevalence of accessory renal arteries in hypertensive patients using MR angiography and to assess the relationship between accessory renal arteries and hypertension risk.

MATERIALS AND METHODS

From 1996 to 2002, 185 hypertensive patients underwent MR angiography of the renal arteries at our institution for assessment of renal artery stenosis. MR angiograms were obtained using a 1.5-T magnet, IV gadolinium, and 3D gradient-echo sequences. Interpretations of the MR angiograms were retrospectively reviewed.

RESULTS

Of 185 hypertensive patients, 45 (24%) showed accessory renal arteries. Of these 45 patients, nine (20%) showed renal artery stenosis and 36 (80%) showed no significant stenosis. Of the 140 patients with a single renal artery, 42 (30%) showed renal artery stenosis and 98 (70%) showed no stenosis. The odds ratio of renal artery stenosis in the accessory renal artery group versus the single renal artery group was 0.58 (95% confidence interval, 0.26-1.3%), which is not statistically significant at a power of 0.85 (chi(2) = 1.705; p = 1.0).

CONCLUSION

We found no statistically significant difference in the prevalence of renal artery stenosis between patients with accessory renal arteries and those without accessory renal arteries. Assuming that the presence of two separate causes of hypertension in the same patient would be unlikely, this finding implies that accessory renal arteries are a vascular anomaly and not a direct cause of hypertension. The findings are potentially relevant in refuting the theory of accessory renal arteries as an anatomically treatable cause of hypertension.

Emergency Doppler evaluation of the liver and kidneys

Doppler ultrasound is useful in the emergent evaluation of the liver and kidney transplant patient. Arterial stenosis, pseudoaneurysm, and venous thrombosis are treatable causes of allograft failure that can be detected easily with color and spectral Doppler. Doppler has a limited but important role in the emergent evaluation of the native liver and kidneys, usually involving prior biopsy or instrumentation.

Renal imaging with ultrasound contrast: current status

The application of UCAs to the kidney is still in its infancy; however, there are several areas of great promise. UCAs may replace CT in complex renal cyst evaluation and follow-up, eliminating the need for costly CT scans with their attendant potential contrast nephrotoxicity. This approach may decrease patient and physician uncertainty and improve diagnostic confidence. The use of UCAs is likely to be clinically useful in the evaluation of the indeterminate small renal mass on CT or MR imaging. Another probable useful application will be in renal artery stenosis. Routine application of UCAs may increase the percentage of diagnostic examinations, increase diagnostic confidence, and decrease examination times. It also will likely become the first line of evaluation in pyelonephritis, and be useful in immediate assessment of residual tumor after radiofrequency ablation. Of course, substantial additional work needs to be performed in large groups of patients to prove this currently optimistic outlook.