Captopril radionuclide test in renovascular hypertension: a European multicentre study. European Multicentre Study Group

Renal Artery Stenosis As Etiology of Recurrent Flash Pulmonary Edema and Role of Imaging in Timely Diagnosis and Management

Renal hypoperfusion from renal artery stenosis (RAS) activates the renin-angiotensin system, which in turn causes volume overload and hypertension. Atherosclerosis and fibromuscular dysplasia are the most common causes of renal artery stenosis. Recurrent flash pulmonary edema, also known as Pickering syndrome, is commonly associated with bilateral renal artery stenosis. There should be a high index of clinical suspicion for renal artery stenosis in the setting of recurrent flash pulmonary edema and severe hypertension in patients with atherosclerotic disease. Duplex ultrasonography is commonly recommended as the best initial test for the detection of renal artery stenosis. Computed tomography (CT) angiography (CTA) or magnetic resonance (MR) angiography (MRA) are useful diagnostic imaging studies for the detection of renal artery stenosis in patients where duplex ultrasonography is difficult. If duplex ultrasound, CTA, and MRA are indeterminate or pose a risk of significant renal impairment, renal angiography is useful for a definitive diagnosis of RAS. The focus of medical management for RAS relies on controlling renovascular hypertension and aggressive lifestyle modification with control of atherosclerotic disease risk factors. The restoration of renal artery patency by revascularization in the setting of RAS due to atherosclerosis may help in the management of hypertension and minimize renal dysfunction.

Renovascular Hypertension

Renovascular disease (RVD) is a major cause of secondary hypertension. Atherosclerotic renal artery stenosis is the most common type of RVD followed by fibromuscular dysplasia. It has long been recognized as the prototype of angiotensin-dependent hypertension. However, the mechanisms underlying the physiopathology of hypertensive occlusive vascular renal disease are complex and distinction between the different causes of RVD should be made. Recognition of these distinct types of RVD with different degrees of renal occlusive disease is important for management. The greatest challenge is to individualize and implement the best approach for each patient in the setting of widely different comorbidities.

The SNMMI and EANM practice guideline for renal scintigraphy in adults

PURPOSE

The Society of Nuclear Medicine and Molecular Imaging (SNMMI) is an international scientific and professional organization founded in 1954 to promote the science, technology, and practical application of nuclear medicine. The European Association of Nuclear Medicine (EANM) is a professional nonprofit medical association that facilitates communication worldwide between individuals pursuing clinical and research excellence in nuclear medicine. The EANM was founded in 1985. SNMMI and EANM members are physicians, technologists, and scientists specializing in the research and practice of nuclear medicine.

METHODS

The SNMMI and EANM will periodically define new guidelines for nuclear medicine practice to help advance the science of nuclear medicine and to improve the quality of service to patients throughout the world. Existing practice guidelines will be reviewed for revision or renewal, as appropriate, on their fifth anniversary, or sooner, if indicated.

CONCLUSION

Each practice guideline, representing a policy statement by the SNMMI/EANM, has undergone a thorough consensus process in which it has been subjected to extensive review. The SNMMI and EANM recognize that the safe and effective use of diagnostic nuclear medicine imaging requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guideline by entities not providing these services is not authorized.

Renal artery stenting for atherosclerotic renal artery stenosis identified in patients with coronary artery disease: Does captopril renal scintigraphy predict outcomes?

The authors evaluated the effectiveness of percutaneous renal revascularization (PRR) with stenting for the treatment of atherosclerotic renal artery stenosis (ARAS) in patients with coronary artery disease and the usefulness of captopril renal scintigraphy for predicting clinical outcomes after PRR. Sixty-four consecutive patients, referred for evaluation of suspected ARAS, after coronary angiography, underwent baseline captopril renal scintigraphy followed by renal angiography. Forty-four patients (68.7%) were diagnosed with a significant ARAS≥ 60% and were treated with PRR plus medical therapy. Twenty-four months after PRR, 86.4% and 73.3% of patients showed a hypertension and renal benefit, respectively. Captopril renal scintigraphy positivity had moderate sensitivity and high specificity in predicting a hypertension and renal benefit. In patients with ARAS≥ 70%, the sensitivity and specificity were 100% for both a hypertension and renal benefit.PRR for ARAS conferred a substantial benefit in patients with a high coronary artery disease burden. Captopril renal scintigraphy was highly accurate in predicting clinical outcomes.

The role of renoscintigraphy and surgery in the management of Page kidney: A case report

RATIONALE

Page kidney is an uncommon condition that hypertension occurs secondary to microvascular ischemia and alternation of small-vessel hemodynamics due to external compression of renal parenchyma and activation of the renin-angiotensin-aldosterone system. There are no specific guidelines for the management of Page kidney in the literatures.

PATIENT CONCERNS

A 17-year-old teenager who had Fontan procedure for tricuspid and pulmonary atresia in early childhood suffered from sudden onset of severe left flank pain during cardiac catheterization procedure. Left renal artery active bleeding with renal parenchyma compression in association with renin-mediated hypertension led to the diagnosis of Page kidney.

DIAGNOSES

Page kidney was diagnosed in this case.

INTERVENTIONS

Urgent embolization was performed to treat left renal artery active bleeding. Because of decreased renal function with elevation of serum creatinine, inadequate blood pressure control with antihypertensive medication, and poor renal blood flow of left kidney, open drainage of perirenal hematoma was done 5 days after catheterization procedure.

OUTCOMES

After the operation, glomerular filtration rate improved immediately, and left flank pain and hypertension resolved at discharge.

LESSONS

The choice of the therapies for Page kidney depended on the clinical presentation of each case. This case pointed out the significance of renoscintigraphy and surgery in the management of Page kidney.

Noninvasive Staging of Kidney Dysfunction Enabled by Renal-Clearable Luminescent Gold Nanoparticles

As a "silent killer", kidney disease is often hardly detected at an early stage but can cause lethal kidney failure later on. Thus, a preclinical imaging technique that can readily differentiate between the stages of kidney dysfunction is highly desired for improving our fundamental understanding of kidney disease progression. Herein, we report that in vivo fluorescence imaging, enabled by renal-clearable near-infrared-emitting gold nanoparticles, can noninvasively detect kidney dysfunction, report on the dysfunctional stages, and even reveal adaptive function in a mouse model of unilateral obstructive nephropathy, which cannot be diagnosed with routine kidney function markers. These results demonstrate that low-cost fluorescence kidney functional imaging is highly sensitive and useful for the longitudinal, noninvasive monitoring of kidney dysfunction progression in preclinical research.

Clinical problems in renovascular disease and the role of nuclear medicine

Although renovascular disease remains defined as a stenosis of the main renal artery or its proximal branches (renal artery stenosis [RAS]), its clinical overview has changed dramatically over the last 15-20 years and its management is more controversial than ever before. The clinical problems, not only diagnosis and treatment but also the relative contribution of different pathophysiological mechanisms involved in the progression of kidney disease, have shifted dramatically. This presentation aims to emphasize the paradigm change revisiting the (recent) past focused on renovascular hypertension (RVH) to the current context of preservation or recovery of threatened renal function in patients with progressive atherosclerotic renovascular disease until its last stage of irreversible "ischemic nephropathy." In the past, the foreground was occupied by RVH, a very rare disease, where the activation of the renin-angiotensin-aldosterone system (RAAS) was supposed to play the major, if not only, role in RVH issues. The retrospective RVH diagnosis was established either on the improvement or, more rarely, on the cure of hypertension after revascularization by, most often, a percutaneous transluminal renal angioplasty with or without a stent placement. At this time, captoptril radionuclide renography was an efficient diagnostic tool, because it was a functional (angiotensin-converting enzyme inhibition), noninvasive test aiming to evidence both the RAAS activation and the lateralization (or asymmetry) of renin secretion by the kidney affected by a "hemodynamically significant" RAS. At present, even if captoptril radionuclide renography could be looked upon as the most efficient (and cost effective in selected high-risk patients) noninvasive, functional test to predict the improvement of hypertension after RAS correction, its clinical usefulness is questioned as the randomized, prospective trials failed to demonstrate any significant benefits (either on blood pressure control or on renal function protection) of the revascularization over current antihypertensive therapy. Today many patients with RVH remain undetected for years because they are treated successfully and at low expense with these new blockers of RAAS. In addition to its well-known role in hemodynamics, angiotensin II promotes activations of profibrogenic and inflammatory factors and cells and stimulates reactive oxygen species generation. The "atherosclerotic milieu" itself plays a role in the loss of renal microvessels and defective angiogenesis. After an "adaptative" phase, ischemia eventually develops and induces hypoxia, the substratum of ischemic nephropathy. Because blood oxygen level-dependent MRI may provide an index of oxygen content in vivo, it may be useful to predict renal function outcome after percutaneous transluminal renal angioplasty. New PET tracers, dedicated to assess RAAS receptors, inflammatory cell infiltrates, angiogenesis, and apoptose, would be tested in this context of atherosclerotic renovascular disease.

Radionuclides in nephrourology, Part 2: pitfalls and diagnostic applications

Radionuclide renal scintigraphy provides important functional data to assist in the diagnosis and management of patients with a variety of suspected genitourinary tract problems, but the procedures are underutilized. Maximizing the utility of the available studies (as well as the perception of utility by referring physicians) requires a clear understanding of the clinical question, attention to quality control, acquisition of the essential elements necessary to produce an informed interpretation, and production of a report that presents a coherent impression based on data contained in the report and that specifically addresses the clinical question. To help achieve these goals, part 1 of this review addressed the available radiopharmaceuticals, quality control, and quantitative indices, including the measurement of absolute and relative renal function. Part 2 assumes familiarity with part 1 and focuses on the common clinical indications of suspected obstruction and renovascular hypertension; part 2 also summarizes the status of radionuclide renal imaging in the evaluation of the transplanted kidney and the detection of infection, discusses potential pitfalls, and concludes with suggestions for future research. The series of SAM questions accompanying parts 1 and 2 has been designed to reinforce and extend points made in the review. Although the primary focus is the adult patient, aspects of the review also apply to the pediatric population.

Renovascular hypertension associated with pseudoaneurysm following blunt trauma

We present the case of a 21-year-old man who developed a renal artery pseudoaneurysm following a 7-foot fall onto his back. He initially presented with gross hematuria, left flank pain, and back pain. He was observed in the hospital for 3 days and discharged. One week later, he was readmitted with headache, nausea, vomiting, seizure activity, and hypertension. Contrast-enhanced computed tomography of the abdomen showed a left renal artery pseudoaneurysm with associated arterial narrowing and delayed ipsilateral renal enhancement. He underwent percutaneous stent-graft placement with resolution of the pseudoaneurysm. He was free of complications and normotensive off antihypertensive medications after 36 months of follow-up. Renal artery pseudoaneurysms are rare and under-recognized complications of blunt abdominal or back trauma that can cause hypertension. Imaging modalities in renovascular hypertension have focused on detecting renal artery stenosis from atherosclerotic disease or fibromuscular dysplasia, with little attention given to renal artery pseudoaneurysms. In addition, first-line treatment for renal artery pseudoaneurysms historically has consisted of angioembolization, yet percutaneous stent-graft placement has emerged as an attractive alternative to preserve vessel patency. We discuss the role of imaging in renovascular hypertension with a focus on renal artery pseudoaneurysms and their prevalence, diagnosis, and treatment.

Diagnostic criteria for renovascular disease: where are we now?

Renovascular disease, especially atherosclerotic renal artery stenosis (ARAS) in older subjects, is commonly encountered in clinical practice. This is at least in part due to the major advances in non-invasive imaging techniques that allow greater diagnostic sensitivity and accuracy than ever before. Despite increased awareness of ARAS, renal revascularization is less commonly performed, likely as a result of several prospective, randomized, clinical trials which fail to demonstrate major benefits of renal revascularization beyond medical therapy alone. Primary care physicians are less likely to investigate renovascular disease and nephrologists likely see more patients after a period of unsuccessful medical therapy with more advanced ARAS. The goal of this review is to revisit current diagnostic and therapeutic paradigms in order to characterize more clearly which patients will likely benefit from further evaluation and intensive treatment of renal artery stenosis.

Glomerular filtration rate measured by (51)Cr-EDTA clearance: Evaluation of captopril-induced changes in hypertensive patients with and without renal artery stenosis

INTRODUCTION

Renal artery stenosis can lead to renovascular hypertension; however, the detection of stenosis alone does not guarantee the presence of renovascular hypertension. Renovascular hypertension depends on activation of the renin-angiotensin system, which can be detected by functional tests such as captopril renal scintigraphy. A method that allows direct measurement of the baseline and post-captopril glomerular filtration rate using chromium-51 labeled ethylenediamine tetraacetic acid ((51)Cr-EDTA) could add valuable information to the investigation of hypertensive patients with renal artery stenosis. The purposes of this study were to create a protocol to measure the baseline and post-captopril glomerular filtration rate using (51)Cr-EDTA, and to verify whether changes in the glomerular filtration rate permit differentiation between hypertensive patients with and without renal artery stenosis.

METHODS

This prospective study included 41 consecutive patients with poorly controlled severe hypertension. All patients had undergone a radiological investigation of renal artery stenosis within the month prior to their inclusion. The patients were divided into two groups: patients with (n=21) and without renal artery stenosis, (n=20). In vitro glomerular filtration rate analysis ((51)Cr-EDTA) and (99m)Tc-DMSA scintigraphy were performed before and after captopril administration in all patients.

RESULTS

The mean baseline glomerular filtration rate was 48.6+/-21.8 ml/kg/1.73 m(2) in the group wuth renal artery stenosis, which was significantly lower than the GFR of 65.1+/-28.7 ml/kg/1.73m(2) in the group without renal artery stenosis (p=0.04). Captopril induced a significant reduction of the glomerular filtration rate in the group with renal artery stenosis (to 32.6+/-14.8 ml/ kg/1.73m(2), p=0.001) and an insignificant change in the group without RAS (to 62.2+/-23.6 ml/kg/1.73m(2), p=0.68). Scintigraphy with technetium-99m dimercapto-succinic acid (DMSA) did not show significant differences in differential renal function from baseline to post-captopril images in either group.

CONCLUSIONS

Captopril induced a decrease in the GFR that could be quantitatively measured with (51)Cr-EDTA. The reduction is more pronounced in hypertensive patients with RAS.

Imaging in the evaluation of renovascular disease

Renovascular disease (RVD) is an important cause of hypertension in children, as it often is amenable to potentially curative treatment. Imaging aimed at finding RVD therefore needs to have high sensitivity so as not to miss important findings. Digital subtraction angiography is the gold standard investigation. Doppler ultrasonography, computed tomography (CT) angiography and magnetic resonance (MR) angiography can all be helpful, but none has, at present, high enough sensitivity to rule out RVD in a child with a suggestion of that diagnosis.

Pre- and postcaptopril renal scintigraphy as a screening test for renovascular hypertension in children

We studied the ability of pre- and postcaptopril renal scintigraphy to predict renovascular disease (RVD) in children. Retrospective review of medical notes and radiology reports of all hypertensive children who had had both pre- and postcaptopril renal scintigraphy with [(99m)Tc] dimercaptosuccinic acid (DMSA) and/or [(99m)Tc] mercaptoacetyltriglycine (MAG3) and digital subtraction angiography (DSA). 81 children aged 1-18 (median 10) years were studied with 62% (51) having a diagnosis of RVD. Main renal artery disease, intrarenal disease, and both main and intrarenal artery disease were present in 25, 14, and 12 patients respectively. The isotope study accurately diagnosed RVD, confirmed by DSA, in 47% (24 of 51) children, with eight false positive studies. The sensitivity, specificity, and positive and negative predictive values of the isotope study to predict RVD were 48%, 73%, 76%, and 51%, respectively. Pre- and postcaptopril renal scintigraphy was unable to predict RVD in children.

[Hypertension in patients with renal artery stenosis]

Renal artery stenosis (RAS) is often present in patients with severe hypertension and atherosclerotic vascular disease. In this setting it is important to screen patients for renovascular disease, e.g. with Duplex-ultrasound, CT- or MR-angiography. The challenge of treating these patients is to find the evidence proving that the RAS is responsible for hypertension and/or renal dysfunction. Measurement of the intra-arterial pressure gradient is necessary in order to determine hemodynamic relevance. On the other side, in these patients hypertension is often of primary and/or renoparenchymatous origin and is aggravated by a renovascular disease. This explains why hypertension cannot be cured even if a high grade stenosis has been removed. In addition, thromb- and cholesterol-embolic material is often mobilized during an invasive procedure and leads to renaparenchymatous ischemia which sustains hypertension after intervention. An individual evaluation of profit versus risk is important for the decision for or against an invasive procedure, especially since there is no sufficient evidence for a decrease of mortality after interventions of RAS. The optimal conservative treatment, including the treatment of atherosclerotic risk factors is recommended.

Advances in noninvasive methods for functional evaluation of renovascular disease

As the number of patients with newly diagnosed renal artery stenosis increases, so has the number of percutaneous transluminal renal-artery angioplasties in the last few years. Deciding the preferred treatment in the clinical setting is fraught with difficulties related to many factors, and there is limited evidence to support angioplasty/stent for any indication. These considerations emphasize the urgent need for improved noninvasive assessment of kidney function in patients with vascular disease. This review will attempt to summarize the available techniques that may potentially be used for measurement of renal function in this context.

Clinical Use of Laboratory Tests for the Identification of Secondary Forms of Arterial Hypertension

The prevalence of secondary hypertension can be underestimated if appropriate tests are not performed. The importance of selecting patients with a high pre-test probability of secondary forms of hypertension is first discussed. The laboratory tests currently used for seeking a cause of hypertension are critically reviewed, with emphasis on their operative features and limitations. Strategies to identify primary aldosteronism, the most frequent form of secondary hypertension, and to determine its unilateral or bilateral causes are described. Treatment entails adrenalectomy in unilateral forms, and mineralocorticoid receptor blockade in bilateral forms. Renovascular hypertension is also a common, curable form of hypertension, that should be identified as early as possible to avoid the onset of cardiovascular target organ damage. The tests for its confirmation or exclusion are discussed. The various tests available for the diagnosis of pheochromocytoma, which is much rarer than the above but extremely important to identify, are also described, with emphasis on recent developments in genetic testing. Finally, the tests for diagnosing some rarer monogenic forms and other renal and endocrine causes of arterial hypertension are explored.

Color Doppler sonography in the study of chronic ischemic nephropathy

In western countries, the risk of cardiovascular disease has increased considerably in recent decades. This trend has been paralleled by an increase in cases of atherosclerotic renal disease, which is related to the improved prognosis of cardiovascular diseases, aging, and the increasing mean age of the general population. It is reasonable to expect that in the near future, there will be a sharp increase in the number of elderly patients with atherosclerotic vascular disease in chronic dialysis programs. The result will be a dramatic rise in the social and economic costs of dialysis that could constitute a true clinical emergency. In this epidemiologic scenario, one of the most important targets of 21st century nephrology will be the early diagnosis of chronic ischemic nephropathy and the development of new and more effective strategies for its treatment.Color Doppler (CD) ultrasonography has displayed high sensitivity, specificity, and positive and negative predictive values in the diagnosis of this disease in selected population, making it an ideal tool for use in screening programs. Eligibility for screening should be based on clinical criteria. For the most part, it will be aimed at adults (especially those who are elderly) with atherosclerotic vascular disease involving multiple districts and chronic kidney disease (CKD), stage 2-3, in the absence of a documented history of renal disease. In these patients, hypertension may be a secondary manifestation or a symptom of the ischemic nephropathy itself. The objectives of sonographic screening should be (1) to identify subjects in the population at risk who are affected by stenosis of the main renal artery (RAS); (2) to identify and characterize patients without RAS who have chronic ischemic nephropathy caused by nephroangiosclerosis and/or atheroembolic disease. The former group will require second-level diagnostic studies or angioplasty with stenting; the latter can be managed conservatively. The most important CD parameters in the workup of suspected RAS are those that are direct signs, i.e., increases in peak systolic velocity (PSV) and diastolic velocity (DV), spectral broadening, and an altered renal:aortic ratio (RAR). Their assessment requires full-length sampling of the renal artery and is associated with greater practical/technical difficulties. Measurement in triplicate of the PSV in the ostial, medial, and hilar segments of both arteries and bilateral measurement of parenchymal resistance indices are usually sufficient to detect the presence of stenosis and refer the patient for second-level studies. Important parameters for estimating the severity of a stenosis include the renal:aortic ratio (>3.5), disappearance of the early systolic peak in segmental vessels, lateralization of the resistance index (ΔRI > 0.05), and the evaluation of the acceleration index (AI) and acceleration time (AT). Second-level imaging studies (CT angiography, MR angiography) are still indispensable for precise definition of the location and extension of the stenosis and the therapeutic approach during digital subtraction angiography (DSA). In the absence of direct or indirect signs of RAS, increases in the intraparenchymal resistance indices (RI > 0.75-0.80; PI > 1.50) associated with systemic atherosclerotic disease are indicative of microcirculatory damage related to nephroangiosclerosis or atheroembolic disease.

Renovascular hypertension in children

Renovascular disease is an uncommon but important cause of hypertension in children. It is usually diagnosed after a long delay because blood pressure is infrequently measured in children and high values are generally dismissed as inaccurate. Many children with renovascular disease have abnormalities of other blood vessels (aorta, cerebral, intestinal, or iliac). Individuals suspected of having the disorder can be investigated further with CT, MRI, or renal scintigraphy done before and after administration of an angiotensin-converting-enzyme inhibitor, but angiography is still the gold standard. Most children with renovascular disease will need interventional or surgical treatment. Endovascular treatment with or without stenting will cure or reduce high blood pressure in more than half of all affected children. Surgical intervention, if needed, should be delayed preferably until an age when the child is fully grown. Modern treatment provided by a multidisciplinary team of paediatric nephrologists, interventional radiologists, and vascular surgeons offers good long-term treatment results.

International Scientific Committee of Radionuclides in Nephrourology (ISCORN) consensus on renal transit time measurements

This report is the conclusion of the international consensus committee on renal transit time (subcommittee of the International Scientific Committee of Radionuclides in Nephrourology) and provides recommendations on measurement, normal values, and analysis of clinical utility. Transit time is the time that a tracer remains within the kidney or within a part of the kidney (eg, parenchymal transit time). It can be obtained from a dynamic renogram and a vascular input acquired in standardized conditions by a deconvolution process. Alternatively to transit time measurement, simpler indices were proposed, such as time of maximum, normalized residual activity or renal output efficiency. Transit time has been mainly used in urinary obstruction, renal artery stenosis, or renovascular hypertension and renal transplant. Despite a large amount of published data on obstruction, only the value of normal transit is established. The value of delayed transit remains controversial, probably due to lack of a gold standard for obstruction. Transit time measurements are useful to diagnose renovascular hypertension, as are some of the simpler indices. The committee recommends further collaborative trials.

Renal athersosclerotic revascularization evaluation (RAVE study): study protocol of a randomized trial [NCT00127738]

Background

It is uncertain whether patients with renal vascular disease will have renal or mortality benefit from re-establishing renal blood flow with renal revascularization procedures. The RAVE study will compare renal revascularization to medical management for people with atherosclerotic renal vascular disease (ARVD) and the indication for revascularization. Patients will be assessed for the standard nephrology research outcomes of progression to doubling of creatinine, need for dialysis, and death, as well as other cardiovascular outcomes. We will also establish whether the use of a new inexpensive, simple and available ultrasound test, the renal resistance index (RRI), can identify patients with renal vascular disease who will not benefit from renal revascularization procedures[1].

Methods/design

This single center randomized, parallel group, pilot study comparing renal revascularization with medical therapy alone will help establish an infrastructure and test the feasibility of answering this important question in clinical nephrology. The main outcome will be a composite of death, dialysis and doubling of creatinine. Knowledge from this study will be used to better understand the natural history of patients diagnosed with renal vascular disease in anticipation of a Canadian multicenter trial. Data collected from this study will also inform the Canadian Hypertension Education Program (CHEP) Clinical Practice Guidelines for the management of Renal and Renal Vascular Disease. The expectation is that this program for ARVD, will enable community based programs to implement a comprehensive guidelines based diagnostic and treatment program, help create an evidence based approach for the management of patients with this condition, and possibly reduce or halt the progression of kidney disease in these patients.

Discussion

Results from this study will determine the feasibility of a multicentered study for the management of renovascular disease.

Atherosclerotic renovascular disease

Atherosclerotic renovascular disease is a combination of renal artery stenosis and renal ischemia. Blood pressure does not rise until the stenosis is 60% or greater. Disease of both large and small blood vessels is often accompanied by the loss of glomerular filtration rate. Activation of the renin-angiotensin-aldosterone system leads to vasoconstriction and salt retention. Risk factors for atherosclerotic renovascular disease include long-standing hypertension, diabetes, smoking and dyslipidemia. The prevalence of the condition in patients with hypertension resistant to two medications is 20%. As yet, there is no single ideal screening test or evidence-based recommended screening algorithm. Magnetic resonance angiography and computed tomography angiography are noninvasive and have high sensitivity and specificity, but also have high costs associated with them. The captopril renal scan has low sensitivity and specificity in people with renal disease (the population most likely to require the test). Doppler ultrasonography has high sensitivity and specificity in experienced hands, and the renal resistance index, which can easily be added to this test, can identify those with microvascular disease who may not benefit from revascularization. The best determinant of patient outcome is not the degree of renal artery stenosis but the degree of renal parenchymal disease. To date, renal revascularization has not been associated with improved renal survival compared with medical treatment alone. Today, the approach to atherosclerotic renovascular disease is determined by the patient's blood pressure and renal function; possibly, in the future, it will be determined by the result of the renal resistance index as part of a screening algorithm. If the blood pressure is uncontrollable or the renal function is deteriorating, the patient should be considered for renal revascularization initially, with a percutaneous endovascular stent. The management of hypertension involves the use of combinations of antihypertensive agents at doses sufficient to control blood pressure. Medical management also includes aggressive lipid-lowering therapy.

Functional MRI of the kidney: tools for translational studies of pathophysiology of renal disease

Magnetic resonance imaging (MRI) provides exquisite anatomic detail of various organs and is capable of providing additional functional information. This combination allows for comprehensive diagnostic evaluation of pathologies such as ischemic renal disease. Noninvasive MRI techniques could facilitate translation of many studies performed in controlled animal models using technologies that are invasive to humans. Such a translation is being recognized as essential because many proposed interventions and drugs that prove efficacious in animal models fail to do so in humans. In this article, we review the state-of-the-art functional MRI technique as applied to the kidneys.

Increased Renal Arterial Resistance Predicts the Course of Renal Function in Type 2 Diabetes With Microalbuminuria

Type 2 diabetic patients often die because of end-stage renal failure, but no definitive reliable factor predicting long-term renal outcome has been identified. We tested whether a renal arterial resistance index (R/I) ≥80, using Doppler ultrasound technique, was predictive of worsening renal function. The primary end points of the study were 1) the course of glomerular filtration rate (GFR) and 2) the albumin excretion rate in 157 microalbuminuric, hypertensive, type 2 diabetic patients after a 7.8-year follow-up period (range 7.1–9.2). Kaplan-Meier curves for the primary end point (decrease of GFR ≥−3.0 ml/min per 1.73 m2 per year) was two to three times more frequently observed in patients with R/I ≥80. Four- to fivefold fewer patients showed a regression to normoalbuminuria during the follow-up period from baseline microalbuminuria in the cohort with R/I ≥80. Overt proteinuria did develop in 24% of patients with R/I ≥80 and in 5% of patients with R/I <80 (P < 0.01). In conclusion, intrarenal arterial resistance appears to play a nontrivial role in deteriorating renal function in type 2 diabetic patients. R/I is a noninvasive diagnostic procedure, which strongly predicts the outcome of renal function in type 2 diabetic patients, even when GFR patterns are still normal.

Interpretation of captopril renography using artificial neural networks

The purpose of this study was to develop a method based on artificial neural networks for interpretation of captopril renography tests for the detection of renovascular hypertension caused by renal artery stenosis and to assess the value of different measurements from the test. A total of 250 99mTc-MAG3 captopril renography tests were used in the study. The material was collected from two different patient groups. One group consisted of 101 patients who also had undergone a renal angiography. The angiographies, which were used as gold standard, showed a significant renal artery stenosis in 53 of the 101 cases. The second group consisted of 149 patients, who's captopril renography tests all were interpreted as not compatible with significant renal artery stenosis by an experienced nuclear medicine physician. Artificial neural networks were trained for the diagnosis of renal artery stenosis using eight measures from each renogram. The neural network was then evaluated in separate test groups using an eightfold cross validation procedure. The performance of the neural networks, measured as the area under the receiver operating characteristic curve, was 0.93. The sensitivity was 91% at a specificity of 90%. The lowest performance was found for the network trained without use of a parenchymal transit measure, indicating the importance of this feature. Artificial neural networks can be trained to interpret captopril renography tests for detection of renovascular hypertension caused by renal artery stenosis. The result almost equals that of human experts shown in previous studies.

Evaluation of Renovascular Hypertension

OBJECTIVE

The main objective of this study was to evaluate a clinically suspected renovascular hypertension (RVH) by means of MRI. It was to find out if functional MRI (fMRI) is able to provide adequate results with regard to MAG3 captopril scintigraphy and if contrast-enhanced MR angiography (MRA) is able to provide adequate results in the stenosis grading compared with the nonselective digital subtraction angiography (DSA).

METHODS

This open, monocentric, prospective, phase 3 study included patients with a clinically suspected RVH. For fMRI a dynamic TurboFLASH sequence and for MRA a single-shot breath-hold flash 3D sequence was performed. Gadodiamide was injected as contrast medium.

RESULTS

Sixty patients were included in the study. The correlation between fMRI and scintigraphy had an accuracy, a sensitivity, and a specificity of 69%, 5%, and 92%, respectively, and correlations between MRA and DSA of 95%, 92%, and 96%.

CONCLUSION

The noninvasive MRA can replace DSA in the diagnosis of renal artery stenosis. However, fMRI can not replace renal scintigraphy.

Guidelines for the Reporting of Renal Artery Revascularization in Clinical Trials

Although the treatment of atherosclerotic renal artery stenosis with use of percutaneous angioplasty, stent placement, and surgical revascularization has gained widespread use, there exist few prospective randomized controlled trials (RCTs) comparing these techniques to each other or against the standard of medical management alone. To facilitate this process as well as help answer many important questions regarding the appropriate application of renal revascularization, well-designed and rigorously conducted trials are needed. These trials must have clearly defined goals and must be sufficiently sized and performed so as to withstand intensive outcomes assessment. Toward this end, this document provides guidelines and definitions for the design, conduct, evaluation, and reporting of renal artery revascularization RCTs. In addition, areas of critically necessary renal artery revascularization investigation are identified. It is hoped that this information will be valuable to the investigator wishing to conduct research in this important area.

The diagnosis and management of renovascular disease: a primary care perspective. Part I. Making the diagnosis

Renovascular disease is a complex disorder, the most common causes of which are fibromuscular dysplasia and atherosclerotic disease. It usually presents in one of three forms: asymptomatic renal artery stenosis, renovascular hypertension, or ischemic nephropathy. This complexity often makes diagnostic and management decisions difficult. This review will be presented in two parts. In Part I, the authors will discuss when to consider and how to go about making the diagnosis. In Part II (in a future issue of The JCH), the authors discuss the management of renovascular disease. The clinical index of suspicion remains paramount in setting the diagnostic strategy. Although it is subject to certain limitations, conventional contrast angiography is usually considered the gold standard in confirming the diagnosis. In addition, there are a number of available noninvasive tests that can aid in decision making. These tests can be divided into those that detect the anatomic presence of a stenosis and those that identify the functional consequences of the renal artery obstruction. No one study is appropriate for every patient. A diagnostic algorithm is proposed at the conclusion of this review.

The right diagnostic work-up: investigating renal and renovascular disorders

Renovascular disease is present in about 10-40% of patients with end-stage renal disease, and constitutes the fastest-growing group of end-stage renal disease patients. The unselective correction of renal artery stenosis has led to disappointing results. Most studies that have compared conservative treatment with angioplasty have found only modest or no beneficial effects of angioplasty on renal function and blood pressure. It is therefore mandatory to evaluate the functional significance of a stenosis before intervention. Patients most likely to respond favourably to revascularization should be identified. Factors that affect outcome include the severity of renal artery stenosis, type of treatment of renal artery stenosis and, most importantly, underlying renal disease, which prevents a favourable response even after successful correction of renal artery stenosis. Doppler ultrasonography to evaluate the renal resistance index [1 - (end diastolic velocity/maximum systolic velocity) x 100] or captopril scintigraphy are the best methods by which to classify patients as responders or non-responders to intervention. In patients with a renal resistance index > or = 80%, improvement of renal function or blood pressure is highly unlikely, despite successful correction of renal artery stenosis. The value of the renal resistance index can also be extended to patients with non-stenotic renal diseases. Identifying patients at risk for irreversible loss of renal function and who may benefit from intervention is a high research priority.

Guidelines for the reporting of renal artery revascularization in clinical trials

Although the treatment of atherosclerotic renal artery stenosis with use of percutaneous angioplasty, stent placement, and surgical revascularization has gained widespread use, there exist few prospective randomized controlled trials (RCTs) comparing these techniques to each other or against the standard of medical management alone. To facilitate this process as well as help answer many important questions regarding the appropriate application of renal revascularization, well-designed and rigorously conducted trials are needed. These trials must have clearly defined goals and must be sufficiently sized and performed so as to withstand intensive outcomes assessment. Toward this end, this document provides guidelines and definitions for the design, conduct, evaluation, and reporting of renal artery revascularization RCTs. In addition, areas of critically necessary renal artery revascularization investigation are identified. It is hoped that this information will be valuable to the investigator wishing to conduct research in this important area.

Usefulness of captopril renography to predict the benefits of renal artery revascularization or captopril treatment in hypertensive patients with diabetic nephropathy

This retrospective study aimed to use captopril renography (CR) for predicting the benefits of captopril treatment in hypertensive patients with diabetic nephropathy. CR was utilized in 60 hypertensive patients with diabetic nephropathy for detecting the probability of renovascular hypertension (RVH) and predicting the benefits of renal artery revascularization or captopril treatment. Ten of the 60 patients showed a high probability of RVH with marked changes of the renogram curve after an oral intake of 50-mg captopril compared to baseline findings. All of the 10 patients confirmed significant main renal artery stenosis in all of them, bilaterally in four patients and unilaterally in the remaining six patients by renal angiographic findings. After successful revascularization, blood pressure was well controlled and renal function was preserved in all of the 10 patients. The other 50 patients showed a low or intermediate probability of RVH with normal findings or unchanged on CR after 50-mg captopril. Then, captopril alone or combination treatment started and continued on 50 patients. After monitoring for at least 6 months, blood pressure was well controlled and renal function was preserved in all the 50 patients on captopril treatment. We conclude that CR should be considered as the standard diagnostic criteria of RVH and may be helpful in predicting the beneficial impact of captopril treatment in hypertensive patients with diabetic nephropathy.

How to diagnose, how to treat: renal artery stenosis-diagnosis and management

Renal artery stenosis is considered to be one of the more frequent causes of secondary arterial hypertension. Through its progression renal artery stenosis can cause renal insufficiency, uncontrolled hypertension, and increased cardiovascular morbidity. A thorough clinical examination and the presence of a typical abdominal bruit may provide helpful hints to identify hypertensive patients with possible renal artery stenosis. Testing for renovascular hypertension includes renal artery imaging, assessment of its functional significance, and evaluation for possible revascularization. Renal artery stenosis secondary to fibromuscular dysplasia should be mechanically corrected. For atherosclerotic renal artery stenosis, medical management can be attempted so long as it does not cause a decline of kidney function. In patients who are candidates for renovascular revascularization, surgical intervention can be helpful in improving blood pressure control and possibly halting the progression of renal failure. Randomized controlled trials comparing direct stenting with other surgical methods are necessary to define the best revascularization strategy in patients with renovascular hypertension. A careful follow-up study after renal artery revascularization should evaluate possible benefits in halting the deterioration of chronic renal insufficiency.

Gadolinium-enhanced 3D MR angiography of renal artery stenosis: a pilot comparison of maximum intensity projection, multiplanar reformatting, and 3D volume-rendering postprocessing algorithms

RATIONALE AND OBJECTIVES

The authors compared diagnostic accuracy of maximum intensity projection (MIP), multiplanar reformatting (MPR), and three-dimensional (3D) volume rendering (VR) in the evaluation of gadolinium-enhanced 3D magnetic resonance (MR) angiography of the renal arteries. They hypothesized that VR is as accurate as or more accurate than MIP and MPR at depicting renal artery stenosis.

MATERIALS AND METHODS

The study group comprised 28 consecutive patients who underwent gadolinium-enhanced 3D MR angiography of the renal arteries. Studies were postprocessed to display images in MIP, MPR, and VR formats. Digital subtraction angiography (DSA), when performed (nine of 28 patients), was the standard for comparison. For each main renal artery, an estimate of percentage stenosis was made for any stenoses detected by three independent radiologists. For calculation of sensitivity, specificity, and accuracy, MR angiographic stenosis estimates were categorized as mild (0%-39%), moderate (40%-69%), or severe (> or = 70%). DSA stenosis estimates of 70% or greater were considered hemodynamically significant.

RESULTS

Analysis of variance demonstrated MIP estimates of stenosis were statistically greater than VR estimates in two readers and greater than MPR estimates in all readers for all patients. MIP images also showed the largest mean difference from DSA stenosis estimates for all three readers. For both VR and MPR, mean differences between MR angiographic stenoses estimates and DSA estimates reached significance for only one reader, whereas, for MIP versus DSA, mean differences reached significance for all three readers. Although not statistically significant compared with DSA, accuracies of VR (87%) and MPR (89%) were greater than that of MIP (81%).

CONCLUSION

In this pilot study, MIP was the least accurate of the three image display algorithms tested. VR and MPR yielded similar values for each method of comparison.

An evidence-based approach to diagnosing renovascular hypertension

Making the diagnosis of potentially reversible renovascular hypertension can be problematic. Although there are a number of noninvasive screening tests available, no one study is appropriate for every patient. In general, the available tests can be divided into those that identify the functional consequences of a renal artery obstruction (angiotensin-converting enzyme inhibitor-augmented renography) and those that identify the anatomic presence of stenosis (duplex ultrasonography, magnetic resonance angiography, and contrast tomography angiography). The most appropriate diagnostic approach is based largely on the clinical index of suspicion, the potential etiology of the renal artery lesion (fibromuscular dysplasia or atherosclerosis), and the individual patient's physiology and presentation. A potential treatment algorithm is presented.

Techniques for predicting a favourable response to renal angioplasty in patients with renovascular disease

Renovascular disease is present in some 10-40% of patients with end-stage renal disease, and constitutes the fastest-growing group of end-stage renal disease patients. The unselective correction of renal artery stenosis has led to disappointing results. Most studies that compared conservative treatment with angioplasty found only modest or no beneficial effects of angioplasty on renal function and blood pressure. It is therefore mandatory to evaluate the functional significance of a stenosis before intervention. Patients with a high likelihood of a favourable response should be identified. Factors that affect outcome include the severity of renal artery stenosis, the procedure used to treat renal artery stenosis (antihypertensive drugs, angioplasty with or without stenting, or surgery), radiocontrast nephrotoxicity, atheroembolism and, most importantly, underlying renal disease, forestalling a favourable response of renal function or blood pressure even after the successful correction of renal artery stenosis. Evaluation of the renal resistance index using Doppler ultrasound or captopril scintigraphy are the best methods by which to classify patients as responders or non-responders to intervention. Each factor has to be considered before the correction of renal artery stenosis to achieve satisfactory results with regard to an improvement in renal function and blood pressure.

Diuretic renography and angiotensin converting enzyme inhibitor renography

Renovascular hypertension and renal outlet obstruction are two clinical conditions well evaluated by nuclear medicine techniques. They both require a specific intervention to challenge a specific aspect of renal functional reserve. Diuretic renography is the oldest common example in nuclear medicine where functional change in the kidney is provoked for diagnostic purposes. The kidney's tubular functional reserve, in this instance, is challenged to induce diuresis and increase urine flow. This intervention permits diuretic renography to retain an essential role in the evaluation of hydroureteronephrosis. Captopril renography is a more recent example of a similar principle and depends on a reactive renin-angiotensin system to identify a kidney responsible for RVH. In both renal outlet obstruction and RVH, an anatomic abnormality is also identified (hydronephrosis and RAS, respectively) at some point in the diagnostic workup. The final diagnosis in each instance, however, depends on evidence for a functional disorder, provoked and measured during the radionuclide interventional examination. These serve as excellent examples of the power of functional imaging to identify specific medical disorders.

Captopril renography and the relevance of abnormal but bilateral identical curves in the diagnosis of renal artery stenosis

BACKGROUND

Captopril renography (CR) has been shown to improve the effectiveness of renal scintigraphy in renovascular hypertension, by inhibiting angiotensin-converting enzyme. CR is particularly sensitive and specific in unilateral renal artery stenosis (RAS), but results in patients with bilateral RAS are less favourable. The aim of this study was to investigate the meaning of abnormal but identical renographic curves in the diagnosis of RAS.

PATIENTS AND METHODS

One hundred and fifty-eight patients clinically suspected for renovascular hypertension underwent CR, using 50 MBq (99)Tc(m)-mercaptoacetyltriglycine ((99)Tc(m)-MAG(3)), prior to performing renal angiography. CR was performed 1 h after captopril administration. Renograms were analysed according to the consensus criteria. All patients underwent angiography, considered as the "gold standard" in the detection of the presence of RAS (stenosis >50% was defined as significant). All kidneys were categorized into three groups, scintigraphically as well as angiographically: no stenosis, unilateral stenosis and bilateral stenosis.

RESULTS

Out of 158 patients 100 (63%) showed a RAS on angiography (58 (37%) unilateral, 42 (26%) bilateral). The sensitivity and specificity of CR evaluated by patient was 83% and 75%, respectively. Thirty patients with completely identical curves were identified, 21 patients with normal curves and nine patients with abnormal identical curves. All but one patient showed no RAS on the angiogram. In this single patient a unilateral stenosis was found.

CONCLUSION

Identical curves on the renogram generally suggest no RAS and are probably due to intrinsic parenchymal disease.

Evaluation and treatment of renal artery stenosis: impact on blood pressure and renal function

The conventional non-invasive tests to diagnose renal artery stenosis in a general hypertensive population are not accurate enough for screening purposes. Magnetic resonance angiography might become the new gold standard, with the advantages of the absence of contrast toxicity, good accuracy, and information on flow characteristics. With regard to the treatment of hypertension in patients with renal artery stenosis, intervention is advised only when blood pressure cannot be controlled by at least three antihypertensive drugs. Patency after stenting is superior to angioplasty, although its clinical benefit has not been proved. As for renal function, evidence - although from uncontrolled studies - for the preservation of renal function by intervention is accumulating, especially in those patients with bilateral stenosis or stenosis in a single functioning kidney.

Renal artery stenosis: a common, treatable cause of renal failure?

Chronic azotemic renovascular disease is common in patients with atherosclerosis. Its prevalence appears to be increasing in the aging population. How often it is the primary cause of end-stage renal disease (ESRD) is not yet certain. Some studies suggest that 10%-40% of elderly hypertensive patients with newly documented ESRD and no demonstrable primary renal disease have significant renal artery stenosis (RAS). Atherosclerotic vascular occlusive disease of the renal arteries does progress, but current rates of progression and occlusion are lower than those reported a decade ago. Methods of identifying patients whose renal function is at true risk from vascular occlusive disease and determining who will benefit from intervention remain elusive. The presence of RAS in an azotemic patient can be assessed with noninvasive and risk-free radiologic techniques, including Duplex doppler velicometry and magnetic resonance angiography. Functional tests that predict the change in renal function after revascularization are not yet available. However, a renal length of greater than 7.5 cm in the absence of renal cysts and a short history of renal functional deterioration indicate a good prognosis. Patients with recent deterioration in renal function, those with bilateral renal artery stenosis or stenosis to a single functioning kidney, those with flash pulmonary edema, advanced chronic renal failure, or ESRD (who have much to gain), those with reversible azotemia during angiotensin-converting enzyme inhibitor (ACEI) or angiotensin receptor antagonist (ARB) therapy, and those whose conditions cannot be managed medically should be considered for revascularization. Results from recent controlled clinical trials of the response to percutaneous transluminal renal artery angioplasty (PTRA) and stenting indicate that improvement in blood pressure control or renal function is not a predictable outcome of renal revascularization. In azotemic groups, 25%-30% of patients achieve important recovery of renal function. Thus, significant progress has been made recently in determining whether RAS is a frequent, treatable cause of renal failure. The decision to recommend revascularization remains a difficult balance between the risks and expense of the procedure and the undoubted benefits that accrue if renal function is successfully stabilized.

Use of Doppler ultrasonography to predict the outcome of therapy for renal-artery stenosis

BACKGROUND

Prospectively identifying patients whose renal function or blood pressure will improve after the correction of renal-artery stenosis has not been possible. We evaluated whether a high level of resistance to flow in the segmental arteries of both kidneys (indicated by resistance-index values of at least 80) can be used prospectively to select appropriate patients for treatment.

METHODS

We evaluated 5950 patients with hypertension for renal-artery stenosis using color Doppler ultrasonography, and we measured the resistance index ([1 - end-diastolic velocity divided by maximal systolic velocity] x 100). Among 138 patients who had unilateral or bilateral renal-artery stenosis of more than 50 percent of the luminal diameter and who underwent renal angioplasty or surgery, the procedure was technically successful in 131 (95 percent). Creatinine clearance and 24-hour ambulatory blood pressure were measured before renal-artery stenosis was corrected; 3, 6, and 12 months after the procedure; and yearly thereafter. The mean (+/-SD) duration of follow-up was 32+/-21 months.

RESULTS

Among the 35 patients (27 percent) who had resistance-index values of at least 80 before revascularization, the mean arterial pressure did not decrease by 10 mm Hg or more after revascularization in 34 (97 percent). Renal function declined (defined by a decrease in the creatinine clearance; of at least 10 percent) in 28 (80 percent); 16 (46 percent) became dependent on dialysis and 10 (29 percent) died during follow-up. Among the 96 patients (73 percent) with a resistance-index value of less than 80, the mean arterial pressure decreased by at least 10 percent in all but 6 patients (6 percent) after revascularization; renal function worsened in only 3 (3 percent), all of whom became dependent on dialysis; and 3 (3 percent) died (P<0.001 for the comparison with patients with a resistance-index value of at least 80).

CONCLUSIONS

A renal resistance-index value of at least 80 reliably identifies patients with renal-artery stenosis in whom angioplasty or surgery will not improve renal function, blood pressure, or kidney survival.

Angioplasty of atherosclerotic and fibromuscular renal artery stenosis: time course and predicting factors of the effects on renal function

The effects of percutaneous transluminal renal angioplasty (PTRA) on the renal function of stenotic kidneys are usually assessed by evaluating the changes in serum creatinine, which is quite a rough indicator of glomerular filtration rate (GFR). In 27 hypertensive patients with 19 atherosclerotic and 11 fibromuscular significant renal artery stenoses, we investigated with renal scintigraphy the short-term (5 days) and long-term (10 months) effects of a technically successful PTRA (in seven cases combined with a stent implantation) on GFR of the stenotic and contralateral kidneys; these measurements were combined with those of plasma renin activity (PRA) and of angiotensin II (AII). We found that in short-term studies after PTRA GFR rose from 29.7 +/- 3.5 to 34.6 +/- 3.1 mL/min and from 36.9 +/- 4.0 to 45.1 +/- 4.3 mL/min, respectively, in atherosclerotic and fibromuscular poststenotic kidneys. In long-term studies GFR further and significantly increased, to 37.8 +/- 3.2 mL/min in the former group, whereas it stabilized in the latter group (46.0 +/- 3.6 mL/min). In patients with fibromuscular stenosis these changes in GFR were associated with clear-cut reductions in blood pressure (BP), PRA, and AII; these decrements also occurred in patients with atherosclerotic stenosis but to a much lesser extent. We also found that in short- and long-term studies the percent of PTRA-induced increments of GFR in the poststenotic kidneys were inversely correlated with the baseline values of GFR. In addition, the absolute and percent increments of GFR were positively correlated with the basal levels of AII. Thus the time course of the improvement in GFR after angioplasty may differ in kidneys, depending on the etiology of the stenosis, in that in those with fibromuscular stenosis it was entirely apparent within a few days whereas in those with atherosclerotic stenosis it required several months to be fully expressed. Also, it appears that the more compromised kidneys are those that benefit most from the dilatation and that AII levels are useful indicators of the possibility that the stenotic kidney will have a favorable functional outcome in terms of restoration of renal blood flow.

Evaluation of duplex ultrasound and captopril renography for detection of renovascular hypertension

BACKGROUND

Renovascular hypertension is the most common form of curable secondary hypertension and, if untreated, may lead to end-stage kidney disease. Given that renal function and hypertension may improve after renal angioplasty, it is pertinent to identify patients with renal artery stenosis. The aim of the present study was to evaluate both duplex ultrasound and captopril renography for detection of renal artery stenosis among hypertensive patients.

METHODS

To avoid selection bias, all patients referred to our center for evaluation of renovascular hypertension were asked to participate in the study. Patients were examined by intra-renal duplex ultrasound (N = 121), measuring pulsatility index and acceleration of the blood flow during early systole. In 98 patients, 99mTc-DTPA captopril renography was performed in conjunction with duplex ultrasound. Renal angiography was performed in all patients regardless of the results of the noninvasive tests.

RESULTS

The prevalence of renal artery stenosis was 19%. In the 98 patients examined by both duplex ultrasound and captopril renography, sensitivity and positive predictive values for detection of a renal artery stenosis of 50% degree or more were 84 and 76%, respectively, for duplex ultrasound, whereas captopril renography was associated with a sensitivity and positive predictive value of 68% for both (P = NS). Specificity and negative predictive values were 94 and 96%, respectively, for duplex ultrasound, whereas the corresponding values for captopril renography were 92% for both (P = NS). Specificity and negative predictive values were 94 and 96%, respectively, for duplex ultrasound, whereas the corresponding values for captopril renography were 92% for both (P = NS).

CONCLUSIONS

Both duplex ultrasound and captopril renography are associated with high specificity and negative predictive values for detection of renal artery stenosis. Sensitivity and positive predictive values are at least as good for duplex ultrasound compared with captopril renography. Given that duplex ultrasound is easier to perform and more cost effective, we propose that it should be the method of first choice when screening for renal artery stenosis in a hypertensive population.