Diagnostic criteria for renovascular disease: where are we now?

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.

Blunt renal trauma-induced hypertension in pediatric patients: a single-center experience

PURPOSE

Children have a greater chance of sustaining a renal injury than adults and higher odds of having a high-grade renal injury. Hypertension is a rare complication of blunt renal trauma, with risk being higher in cases of major renal trauma. We reviewed the cases of pediatric blunt renal trauma-induced hypertension in our tertiary referral center in an attempt to better understand this rare condition.

STUDY DESIGN

A retrospective evaluation of children under the age of 18 who were admitted to our department during the last 20 years and were diagnosed with blunt renal trauma.

RESULTS

Twenty-three children presented with blunt renal trauma, one of whom was treated with emergency nephrectomy. Four children (18%) developed post-traumatic hypertension. All four cases were associated with a reduction in blood flow to the kidney, either through injury to the renal artery (in three cases) or through extrinsic compression of the kidney by a large perirenal hematoma (Page kidney; in one case). The Page kidney case developed hypertension during the initial hospitalization, and it resolved spontaneously after five months through the gradual resorption of the perirenal hematoma. Among the three cases of renal artery injury, hypertension during the initial hospitalization was only observed in one case, with hypertension in the other two cases manifesting after two months and four years, respectively. All three cases of renal artery injury resulted in a complete loss of function of the injured kidney, and two cases were treated with nephrectomy. Following nephrectomy, the blood pressure level returned to normal within a few days.

DISCUSSION

Development of hypertension following a blunt renal trauma can be heterogenous, with the time of manifestation stretching between days after the accident and years thereafter. Children have a higher risk of renal trauma and, according to published data out of the National Trauma Data Bank, a 20-times higher risk of renal artery injury in comparison to the adult population. Large multicenter studies are required to answer the question of whether children are therefore more prone to blunt renal trauma-induced hypertension than adults.

CONCLUSIONS

Our study highlights the importance of blood pressure monitoring in children following blunt renal trauma, as post-traumatic hypertension can develop even years after the accident. In cases of a poorly functioning kidney, nephrectomy may be regarded as a curative therapy.

Ischemic Nephropathy Following Occlusion of Abdominal Aortic Aneurysm Graft: A Case Report

In this report, we present a case of a 55-year-old female with a past medical history of abdominal aortic aneurysm (AAA) graft, femoral-femoral bypass graft, questionable history of chronic kidney disease (CKD), abdominal hernia repair, alcoholic pancreatitis, chronic abdominal pain on opioids, and tobacco abuse who presented with acute on chronic abdominal pain with an unexplained rise of creatinine and anuria. The patient was found to have complete occlusion of AAA graft and was determined to have ischemic nephropathy (IN).

Atherosclerotic-nephropathy: an updated narrative review

The increased prevalence of chronic kidney disease (CKD) in elderly patients recognizes, as main cause, the long-term exposure to atherosclerosis and hypertension. Chronic ischemic damage due to critical renal arterial stenosis induces oxidative stress and intra-renal inflammation, resulting in fibrosis and microvascular remodelling, that is the histological picture of atherosclerotic renal vascular disease (ARVD). The concomitant presence of a long history of hypertension may generate intimal thickening and luminal narrowing of renal arteries and arterioles, glomerulosclerosis, interstitial fibrosis and tubular atrophy, more typically expression of hypertensive nephropathy. These complex mechanisms contribute to the development of CKD and the progression to End Stage Kidney Disease. In elderly CKD patients, the distinction among these nephropathies may be problematic; therefore, ischemic and hypertensive nephropathies can be joined in a unique clinical syndrome defined as atherosclerotic nephropathy. The availability of novel diagnostic procedures, such as intra-vascular ultrasound and BOLD-MRI, in addition to traditional imaging, have opened new scenarios, because these tools allow to identify ischemic lesions responsive to renal revascularization. Indeed, although trials have deflated the role of renal revascularization on the renal outcomes, it should be still used to avoid dialysis initiation and/or to reduce blood pressure in selected elderly patients at high risk. Nonetheless, lifestyle modifications (smoking cessation, increased physical activity), statins and antiplatelet use, as well as cautious use of renin-angiotensin system inhibitors, remain the main therapeutic approach aimed at slowing the renal damage progression. Mesenchymal stem cells and Micro-RNA are promising target of anti-fibrotic therapy, which might provide potential benefit in ARVD patients, though safety and efficacy profile in humans is unknown too.

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.

Diagnostic Role of Renal Doppler Ultrasound and Plasma Renin Activity as Screening Tools for Renovascular Hypertension in Children

OBJECTIVES

The diagnostic role of an ultrasound (US) and plasma renin activity (PRA) combination is unknown, despite the usefulness of Doppler US as a screening tool for renovascular hypertension (RVHT). The purpose of this study was to evaluate the diagnostic usefulness of US for RVHT in children stratified according to PRA.

METHODS

We identified 336 children who underwent renal Doppler US examinations for hypertension and divided them into a high-renin group (n = 177) and a normal-renin group (n = 159) based on PRA and stratified them by age. The Doppler US findings were retrospectively reviewed, and computed tomographic angiography (CTA) for the same children was used as the reference standard.

RESULTS

In the high-renin group, 36 patients had positive Doppler US findings that were confirmed by CTA in 32 cases. The sensitivity and specificity values for Doppler US in the high-renin group were 84.2% and 93.6%, respectively. In the normal-renin group, 10 patients had positive Doppler US findings; these positive findings were confirmed by CTA in 9 cases. The sensitivity and specificity values for US in the normal-renin group were 100.0% and 100.0%. There were anatomic variations (n = 3) and segmental artery stenosis (n = 2) among the cases with false-negative US findings, which were confirmed by CTA.

CONCLUSIONS

If patients have high PRA, a Doppler US examination should be performed with caution to avoid false-negative detection. If patients have normal PRA, renal Doppler US might be adequate for diagnosis of RVHT to avoid unnecessary CTA.

Renal Arterial Disease and Hypertension

Renal artery disease produces a spectrum of progressive clinical manifestations ranging from minor degrees of hypertension to circulatory congestion and kidney failure. Moderate reductions in renal blood flow do not induce tissue hypoxia or damage, making medical therapy for renovascular hypertension feasible. Several prospective trials indicate that optimized medical therapy using agents that block the renin-angiotensin system should be the initial management. Evidence of progressive disease and/or treatment failure should allow recognition of high-risk subsets that benefit from renal revascularization. Severe reductions in kidney blood flow ultimately activate inflammatory pathways that do not reverse with restoring blood flow alone.

To Stent or Not to Stent? Update on Revascularization for Atherosclerotic Renovascular Disease

Renal artery stenosis (RAS) is increasingly encountered in clinical practice. The two most common etiologies are fibromuscular dysplasia (FMD) and atherosclerotic renal artery disease (ARAS), with the latter accounting for the vast majority of cases. Significant RAS activates the renin-angiotensin-aldosterone system and is associated with three major clinical syndromes: ischemic nephropathy, hypertension, and destabilizing cardiac syndromes. Over the past two decades, advancements in diagnostic and interventional techniques have led to improved detection and the widespread use of endovascular renal artery revascularization strategies in the management of ARAS. However, renal artery stenting for ARAS remains controversial. Although several studies have demonstrated some benefit with renal artery revascularization, this has not been to the extent anticipated or predicted. Moreover, these trials have significant flaws in their study design and are hampered with inherent bias which make their interpretation challenging. In this review, we evaluate the existing body of evidence and offer an approach to the management of patients with ARAS in light of the current literature. From the data provided, identification of subgroup of patients, namely, those with a hemodynamically significant RAS in the context of progressive renal insufficiency and/or deteriorating arterial hypertension, seems possible and may derive clinical benefit from ARAS stent revascularization. Appropriate patient selection is therefore the key and more robust studies are required.

Progress in the treatment of atherosclerotic renovascular disease: the conceptual journey and the unanswered questions

Over the past decades, management of atherosclerotic renovascular disease (ARVD) has undergone significant progress, in parallel with increased knowledge about the complex pathophysiology of this condition. Modern multi-targeted medical management of atherosclerosis has driven a change in both the natural history and the clinical outcomes of ARVD. Progression to total renal artery occlusion is a much less common occurrence and while early studies have reported that up to 41% of patients reached renal end-points over a mean follow-up of 44 months, the latest randomized controlled trials have shown that progressive renal impairment occurs in 16-22% of patients, with <8% of patients reaching end-stage kidney disease (ESKD) over a similar time-frame. However, the results of the latest large ARVD trials investigating the effect of renal stenting upon clinical outcomes have been influenced by selection bias as high-risk patients with clinically significant renal artery stenosis (RAS) have largely been excluded from these studies. Although the neutral results of these trials have shown uncertainty about the role of revascularization in the management of patients with ARVD, there is evidence that revascularization can optimize outcomes in selected patients with a high-risk clinical phenotype. Future challenges lie in identifying important subgroups of patients with critical RAS and viable kidneys, while continuing to develop strategies to protect the renal parenchyma and hence improve clinical outcomes.

From the 1990s to CORAL (Cardiovascular Outcomes in Renal Atherosclerotic Lesions) trial results and beyond: does stenting have a role in ischemic nephropathy?

The prevalence of atherosclerotic renal artery stenosis is high, ∼7% in individuals older than 65 years and ∼50% in patients with diffuse arterial disease, and it is increasingly frequent in an aging population. About 10% to 15% of atherosclerotic renal artery stenosis cases lead to the development of resistant hypertension and/or ischemic nephropathy. The management of ischemic nephropathy may include medical therapy and/or revascularization. In the past, revascularization required surgical bypass or endarterectomy, accompanied by the morbidity and mortality associated with a major surgical procedure. During the last few decades, less invasive endovascular procedures such as percutaneous transluminal renal artery angioplasty with stent placement have become available. At the same time, new antihypertensive and cardiovascular drugs have been developed, which may preclude revascularization, at least in some cases. The indications of each of these therapeutic options have changed over time. This review offers a temporal perspective on the course of technical and scientific advances and the accompanying change in clinical practice for the treatment of ischemic nephropathy. The latest randomized clinical trials, including the CORAL (Cardiovascular Outcomes in Renal Atherosclerotic Lesions) trial, the largest on the subject, as well as a meta-analysis of these studies, have indicated that the best approach is medical therapy alone. There is evidence that revascularization brings no additional benefit, at least in low-risk and stable atherosclerotic renal artery stenosis. High-risk patients, especially those with recurrent flash pulmonary edema, could benefit from percutaneous transluminal renal artery angioplasty and stent placement, but there is no definitive evidence and the treatment choice should take into account the risks and potential benefits of the procedure.

Endothelin-a receptor antagonism after renal angioplasty enhances renal recovery in renovascular disease

Percutaneous transluminal renal angioplasty/stenting (PTRAS) is frequently used to treat renal artery stenosis and renovascular disease (RVD); however, renal function is restored in less than one half of the cases. This study was designed to test a novel intervention that could refine PTRAS and enhance renal recovery in RVD. Renal function was quantified in pigs after 6 weeks of chronic RVD (induced by unilateral renal artery stenosis), established renal damage, and hypertension. Pigs with RVD then underwent PTRAS and were randomized into three groups: placebo (RVD+PTRAS), chronic endothelin-A receptor (ET-A) blockade (RVD+PTRAS+ET-A), and chronic dual ET-A/B blockade (RVD+PTRAS+ET-A/B) for 4 weeks. Renal function was again evaluated after treatments, and then, ex vivo studies were performed on the stented kidney. PTRAS resolved renal stenosis, attenuated hypertension, and improved renal function but did not resolve renal microvascular rarefaction, remodeling, or renal fibrosis. ET-A blocker therapy after PTRAS significantly improved hypertension, microvascular rarefaction, and renal injury and led to greater recovery of renal function. Conversely, combined ET-A/B blockade therapy blunted the therapeutic effects of PTRAS alone or PTRAS followed by ET-A blockade. These data suggest that ET-A receptor blockade therapy could serve as a coadjuvant intervention to enhance the outcomes of PTRAS in RVD. These results also suggest that ET-B receptors are important for renal function in RVD and may contribute to recovery after PTRAS. Using clinically available compounds and techniques, our results could contribute to both refinement and design of new therapeutic strategies in chronic RVD.

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.

Management of atherosclerotic renovascular disease after Cardiovascular Outcomes in Renal Atherosclerotic Lesions (CORAL)

Many patients with occlusive atherosclerotic renovascular disease (ARVD) may be managed effectively with medical therapy for several years without endovascular stenting, as demonstrated by randomized, prospective trials including the Cardiovascular Outcomes in Renal Atherosclerotic Lesions (CORAL) trial, the Angioplasty and Stenting for Renal Artery Lesions (ASTRAL) trial and the Stent Placement and Blood Pressure and Lipid-Lowering for the Prevention of Progression of Renal Dysfunction Caused by Atherosclerotic Ostial Stenosis of the Renal Artery (STAR) and ASTRAL. These trials share the limitation of excluding subsets of patients with high-risk clinical presentations, including episodic pulmonary edema and rapidly progressing renal failure and hypertension. Although hemodynamically significant, ARVD can reduce renal blood flow and glomerular filtration rate; adaptive mechanisms preserve both cortical and medullary oxygenation over a wide range of vascular occlusion. Progression of ARVD to severe vascular compromise eventually produces cortical hypoxia, however, associated with active inflammatory cytokine release and cellular infiltration of the renal parenchyma. In such cases ARVD produces a loss of glomerular filtration rate that no longer is reversible simply by restoring vessel patency with technically successful renal revascularization. Each of these trials reported adverse renal functional outcomes ranging between 16 and 22% over periods of 2-5 years of follow-up. Blood pressure control and medication adjustment may become more difficult with declining renal function and may prevent the use of angiotensin receptor blocker and angiotensin-converting enzyme inhibitors. The objective of this review is to evaluate the current management of ARVD for clinical nephrologists in the context of recent randomized clinical trials and experimental research.

Pregnancy and delivery in women with renovascular hypertension due to multiple intrarenal microaneurysms: a report of two cases

We herein report two cases of pregnant women who had chronic hypertension caused by renovascular hypertension due to multiple intrarenal microaneurysms from unknown causes, who had similar clinical courses. During the first pregnancy, both women developed uncontrollable severe hypertension that finally led to superimposed preeclampsia; however, during the second pregnancy, the blood pressure was controlled well, and the clinical courses were uneventful. These cases suggest that an uneventful term delivery may be achieved with adequate blood pressure control in pregnant women with chronic hypertension caused by renovascular hypertension, and a prior eventful clinical course of delivery does not affect the subsequent clinical course.