Renal vein renin measurements accurately identify renovascular hypertension caused by total occlusion of the renal artery

Revascularization for Renovascular Disease: A Scientific Statement From the American Heart Association

Renovascular disease is a major causal factor for secondary hypertension and renal ischemic disease. However, several prospective, randomized trials for atherosclerotic disease failed to demonstrate that renal revascularization is more effective than medical therapy for most patients. These results have greatly reduced the generalized diagnostic workup and use of renal revascularization. Most guidelines and review articles emphasize the limited average improvement and fail to identify those clinical populations that do benefit from revascularization. On the basis of the clinical experience of hypertension centers, specialists have continued selective revascularization, albeit without a summary statement by a major, multidisciplinary, national organization that identifies specific populations that may benefit. In this scientific statement for health care professionals and the public-at-large, we review the strengths and weaknesses of randomized trials in revascularization and highlight (1) when referral for consideration of diagnostic workup and therapy may be warranted, (2) the evidence/rationale for these selective scenarios, (3) interventional and surgical techniques for effective revascularization, and (4) areas of research with unmet need.

A simple, refined approach to diagnosing renovascular hypertension in children: A 10-year study

BACKGROUND

Despite advances in non-invasive vascular imaging, detection of renal artery stenosis via catheter angiography is the criterion standard for the diagnosis of renovascular hypertension (RVH). However, because of lack of evidence, the utility of various blood tests and imaging modalities remains unclear.

METHODS

We retrospectively analyzed the utility of blood tests (plasma renin activity [PRA], aldosterone, and renal vein renin [RVR] values) and imaging studies (computed tomography angiography [CTA], kidney ultrasonography [US]) by comparing them with catheter angiography. Ten pediatric patients with RVH at two institutions from January 2008 to December 2017 were recruited. The sensitivities for diagnosing RVH via imaging and blood tests (kidney [US], PRA, and aldosterone) were derived by examining patient records. Furthermore, the sensitivity and specificity of CT angiography were calculated by considering both the affected and non-affected renal arteries of the patients.

RESULTS

A high sensitivity for diagnosing RVH via kidney US (89%) and PRA (80%) was observed. The sensitivity and specificity of CTA were 100%, each. RVR sampling did not aid in the diagnosis of RVH; only two of six patients with unilateral RVH showed significant laterality of RVR boundary ratios. Renal scintigraphy facilitated detection of a non-functional kidney (split renal function <5%).

CONCLUSIONS

RVH in children could be diagnosed utilizing non-invasive blood and imaging tests, without catheter angiography. We recommend kidney length measurement along with measurement of PRA level, as a simple and highly useful screening test, followed by CTA as a diagnostic test.

Atherosclerotic Renal Artery Stenosis: Should we Intervene Earlier?

Purpose of Review

Randomized trials have failed to show clinical benefit in patients with atherosclerotic renal artery stenosis who were treated with angioplasty with or without stenting. However, these studies were done in patients with a high-grade stenosis. This paper examines whether there are arguments to consider patients with low-grade stenosis for angioplasty.

Recent Findings

Patients with low-grade (< 50%) atherosclerotic renal artery stenosis have an excess risk for cardiovascular and renal complications. This could be related to inflammatory factors being generated by the stenotic kidney. Moreover, even a kidney with low-grade stenosis clears less or produces more of the natural nitric oxide inhibitor ADMA.

Summary

Patients with low-grade atherosclerotic renal artery stenosis have an increased risk for a variety of complications. In addition, the abnormality is progressive. There is a case for setting up a prospective trial to examine whether angioplasty confers benefit in patients with low-grade renal artery stenosis.

Hypertension: The role of biochemistry in the diagnosis and management

Hypertension is defined as a persistently elevated blood pressure ≥140/90mmHg. It is an important treatable risk factor for cardiovascular disease, with a high prevalence in the general population. The most common cause, essential hypertension, is a widespread disease - however, secondary hypertension is under investigated and under diagnosed. Collectively, hypertension is referred to as a "silent killer" - frequently it displays no overt symptomatology. It is a leading risk factor for death and disability globally, with >40% of persons aged over 25 having hypertension. A vast spectrum of conditions result in hypertension spanning essential through resistant, to patients with an overt endocrine cause. A significant number of patients with hypertension have multiple cardiovascular risk factors at the time of presentation. Both routine and specialised biochemical investigations are paramount for the evaluation of these patients and their subsequent management. Biochemical testing serves to identify those hypertensive individuals who are at higher risk on the basis of evidence of dysglycaemia, dyslipidaemia, renal impairment, or target organ damage and to exclude identifiable causes of hypertension. The main target of biochemical testing is the identification of patients with a specific and treatable aetiology of hypertension. Information gleaned from biochemical investigation is used to risk stratify patients and tailor the type and intensity of subsequent management and treatment. We review the approach to the biochemical investigation of patients presenting with hypertension and propose a diagnostic algorithm for work-up.

Mild Renal Artery Stenosis Can Induce Renovascular Hypertension and is Associated with Elevated Renal Vein Renin Secretion

Renovascular hypertension is a syndrome which encompasses the physiological response of the kidney to changes in renal blood flow and renal perfusion pressure. Such physiological changes can occur with renal artery occlusion irrespective of the severity of the lesion. We have analyzed hypertensive patients with mild renal artery stenosis and compared them to patients with no stenosis. Renal vein renin sampling from catheterization of the renal vein was performed in all these patients. Patients with mild stenosis had higher renal vein renin ratio (3.01 ± 1.5) than the patients with no stenosis (1.10 ± 0.29; p = 0.002). Patients with mild stenosis were also found to have higher diastolic blood pressure and renal artery resistive indices when compared to patients with no stenosis. We therefore conclude that mild stenosis can precipitate renin-mediated hypertension in renovascular stenosis and also emphasis that parameters pertinent to renal physiology need to be evaluated before considering treatment options in patients with renal artery stenosis and medical management with RAAS blockade is the preferred modality of therapy for patients with renin-mediated hypertension.

Reninoma: the importance of renal vein renin ratios for lateralisation and diagnosis

BACKGROUND/AIM

Reninomas are rare juxtaglomerular tumours which can cause severe hypertension and hypokalaemia. Diagnosis can be problematic and these tumours can be difficult to locate on imaging. In this report we aim to demonstrate the value of carefully performed renal vein renin ratios (RVRRs) to assist in locating these tumours.

METHOD/RESULTS

We report on 3 patients diagnosed with reninoma in our unit. The patients were all female, young (17, 16 and 30 years), severely hypertensive and hypokalaemic (2.5, 2.5 and 3.1 mmol/l). Plasma renin activity (PRA) was elevated (31.9, 274 and 175 ng/ml/h), and aldosterone was high-normal (19.9 ng/dl) or elevated (207 and 109.3 ng/dl). Renal artery stenosis was excluded by renal artery Doppler, DTPA scan and angiography. Renal CT detected the lesion in 2 patients, with one lesion visible on pre- and post-contrast CT and the other on post-contrast CT only. RVRRs were performed several weeks after withdrawing interfering medications, maintaining a <40 mmol/day low-sodium diet and maintaining recumbency overnight the night before and during the procedure. Ratios before and after captopril or enalaprilat administration were obtained and lateralised the tumours in all 3 cases (dominant/non-dominant ratios of 2.3, 4.3 and 3.8). All of the patients underwent nephrectomy yielding a typical juxtaglomerular tumour and resulting in cure of hypertension and hypokalaemia.

CONCLUSIONS

Reninoma should be suspected in young hypertensives (especially females) with significant hypokalaemia and high PRA or direct renin concentration after renovascular hypertension has been excluded. CT imaging and carefully performed RVRRs provide the highest likelihood of locating these tumours.

Marked improvement of renal failure and severe hypertension after renal artery stenting in the solitary functioning kidney

Atherosclerotic renal artery stenosis (ARAS) can cause resistant hypertension, progressive renal failure and/or cardiorenal syndrome. Although no randomized study to demonstrate the superiority of renal stenting over medical treatment is available, a case-sensitive approach is required for the treatment of ARAS. Here, we describe a case report of a symptomatic ARAS patient with a solitary functioning kidney in which successful detection of ARAS by ultrasonography examination with the Doppler method and timely renal artery stenting were performed. <Learning objective: The clinical efficacy of renal artery stenting for symptomatic ARAS as a method of lowering blood pressure and preventing deterioration in renal function remains unproven. However, renal artery stenting performed based on enough investigation of clinical course and information by ultrasonography examination with Doppler method results in benefit to the patient with ARAS.>.

Percutaneous revascularization for ischemic nephropathy: the past, present, and future

Occlusion of the renal arteries can threaten the viability of the kidney when severe, in addition to accelerating hypertension and circulatory congestion. Renal artery stenting procedures have evolved from a treatment mainly for renovascular hypertension to a maneuver capable of recovering threatened renal function in patients with “ischemic nephropathy” and improving management of congestive heart failure. Improved catheter design and techniques have reduced, but not eliminated hazards associated with renovascular stenting. Expanded use of endovascular stent grafts to treat abdominal aortic aneurysms has introduced a new indication for renal artery stenting to protect the renal circulation when grafts cross the origins of the renal arteries. Although controversial, prospective randomized trials to evaluate the added benefit of revascularization to current medical therapy for atherosclerotic renal artery stenosis until now have failed to identify major benefits regarding either renal function or blood pressure control. These studies have been limited by selection bias and have been harshly criticized. While studies of tissue oxygenation using blood oxygen level dependent (BOLD) MR establish that kidneys can adapt to reduced blood flow to some degree, more severe occlusive disease leads to cortical hypoxia associated with microvascular rarefication, inflammatory injury and fibrosis. Current research is directed toward identifying pathways of irreversible kidney injury due to vascular occlusion and to increase the potential for renal repair after restoring renal artery patency. The role of nephrologists likely will focus upon recognizing the limits of renal adaptation to vascular disease and identifying kidneys truly at risk for ischemic injury at a time point when renal revascularization can still be of benefit to recovering kidney function.

Osteogenesis imperfecta with right renal artery occlusion

We here report a case of osteogenesis imperfecta who presented with severe hypertension and left ventricular failure and had right renal artery occlusion. The case is very interesting as renal artery occlusion has not been reported earlier in osteogenesis imperfecta.

Endovascular intervention for renal artery stenosis

Renovascular diseases are common conditions with important implications on cardiovascular morbidity and mortality. Renal artery stenosis (RAS) is present in 1-5% of patients with hypertension (HTN) in the US with the vast majority of caused by atherosclerosis. Atherosclerotic RAS is related not only to uncontrolled HTN, but also to renal dysfunction. Atherosclerotic RAS in the USA has been reported to account for approximately 14-16% of new patients requiring dialysis each year. Hence a concerted effort was made in the last decade to treat renovascular stenosis using newly developed endovascular therapies to improve cardiovascular morbidity and renal function. A review on new advances in the endovascular management of renal artery stenosis with low profile stents, embolic protection devices, and drug eluting stents is presented.

Renovascular hypertension and ischemic nephropathy

Renovascular disease remains among the most prevalent and important causes of secondary hypertension and renal dysfunction. Many lesions reduce perfusion pressure including fibromuscular diseases and renal infarction, but most are caused by atherosclerotic disease. Epidemiologic studies establish a strong association between atherosclerotic renal-artery stenosis (ARAS) and cardiovascular risk. Hypertension develops in patients with renovascular disease from a complex set of pressor signals, including activation of the renin-angiotensin system (RAS), recruitment of oxidative stress pathways, and sympathoadrenergic activation. Although the kidney maintains function over a broad range of autoregulation, sustained reduction in renal perfusion leads to disturbed microvascular function, vascular rarefaction, and ultimately development of interstitial fibrosis. Advances in antihypertensive drug therapy and intensive risk factor management including smoking cessation and statin therapy can provide excellent blood pressure control for many individuals. Despite extensive observational experience with renal revascularization in patients with renovascular hypertension, recent prospective randomized trials fail to establish compelling benefits either with endovascular stents or with surgery when added to effective medical therapy. These trials are limited and exclude many patients most likely to benefit from revascularization. Meaningful recovery of kidney function after revascularization is limited once fibrosis is established. Recent experimental studies indicate that mechanisms allowing repair and regeneration of parenchymal kidney tissue may lead to improved outcomes in the future. Until additional staging tools become available, clinicians will be forced to individualize therapy carefully to optimize the potential benefits regarding both blood pressure and renal function for such patients.

The role of percutaneous revascularization for renal artery stenosis

Renal artery stenosis (RAS) is usually caused by atherosclerosis or fibromuscular dysplasia. RAS leads to activation of the renin-angiotensin-aldosterone system and may result in hypertension, ischemic nephropathy, left ventricular hypertrophy and congestive heart failure. Management options include medical therapy and revascularization procedures. Recent studies have shown angiotensin receptor blockers (ARB) and angiotensin converting enzyme inhibitors (ACE-I) to be highly effective in treating the hypertension associated with RAS and in reducing cardiovascular events; however, they do not correct the underlying RAS and loss of renal mass may continue. Renal artery angioplasty was first performed by Gruntzig in 1978. The routine use of stents has increased technical success rates compared with angioplasty, and surgery is now only rarely performed. Although numerous case series claimed benefit in terms of blood pressure control, no adequately powered randomized, controlled, prospective study of renal artery interventions has reported their effect on cardiovascular morbidity or mortality. The CORAL trial, an ongoing study of renal artery stent placement and optimal medical therapy (OMT) funded by the National Institutes of Health, is the first study to attempt to do so. Until the CORAL trial results are in, physicians will continue to be faced with difficult choices when determining the optimal management for RAS patients and deciding which, if any, patients should be offered revascularization.

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.

[Abdominal aortic aneurysm and renovascular disease]

Recent technological advances in the diagnosis and therapy of abdominal aortic aneurysm and renovascular disease are continuing to bring about changes in the way patients suffering from these conditions are treated. The prevalence of both these conditions is increasing. This is due to greater life-expectancy in patients with arteriosclerosis, a pathogenetic factor underlying both conditions. The application of diagnostic imaging techniques to non-vascular conditions has led to the early diagnosis of abdominal aortic aneurysm. Clinical suspicion of reno-vascular disease can be confirmed easily using high-resolution diagnostic imaging modalities such as CT angiography and magnetic resonance angiography. Endovascular intervention is successfully replacing conventional surgical repair techniques, with the result that it may be possible to improve outcome in both conditions using effective and minimally invasive approaches. Future technological developments will enable these endovascular techniques to be applied in the large majority of patients with abdominal aortic aneurysm or renovascular disease.

Renovascular Hypertension: Current Concepts

Hypertension produced by renal artery occlusive disease is an important secondary form of hypertension. Clinicians commonly encounter forms of renal arterial disease of varying severity, many of which are of little hemodynamic significance when first detected. Experimental studies emphasize that transient activation of the renin-angiotensin-aldosterone system is necessary for initiation of renovascular hypertension. At some point, angiotensin II activates additional mechanisms responsible for sustained increased blood pressure including sodium retention, endothelial dysfunction, and vasoconstriction related to production of reactive oxygen species. Widespread application of agents that block the renin-angiotensin system, including angiotensin-converting enzyme inhibitors and angiotensin-receptor blockers, render many patients with unilateral renal arterial disease manageable primarily by medical means for many years. In the setting of high a priori likelihood of renovascular disease, recognizing the potential for disease progression during medical therapy and individually evaluating the risks and benefits of renal revascularization are important tasks. Recent prospective studies show limited, but real, benefit regarding blood pressure control for patients with atherosclerotic disease. Whether earlier renal revascularization offers benefits regarding improved morbidity and mortality from cardiovascular end point reduction is an important question to be addressed in multicenter, prospective, randomized trials. Our paradigm stresses the fact that patients with renovascular hypertension require intensive blood pressure control and cardiovascular risk factor intervention, both before and after revascularization. Hence, management of such patients requires close attention and periodic review regarding restenosis and progression of vascular disease.

Renal angioplasty and stenting with distal protection of the main renal artery in ischemic nephropathy: early experience

PURPOSE

We present a retrospective review of a single tertiary hospital experience in renal artery stent revascularization with distal protection in patients with ischemic nephropathy. The objectives of the study included preliminary assessment of the effect of distal protection on procedure-related acute deterioration in renal function and on renal salvage.

MATERIAL AND METHODS

All patients had significant atherosclerotic main renal artery stenosis, documented at preprocedural imaging, and a degree of chronic renal impairment before revascularization. Forty-six renal arteries were treated in 37 patients with preprocedural renal impairment, which was mild in 10 patients, moderate in 19 patients, and severe in 8 patients. Median patient age was 72 years (range, 59-85 years). All patients underwent primary stenting of renal artery ostial stenoses with adjuvant use of a filter device (Angioguard guide wire system; Cordis Corp, Division of Johnson & Johnson, Miami, Fla) in the distal main renal artery. The filter baskets were recaptured for pathologic analysis.

RESULTS

Overall, in 95% of patients, including all patients with preprocedural mild or moderate renal impairment, renal function was stabilized or improved after revascularization. In 5% of patients decline in renal function was unchanged. No patients had acute postprocedural deterioration. Mean follow-up was 12.5 months (range, 2-28 months). These results are better than in most reports in the literature and also better than in a historical group of similar patients with ischemic nephropathy who underwent stent revascularization without distal protection at the same institution. The improved results are thought to be due to prevention of cholesterol atheroembolization during the procedure by the distal filter baskets. Sixty-five percent of the distal protection baskets contained embolic material, including fresh thrombus, chronic thrombus, atheromatous fragments, and cholesterol clefts.

CONCLUSION

A distal protection device may significantly improve results during stent revascularization. There are a number of unique demands on a renal protection device, and the ideal device has not yet been developed.

Managing renal arterial disease and hypertension

Treating patients with renovascular disease is complex, particularly as imaging and medical techniques become more effective. Atherosclerotic renal artery disease is present in 7% of the general population above age 65 and in 20 to 45% of patients with coronary disease or aortoiliac disease. Most patients are treated medically, but when progressive hypertension, renal insufficiency, or circulatory congestion develops, revascularization should be considered. Endovascular procedures with arterial stents are now widely employed. These procedures sometimes offer major benefits in blood pressure control and stabilization of renal function. Stent procedures continue to entail hazards, including atheroemboli, arterial dissections, and thrombosis, in addition to restenosis rates of 14 to 20%. Small, randomized trials to date demonstrate no survival benefit to either endovascular or surgical revascularization as compared with medical management. Recognizing renal artery disease and directing revascularization procedures to those with the most benefit remains a premier challenge for the clinician.