Invited Review: “Percutaneous revascularization for ischemic nephropathy: Past, Present and Future”Stephen C. Textor, Nephrology and Hypertension, Mayo Clinic; Correspondence: Stephen C. Textor, M. D., Division of Nephrology and Hypertension, Mayo Clinic, Rochester MN 5.
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Fax: 5. 07- 2. 66- 7. Email: ude. oyam@nehpets. The publisher's final edited version of this article is available at Kidney Int.
See other articles in PMC that cite the published article. Abstract. 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.“It was the best of times, it was the worst of times, it was the age of wisdom, it was the age of foolishness, it was the epoch of belief, it was the epoch of incredulity…”Charles Dickens: A Tale of Two Cities. Introduction. Rarely have competing technical advances in medicine, as in the case of managing renal artery stenosis by endovascular stenting or antihypertensive medical therapy, become so successful over precisely the same time interval.
On the one hand, restoring blood flow to an ischemic kidney beyond vascular occlusion seems to provide an obvious means to restore kidney function and improve blood pressure, sometimes dramatically. One the other hand, prospective trials seeking to define the role for renal revascularization up to now have failed to establish a compelling added benefit for endovascular stenting when added to effective medical regimens [1][2]. Clinicians caring for patients with renovascular disease understandably find themselves confused by ambiguous clinical observations and disappointing results from prospective randomized trials. Many argue that the trials have been flawed and potentially misleading [3][4]. Issues of patient selection, statistical quirks, professional bias and flawed study designs continue to leave the role of stenting a matter of active debate and sometimes obscure basic truths that interfere with optimal patient care. To complicate matters further, newer aortic procedures for treatment of abdominal aneurysms introduce a new potential source of renal artery occlusion that can threaten kidney viability.
The purpose of this review is to place the role of renal revascularization into context as a tool for management of atherosclerotic renal disease threatening renal function and blood pressure control. PAST: Renal artery occlusion as a cause of Hypertension. It has been nearly 8. Goldblatt and Loesch established that sustained reduction of renal blood flow can raise systemic arterial pressure [5; 6].
Original Article. Preoperative Biliary Drainage for Cancer of the Head of the Pancreas. Niels A. van der Gaag, M.D., Erik A.J. Rauws, M.D., Ph.D., Casper H.J. van Eijck, M.D., Ph.D., Marco J. Bruno, M.D., Ph.D., Erwin van der. 85 4.1 ELECTRICAL MACHINES-I L. T. P 4 - 3 RATIONALE Electrical machines is a subject where a student will deal with various types of electrical machines which are employed in industries, power stations. Review Article. Mechanisms of Disease. Franklin H. Epstein, M.D., Editor. Acute-Phase Proteins and Other Systemic Responses to Inflammation. Cem Gabay, M.D., and Irving Kushner, M.D. N Engl J Med 1999; 340:448-454 February 11.
Since then, renovascular occlusion has been among the most extensively studied forms of experimental hypertension. Indeed, the premise that signals originating from the kidney could not only affect urine formation and solute excretion, but could also modify systemic hemodynamics, endocrine systems, central and peripheral nervous system pathways, vascular structure, cardiac function and systemic resistance provide the foundation for whole systems of understanding of animal and human physiology [7] [8]. From a clinical perspective, recognition that reduced renal blood flow sometimes triggers renovascular hypertension and can impair glomerular filtration provides a prototype for “secondary hypertension” that can sometimes be “cured” or “improved” after restoring kidney perfusion by revascularization. It should be emphasized that before surgical revascularization was technically possible in the 1. These sometimes included surgical thoraco- abdominal sympathectomy and/or nephrectomy to remove a “pressor” kidney [9].
Since that time, progress regarding imaging of the vascular anatomy, identification of pressor hormones from the kidney, and restoration of blood supply through endovascular methods has been stunning [1. The ability to safely reach the vascular bed of major renal arteries and to restore blood flow allows endovascular intervention for many patients that would never be considered for open surgical procedures. Initial renovascular imaging and surgical reconstruction. Vascular surgical techniques in the 1. Partly because of these developments, intravascular contrast agents and vascular imaging became important to establish the diagnosis and anatomy of vascular disease. Early imaging of the abdominal aorta was undertaken through translumbar placement of a needle for contrast injection.
EE 0301 - ELECTRICAL AND ELECTRONICS MEASUREMENTS AND INSTRUMENTATION Page No. s 17 Dynamometer type wattmeter Sawhney AK, A course in Electrical and electronic Measurement and Instrumentation, Dhanpat Rai & sons, New.
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- Invited Review: “Percutaneous revascularization for ischemic nephropathy: Past, Present and Future”.
Success at developing flexible catheters that could be introduced via a guidewire placed into the femoral artery came later and has been attributed to successful use of the “Seldinger technique” [1. This was followed by a remarkable series of technical innovations in catheter design to allow selective imaging of vascular structures and selective venous sampling, including measurement of renal vein renin levels [1.
Cooperative Study of Renovascular Hypertension. Initial success at surgically restoring renal function after acute occlusion was followed by attempts to treat renal artery stenosis to improve blood pressure control. Detailed studies of individual kidney function based on measuring inulin clearance and para- amino- hippurate (PAH) testing could identify when blood flow to the kidney had been reduced sufficiently to reduce urine flow, increase sodium reabsorption, but continued have glomerular filtration [1. The potential morbidity—and mortality—associated with renal artery surgery also led to concerns about the risks of surgical reconstruction and emphasized the need to select patients carefully that might benefit. In this context, early studies supported by the National Institutes of Health were undertaken to define clinical features, optimal imaging, diagnostic patterns and outcomes of surgery for renovascular disease [1. This landmark study provided a registry of more than 5. These studies provided a series of seminal papers regarding clinical features and comorbidity with atherosclerotic renal arterial disease [1.
These studies also identified a mortality risk above 6% associated with aortic surgery that limited the range of candidates most centers would consider for surgery. Renovascular surgery became a highly specialized clinical skill limited to high volume centers with focused interest, as Novick reviewed [1. It remains so today. Recent History: Establishing the role of vascular occlusion as a cause of renal insufficiency. In view of the complexity and potential risks, the decision to undertake surgical revascularization routinely included multiple clinicians, including hypertension specialists, nephrologists, cardiovascular specialists, radiologists and surgeons. Determining the likelihood of clinical improvement in blood pressure control was an overriding concern, moreso than any potential recovery of kidney function.
In the 1. 97. 0’s, measurement of the putative pressor signal for renovascular hypertension, plasma renin activity, became widely available and led to a series of seminal papers regarding lateralization of renin secretion from the affected kidneys [1. Early experience with surgical revascularization cast doubt that patients with reduced GFR would gain much benefit regarding blood pressure control from restoring blood supply.
Such patients routinely were excluded from consideration for renovascular surgery, based both on experimental and clinical data suggesting that parenchymal damage to the “contralateral” kidney opposite the stenotic kidney would obviate a benefit regarding blood pressure control [2. Remarkably, the concept that chronic vascular occlusion might be a reversible cause of renal insufficiency surfaced only in the 1. Recognition that atherosclerotic disease poses a risk of progressive vascular occlusion that could be stabilized or reversed regarding renal failure gradually led some centers to shift from “cure of hypertension” to “preservation of renal function” as a primary indication for revascularization [2. Identification of the concept of “critical perfusion pressure” for continued renal function that could be reversed by restoring renal blood flow supported this premise [2.