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Query: UMLS:C0920646 (renal ischemia)
 2,515 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Atherosclerotic disease is the most common pathologic condition of renal artery stenosis, which typically compromises the ostium or the proximal 1-2 cm of renal arteries and is also usually present in the abdominal aorta. Fibromuscular dysplasia is the second most common cause of renal artery stenosis (RAS) which usually involves the distal two-third of the main renal artery with bed-like stenosis alternating with small fusiform or saccular aneurysms. Magnetic Resonance Angiography (MRA) was initially performed without contrast media injection using two- or three-dimensional Time-of-Flight (TOF) or Phase-Contrast (PC) techniques. Sensitivity and specificity of non-enhanced MRA in detection of proximal RAS are comprised between 53%-100% and 47%-97% respectively (table I). Main limitations of non-enhanced MRA are the long acquisition time, i.e. 5-8 min, the short field of view with lack of kidney visualization and major artifacts. Recent improvements allowed a three-dimensional acquisition during a single breath-hold (18-23 sec), associated to a bolus injection of a gadolinium chelate demonstrating a lack of nephrotoxicity. 3D gadolinium-enhanced ultrafast gradient-echo MRA techniques (3D enhanced-MRA) requires a precise technique. Firstly, kidney localization and morphologic imaging is performed before a 3D MRA data acquisition without injection (fig. 1). Secondly two successive 3D MRA sequences are performed synchronized with the gadolinium chelate bolus injection: the first acquisition corresponds to the arterial enhancement (fig. 4) and the second one to the venous enhancement. At last, a three-dimensional phase contrast could also be performed. After data acquisition, image post-processing is performed including image subtraction, maximum intensity projection (MIP) and reformation images of each renal artery, the abdominal aorta and its main branches (fig. 2, 3). The normal findings, pitfalls and anatomic variation are explained in detail. Particularly, when 3D enhanced MR angiography shows a normal artery, it is considered to be normal. It is also important to be aware of the existence of accessory or aberrant renal arteries that are well diagnosed by 3D enhanced MRA in 75% to 100% of the cases (fig. 2). 3D enhanced-MR angiography present several advantages in comparison to nonenhanced MRA: 1) a great field-of-view (30-36 cm) could be used allowing visualization of the abdominal aorta as well as its main branches; 2) the fast acquisition time allows an arterial imaging followed by a venous enhancement; 3) the kidneys are analyzed: kidney length, cortical thickness, corticomedullary differentiation and renal enhancement are well evaluated; 4) an accurate sensitivity and specificity in detection of proximal RAS comprised between 88%-100% and 71%-100% respectively (table II). Because a severe RAS (i.e. degree of stenosis > 50%) may cause renal ischemia leading to a blood pressure elevation that is often difficult to control with medical therapy, imaging has to assess the severity of RAS. MRA assessment of hemodynamic significance of RAS can be further refined by considering additional factors (fig. 4): arterial stop of signal, post stenotic dilatation, delayed renal enhancement and functional changes in the renal parenchyma (i.e. reduced kidney length and parenchymal thickness, loss of corticomedullary differentiation) (fig. 1). Precise evaluation of degree of stenosis requires the development of dedicated software such as MARACAS (MAgnetic Resonance Angiography Computer ASsisted analysis) software (fig. 5). In conclusions, 3D enhanced MRA allows an accurate diagnosis of proximal RAS, mainly due to atherosclerosis, without the risks associated with nephrotoxic contrast agents, ionizing radiation or arterial catheterization.
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PMID:[Diagnosis of renal artery stenosis with magnetic resonance angiography and stenosis quantification]. 1114 91

The general use of bilateral rather than separate renal function evaluation has led to the publication of conflicting results concerning the effect of percutaneous transluminal renal angioplasty (PTRA) on renal function, especially in patients with atherosclerotic renal artery stenosis. The aim of this study was to evaluate prospectively, in standardized conditions, split renal function (SRF) and GFR outcome after successful PTRA, by measuring single kidney GFR with synchronous inulin or (51)Cr-ethylenediaminetetraacetic acid clearance and (99m)Tc-diethylenetriamine pentaacetic acid scintigraphy, in a well-defined population of patients with unilateral renal artery stenosis. Thirty-two consecutive hypertensive patients (18 with atherosclerotic and 14 with dysplastic disease) with significant unilateral stenosis of the main native renal artery (> or = 60%) and normal renal function were included in the study. Renal and angiographic follow-up evaluations were performed 6 mo after PTRA. PTRA alone or combined with stenting (n = 2) was technically successful in all patients. Repeat PTRA was necessary in two patients, evaluated 6 mo after the second PTRA. Six mo after PTRA, total GFR had increased slightly but significantly in the 29 patients with positive lateralization indices. SRF and single-kidney GFR of the stenotic kidney increased significantly, whereas concurrently the GFR and SRF of the nonstenotic kidney decreased significantly. Six mo after successful PTRA reducing renal ischemia, a reversal of both the hypoperfusion of the stenotic side and the hyperperfusion of the nonstenotic side was observed, which was accompanied by a slight increase in total GFR.
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PMID:Split renal function outcome after renal angioplasty in patients with unilateral renal artery stenosis. 1137 47

Screening for renal artery stenosis is indicated in patients with suspected renovascular hypertension or ischemic nephropathy to identify those who could benefit from renal artery interventions. The critical requirements for a clinically useful screening test include safety, low cost, and a high sensitivity or low false-negative rate. Arteriography remains the "gold standard" for the anatomic diagnosis of renal artery disease, but it is unsuitable for screening because of its high cost and invasive nature. Although renal duplex scanning technically is difficult, experienced laboratories have been able to achieve sensitivities and specificities in the range of 93% to 98% for identification of stenoses in the main renal arteries. Renal duplex scanning also provides a method for assessing the renal parenchyma and predicting the clinical outcome of renal revascularization. The principal limitation of renal duplex scanning is failure to identify accessory renal arteries. The finding of one or more widely patent main renal arteries makes ischemic nephropathy unlikely, because this condition results from "total" renal ischemia. However, renovascular hypertension can be present with normal main renal arteries when there are isolated stenoses involving accessory renal arteries, so further testing may be indicated in selected hypertensive patients with normal main renal arteries by duplex scanning. Currently, duplex scanning in a qualified vascular laboratory arguably is the best screening test for renal artery stenosis. Other methods for assessing the renal arteries, particularly spiral computed tomography and magnetic resonance angiography, are evolving rapidly and also may play a role in screening of selected patients.
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PMID:Is duplex scanning the best screening test for renal artery stenosis? 1156 Dec 78

The role of nitric oxide (NO) and prostaglandins (PG) in modifying renal hemodynamics was examined in clipped and nonclipped kidneys of unilateral renal artery stenosis. Chronic unilateral renal ischemia was established by 4-wk-clipping the left renal artery of canine kidneys, and renal interstitial nitrate+nitrite and PGE(2) contents were evaluated by the microdialysis technique. Unilateral renal artery stenosis caused 45 +/- 1 and 73 +/- 1% decrements in renal plasma flow (RPF) in moderately and severely clipped kidneys and 21 +/- 3% decrements in nonclipped kidneys with severe stenosis. Renal nitrate+nitrite decreased in moderately (-31 +/- 1%) and severely clipped kidneys (-63 +/- 4%). N(omega)-nitro-L-arginine methyl ester reduced RPF (-56 +/- 3%) and glomerular filtration rate (GFR; -54 +/- 3%) in moderately clipped kidneys, whereas this inhibitory effect was abolished in severely clipped kidneys. In contrast, renal PGE(2) contents increased modestly in moderate clipping and were markedly elevated in severely clipped kidneys (from 111 +/- 7 to 377 +/- 22 pg/ml); sulpyrine impaired renal hemodynamics only in severely clipped kidneys. In contralateral nonclipped kidneys, although renal PGE(2) was not increased, sulpyrine reduced RPF (-32 +/- 1%) and GFR (-33 +/- 3%) in severe stenosis. Collectively, NO plays a substantial role in maintaining renal hemodynamics both under basal condition and in moderate renal artery stenosis, whereas the contributory role shifts from NO to PG as renal artery stenosis progresses. Furthermore, because intrarenal angiotensin II is reported to increase in nonclipped kidneys, unilateral severe ischemia may render the nonclipped kidney susceptible to PG inhibition.
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PMID:Stenosis-dependent role of nitric oxide and prostaglandins in chronic renal ischemia. 1193 96

Renovascular hypertension is a clinical situation characterized by high blood pressure in the presence of renal ischemia mainly related to atherosclerotic or fibromuscular dysplasic narrowing of the renal artery (ies). This diagnosis is often "a posteriori" validated, because the discovery of a significant renal artery stenosis is not obligatory responsible of the blood pressure elevation. This article proposes a diagnostic strategy for exploring patient with this suspected secondary cause of hypertension before proposing an invasive approach (intra-arterial angiography) possibly followed by a revascularization. However, the methods for exploring such population are mainly based on patient characteristics and local expertise and habits. These must thus be individualized. First, clinical symptoms or signs frequently associated with hypertension and renal artery stenosis must be searched. If present, a non invasive and functional exploration of the renal arteries is to be proposed (Captopril radioisotope renography, colour duplex sonography) followed by magnetic resonance angiography or spiral computer tomography angiography if the clinical suspicion index is moderate or high. If this is very high, an intra-arterial arteriography could immediately be performed if not too dangerous. On the opposite site, if the clinical index is low, it is recommended to follow clinically and to treat risk factors.
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PMID:Diagnostic criteria for renovascular hypertension. 1213 34

Chronic renal ischemia caused by renal artery stenosis (RAS) elicits a complex biologic response. Although the traditional pathophysiologic pathways underlying renal ischemia have been well studied, there is emerging evidence that additional mechanisms may be responsible for producing many of the hemodynamic alterations and end-organ injury seen in patients with RAS, including persistent hypertension, renal insufficiency, and cardiac disturbance syndromes. A better understanding of these mechanisms may allow earlier identification of RAS, provide markers to predict the response to revascularization, or allow unique therapeutic targets for drug development. This and a subsequent article will explore the pathophysiologic and clinical implications of chronic renal ischemia.
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PMID:Chronic renal ischemia: pathophysiologic mechanisms of cardiovascular and renal disease. 1242 6

Chronic renal ischemia caused by atherosclerotic renal artery stenosis (RAS) is gaining recognition as a potentially important risk factor for cardiovascular (CV) morbidity and mortality. The etiology of increased risk of CV events is multifaceted and includes direct physiologic changes that increase risk as well as intermediate clinical effects that are associated with worse outcome. Physiologic changes associated with increased CV risk in patients with RAS include increased production of fibrogenic and vasoactive peptides such as renin, angiotensin, endothelin, and catecholamines, as well as endothelial cell dysfunction. Clinical intermediate conditions associated with higher incidences of CV events seen in patients with renal ischemia include hypertension, systemic atherosclerosis, chronic renal failure, and left ventricular hypertrophy and dysfunction. More thorough understanding of the myriad physiologic changes seen in patients with RAS will likely improve patient selection for renal artery revascularization. Clinical trials should examine a full range of CV and renal outcomes, not just blood pressure, to adequately assess the merits of revascularization.
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PMID:Chronic renal ischemia: implications for cardiovascular disease risk. 1247 Nov 81

In an effort to identify preoperative and perioperative factors impacting outcome in repair of juxtarenal abdominal aortic aneurysm (JRAAA), hospital records and CT scans (for calcification, intraluminal thrombus, and aortic diameter) of all patients undergoing JRAAA repair over the past 10 years were reviewed. The 87 men and 25 women had a mean age of 72, and a mean maximal aortic diameter of 6.2 cm. Renal artery stenosis (RAS) and iliac disease were present in 13 (11%) and 40 patients (35%), respectively. Comorbidities included coronary artery disease (n = 49, 44%), COPD (n = 28, 25%), diabetes mellitus (n = 10, 9%), and preoperative renal insufficiency (PRI; Cr >1.4 mg/dL; n = 14, 12%). A midline incision was used in most of the patients (n = 98, 88%). The proximal aortic clamp was placed in the supraceliac (SC) position in 92 (82%) patients, and directly above one or both renal arteries in 20 (18%) patients. The overall mortality was 6% (n = 7). Cardiac complications occurred in 26 patients (23%); pulmonary, in 22 (20%); renal, in 14 (12%); and gastrointestinal, in 10 (9%). No patient experienced mesenteric ischemia. Mean elevation in creatinine was greater in patients with PRI (1.8 mg/dL vs. 0.13 mg/dL, p = 0.04). Mean blood loss (EBL) was 2701 +/- 189 cc, and mean LOS was 16.1 +/- 1.7 days. Age >70 was associated with increased length of stay (LOS) (12.1 days vs. 18.6 days, p = 0.05) and higher mortality (0 vs. 10%, p = 0.02); otherwise there were no significant relationships between pre- and perioperative parameters and any of the measured outcomes including death, postoperative RI, and LOS. Preferential SC clamping may substantially reduce complications of JRAAA repair (such as mesenteric and renal ischemia) related to proximal cuff disease, but cannot overcome the deleterious affects of advanced age and PRI.
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PMID:Optimal operative strategies in repair of juxtarenal abdominal aortic aneurysms. 1252

We report the case of a 71-year-old male, submitted to percutaneous transluminal renal angioplasty (PTA) plus stent implantation following the confirmation, at intravascular ultrasound, of severe unilateral renal artery stenosis in the setting of a single functional kidney and of evidence of renal insufficiency (serum creatinine value 300 mumol/l). At 6 months of follow-up the serum creatinine levels had returned to normal (98 mumol/l). This case shows the role of direct PTA on the overall renal function in a case of global renal ischemia.
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PMID:Effect of renal artery stenting on the progression of renovascular renal failure: a case of intravascular ultrasound-confirmed renovascular disease. 1261 Nov 27

Renal ischemia due to renal artery stenosis (RAS) is an important cause of secondary hypertension and renal insufficiency. Several methods are available to diagnose RAS; however, the identification of clinically significant lesions remains problematic. We measured the translesional systolic pressure gradient (TSPG) with a 4 Fr catheter and a 0.014" pressure-sensing guidewire and compared these data to angiographic findings. The TSPG obtained by pressure-sensing guidewire correlated more strongly with angiographic minimal lumen diameter (r(2) = 0.801) than those obtained by 4 Fr catheter (r(2) = 0.360). The relationship of TSPG with percent stenosis was not strong, regardless of the method used (r(2) = 0.228 with pressure-sensing guidewire, 0.358 with 4 Fr catheter). Using a 0.014" pressure-sensing guidewire is effective for assessing TSPG and provides a more reliable indication of stenosis significance than use of a 4 Fr catheter.
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PMID:Utility of a 0.014" pressure-sensing guidewire to assess renal artery translesional systolic pressure gradients. 1282 64


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