Renal artery stenosis: anatomic classification for percutaneous transluminal angioplasty

Renal artery stent in solitary functioning kidneys: 77% of benefit: A systematic review with meta-analysis

BACKGROUND

Solitary functioning kidney (SFK) is tough issue to address in clinical, mostly developed from renal artery stenosis (RAS) in adults. Although renal artery stent is widely used to help SFK patients, the efficacy of the stent is still disputable. This study is aimed at reviewing a series of SFK cases to draw a conclusion about the efficacy of renal artery stent.

METHODS

All related papers published in PubMed, Web of Science, EMBASE, and Cochrane Library were searched. Studies or subsets were included only if they satisfied certain criteria. The benefit rate which equaled the rate of improvement subjoining the rate of stabilization was calculated. All analyses were conducted with Stata version 12.0 (Stata Corporation, College Station, TX).

RESULTS

According to 7 papers on the efficacy of renal artery stent, 253 SFK patients were included. The result revealed that the renal artery stent could help SFK patients to improve or stabilize their renal function (RF). The benefit rate was 0.77, with 95% confidence interval between 0.72 and 0.83.

CONCLUSIONS

With proper patient selection, renal artery stent could benefit SFK patients with a percentage odd of 0.77 to improve or stabilize the RF.

Renovascular Hypertension

Hypertension constitutes a major health problem and the challenge is to identify patients having ‘surgically’ curable renal vascular disease among the majority with so-called essential hypertension. The best of unsatisfactory diagnostic tests are renography and plasma renin activity both before and during angiotensin II blockade. The necessity of better screening tests has increased because of the recent advances in surgical techniques and especially percutaneous transluminal renal angioplasty. The latter has definitely become the method of choice for correction of suspected hemodynamically significant artery stenoses whenever technically feasible. With improved angioplasty techniques the risk of treating renal artery stenosis without hemodynamic and clinical importance (so-called cosmetic repair) has increased. Unfortunately randomized trials including surgery versus angioplasty are not available. It should be kept in mind that only after correction of the stenosis is achieved and the blood pressure has become normal, can the diagnosis of renovascular hypertension be made with certainty.

Stenting of the Renal Artery to Improve Renal Function Prior to Thoracoabdominal Aneurysm Repair

Purpose:

To report the successful staged treatment of a patient with a thoracoabdominal aortic aneurysm (TAA), who presented with renal insufficiency attributable to renal artery stenosis.

Methods and Results:

A 66-year-old woman with a 6-cm Crawford type IV TAA presented with uncontrolled hypertension (240/130 mmHg), worsening congestive heart failure, and progressive renal insufficiency (serum creatinine 3.8 mg/dL) caused by renal artery stenosis to a solitary functioning kidney. Renal artery stenting restored normal renal and pulmonary function, and elective TAA repair 6 weeks after percutaneous stenting was uneventful. Restenosis (50% diameter reduction) in the renal artery was found 10 months later and treated with repeat dilation. Secondary patency was maintained at follow-up 21 months after redilation.

Conclusions:

It appears feasible to use preliminary renal artery stenting to reduce operative risk in TAA surgical candidates with renal insufficiency secondary to renal artery stenosis.

The renal artery ostium flow diverter: structure and potential role in atherosclerosis

Initiation of renal atherosclerosis occurs primarily at the caudal region of the renal artery ostium. To date, no mechanism for initiation of atherosclerosis at this site has been substantiated. Herein, we identify a renal artery flow diverter on the caudal wall of the renal artery ostium that directs flow into the renal artery and selectively retains LDL, an initial step in atherosclerosis. High-resolution ultrasound revealed the generation of flow eddies by the caudal diverter in vivo, consistent with a role in directing aortic flow to the renal artery. Two-photon excitation en face microscopy of the diverter revealed a substantial reduction in the elastic lamina exposing potential retention sites for LDL. Fluorescent LDL was selectively retained by the renal artery diverter, consistent with its molecular structure. We propose that the rigid macromolecular structure of the renal artery ostium diverter is required for its vascular function and contributes to the initiation of renal atherosclerosis by the retention of LDL.

The current state of endovascular therapy in the evaluation and management of renovascular disease

Hypertension is the most common reason for physician office visits among nonpregnant adults in the United States; up to one-third of Americans over the age of 18 have been diagnosed with hypertension. Patients with physiologically significant renal artery stenosis often go unnoticed because hypertension can often be well controlled with antihypertensive medications. As a result, screening for renovascular causes of hypertension is rarely done. However, the likelihood of renovascular disease increases in patients with acute, severe, or refractory hypertension and should be explored in patients who fall into these categories. Renovascular disease is a crucial consideration in the management of hypertension due to its increasing incidence and its potential for reversibility. Although renovascular disease accounts for less than 1% of patients with mild hypertension, it is estimated that between 10 and 45% of white patients with severe or malignant hypertension have renal artery stenosis (RAS). In this population, diagnosing and treating RAS can have a profound and long-lasting effect on the treatment of hypertension.

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.

Novel stent system for accurate placement in aorto-ostial renal artery disease: preclinical study in porcine renal artery model

BACKGROUND

Treatment of aorto-ostial renal artery stenosis has been associated with a lower procedural success and higher complication and restenosis rate, as compared to nonostial lesions. The design and delivery of currently available stent systems in ostial lesions can result in inaccurate stent positioning and placement leading to stent protrusion into the parent vessel lumen or geographic miss. A novel stent system (SquareOne Inc., Campbell, CA, USA) has been designed specifically for aorto-ostial lesions in the renal artery. This stent system aims to provide both tactile and visual confirmation of the ostium at the aorta, allow for improved accuracy during stent positioning and placement, provide complete scaffolding of the lesion at the aortic junction to the native vessel, and enable future vessel reaccess.

METHODS

Stents (n=12) were implanted in both renal arteries of six swine. For histology, two animals were euthanized immediately after stent implantation, and each two animals were then followed up at 2 and 4 weeks, respectively. Intravascular ultrasound (IVUS) studies were performed immediately after stent implantation and at follow-up.

RESULTS

Proper stent positioning and implantation was obtained in all animals. Angiographic and IVUS assessments indicated no dissection or thrombus formation. Histology demonstrated good apposition and endothelialization of the stent strut surface.

CONCLUSION

The unique flared shape of this novel ostial stent system allows for improved accuracy during stent positioning and placement, as well as complete apposition and coverage/scaffolding of the similarly-shaped luminal ostium. Future studies will determine if this novel stent system fulfills the unmet clinical need in aorto-ostial stenoses.

Ischemic nephropathy

Ischemic nephropathy is an independent pathway towards end-stage renal disease. Its prevalence is estimated to be significant and increasing among populations with vascular disease, hypertension, and chronic renal failure. Angiography remains the gold standard for evaluation of ischemic nephropathy; however, selection by clinical criteria and noninvasive screening with ultrasound are recommended for most patients. Surgical revascularization of ischemic kidneys can halt or reverse deterioration of renal function and is preferable to medical treatment. Direct comparison of angioplasty and stent placement with surgery is needed.

Delay of dialysis in end-stage renal failure: Prospective study on percutaneous renal artery interventions

BACKGROUND

Renal artery stenosis (RAS) is a cause of end-stage renal failure. We studied the effect of percutaneous renal artery intervention (PRI) in patients with advanced, progressive disease at risk for renal failure, hypothesizing a beneficial effect.

METHODS

Thirty-nine primary and 14 secondary PRIs were performed on 28 patients with atherosclerotic RAS, serum creatinine >300 micromol/L, and progressive loss of renal function >/=1 year before PRI. Renal function and RA patency were prospectively followed for 12 months after primary and secondary PRI. The intervention's effect on the progressive loss of renal function was calculated by comparing reciprocal slopes of serum creatinine against time before and after PRI.

RESULTS

Progression of renal failure slowed significantly following PRI. Mean (+/-SE) slopes of reciprocal serum creatinine values were: 6.69 +/- 0.97 L micromol(-1) day(-1) (x10(-6)) before and 6.76 +/- 3.03 L micromol(-1) day(-1) (x10(-6)) after PRI (P= 0.0007). Fifteen patients (53.5%) showed improvement or stabilization of progressive renal dysfunction. Out of 11 patients expected to become dialysis dependent within one year, 8 (72.7%) experienced an improvement in renal function sufficient to remain dialysis-free. Favorable outcome correlated with a lower creatinine level (P= 0.0137) and a more negative slope of progression (r= 0.49, P= 0.020) at entry. Mortality was 10.7%, and rate of local complications was 7.1%. Deterioration of renal function following PRI was suspected in 17.9% of patients.

CONCLUSION

PRI may improve renal function and ultimately delay dialysis in patients with advanced renal failure. Possible advantages must be weighed against the risk of renal failure advancement and high procedure-related complication rate.

Current issues in the diagnosis and management of patients with renal artery stenosis: a cardiologic perspective

Renal artery stenosis most often is caused by atherosclerosis. Although patients with renal artery stenosis can be managed conservatively, renal revascularization may be indicated, particularly in patients with refractory hypertension on a multidrug regimen and patients with declining renal function. Duplex ultrasonography of the renal arteries and magnetic resonance angiography are currently the most efficient noninvasive methods for the evaluation of renal artery stenosis. Selective digital subtraction renal arteriography remains the gold standard for the definitive diagnosis. In selected patients undergoing coronary studies and angiography immediately after the coronary procedure can be efficient. Atherosclerotic renal artery lesions, which commonly affect the renal artery ostium, can be treated safely and effectively with balloon-expandable stents. Successful angioplasty commonly results in improved control of hypertension, but an overall benefit on renal function and/or patient survival has not been shown. Generally the risk/benefit ratio of renal artery stenting seems favorable, but further randomized studies are needed for evidence-based decision making. All patients with atherosclerotic renal artery stenosis should receive rigorous secondary prevention measures including platelet inhibitors, statins, and beta-blockers.

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.

Atherosclerotic renal arterial stenosis: clinical outcomes of stent placement for hypertension and renal failure

PURPOSE

To assess technical success rates and long-term clinical outcomes of primary renal arterial stent placement in atherosclerotic renal arterial stenosis (RAS).

MATERIALS AND METHODS

Primary stent placement was performed in 100 consecutive patients with atherosclerotic RAS. Indications for treatment were resistant hypertension (n = 25), impaired renal function, (n = 50), and both (n = 25). Immediate technical results were evaluated with angiography. Clinical outcomes were assessed with serial systolic and diastolic blood pressure and serum creatinine values obtained from retrospective review of case notes. Results obtained every 6 months after the procedure were compared with those obtained at the time of the procedure with the paired t test. Radiologic reports were evaluated for immediate and case notes for delayed complications.

RESULTS

Technical success was achieved in 120 (95.2%) of 126 RAS in 95 patients. Mean follow-up was 25 months (median, 24 months; range, 1-66 months). Resistant hypertension was cured in two (4.2%) of 48 patients, had improved in 38 (79.1%), and had failed to respond to treatment in eight (16.7%). Mean systolic and diastolic blood pressures were significantly lower at 6, 12, 18, 24, and 30 months (P <.01) than before the procedure. Among 65 patients treated for renal impairment, renal function improved in 20 (30.8%), stabilized in 25 (41.7%), and continued to deteriorate in 20 (30.8%). The mean serum creatinine level did not show significant change with time for this group. In the improved subgroup, it was significantly higher at 6, 12, 18, 24, 36, and 42 months (P <.05) than prior to the procedure. Procedure-related complications occurred in 18 (18%) cases: Ten were minor and self-limiting and eight were major and included two procedure-related deaths.

CONCLUSION

In atherosclerotic RAS, primary stent deployment has a high technical success rate, producing clinical benefits in the majority of patients when performed for resistant hypertension and recovery of renal function.

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.

Renal artery stenting for renal insufficiency in solitary kidney in 26 patients

OBJECTIVE

to present our experience with stent placement in renal arteries in solitary kidneys for treating renal insufficiency.

DESIGN

retrospective analysis.

MATERIALS

in 26 patients with solitary kidney (17 men, 9 women, mean age: 63 years), presented with renal insufficiency (se-creat >0.144 mmol/l), stent was placed in a stenosed renal artery. We analysed the clinical outcome, based on the level of creatinine at 3 months following the procedure. Clinical benefit was considered when there was a decrease compared to the baseline creatinine by >20% or a stabilisation of the creatinine value (+/-20% of the baseline).

RESULTS

in 16 of the 26 patients (62%), clinical benefit was achieved. However, 38% of the study population, renal function continued to deteriorate. Baseline creatinine value was the single best predictor for clinical benefit achievement (odds ratio: 13; 95% confidence intervals: 1.6-107, p=0.01).

CONCLUSION

renal stenting results in improvement or stabilisation of renal function in the majority of the patients with solitary kidneys and renal artery stenosis, presenting with renal insufficiency. Because best outcome was observed mainly in those patients with not progressed renal insufficiency, intervention should be focused on that group.

Endovascular treatment of renal artery stenosis

Significant changes have occurred in the treatment of renal artery disease over the past few years. Although excellent clinical results can be obtained with surgery, percutaneous transluminal renal angioplasty has proved similarly efficacious and is now the treatment of choice for nonostial atherosclerotic stenoses and fibromuscular dysplasia. The introduction of stents has become a valuable adjunctive therapy for postangioplasty restenosis and dissection.

Stent placement in ostial and nonostial atherosclerotic renal arterial stenoses: a prospective follow-up study

PURPOSE

To compare the results of balloon percutaneous transluminal renal angioplasty (PTRA) and stent placement in atherosclerotic ostial, proximal, and isolated truncal stenoses.

MATERIALS AND METHODS

Between January 1994 and April 1998 the authors prospectively followed up 163 consecutive patients with 200 atherosclerotic renal arterial lesions after primary PTRA or primary stent placement. Duplex ultrasonography was performed 1 day and 3, 6, and 12 months later.

RESULTS

The primary 12-month PTRA patency rates were 34% (21 of 33 atherosclerotic lesions) for ostial stenoses, 65% (20 of 60) for proximal stenoses, and 83% (five of 30) for truncal stenoses (chi(2) value, 15.63; P <.001). The corresponding stent patency rates were 80% (four of 21), 72% (nine of 34), and 66% (five of nine), respectively (chi(2) value, 4.11; not significant). Significant stent-related reduction in risk of restenosis was limited to the ostial stenoses (P =.002).

CONCLUSION

Renal arterial stent placement considerably improves patency in ostial stenoses, but compared with the technically successful PTRA, it does not significantly improve primary patency in proximal and isolated truncal renal arterial stenoses.

Laparoscopic aortorenal bypass

BACKGROUND AND PURPOSE

Open surgical renovascular repair, although producing excellent results, confers significant operative morbidity. As a result, less morbid procedures such as percutaneous balloon angioplasty and stenting have gained increasing acceptance. Laparoscopic techniques have not previously been applied to renal revascularization. The aim of this study was to demonstrate the technical feasibility and the long-term clinical and pathologic outcomes of laparoscopic aorto-left renal artery bypass in a chronic porcine model.

MATERIALS AND METHODS

Eight animals were used in the study. All laparoscopic suturing and knot-tying were performed intracorporeally using free-hand techniques. The following operative steps were employed: (1) aortic dissection and cross-clamping; (2) transection and refashioning of the left renal artery ostium; (3) in-situ renal hypothermia; (4) end-to-side aorto-left renal artery anastomosis; and (5) aortic unclamping. In situ renal hypothermia was achieved laparoscopically by infusion of ice-cold heparinized saline into the renal artery through a balloon catheter.

RESULTS

All eight pigs underwent laparoscopic aortorenal bypass successfully. The median surgical time was 110 minutes, and the aortic cross-clamping time was 45.5 minutes. The median anastomotic time was 40 minutes, and the renal warm ischemia time was 9 minutes. The median estimated blood loss was 30 mL. An intraoperative complication of suture breakage leading to anastomotic hemorrhage occurred in one animal; the problem was corrected laparoscopically. Postoperatively, one animal died from pneumonia. The remaining seven animals experienced no postoperative complications and were euthanized, one each at postoperative day 0 and 1 and week 1, 2, 3, 4, and 6. The median preoperative and postoperative (at euthanasia) serum creatinine values (1.15 mg/dL v 1.2 mg/dL; P = 0.39) were similar. However, compared with preoperative peripheral renin activity (0.25 microg/L per hour), the postoperative peripheral renin activity was elevated (0.9 microg/L per hour; P = 0.047). Autopsy revealed a grossly normal left kidney, with Doppler confirmation of flow in the repaired renal artery in all seven animals. Ex vivo angiography confirmed a patent anastomosis. On histopathology examination, the early left renal parenchymal specimens revealed transient, mild acute tubular necrosis that resolved over sequential specimens without significant long-term sequelae. Histologic analysis of the aorto-left renal artery anastomotic site revealed gradual endothelialization with time.

CONCLUSIONS

Laparoscopic aortorenal artery revascularization is technically feasible. Our chronic animal model has demonstrated durable success over a 6-week follow-up. This study represents the initial report in the literature.

Inter-observer variability in the angiographic assessment of renal artery stenosis. DRASTIC study group. Dutch Renal Artery Stenosis Intervention Cooperative

OBJECTIVE

To assess inter-observer agreement in the interpretation of renal angiograms.

DESIGN

Comparison of the assessment of renal angiograms by three experienced radiologists, who evaluated the number of renal arteries and the presence, location, aspect and severity of a renal artery stenosis.

SETTING

General hospital and university hospital serving urban and rural populations.

PATIENTS

Patients with difficult-to-treat hypertension referred for diagnostic work-up; 312 angiograms with the intra-arterial digital subtraction technique were obtained from 289 consecutive patients.

MAIN OUTCOME MEASURES

Inter-observer agreement was tested for the following parameters: number of arteries per kidney, presence of stenosis, location of stenosis (truncal, ostial), aspect of stenosis (concentric, eccentric, post-stenotic dilatation), severity of stenosis (reduction of lumen diameter in categories of 30%, 40%, etc. to 100%), and overall quality of the angiographic images. Kappa (kappa) values and weighted kappa between the three pairs of radiologists were used as estimates of inter-observer agreement

RESULTS

Agreement about the number of renal arteries was reasonable (kappa = 0.50-0.72), as was agreement about the presence of stenosis (kappa = 0.68-0.86). Agreement about stenosis location and aspect was poor (kappa = 0.26-0.47 and kappa = 0.15-0.26, respectively). There was general agreement about the severity of stenosis (weighted kappa = 0.65-0.70), but it was not possible to distinguish between 50 and 60% stenosis or between 60 and 70% stenosis (kappa < 0.40). No correlation was found between agreement on severity of stenosis and the quality of the images.

CONCLUSIONS

It is not realistic to make statements about what degree of renal artery stenosis is clinically significant, as long as the intra-arterial angiogram with digital subtraction remains the gold standard. It is likewise risky to rely too strongly on stenosis morphology as visualized by renal angiography in choosing between balloon angioplasty and stent deployment.

The Erasme study: a multicenter study on the safety and technical results of the Palmaz stent used for the treatment of atherosclerotic ostial renal artery stenosis

PURPOSE

To assess, in a multicenter setting, safety, technical results, and restenosis rate of the Palmaz stent for treatment of atherosclerotic ostial renal artery stenosis.

METHODS

Ten centers enrolled 106 patients (120 treated renal artery stenoses) in the study. Patient selection was based on unsuccessful percutaneous transluminal renal angioplasty (residual stenosis >/= 20%) performed for treatment of ostial stenosis >/= 50%, in patients with hypertension and/or impaired renal function. Safety was assessed by means of the complication rate, and technical results by the number of successful stent placements and occurrence of restenosis (>50%) at intraarterial angiographic follow-up.

RESULTS

Stent placement was successful (n = 112) or partially successful (n = 5) in 117 (98%) arteries. Complications occurred in 19 procedures; seven were of serious clinical significance. Angiographic follow-up was performed in 89 of 117 (76%) cases, at a mean of 8 months (range 2. 5-18 months). Fifteen stents (16.9%) showed restenosis (at a mean of 8.5 months), of which 10 were successfully redilated.

CONCLUSION

Renal artery stenting has a high technical success rate, a complication rate comparable to percutaneous transluminal renal angioplasty, and a low rate of restenosis at 8 months angiographic follow-up.

Duplex ultrasonography in assessing restenosis of renal artery stents

PURPOSE

To determine the accuracy and optimal threshold values of duplex ultrasonography (US) in assessing restenosis of renal artery stents.

METHODS

Twenty-four consecutive patients with 33 renal arteries that had previously been treated with placement of a Palmaz stent underwent duplex US prior to intraarterial digital subtraction angiography (DSA), which was the reference standard. Diagnostic accuracy of in-stent peak systolic velocity (PSV) and reno-aortic ratio (RAR = PSV renal stent/PSV aorta) in detecting > 50% in-stent restenosis were evaluated by the receiver operating characteristic curve. Sensitivity and specificity were determined using the optimal threshold values, and using published threshold values: RAR > 3.5 and in-stent PSV > 180 cm/sec.

RESULTS

Six examinations were technically inadequate. Nine stents had residual or restenosis > 50% at DSA. The two duplex parameters were equally accurate since areas under the curves were similar (0.943). With optimal threshold values of 226 cm/sec for PSV and 2.7 for RAR, sensitivities and specificities were 100% and 90%, and 100% and 84%, respectively. Using the published duplex criteria resulted in sensitivities and specificities of 100% and 74% for PSV, and 50% and 89% for RAR.

CONCLUSION

Duplex US is a sensitive modality for detecting in-stent restenosis if laboratory-specific threshold values are used.

Atherosclerotic renal artery stenosis: from diagnosis to treatment

Renovascular hypertension represents a form of correctable hypertension and preventable renal failure. Such patients need to be identified early so that specific therapy can be instigated. Patient identification requires a high index of suspicion in patients with certain clinical features. Subsequent non-invasive imaging may result in angiography which is required for diagnostic purposes and for planning intervention. Correctable therapy takes one of two forms, namely percutaneous transluminal renal angioplasty, with or without stenting, or surgical revascularisation, together with modification of underlying risk factors.

Carbon dioxide digital subtraction angiography for renal artery stent placement

PURPOSE

To determine the efficacy of renal artery stent placement with use of carbon dioxide as the primary contrast agent.

MATERIALS AND METHODS

Seventeen hypertensive patients with renal ostial stenosis were evaluated and underwent stent placement with use of CO2 digital subtraction angiography (DSA). Besides hypertension, 11 patients had decreased renal function, three had iodinated contrast material allergy, one patient had both, and two had neither. Supplemental iodinated contrast material (25 mL or less) was used in five patients. Preprocedure and postprocedure serum creatinine levels were obtained to evaluate the effect of CO2 on renal function. Arteriography was used to evaluate stent positioning.

RESULTS

Twenty-three Palmaz stents were placed in 17 patients. Six placements were bilateral, with a total of nine right and 14 left. No additional stents were required to correct malposition. One patient had a mildly significant, yet transient, rise in the postprocedure creatinine level. This patient received 10 mL of iodinated contrast material in addition to CO2. There were no allergic reactions.

CONCLUSION

The utilization of CO2 DSA facilitates the accurate placement of renal artery stents by eliminating the concern for contrast material-associated nephropathy and allergy. These attributes, coupled with the benefit of low viscosity, permit unrestricted imaging, guidance, and precise positioning not afforded by iodinated contrast material.

Fluoroscopic landmarks for optimal visualization of the proximal renal arteries

PURPOSE

To accurately determine the in vivo orientation of the origin of the renal arteries from the aorta relative to a fluoroscopic bony landmark for optimal diagnostic arteriography and renal artery stent placement.

MATERIALS AND METHODS

One hundred sixty abdominal computed tomography (CT) scans of patients in eight age groups (20-90 years) were reviewed to determine the angle of the origins of the renal arteries from the aorta relative to the long axis of the L-1 spinous process (L1SP).

RESULTS

The right renal artery arises ventrally at an angle of 30 degrees (standard deviation [SD] = 15 degrees) from a plane orthogonal to the long axis of the L1SP. The left renal artery arises dorsally at an angle of 7 degrees (SD = 13 degrees) relative to the same plane.

CONCLUSIONS

The optimal initial angle for angiographic evaluation of the origin of the renal artery and for renal artery stent placement is 30 degrees left anterior oblique (LAO) relative to the L1SP for the right renal artery and 7 degrees LAO for the left renal artery. Unfortunately, there is variability in the angle of the renal artery origins from the aorta which cannot be controlled for using this technique. In some patients, additional views will be necessary to optimally depict the origins of the renal arteries.

Salvage of the solitary kidney by insertion of a renal artery stent

OBJECTIVE

The purpose of the study was to evaluate the use of renal artery stents in the solitary functioning kidney of patients who have impaired renal function as a result of atherosclerotic renovascular disease by assessing primary patency, renal function outcome, and complication rates during a mean follow-up period of 15 months.

MATERIALS AND METHODS

The Palmaz stent was placed in the arteries of 21 patients with solitary functioning kidneys. All patients had impaired renal function (creatinine level >150 micromol/l), and four patients were undergoing renal dialysis. Indications for stenting were recoil after percutaneous transluminal angioplasty (n = 12), arterial dissection after angioplasty (n = 2), restenosis after angioplasty (n = 1), and as the primary intervention (n = 6). Follow-up angiography was performed in 16 patients (76%).

RESULTS

Initial technical success was achieved in all patients (residual stenosis, <5%). At follow-up (range, 6-25 months), renal function had returned to normal in five patients (24%), improved in four patients (19%), stabilized in six patients (29%), and deteriorated in six patients (29%). Dialysis has been discontinued in all four dialysis patients. Major complications occurred in four patients (19%), including one death within 30 days of stenting. No significant restenoses were seen on follow-up angiography.

CONCLUSION

Placement of renal artery stents in the solitary kidney led to benefits in 70% of patients treated, including improved renal function in nine patients (43%) and stabilization in six patients (29%). In this high-risk group of patients, we advocate renal artery stenting as a relatively safe procedure to salvage the solitary kidney.

Primary stenting of atherosclerotic renal artery ostial stenosis

Percutaneous transluminal angioplasty for atherosclerotic ostial lesions of the renal arteries has resulted in high restenosis rates. Recent reports of angioplasty with intravascular stenting show improved results over angioplasty alone. The purpose of this study is to review the results of primary stenting of ostial renal artery stenosis at our institution. Twenty one patients (11 men, 10 women, age 63 +/- 11 years), with atherosclerotic renal artery ostial stenosis in association with hypertension or renal insufficiency underwent renal angioplasty with primary stenting during a 2-year period. Medical records were reviewed for indications, technical success, complications, restenosis, response of hypertension and response of renal insufficiency. A technical success was defined as a normal postprocedure arteriogram with no residual stenosis and no residual gradient. Restenosis was defined as > or =60% diameter reduction identified by arteriography, or duplex scan demonstrating a renal artery to aortic ratio of > or =3.5. Thirty-three stents were placed in 25 arteries with four patients having bilateral procedures. All patients were hypertensive. Nine patients (43%) had chronic renal insufficiency (creatinine > or =1.5 mg/dl). One patient was on hemodialysis. The immediate technical success rate was 95%. Six complications occurred in four patients (two pseudoaneurysms, two dissections requiring additional stents, renal failure, and atheroembolization). Mean arterial blood pressure improved from 117 +/- 13.4 to 103 +/- 12.8 mmHg (p = 0.002) after stenting. Serum creatinine levels decreased from 1.48 +/- 0.57 to 1.31 +/- 0.41 (p = 0.07). Eight patients developed restenosis. The mean follow up was 13 +/- 7 months. Life table analysis showed a cumulative restenosis rate of 65 +/- 18% at 24 months. We advise caution in the application of renal stenting for the treatment of ostial lesions, particularly in patients for whom standard surgical revascularization options are available.

Stenting of the renal artery to improve renal function prior to thoracoabdominal aneurysm repair

PURPOSE

To report the successful staged treatment of a patient with a thoracoabdominal aortic aneurysm (TAA), who presented with renal insufficiency attributable to renal artery stenosis.

METHODS AND RESULTS

A 66-year-old woman with a 6-cm Crawford type IV TAA presented with uncontrolled hypertension (240/130 mmHg), worsening congestive heart failure, and progressive renal insufficiency (serum creatinine 3.8 mg/dL) caused by renal artery stenosis to a solitary functioning kidney. Renal artery stenting restored normal renal and pulmonary function, and elective TAA repair 6 weeks after percutaneous stenting was uneventful. Restenosis (50% diameter reduction) in the renal artery was found 10 months later and treated with repeat dilation. Secondary patency was maintained at follow-up 21 months after redilation.

CONCLUSIONS

It appears feasible to use preliminary renal artery stenting to reduce operative risk in TAA surgical candidates with renal insufficiency secondary to renal artery stenosis.

Ostial renal artery stenosis angioplasty: immediate and mid-term angiographic and clinical results

PURPOSE

To report the immediate results and the clinical and angiographic outcome of percutaneous angioplasty in patients with ostial renal artery stenosis.

MATERIAL AND METHODS

Retrospective review of 52 percutaneous transluminal renal angioplasty (PTRA) procedures for strictly defined ostial atherosclerotic renal artery stenosis in 50 consecutive patients, selected among 670 PTRAs performed between 1983 and 1993.

RESULTS

Immediate angiographic success was achieved in 30 arteries (58%) and improvement was achieved in 15 arteries (29%). The procedure was a failure in seven lesions (13%). PTRA was followed by a stent implantation in three lesions (6%). Two patients (4%) died within the first month after PTRA and a major complication occurred in seven other patients (13%). At a mean follow-up of 20.6 months, both systolic and diastolic blood pressure decreased significantly (P = .0006 and P = .0057 respectively). Renal function did not change significantly (P = .73). One patient was lost during follow-up. At angiographic control (mean, 11 months), restenosis occurred in 27% of the cases. There was no recurrence of pulmonary edema at a mean follow-up of 32 months in 50% of the 12 patients who experienced one episode or more before PTRA.

CONCLUSIONS

True ostial renal artery stenosis is rare and often reflects severe and multifocal atheromatous disease. In these patients, PTRA might be considered an acceptable and relatively safe treatment that improves blood pressure and stabilizes renal function.

Percutaneous transluminal angioplasty in the treatment of renovascular hypertension: sequential prospective study

OBJECTIVE

To evaluate the use of percutaneous transluminal renal angioplasty (PTRA) in the treatment of renal vascular hypertension.

DESIGN

Sequential prospective PTRA treatment of severe arterial hypertension, screening by the captopril test, confirmed by renal arteriography, and the result evaluated by post-PTRA arteriography, blood pressure measurement and renal function. SITE: Vascular Surgery, angioradiology sector, and Nephrology outpatients department of the Federal University of São Paulo-Paulista School of Medicine, São Paulo, Brazil, a tertiary health-care institution.

PARTICIPANTS

PTRA was employed on 32 patients screened by clinical examination, captopril test and renal arteriography.

EVALUATION

PTRA results were evaluated by the criteria of the Cooperative Study of Renovascular Hypertension.

RESULTS

After PTRA the completion arteriography showed no renal stenosis in 24 patients (75%), residual stenosis (20-50%) in 3 (9.4%) and no change in 5 (15.6%). The blood pressure results were: 3 patients (9.4%) were cured, 24 (75%) improved and 5 (15.6%) were unchanged. We observed normal renal function before and after PTRA in 25 patients (78%); altered pre- and improved post-PTRA in 2 (6.3%); post-PTRA remained unaltered in 2 (6.3%); and altered pre- and worsened post-PTRA in 3 (9.4%). Recurrence of stenosis occurred in one patient after 8 months.

CONCLUSIONS

PTRA is a convenient procedure, relatively safe and an effective complementary method of medical therapy for controlling renovascular hypertension.

Ischemic renal disease: an emerging cause of chronic renal failure and end-stage renal disease

Ischemic renal disease (IRD) is defined as a clinically important reduction in glomerular filtration rate or loss of renal parenchyma caused by hemodynamically significant renal artery stenosis. IRD is a common and often overlooked clinical entity that presents itself in the setting of extrarenal arteriosclerotic vascular disease in older individuals with azotemia. Eleven to 14% of end-stage renal disease (ESRD) cases are attributable to chronic IRD. A high percentage of patients entering ESRD programs are hypertensive. Many patients with a presumed diagnosis of hypertensive nephrosclerosis actually have undiagnosed ischemic nephropathy as the etiology of their ESRD. It is important for the clinician to identify IRD, because IRD is a potentially reversible cause of chronic renal failure in a hypertensive patient. Atherosclerotic renal artery disease is common among patients with coronary artery disease and aortic and peripheral vascular disease. Atherosclerotic renal artery disease is a progressive disorder, and its progression is associated with loss of renal mass and functioning. A decrease in glomerular filtration rate sufficient to cause an elevation of the serum creatinine concentration requires injury to both kidneys. Consequently, IRD can arise from one of two main clinical situations: bilateral hemodynamically significant renal artery stenosis leading to bilateral renal ischemia; and hemodynamically significant renal artery stenosis in a solitary functioning kidney, or in a kidney that is providing the majority of a patient's glomerular filtration. The primary reason for establishing the diagnosis of IRD is the hope that correction of a renal artery stenosis will lead to improvement of renal function, or a delay in progression to ESRD. There are six major clinical settings in which the clinician could suspect IRD: acute renal failure caused by the treatment of hypertension, especially with angiotensin converting enzyme inhibitors; progressive azotemia in a patient with known renovascular hypertension; acute pulmonary edema superimposed upon poorly controlled hypertension and renal failure; progressive azotemia in an elderly patient with refractory or severe hypertension; progressive azotemia in an elderly patient with evidence of atherosclerotic disease; and unexplained progressive azotemia in an elderly patient. Noninvasive testing modalities that have been used recently include the angiotensin converting enzyme inhibitor renal scan, duplex Doppler sonography, magnetic resonance angiography, and the spiral computed tomography. Treatment methods include percutaneous transluminal angioplasty, endovascular stenting, and surgical revascularization. The results of treatment for preservation of renal function have been encouraging, with stabilization or improvement in renal function observed in a significant proportion of cases.

Supraceliac aortorenal bypass

PURPOSE

To determine the efficacy and durability of supraceliac aortorenal bypass grafting for symptomatic atherosclerotic renal artery disease.

METHODS

Retrospective review of a 10-year, single-institution experience.

RESULTS

Seventeen patients underwent 27 bypass procedures (seven unilateral, 10 bilateral) for atherosclerotic renovascular hypertension. The patients' mean age was 62.7 +/- 8.8 years. Diffuse aortoiliac and visceral atherosclerosis was confirmed on arteriogram; most (88%) celiac axis branches and all infrarenal aortas and common iliac arteries were found unsuitable for use as a donor vessel. Twenty-six bypass procedures (96%) were performed with autologous vein grafts. Seventeen bypass procedures (63%) were performed during partial aortic occlusion. There were no operative deaths or early occlusions. Postoperative complications occurred in four patients (24%). The mean duration of follow-up was 28 +/- 19 months (range, 2 to 69 months). By life table analysis, the 5-year primary patency and assisted primary patency rates were 95% and 100%, respectively. The mean systolic blood pressure decreased from 180 +/- 38 mm Hg to 135 +/- 20 mm Hg (p = 0.0003), and the mean diastolic blood pressure decreased from 96 +/- 16 mm Hg to 77 +/- 9 mm Hg (p = 0.0002). The number of antihypertensive medications decreased from 2.8 +/- 1.2 to 1.4 +/- 1.0 (p = 0.002). Significant improvement in serum creatinine level was seen among patients with preoperative renal insufficiency. Hypertension was cured in 29%, improved in 53%, and unchanged in 18%. During late follow-up, only four patients (24%) required subsequent aortic reconstruction.

CONCLUSION

Supraceliac aortorenal bypass grafting is a safe and durable alternative for renal artery revascularization. This technique should be considered in patients who have diffuse infrarenal aortoiliac and visceral artery occlusive disease and require renal revascularization procedures.

Renal artery stent placement in renal artery stenosis: technical and early clinical results

We report the technical and early clinical results of renal artery stent placement in 29 consecutive patients treated at a single centre over a 30-month period, employing the Palmaz balloon-expandable stent. Of 32 arteries treated, 23 (72%) were atheromatous, ostial stenoses. Immediate technical success was achieved in all 29 patients. Follow-up angiography was performed on 25 patients at 6.7 months (mean) and demonstrated a patient restenosis rate of 16%. All surviving patients were followed up for a minimum of 6 months. Blood pressure control was improved in eight (50%) of hypertensive patients, and renal function improved in seven (33%) and stabilized in six (29%) patients with chronic renal impairment (serum creatinine > 150 mumols/l). Complications occurred in seven (24%) of patients, including one procedure-related death. Our experience indicates that stent placement has an initial high technical success rate in renal artery stenosis and that this patency is maintained at repeat angiography with a low restenosis rate. Renal artery stenting is likely to extend the role of percutaneous renal revascularization especially in atheromatous ostial lesions. A randomized trial will be required to evaluate its role compared with balloon angioplasty.