Revascularization for atherosclerotic renal artery stenosis: the treatment of choice?

Atherosclerotic renal artery stenosis (ARAS) is an important cause of renal dysfunction and secondary hypertension, and is associated with adverse cardiovascular events and increased mortality. The natural history of ARAS is characterized by anatomic disease progression and/or renal dysfunction in only a minority of patients. Medical therapy for ARAS is directed primarily toward blood pressure control and cardiovascular risk factor reduction. Renal artery revascularization is an additional treatment option for ARAS associated with ischemic nephropathy or severe, poorly controlled hypertension despite aggressive medical therapy. Unfortunately, the benefits associated with revascularization versus medical therapy alone remain unproven. Renal artery revascularization may be accomplished through open surgical revascularization or angioplasty and stenting. Although surgical renal revascularization is associated with more durable results and relatively lower risk for postoperative renal function decline, the increased risk of death or major complications associated with this management approach limit its use in patients with significant comorbidities. Renal artery angioplasty and stenting is being utilized with increasing frequency but is of uncertain benefit and is associated with rates of post-intervention renal function improvement and deterioration that are approximately equal. Renal function outcomes associated with angioplasty and stenting may be improved through a selective treatment approach and utilization of distal embolic protection. Renal artery revascularization represents the only treatment alternative for patients unresponsive to medical management, and is therefore the 'treatment of choice' in this select group. Results of ongoing randomized trials are eagerly anticipated and may provide useful guidance for future management of ARAS.     

Doppler ultrasonography in posttransplant renal artery stenosis: a reliable tool for assessing effectiveness of revascularization?

BACKGROUND: Renal artery stenosis is usually treated by angioplasty and stenting, but the effectiveness of graft perfusion is difficult to establish on clinical grounds. METHODS: We compared changes in Doppler ultrasound parameters such as resistive index and peak systolic velocity with concomitant changes in renal vascular resistances, renal blood velocity, and wall shear stress measured before and 1 month after percutaneous transluminal angioplasty and stenting in 12 renal transplant patients with renal artery stenosis. RESULTS: After revascularization, peak systolic velocity and resistive index normalized in all patients. Changes in peak systolic velocity (-72%; P<0.001 vs. basal) were positively correlated (P<0.0001; r=0.87) with those in renal blood velocity (-88%; P<0.01 vs. basal) and with those (P<0.0005; r=0.80) in wall shear stress (-97%; P<0.005). Changes in resistive index (+21%; P<0.005) were negatively correlated (P=0.009; r=0.51) with those in renal vascular resistances (-40%; P<0.01). Changes in Doppler parameters (resistive index and peak systolic velocity) reflected those in renal vascular resistances and renal blood velocity with 100% sensitivity and specificity. CONCLUSIONS: Doppler ultrasound is a reliable, noninvasive, and easily available tool for identifying subjects who may benefit from kidney graft revascularization and to assess the effectiveness of the procedure.     

Vascular surgeons--do they make a difference in peripheral vascular disease?

BACKGROUND: The purpose of this study was to quantitate the effect of surgeons with added qualifications in general vascular surgery on aortic and peripheral vascular surgery performed in a community hospital. METHODS: We performed a retrospective study covering a 22-year period and comparing indications, procedures, and results of surgeons who had added qualifications in general vascular surgery with those of board certified general and thoracic surgeons in a private hospital. In Period I (1975-1982), there were 702 vascular procedures all performed by thoracic (65%) and general (35%) surgeons. In Period II (1982-1997), there were 2590 vascular procedures performed by vascular surgeons (73%), general surgeons (7%), and thoracic surgeons (20%). A further comparison was done to examine the results of surgeons with added qualifications in general vascular surgery with board certified general and thoracic surgeons within Period II. RESULTS: The volume and frequency of different types of vascular surgery changed significantly from Period I to Period II with lower extremity prosthetic reconstructions decreasing from 12% to 8.2% and autogenous lower extremity bypasses increasing from 15% to 36%. The percentage of distal reconstructions increased significantly from 27% of the total vascular surgeries in Period I to 44.3% in Period II. In Period II, vascular surgeons operated on older patients, had decreased mortality, decreased length of stay, and performed more distal bypasses than board certified general and thoracic surgeons. CONCLUSIONS: The development of vascular surgery as a separate specialty appears to have had a beneficial effect on the types of vascular surgery and the results when compared in a contemporaneous or retrospective fashion.     

Stenting of renal artery stenosis: is it beneficial in chronic renal failure?

BACKGROUND: The utility of renal artery stenting (RS) in preserving renal function (RF) is not well established. Our prospective study aimed to examine the clinical effects of RS in patients with proximal renal artery stenosis and chronic renal failure (CRF). METHODS: Fifty-two patients, with atherosclerotic renal artery stenosis (ARAS) and renal impairment underwent successful monolateral (33 patients) or global RS (19 patients: six bilateral stenting, two surgical solitary kidney and 11 functional solitary kidney). Patients were considered eligible if they had at least a mild renal impairment (serum creatinine (Cr) >1.5 mg/dL). To assess a significant change in RF, we compared the slopes of the regression lines derived from the reciprocal of Cr vs. time, plotted before and after stenting. Patients had a median post-procedure follow-up of 24 months (range 9-54). RESULTS: Before stenting all patients exhibited a negative slope, indicating progressive renal failure. After stenting the slopes became positive in eight patients (15.5%), indicating a significant improvement in RF; in 31 patients (59.5%) the slopes were not significantly different from 0 and were associated with a stable RF, while 13 patients (25%) presented negative slopes and showed a continuous reduction in RF. Previous serum Cr, initial diameter of the treated kidney, vascular resistive index, and mono vs. global stenting were not significantly associated to post stenting RF. CONCLUSIONS: RS appears to be associated with RF stabilization in the majority of patients with CRF.     

Atherosclerotic renal artery stenosis: overtreated but underrated?

Despite evidence of only moderate clinical benefit, application of renal endovascular stent procedures has increased at least four-fold in the past decade. Medicare is reviewing national coverage regarding reimbursement, questioning whether outcome data warrant many of these procedures. Several prospective, randomized trials are now in progress to compare outcomes with optimized medical therapy with and without stenting. Current imaging methods establish primarily the presence and severity of vascular occlusive disease. Optimal treatment for individual patients remains in flux and is reviewed here. Most important, nephrologists await development of tools to predict reliably when renal parenchymal injury is beyond recovery and/or when revascularization can produce meaningful salvage of kidney function.     

Is duplex scanning the best screening test for renal artery stenosis?

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.     

Renal stenting for incidentally discovered renal artery stenosis: is there any outcome benefit?

We evaluated whether there was a clinical outcome benefit in patients incidentally discovered to have high-grade renal artery stenosis (RAS) and treated with percutaneous transluminal renal angioplasty and stenting (PTRAS) at the time of angiogram for another indicated procedure. A retrospective chart review was performed on all patients undergoing renal arteriography over 4 years at our academic tertiary-care referral center. Review of catheterization reports was used to identify patients diagnosed with high-grade RAS (reduction of > or =70% luminal diameter by arteriogram). Patients treated with PTRAS were identified. Baseline and postprocedure blood pressure (BP, an average of at least three independent measurements), glomerular filtration rate, serum creatinine, and antihypertensive medication regimen were compared for 12 months of follow-up. Over 4 years, 124 patients underwent renal arteriography and 78 (63%) were diagnosed with high-grade RAS. Fifty-eight patients (74% of those with high-grade RAS) received PTRAS. Patients treated with PTRAS had similar baseline characteristics to those with high-grade RAS with no intervention, with the exception of lower diastolic BP (DBP; 74 +/- 11.2 vs. 80 +/- 14.2 mm Hg, p = 0.04) and a higher proportion of hyperlipidemia (78 vs. 55%, p = 0.05). Thirty-eight out of 58 PTRAS patients (66%) received sufficient follow-up to assess outcomes. When baseline and postprocedure variables were compared in PTRAS patients with 12-month follow-up, there was a reduction in systolic BP (SBP, 153 +/- 20.8 vs. 136 +/- 27.2 mm Hg, p = 0.01) and mean arterial pressure (MAP, 103 +/- 11.2 vs. 95 +/- 14 mm Hg, p = 0.04). When these patients were stratified by those with an increase, decrease, or no change in postprocedure antihypertensive medications, significant reductions in SBP, MAP, and DBP were noted only in the patient population that also had an increase in the number of antihypertensive medications. No differences in renal insufficiency were detected. Patients with high-grade RAS incidentally discovered during arteriography performed for extrarenal disease and treated with PTRAS have a modest reduction in BP, which is significant only in those patients with an increased number of antihypertensive medications postprocedure. Caution must be taken in stenting patients with incidental RAS as outcome benefit may be minimal when compared to medical management only.     

Case report of transplant renal artery stenosis secondary to mechanical renal artery kinking: Balloon angioplasty as a supportive diagnostic tool?

Introduction and importanceRenal vascular complications are a significant cause of morbidity in living donor renal transplantation. Among renal vascular complications, transplant renal artery stenosis (TRAS) secondary to mechanical kinking is a rare but important cause of early graft dysfunction. Identifying this phenomenon and correcting the underlying cause is critical to graft viability in the post-operative period. This case illustrates the importance of balloon angioplasty in identifying this complication and prompting surgical correction.Case presentationWe describe the case of a 67-year-old male who received a right-sided living donor kidney graft for Stage IV Chronic Kidney Disease secondary to biopsy proven Ig-A nephropathy. In the post-operative course, serum creatinine remained elevated and Doppler showed low-normal vascular flow velocities. Renal angiogram indicated transplant renal artery stenosis secondary to the rare phenomenon of mechanical kinking. Findings noted during unsuccessful angioplasty supported the diagnosis and surgical repositioning of the graft provided definitive repair. Post-operative serum creatine trended down and urine output improved within 24 h. Patient was stable at two month follow up.Clinical discussionTransplant renal artery stenosis secondary to mechanical kinking can cause significant graft dysfunction in the post operative period. Previous case reports and literature review has found balloon angioplasty to be ineffective in correcting this underlying cause of TRAS. In line with previous reports, balloon angioplasty failed to correct the stenosis; however, this provided additional diagnostic information by identifying the kink and prompting surgical repair.ConclusionTransplant renal artery stenosis secondary to mechanical kinking can be difficult to identify by renal angiogram alone. Attempted balloon angioplasty can confirm the diagnosis and prompt definitive surgical repair.     

Hyponatraemic–hypertensive syndrome in a 15-month-old child with renal artery stenosis

In this report we present the case of a 15-month-old girl with hyponatraemic–hypertensive syndrome (HHS) caused by stenosis of the left renal artery. On sonographic examination the contralateral non-stenotic kidney appeared enlarged and with cortical hyperechogenicity mimicking a parenchymal lesion. After successful percutaneous transluminal angioplasty, when the girl became normotensive, her serum electrolyte and acid–base balance became normal within a few days. The contralateral non-stenotic kidney hyperechogenicity also disappeared, but only after a period of 6 months, suggesting parenchymal damage due to tubulointerstitial injury, even though reversible. Our case confirms that renovascular hypertension may rarely also be present with HHS in children and that metabolic and morphological alterations are reversible after the resolution of arterial stenosis.     

How to limit screening of patients for atheromatous renal artery stenosis in two-drug resistant hypertension?

BACKGROUND: The DRASTIC model based on nine variables (age, gender, recent onset of hypertension, smoking status, body mass index (BMI), abdominal bruit, atherosclerosis, dyslipidemia and creatininemia) has been proposed to predict renal artery stenosis (RAS) occurrence. METHODS: In a prospective multicenter study, the clinical usefulness of the DRASTIC model was checked in 336 patients with two-drug resistant hypertension. RAS was excluded using at least color Doppler sonography. RAS was diagnosed using at least renal angiography. The statistical dependence (Z(Rho)) analysis was applied to investigate further the relationships between each variable and presence of RAS. Results: The prevalence of RAS (n=51) was 15%. The goodness-of-fit test that compared observed RAS to predicted RAS using the DRASTIC model was not significant. Accordingly, the multivariate logistic regression indicated that only three parameters (abdominal bruit, atherosclerotic vascular disease and BMI <25 kg/m2) were significantly linked to RAS. The Z(Rho) methodology revealed that calculated renal function <60 ml/min and age >58 yrs (median) were also significantly linked to RAS. No variable or combination of variables offered satisfactory positive predictive values for the RAS diagnosis. The combination of the five significantly linked variables had a negative predictive value of 98%, and allowed RAS detection with a sensitivity of 96%. In our population, RAS screening could have been avoided in 30% of our patients screened. CONCLUSIONS: The DRASTIC model was unsuitable for clinical use in our sample population. In our population, renal arteries were considered stenosis free with a probability of 98% in refractory hypertensive overweight patients, aged < or = 58 yrs, with satisfactory renal function and without both abdominal bruit and atherosclerotic vascular disease.     

Is ghrelin a biomarker for mortality in end-stage renal disease?

Ghrelin is involved in the pathogenesis of protein-energy wasting (PEW), inflammation, and cardiovascular complications in end-stage renal disease (ESRD). Plasma ghrelin may prove to be a powerful biomarker of mortality in ESRD but should be considered in the context of assay specificity, other weight-regulating hormones, nutritional status, systemic inflammation, and cardiovascular risk factors. ESRD patients with PEW, systemic inflammation, and low ghrelin and high leptin concentrations have the highest mortality risk and may benefit the most from ghrelin therapy.     

Symposium: controversies in cerebrovascular disease 2. Should patients be screened for asymptomatic carotid artery stenosis?

Objective

To evaluate, against published guidelines, the potential role of screening to reduce the risk of stroke and death from asymptomatic carotid artery stenosis (ACAS).

Data sources

Papers selected for review were identified through a GRATEFUL MED literature search, from personal files and from references documented in identified papers.

Study selection

Population studies concerning disease prevalence, natural history studies related to risk of stroke, randomized controlled trials related to carotid endarterectomy and natural history studies related to the risk of developing ACAS were considered for review.

Data extraction

An estimate was made of the potential for stroke resulting from ACAS in the general population. This was evaluated against the positive predictive value of duplex scanning, and the number of patients needing to be screened to prevent a stroke was estimated.

Data synthesis

The prevalence of ACAS in the general population was estimated to range from 2% to 8% for ACAS 50% or greater and to range from 1% to 2% for ACAS 80% or greater. The yearly risk of stroke or death from undetected ACAS was estimated to be 0.16% for ACAS 50% or greater and 0.06% for ACAS 80% or greater. The estimated number of patients needing to be screened to prevent 1 stroke would range from 850 to 1700 (and potentially as high as 8500).

Conclusions

General screening for ACAS to prevent stroke and death cannot be recommended when evaluated against available guidelines. The decision to screen individual patients will require judgement, continued evaluation and surveillance of the results of such screening by the treating physician.