Renal artery stenosis and ischemic nephropathy

Renal artery stenosis (RAS), in its most severe form, can result in diminished renal function and loss of kidney mass. The prevalence of ischemic nephropathy is greatly under-appreciated in the elderly population and is the source of substantial morbidity and mortality. Diagnostic tests for RAS in patients with renal insufficiency are problematic, and medical therapy does little to slow the natural progression of the disease. Renal artery stenting can achieve long-term vessel patency and has been shown to preserve renal function. Proper technique and careful case selection are critical to the success of such procedures. Large-scale trials are needed to clearly identify groups of patients who will benefit most from percutaneous revascularization.

Renal artery stenosis: a common, treatable cause of renal failure?

Chronic azotemic renovascular disease is common in patients with atherosclerosis. Its prevalence appears to be increasing in the aging population. How often it is the primary cause of end-stage renal disease (ESRD) is not yet certain. Some studies suggest that 10%-40% of elderly hypertensive patients with newly documented ESRD and no demonstrable primary renal disease have significant renal artery stenosis (RAS). Atherosclerotic vascular occlusive disease of the renal arteries does progress, but current rates of progression and occlusion are lower than those reported a decade ago. Methods of identifying patients whose renal function is at true risk from vascular occlusive disease and determining who will benefit from intervention remain elusive. The presence of RAS in an azotemic patient can be assessed with noninvasive and risk-free radiologic techniques, including Duplex doppler velicometry and magnetic resonance angiography. Functional tests that predict the change in renal function after revascularization are not yet available. However, a renal length of greater than 7.5 cm in the absence of renal cysts and a short history of renal functional deterioration indicate a good prognosis. Patients with recent deterioration in renal function, those with bilateral renal artery stenosis or stenosis to a single functioning kidney, those with flash pulmonary edema, advanced chronic renal failure, or ESRD (who have much to gain), those with reversible azotemia during angiotensin-converting enzyme inhibitor (ACEI) or angiotensin receptor antagonist (ARB) therapy, and those whose conditions cannot be managed medically should be considered for revascularization. Results from recent controlled clinical trials of the response to percutaneous transluminal renal artery angioplasty (PTRA) and stenting indicate that improvement in blood pressure control or renal function is not a predictable outcome of renal revascularization. In azotemic groups, 25%-30% of patients achieve important recovery of renal function. Thus, significant progress has been made recently in determining whether RAS is a frequent, treatable cause of renal failure. The decision to recommend revascularization remains a difficult balance between the risks and expense of the procedure and the undoubted benefits that accrue if renal function is successfully stabilized.

Outcome of renal artery reconstruction: analysis of 687 procedures

OBJECTIVE

To evaluate the short- and long-term results of surgical reconstruction of the renal arteries, the authors review their experience with more than 600 reconstructions performed over a 12-year period.

SUMMARY BACKGROUND DATA

Reconstruction of the renal arteries, whether for primary renal indications or concomitantly with aortic reconstruction, has evolved over the past 40 years. There is concern that renal artery reconstructions carry significant rates of mortality and morbidity and may fare poorly compared with less-invasive procedures.

METHODS

From 1986 to 1998, 687 renal artery reconstructions were performed in 568 patients. Of these, 105 patients had simultaneous bilateral renal artery reconstructions. Fifty-six percent of the patients were male; 11% had diabetes; 35% admitted to smoking at the time of surgery. Mean age was 67 (range, 1 to 92). One hundred fifty-six (23%) were primary procedures and the remainder were adjunctive procedures with aortic reconstructions; 406 were abdominal aortic aneurysms and 125 were aortoiliac occlusive disease. Five hundred procedures were bypasses, 108 were endarterectomies, 72 were reimplantation, and 7 were patch angioplasties. There were 31 surgical deaths (elective and emergent) in the entire group for a mortality rate of 5.5%. Predictors of increased risk of death were patients with aortoiliac occlusive disease and patients undergoing bilateral simultaneous renal artery revascularization. Cause of death was primarily cardiac. Other nonfatal complications included bleeding (nine patients) and wound infection (three patients). There were 9 immediate occlusions (1.3%) and 10 late occlusions (1.5%). Thirty-three patients (4.8%) had temporary worsening of their renal function after surgery.

CONCLUSION

Renal artery revascularization is a safe and durable procedure. It can be performed in selected patients for primary renovascular pathology. It can also be an adjunct to aortic reconstruction with acceptable mortality and morbidity rates.

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.

Surgical results of abdominal aortic aneurysm repair in patients with chronic renal dysfunction

The purpose of this study was to determine the influence of preoperative renal dysfunction on the outcome of patients undergoing elective, infrarenal abdominal aortic aneurysm (AAA) repair. Patients undergoing AAA repair from 1984 to 1996 (n = 250) were divided into 2 groups, according to their preoperative serum creatinine levels: > or = 1.5 mg/dl (group A, n = 33) and < 1.5 mg/dl (group B, n = 217). There was no apparent difference in the incidences of preoperative risk factors, excluding ischemic heart disease, between the groups. The mortality rates of the 2 groups did not differ (9.9% vs 3.2% in groups A and B, respectively, p = 0.13), but the morbidity rate of group A (30.3%) was significantly higher than that of group B (12.9%, p = 0.0095). The 5-year cumulative survival rate of group A patients was 60%, which was significantly lower (p < 0.0001) than that of group B patients (84%). Five group A patients underwent simultaneous renal artery reconstruction, which relieved postoperative renal deterioration in 4, although 2 of them developed chronic renal failure requiring hemodialysis over 5 years after the operation. These findings suggest that morbidity and long-term survival in patients with renal dysfunction can be severe after AAA repair and that simultaneous renal artery reconstruction may delay renal function decline.

Long-term survival after surgical revascularization for atherosclerotic renal artery disease

PURPOSE

We analyzed the long-term clinical outcome and survival after surgical revascularization for atherosclerotic renal artery stenosis.

MATERIALS AND METHODS

The study group comprised 222 patients who underwent surgical revascularization for atherosclerotic renal artery stenosis between 1974 and 1987. The indications for performing surgical revascularization were treatment of hypertension in 60 patients, preservation of renal function in 12, and control of hypertension and preservation of renal function in 148. Postoperative blood pressure, renal function and survival data were analyzed during a mean followup of 7.4 years.

RESULTS

There were 5 operative deaths (2.2%) and postoperative thrombosis or stenosis of the repaired renal artery occurred in 16 patients (7.3%). Long-term cure or improvement of renovascular hypertension was achieved in 72.4% of patients. Preoperative renal function correlated significantly with a favorable blood pressure response to surgical revascularization (p = 0.013). Long-term improvement or stabilization of renal function was achieved in 71.3% of patients. Preoperative renal function (p = 0.034) and bilateral atherosclerotic renal artery stenosis (p = 0.04) correlated significantly with a favorable renal function result after surgical revascularization. Actuarial 5 and 10-year survivals for the entire series from the time of surgical revascularization were 81 and 53%, respectively. The expected 5 and 10-year survivals for a comparable healthy population are 89 and 77%, respectively. Using a multivariate analysis, factors correlating with diminished long-term survival were age older than 60 years (p = 0.002), coronary artery disease (p = 0.031), and previous vascular operations (p = 0.001).

CONCLUSIONS

These data support the long-term therapeutic efficacy of surgical revascularization in patients with atherosclerotic renal artery stenosis. The merits of newer forms of therapy, such as percutaneous transluminal angioplasty and endovascular stenting, must ultimately be weighed against these results.

Atherosclerotic ischemic renal disease

Over the past decade, ischemic nephropathy has gained recognition as a distinct and treatable clinical entity. Atherosclerotic renal artery stenosis is the leading cause of ischemic renal disease. Among the aging population entering renal replacement programs, both renal artery and systemic atherosclerosis are common. Over recent years, patients with ischemic renal disease are presenting later and have diffuse atherosclerosis and other comorbid conditions. Improved screening techniques, patient selection, and interventional approaches have resulted in better outcomes in most centers. Percutaneous transluminal renal angioplasty has emerged as the treatment of choice in some centers for nonostial renal artery stenosis. Both percutaneous transluminal renal angioplasty and surgical repair have proven beneficial for renal function salvage. Many studies have elegantly demonstrated the pathophysiologic consequences of acute ischemia to the kidney. The concepts derived from acute studies have served as a springboard for considering the adaptive and maladaptive renal responses to chronic ischemia.

Revascularization of the solitary kidney: a challenging problem in a high risk population

BACKGROUND

Patients with significant atherosclerotic stenosis involving the artery to a solitary functioning kidney present a clinical challenge.

METHODS

From August 1987 through August 1995, 35 of these patients (average age, 68.4 +/- 6.9 years) were treated. Comorbid conditions included previous myocardial infarction in 23% of the patients, congestive heart failure (CHF) in 34%, chronic obstructive pulmonary disease in 20%, and diabetes in 20%. The average creatinine level of the patients was 2.5 +/- 1.5 mg/dl. Indications for revascularization were hypertension in 86%, hypertensive crisis with CHF in 17%, and renal insufficiency in 69%. Procedures performed included 19 extra-anatomic bypasses, 8 concomitant with infrarenal aortic reconstruction and 2 concomitant with thoracoabdominal aortic aneurysm repair; 1 visceral segment endarterectomy; 1 renal artery endarterectomy with reimplantation; I superior mesenteric to renal artery bypass; 1 aortorenal bypass; and 2 percutaneous angioplasties with staged nephrectomies.

RESULTS

At discharge, 91% of patients had stable or improved renal function with an average creatinine level of 1.7 +/- 0.8 mg/dl. Hypertension was cured or improved in 85%. Perioperative mortality was 6%, and major morbidity was 43%, including the need for permanent (9%) and temporary (9%) dialysis, respiratory insufficiency (18%), two early reoperations, six cardiac complications, one case of gastrointestinal bleeding, and one stroke. In the follow-up period (mean duration, 39.2 months), survival has been 73%, and no additional patients have required dialysis.

CONCLUSIONS

Although significant perioperative morbidity exists in this high risk population, the long-term preservation of renal function and improvement in hypertension make solitary renal revascularization worthwhile.

The case for renal revascularization

This report reviews renovascular disease, hypertension and renal parenchymal dysfunction. The primary lesions responsible are discussed as well as the strategies for restoring normal renal perfusion. The natural history studies document progressive impairment of renal perfusion and the consequence of renal dysfunction. Renal revascularization interrupts this pathway by relieving or lessening hypertension and preserving renal function which are the therapeutic options.