Baseline renal function and surgical revascularization in atherosclerotic renal arterial disease in the elderly

The impact of atherosclerotic renovascular disease on diabetic renal failure

Atherosclerotic renovascular disease (ARVD) is common in the general population, and its prevalence increases with age. Parallel studies show it is also common in patients with diabetes. The widespread use of angiotensin converting enzyme inhibitors and angiotensin receptor antagonists for heart and kidney disease might therefore expose arteriopathic diabetic patients to potential harm if they had critical renal artery stenosis. This review looks at the natural history of ARVD in the diabetic and non-diabetic populations: while it is common, it only rarely leads to renal failure. Hence intervention to revascularize ischaemic kidney son the basis of radiological appearances alone may subject some patients to unnecessary therapy. Although untested by randomized trial, a policy of watchful waiting may be the simplest strategy for most diabetic patients with suspected ARVD, reserving angiography and angioplasty (usually backed up by a stent) for those with an abrupt decline in renal function and no other cause for renal deterioration. Future clinical trials may better define subgroups of patients who will truly benefit from renal revascularization.

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.

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.

Magnetic resonance angiography in progressive renal failure: a technology assessment

The objective of this study was to assess the cost-effectiveness of magnetic resonance angiography (MRA) imaging for renal artery stenosis (RAS) in people with progressive renal failure (PRF). We created a simulation model to determine the incremental cost-effectiveness of MRA screening in PRF compared with the fallback strategy of not screening. Costs, probabilities, and utilities were estimated from the literature and from institutional data. A three-state Markov model was used to simulate the progression from PRF to end-stage renal disease and death. In our baseline analysis, assuming a sensitivity of 0.85 and a specificity of 0.8 of MRA for RAS, we obtained an incremental cost-effectiveness of MRA screening compared with no screening of $2,214 per quality-adjusted life year saved, which is less than many commonly performed procedures. Under our baseline assumptions, if the receiver-operating characteristic curve of MRA for RAS is better than the chance curve, then MRA screening would be cost-effective. The analysis was most sensitive to assumptions about renal function after correction of RAS and prevalence of RAS, although the results show that MRA remains cost-effective for reasonable ranges of these assumptions. The use of MRA in PRF would be a worthwhile investment of resources in comparison with many currently funded procedures. The expense and morbidity associated with end-stage renal disease make any reasonable way of delaying or preventing the disease worth examining in detail.

Management of atherosclerotic renal artery disease in younger patients

From 1970 to 1990, 57 patients 50 years old or younger were treated for hypertension caused by atherosclerotic renal artery disease. Predisposing factors for atherosclerosis included smoking in 43 cases, hyperlipidemia in 15, diabetes in 8 and hyperuricemia in 8. Of the patients 47 had a family history of atherosclerotic vascular disease or a significant related disorder. Evidence of generalized atherosclerosis was present in 55 patients. Atherosclerotic renal artery disease was present unilaterally in 16 cases, bilaterally in 39 and in a solitary kidney in 2. Of the patients 34 were treated surgically, 20 medically and 2 by percutaneous angioplasty. Surgically treated patients experienced significant postoperative improvement in blood pressure (p = 0.001) and renal function (p = 0.05). Medically treated patients experienced significant improvement in blood pressure (p = 0.03) but renal function deteriorated. Younger patients with atherosclerotic renal artery disease suffer from a more severe and accelerated form of atherosclerosis than older patients. Although blood pressure control can be achieved with medical treatment, surgical revascularization offers the best opportunity for stabilization or improvement of renal function.