Progressive renal dysfunction despite successful renal artery angioplasty in a single kidney

Controversies in renal artery stenosis: a review by the American Society of Nephrology Advisory Group on Hypertension

Renovascular hypertension is a recognized secondary potentially curable cause of hypertension since the work of Harry Goldblatt. Operative treatments for renal artery stenosis (RAS) have been offered for decades and percutaneous interventions have been widely available for 20 years. Stenting has largely obviated recurrence and modern techniques have contributed greatly to the safety of the procedure. Nevertheless, controversy abounds and prospective randomized trials have not successfully documented the value of intervention in patients with atherosclerotic RAS. The patient population has also changed remarkably. Whereas earlier patients with RAS were identified on clinical grounds, RAS is now commonly found serendipitously during angiography for other reasons. Whether or not these patients benefit from 'drive by' stenting is unknown. The practice may be hazardous and should be critically examined. A dialog and closer cooperation between cardiologists and nephrologists is warranted and organized programs should be formulated to address this problem.

MR-derived renal morphology and renal function in patients with atherosclerotic renovascular disease

Appropriate selection of patients with atherosclerotic renovascular disease (ARVD) for revascularization might be improved if accurate non-invasive investigations were used to assess severity of pre-existing parenchymal damage. The purpose of this study was to evaluate the associations between magnetic resonance imaging (MRI)-measured renal morphological parameters and single-kidney glomerular filtration rate (GFR) in ARVD. Three-dimensional (3D)-MRI was performed on 35 ARVD patients. Renal bipolar length (BL), parenchymal volume, parenchymal (PT), and cortical thicknesses (CT) were measured in 65 kidneys. Thirteen kidneys were supplied by normal vessels, 13 had insignificant (<50%) renal artery stenosis (RAS), 33 significant (>or=50%) RAS, and six complete vessel occlusion. All patients underwent radioisotopic measurement of single-kidney GFR (isoSK-GFR). Overall, 3D parameters such as parenchymal volume were better correlates of isoSK-GFR (r=0.86, P<0.001) than BL (r=0.78, P<0.001), PT (r=0.63, P<0.001) or CT (r=0.60, P<0.001). Kidneys with >or=50% RAS did show significant reduction in mean CT compared to those supplied by normal vessel (5.67+/-1.63 vs 7.28+/-1.80 mm, P=0.002; 22.1% reduction) and an even greater loss of parenchymal volume (120.65+/-47.15 vs 179.24+/-86.90 ml, P<0.001; 32.7% reduction) with no significant reduction in BL. In a proportion of >or=50% RAS kidneys, a disproportionately high parenchymal volume to isoSK-GFR was observed supporting a concept of 'hibernating parenchyma'. 3D parameters of parenchymal volume are stronger correlates of isoSK-GFR than two-dimensional measures of BL, PT or CT. 3D morphological evaluation together with isoSK-GFR might be useful in aiding patient selection for renal revascularization. Kidneys with increased parenchymal volume to SK-GFR might represent a subgroup with the potential to respond beneficially to angioplasty.

A Review of the Current Treatment of Renal Artery Stenosis

PURPOSE

Atherosclerotic renal artery stenosis (ARAS) is associated with morbidity and mortality consequent to progressive ischemic renal failure and the cardiovascular consequences of hypertension. There is considerable uncertainty concerning the optimal management of patients with this condition. This review considers the aetiological factors and the physiologic consequences of ARAS and compares the results of clinical studies of medical and endovascular therapies on blood pressure control and preservation of renal function.

RESULTS

Although, in patients with fibromuscular disease the results of percutaneous transluminal angioplasty (PTA) are clearly superior to medical therapy and surgery, in asymptomatic patients with ARAS the antihypertensive benefits and preservation of renal function of endovascular, surgical and medical therapies appear similar. In selected symptomatic patients interventions may, however, be life-saving. Surgery is generally reserved for arterial occlusions with preserved renal parenchyma and function.

CONCLUSIONS

The results of larger, multicentre, randomised, controlled trials are required to clearly clarify the role of interventional therapy in asymptomatic patients.

Renovascular disease

The gold standard for the diagnosis of renal artery stenosis is angiography, with response to treatment the proof of its significance. Non-invasive methods of investigation are required and are now available including functional imaging, ultrasound, CT and MR angiography and the merits and limitations of these tests are discussed.

Individual kidney function in atherosclerotic nephropathy is not related to the presence of renal artery stenosis

BACKGROUND

Atherosclerotic renovascular disease is increasingly recognized as an important cause of renal failure in patients over 60 years of age but the processes leading to renal dysfunction have not been defined. We have examined the relationship between renal artery stenosis and individual renal function in patients with atherosclerotic renal artery stenosis.

METHODS

In this prospective descriptive study over a 25-month period, we examined the relationship between the presence of renal artery stenosis and single kidney glomerular filtration rate (SKGFR). SKGFR was measured using a novel method of synchronous (51)Chromium ethylenediamine tetraacetic acid glomerular filtration rate ((51)CrEDTA-GFR) and (99m)Technetium dimercaptosuccinic acid ((99m)TcDMSA) scintigraphy. We studied 79 patients with a mean age of 68.9 years (25.2-88.2), 44 males and 35 females. The mean age of the males was 70 years (60-80) and females 67 years (25.2-88.2).

RESULTS

We found that the precision of the SKGFR was 2 ml/min. For paired kidneys we found: (i) no significant difference between kidneys with stenosis (17.3 ml/min) compared to those without stenosis (13.6 ml/min) (P=0.22); (ii) kidneys with occluded renal arteries had significantly less function (2.6 ml/min) than those without occlusion (24.5 ml/min) (P<0.05). When degree of renal arteries stenosis was correlated with SKGFR there was a reduction with an increasing degree of stenosis (<30% 27 ml/min, 30-60% 17.7 ml/min, >60% stenosis 15 ml/min, P=0. 016).

CONCLUSIONS

These data demonstrate that SKGFR provides a reproducible measure of individual kidney function. There was a similar impairment of function in paired kidneys with and without renal artery stenosis, but occlusion was associated with significant reduction in function compared to the contralateral kidney. This suggests that there is a process causing renal dysfunction in patients with atherosclerotic disease independent of renal artery narrowing.

Proteinuria in atherosclerotic renovascular disease

Proteinuria is well described in atherosclerotic renovascular disease (ARVD), but the prevalence is unknown, and the pathogenesis may vary between patients. Substantial proteinuria (> 2 g/day) however, would be regarded by many as atypical of ARVD. We studied 94 patients (52 male) with ARVD, median age 67 years (range 49-87). Digital subtraction angiography was performed on all patients. Protein was assayed in 24-h urine samples and GFR derived using the Cockroft-Gault formula. Forty-nine patients (52%) had proteinuria < 0.5 g/24 h. Proteinuria increased with worsening renal function. Biopsies from seven non-diabetic patients with substantial proteinuria showed: minimal changes (1); glomerular sclerosis with marked ischaemic changes (3); focal glomerulosclerosis (2); and athero-emboli (1). Proteinuria, rather than being indicative of other pathology, is often a marker of severity of parenchymal disorder in atherosclerotic nephropathy, which itself is the major determinant of renal dysfunction in patients with ARVD.

Atherosclerotic nephropathy

BACKGROUND

Lipid moieties may have direct or indirect effects on the kidney. The association of aortic atherosclerosis and renal artery stenosis has focused interest on this as an important cause of end-stage renal failure. This article seeks to examine the evidence for the entity of atherosclerotic nephropathy.

METHODS

Published data on the incidence of atherosclerotic renal artery stenosis as the cause of end-stage renal failure are presented, as well as the associated features of atherosclerotic renal stenosis.

RESULTS

Atherosclerotic renal artery stenosis (ARAS) has been estimated to be the cause of between 14 and 25% of patients reaching end-stage renal failure in older age groups. There is considerable evidence of proteinuria in patients with ARAS. Recent data have shown that renal length may decrease by 1 cm or more in 35% of kidneys with > 60% stenosis. However, other data suggest that renal function in kidneys without renal artery stenosis but with contralateral renal artery stenosis may be similarly decreased.

CONCLUSION

Many processes contribute to renal dysfunction in atherosclerotic aortic disease. Although ischemia may play a role, there is considerable evidence that processes such as atheroembolic disease may be important, and it would be better to use the term "atherosclerotic nephropathy" for this important disease entity.

Endovascular stents for renal artery revascularization

Revascularization cures or attenuates the clinical manifestations of renal artery stenosis (hypertension, ischemic nephropathy, pulmonary edema, angina, and congestive heart failure). Traditional approaches have been sub-optimal due to low rates of success and long-term patency after angioplasty, and to relatively high rates of perioperative morbidity and mortality. Endovascular stent placement is an alternative interventional method for renal artery revascularization. Technical success rates are excellent, and the impact on clinical outcomes (blood pressure, renal function, and cardiac complications) is promising.

Ostial renal artery stent placement for atherosclerotic renal artery stenosis in patients with coronary artery disease

To test the utility of endoprosthetic treatment for ostial renal artery stenosis, and to examine blood pressure and its treatment, serum creatinine, and restenosis rate, 44 ostial renal stent placements were performed in 30 patients with concomitant coronary artery disease, arterial hypertension, and the indication for angiotensin converting enzyme (ACE) therapy. There was a marked decrease in systolic and diastolic blood pressure (163+/-30 to 145+/-17 and 93+/-18 to 83+/-10 mm Hg; P < 0.008) with a decrease in number of medication (3.2+/-0.9 to 2.8+/-1.0; P = 0.005). In 5 out of 8 patients not receiving an ACE inhibitor, this drug could be added. Serum creatinine changed from 1.46+/-0.7 mg/dl to 1.39+/-0.58 mg/dl (P = ns). Three patients showed restenosis (12.5%). Ostial stenting lowers blood pressure, decreases antihypertensive drugs and increases medication flexibility.