Comparative Analysis of Percutaneous Transluminal Angioplasty and Operation for Renal Revascularization

Luke S. Erdoes, MD, Scott S. Berman, MD, Glenn C. Hunter, MD, and Joseph L. Mills, MD

0 Contemporary patients requiring renal revascularization often have diffuse atherosclerosis, and increasingly undergo intervention for salvage of renal function rather than control of hypertension alone. Risk-benefit analyses and outcome data are difficult to obtain, since few reports have analyzed a modern, unselected series of consecu- tive patients subjected to renal revascularization by surgical as well as interventional techniques. We reviewed our &year experience with 76 consecutive renal revascularizations in 63 patients. Indications for intervention were hypertension and renal salvage, 60% (n = 38); hypertension, 24% (n = 15); renal salvage, 9.5% (n = 6); and other, 6.5% (n = 4). Ninety-four percent (n = 59) of patients had atherosclerotic occlusive disease of the renal arteries. Percutaneous transluminal angioplasty (PTA) was initially performed on 18 renal arteries in 16 patients, of whom 56% (n = 9) subsequently required surgical reconstruction. Fifty-eight surgical reconstructions were performed in 56 patients and consisted of aortorenal bypass (n = 27), aortorenal endarterectomy (n = 18), and extra-anatomic bypass (n = 13). Concomitant aortic replacement was required in 57% (n = 32) of patients. Preoperative risk factors and operative indications did not differ between the PTA and surgical reconstruction groups. Morbidity and mortality rates associated with PTA were 33% and 4.8%, respectively, while for surgical treatment the morbid- ity rate was 7% and the mortality rate 5.3% (f = NS). Functional improvement was achieved in 74% of surgically treated patients compared with 22% of PTA-treated patients (P < 0.01). Actuarial renal artery primary patency at 48 months was 81% for the surgery group and 17% for the PTA group (p < 0.01). Aortorenal bypass, endarterec- tomy, and extra-anatomic bypass were equally efficacious (P > 0.05). The results of surgical reconstruction are excellent, offering more durable patency and functional improvement than PTA, without increased risk. The opera- tion should be tailored to fii the individual patient’s disease, since the results of endarterectomy and bypass procedures are equivalent. 0 1996 by the National Kidney Foundation, Inc.

INDEX WORDS: Renal artery disease; angioplasty; renal artery bypass.

S EVERAL recent studies have documented an apparent change in the indications for re-

nal revascularization.‘-” In contrast to previous reports of studies of younger patients with hyper- tension and a high incidence of renal artery fi- bromuscular dysplasia,2 contemporary series fea- ture older patients with diffuse atherosclerosis and a high incidence of renal dysfunction. De- spite these differences, the results and durability of surgical revascularization have been excel- lent.4-7

Although it is appealing to use medical therapy in severely ill patients with renovascular hyper-

From the Section of Vascular Surgery, Department of Sur- gery, The University of Arizona Health Sciences Center, Tuc- son, AZ.

Received July 13, 1995; accepted in revised form Decem- ber 14, 1995.

Presented at the 19th Annual Meeting of the Southern Association for Vascular Surgery, January 25-28, 1995, Can- curt, Mexico.

Address reprint requests to Scott S. Berman, MD, Section of Vascular Surgery, University of Arizona Health Sciences Center, I.501 N Campbell Ave, Room 5406, Tucson, AZ 8.5724.

0 1996 by the National Kidney Foundation, Inc. 0272~6386/96/2704-0005$3.00/O

tension, it is less successful than other available therapies. ‘J The natural history of severe renal artery stenosis is progression and ultimate occlu- sion.’ Azotemia is also progressive, with a sig- nificant number of patients becoming dialysis dependent. lo,’ ’ Poorly controlled hypertension undoubtedly contributes to morbidity and mortal- ity secondary to stroke and myocardial infarction.

It has been suggested that percutaneous trans- luminal angioplasty (PTA) is the therapy of choice for renal artery stenosis.‘2-‘6 Patients af- flicted with fibromuscular dysplasia are improved or cured of their hypertension in 92% of cases; moreover, this improvement appears durable.‘4,‘5 Results are far less encouraging for atheroscle- rotic lesions, particularly those involving the re- nal artery ostium. Although initial success rates in the range of 85% have been reported, the long- term restenosis rate approximates 35%. I7

Surgical options for the treatment of reno- vascular disease consist of endarterectomy, by- pass with autologous or prosthetic conduits, and extra-anatomic bypass.’ While endarterectomy is well suited to patients with focal disease or those who also require aortic replacement,” aortorenal bypass has become the standard and yields excel-

496 American Journal of Kidney Diseases, Vol 27, No 4 (April), 1996: pp 496-503

TECHNIQUES OF RENAL REVASCULARIZATION 497

lent long-term results.4.7 In selected patients, ex- tra-anatomic bypass is a useful option because it avoids aortic clamping and direct operation on a diseased aorta.7 The superiority of any one of these techniques over the others has not been established.

This study was undertaken to compare the re- sults of angioplasty with operation in a contem- porary patient group with a high prevalence of systemic atherosclerosis and renal dysfunction. A second objective was to determine the results and durability of the various surgical revascular- ization techniques.

PATIENTS AND METHODS

The records of 63 patients in whom 76 consecutive renal artery revascularizations were performed at the University Medical Center and the Tucson Veteran’s Affairs Medical Center during the period from January 1989 through June 1994 were reviewed in detail. Demographic data, preopera- tive blood pressure, and medication history were recorded as well as renal function and all diagnostic test results. The indication for intervention was recorded along with the details of the particular procedure(s). Concomitant aortic reconstruc- tions or other vascular procedures including their indications were noted. The patients were evaluated at least yearly in the clinic for blood pressure measurement and serum creatinine determination. Objective patency data were obtained with one or a combination of arteriography, isotope renography, duplex imaging, or computed tomographic imaging. If objec- tive patency data were not available, patency was inferred by the maintenance or improvement of the initial postoperative status (particularly if revascularization was done to a single kidney).

Surgical therapy was chosen for 32 patients in need of concomitant aortic reconstruction, for 20 patients with ostial lesions considered to be at low surgical risk, for two patients with traumatic dissection of the renal artery, and for nine patients with failed angioplasty. In contrast, PTA was the selected first-line therapy for two patients with fibromuscular disease, for seven patients with mid-artery lesions, and for seven patients with selected ostial lesions who were consid- ered poor surgical candidates. Patients were excluded if they had reconstruction of widely patent renal arteries as part of another procedure, or underwent accessory renal artery reim- plantation during aortic surgery. Patients with renal transplant arterial stenoses were likewise excluded.

Patient outcome data for blood pressure control and renal function were defined according to the standards set forth in the original Cooperative Study on Renovascular Hyperten- sion” with modifications as outlined by Dean et al.” Cured patients had a diastolic blood pressure less than 95 mm Hg without medication. Improved blood pressure was defined by a reduction of two antihypertensive medications and main- taining a diastolic blood pressure less than 9.5 mm Hg, or a reduction of one medication with a moderate (diastolic blood pressure < 20 mm Hg) or a significant (diastolic blood pres-

sure > 20 mm Hg) decrease in pressure with no increase in the number of medications. Renal dysfunction was defined as a serum creatinine greater than 1.5 mg/dL. In patients with renal dysfunction, improvement was noted by a decrease in the preoperative serum creatinine of at least 20% at the time of hospital discharge. For the purposes of statistical analysis, the term “functional improvement” was defined as a postpro- cedural improvement in blood pressure and/or renal function (using the above criteria). Patients were considered to have a single kidney if (1) the other kidney was congenitally or surgically absent, (2) there was no visible nephrogram on renal arteriography, or (3) less than 10% of the kidney func- tion resided in one kidney by the isotope renogram.

Failure of PTA or operation was defined by technical fail- ure of the procedure or late occlusion or recurrence of at least 70% stenosis in the treated artery. In our series these events were always coincident with recurrence or continuation of the presenting symptoms (hypertension and/or renal dysfunc- tion). If patients failed PTA and required surgical salvage, the patient was then entered into the surgical results for the treated artery or arteries.

Statistical analysis was performed using the Statview soft- ware package (Abacus Concepts, Inc, Berkeley, CA) and a Macintosh computer (Apple Computer, Inc, Cupertino, CA). Continuous data were compared using the unpaired Student’s r-test. Nonparametric data were compared using chi-square and Fisher’s exact test analyses. Actuarial renal artery pat- ency was calculated using the life-table methods and compar- isons made using the log-rank test according to the reporting standards of the Society for Vascular Surgery and the Intema- tional Society for Cardiovascular Surgery.*’

RESULTS

Review of medical records, surgery logs, and interventional radiology logs revealed 63 patients undergoing 76 renal artery revascularizations during the study period. Patients with renovascu- lar disease who were not referred to either the vascular surgery or interventional radiology ser- vices were not included. The study group com- prised 49 males and 14 females. Patients pre- sented to the vascular service for various reasons: 35 for poorly controlled hypertension (55.5%), 19 for evaluation of abdominal aortic aneurysm or vascular occlusive disease (30%), six for acutely worsening renal function (9.5%), and three for other causes (5%). Of the 41 patients specifically evaluated for renovascular disease, 38 had preoperative renal scans, of which 18 were performed with captopril, and 20 had color flow duplex imaging of the renal arteries. Six of the 19 patients evaluated for other vascular dis- ease had preoperative renal scans and three had color flow duplex imaging. All but two of the 63 total patients underwent preoperative arteriogra-

498 ERDOES ET AL

phy. The two cases without arteriography were both emergent (ruptured aortic aneurysm and traumatic disruption of the renal artery). Other diagnostic tests (including renal vein renin assays) were performed infrequently and were not analyzed in this review. All renal scans showed decreased perfusion on the appropriate side or bilaterally. Captopril isotope renography was positive in 13 of 18 studies, equivocal in four, and incorrect in one. Duplex imaging showed increased renal artery velocities and in- creased renal to aortic ratios in 17 patients; the remaining six studies were not interpretable due to poor visualization of the renal arteries.

In the 16 patients undergoing 18 PTAs (two bilateral), nine patients (56%) subsequently re- quired surgical revascularization and seven pa- tients (44%) were treated with PTA alone. Surgi- cal revascularization was performed in 56 patients and included aortorenal bypass in 27, aortorenal endarterectomy in 18, and extra-ana- tomic bypass in 13 patients (numbers include redo procedures for two patients). Concomitant aortic replacement was performed in 32 of 56 patients (57%). Of the surgical procedures per- formed, 40 were unilateral and 16 were bilateral renal artery reconstructions. Concomitant mesen- teric bypass was performed in three patients.

There were 10 patients with single kidneys under- going revascularization. Seven were treated surgi- cally and three were treated with PTA. All three angioplasty patients failed and were salvaged with successful surgical revascularization (Pig 1).

Risk factors did not differ significantly be- tween the PTA and surgical groups (Table 1); however, the mean age in the PTA group was significantly lower than in the surgery group. Overall, the indications for intervention (Table 2) included both renal salvage and hypertension in 38 patients (60%), hypertension alone in 15 patients (24%), renal salvage alone in six patients (9.5%), and other disease states in four patients (6.5%). The distribution of indications was not significantly different between the PTA and sur- gery groups. For the entire series, 59 patients (94%) had atherosclerotic occlusive disease as the underlying renal artery pathology, with trauma and fibromuscular dysplasia accounting for two patients each (Table 2).

Stenoses involving the ostium of the renal ar-

tery were present in 67 of the 90 renal arteries treated (74%). Mid-artery lesions were present in 22 arteries (25%) and a distal lesion was pres- ent in one (1%). In the surgically treated group there were 60 (83.3%) ostial lesions, 11 (15.3%) mid-artery lesions, and one (1.4%) distal steno- sis. In contrast, 11 (61%) of the arteries undergo- ing PTA were mid-artery lesions and seven (39%) were ostial stenoses. Of the nine PTA pa- tients requiring surgical salvage, five had ostial lesions, three had non-ostial lesions, and one had both types of lesions.

Clinical follow-up was complete in 50 of 59 (85%) surviving patients. Postoperative imaging studies were obtained in 30 of 50 surviving patients and included 14 nuclear isotope scans, nine arte- riograms, five color-flow Doppler ultrasound scans, and three computed tomographic scans. In patients without imaging studies, renal artery patency was inferred by preservation of postoperative blood pres- sure control and/or renal function during the follow- up period. The treatment results are displayed in Table 3. Functional improvement was achieved in blood pressure and/or renal function in 74% of pa- tients treated surgically compared with 22% treated with PTA (P < 0.01).

Morbidity and mortality results were comparable for the two treatment groups. In the surgery group, three patients died (5.3%) and significant morbidity occurred in four patients (7%). Complications en- countered with the surgically treated patients in- cluded atheroembolism (two), myocardial infarction (one), and chylous ascites (one). In the PTA group, mortality occurred in one patient (4.8%) with major morbidity occurring in six patients (33%), including acute failure of the PTA in five patients and renal artery dissection in one patient.

By life-table analysis, actuarial renal artery pat- ency at 48 months following surgical revasculariza- tion was 81% compared with 17% following PTA (P < 0.01) (Fig 2). When the specific surgical revas- cularization techniques were compared there were no statistically significant differences in functional outcome, patency, or morbidity and mortality. These data are summarized in Table 4.

DISCUSSION

Several reports have noted the changing indi- cations for renal revascularization. Contempo- rary patients are older and more likely to have

TECHNIQUES OF RENAL REVASCULARIZATION 499

Table 1. Demographic Data for Renal Artery Revascularization Patients

Surgery (%) (n = 47)

Age (mean ? SEM) Smoking Hypertension Diabetes CAD Hyperlipidemia

65.2 t 1.3 34 (72) 43 (91)

9 (1% 25 (53) 16 (34)

PTA (%) (n = 16)

56.6 -t 4.6 11 (69) 16 (100)

3 (1% 11 (69)

6 (36)

Probability Values

0.02 NS NS NS NS NS

Abbreviation: CAD, coronary artery disease.

Fig 1. (A) Preangioplasty appearance of the left re- nal artery (arrow) in a heart transplant recipient with a single left kidney who was admitted with flash pul- monary edema. (B) Postangioplasty appearance of the left renal artery (arrow) with residual significant steno- sis. (C) Six-month follow-up arteriogram after a suc- cessful spleno-renal bypass with end-to-end anasto- mosis (arrow) between the splenic and left renal arteries.

diffuse atherosclerosis, concomitant aortic dis- ease, and significant renal dysfunction.“” The natural history of medically treated renovascular lesions also has been defined, with progression of the disease documented in 20% to 40% of arteries, often resulting in renal artery occlusion.’ It has been estimated that one third of elderly hypertensive patients with evidence of decreased renal function and coronary artery or peripheral vascular disease have renal artery stenosis.22 Fur- thermore, renovascular occlusive disease is the suspected etiology of renal failure in up to 15% of the current dialysis-dependent population.”

500 ERDOES ET AL

Table 2. indications for Intervention and Etiology of Renal Artery Stenosis

Surgery (%) (n = 47)

PTA (%) (n = 16)

Probability Value

Indication

HTNKRI HTN CRI Other

Etiology

AS0 FMD Trauma/other

29 (62) 9 (56) NS

10 (21) 5 (31) NS 4 (8.5) 2 (13) NS 4 (8.5) 0 NS

45 (96) 14 (87) NS

0 2 (13) NS 2 (4) 0 NS

Abbreviations: HTN, hypertension; CRI, chronic renal insufficiency; ASO, atherosclerotic occlusive disease; FMD, fibromuscular dysplasia.

These data suggest that an aggressive approach to renal revascularization is warranted both for renal salvage and to ameliorate the late conse- quences of poorly controlled hypertension.

The methods available for the treatment of re- nal artery stenoses comprise the two broad cate- gories of percutaneous transluminal angioplasty and surgical reconstruction. Angioplasty has been well accepted as a treatment for fibrodys- plastic lesions of the renal arteries,‘,‘4%‘5 but its role in atherosclerotic lesions, particularly those involving the ostium of the renal artery, is less clear. ‘3 Despite three recent reports detailing improved results with PTA for ostial steno- ses, 12,24,25 numerous studies have reported sub- optimal results with such atherosclerotic le- sions. ‘*2627 In the present study, the vast majority (76%) had ostial renal artery lesions, although in the subset treated with PTA, 61% had non-ostial lesions. In the surgery group 16 patients (29%) underwent bilateral revascularization compared

Table 3. Functional Outcome for Renal Artery Revascularization

Improved Worse vd w

No Change

(“W

Surgery 43 (74) 9 (16) 6 (10) PTA 4 (22) 5 (26) 9 (50)

NOTE. Chi-square = 18.1, P < 0.01 for surgery versus PTA.

loo%n

! !

: :

: u . . . . . . . . .

P 40% : i ,...m. I.... mm...a.- . . . . . I

5 : .

u 20% : : .m.mD.ls..mDi

0%: I I 1 I I I I 1 0 8 12 18 24 30 36 42 48

Follow-up (months)

Surgery PTA

Fig 2. Actuarial patency of renal arteries following revascularization by surgical methods or PTA. Pat- ency at 48 months is superior for surgical treatment (81%) compared with PTA (17%) (f < 0.01, log-rank).

with two patients (12.5%) in the PTA group. Since this was a nonrandomized study, selection of surgery and PTA was guided by traditional criteria. This observation explains the higher in- cidence of ostial and bilateral lesions in the surgi- cal group. Similar to other reports, non-ostial fi- bromuscular dysplastic lesions reponded most favorably to PTA, accounting for two of the four patients (50%) with favorable outcomes. The other two patients with favorable responses from PTA had focal mid-artery lesions. As most of the PTA failures were in patients with ostial ste- noses, the relative ineffectiveness of treating os- tial lesions with percutaneous transluminal angioplasty seems to be supported by our data; however, the number of patients in our study is small.

Renal angioplasty is initially successful in

Table 4. Functional Outcome for Surgical Renal Artery Revascularization Techniques

Improved Worse No Change

W) (W w

Aortorenal bypass 20 (74) 4 (15) 3 (11)

Aortorenal endarterectomy 16 (89) 0 2 (11) Extra-anatomic bypass 7 (54) 5 (38) 1 (8)

NOTE. Chi-square = 8.6, P = 0.07 for aortorenal bypass versus aortorenal endarterectomy versus extra-anatomic bypass.

TECHNIQUES OF RENAL REVASCU!JWZAT~ON 501

70% to 95% of cases, but limited long-term fol- low-up data suggest a restenosis rate of 20% to 40%.‘,‘2-17 Proponents of angioplasty argue that renal PTA is safer and yields better results due to advances in balloon catheter and guidewire technology.2’ Losinno et al reported the best re- sults to date for angioplasty, with an 82% renal artery patency at 5 years and a relatively low (21%) incidence of recurrent hypertension.r6 However, an analysis of 10 studies with 691 ar- teries undergoing PTA disclosed an overall cure rate for hypertension of 24% and improvement in an additional 43%.17 Only 67% of these pa- tients were treated for atherosclerotic lesions, and the results in the atherosclerotic group were noted to be inferior to those in the fibromuscular dysplasia group. These data led to the conclusion that the benefit of angioplasty in atherosclerotic patients was small and should be compared with medical therapy in a randomized series.

Only one report has compared the results of renal PTA with surgical reconstruction in a ran- domized fashion.24 Renal PTA was successful in 83% of patients, while surgery achieved success in 97%. The primary patency rates after 24 months were 75% in the PTA group compared with 96% in the operative group, yet the second- ary patency rates were similar at 90% and 97%, respectively. The improved secondary patency rate for angioplasty was obtained by repeat PTA in two patients and by crossover to surgical ther- apy in four patients. If one includes technically unsuccessful PTA as a treatment failure, there were 11 failures in 29 patients at 24 months. This was a highly selected group of relatively young, nondiabetic patients with unilateral renal artery stenosis. The applicability of these results to con- temporary patient populations with diffuse ath- erosclerosis is questionable.

Stenting of the renal arteries does not appear to significantly reduce the incidence of restenosis and the complication rate is higher than with PTA alone.28-‘4 In the available series, the restenosis rate varies from 33% to 58%, but the numbers of patients are small and follow-up is limited. The ultimate place of renal artery stents in our treatment armamentarium requires further study.

Weibull et al performed a cost-benefit analy- sis of a series of patients undergoing either PTA or surgical reconstruction for renal revasculariza-

tion.‘5 At a median follow-up of 48 months, pri- mary patency was better in the surgical group, but secondary patencies were equal at 100%. The median cost of reconstructive surgery was 12% higher than for renal PTA, which was a nonsig- nificant difference. Although the initial costs were lower with PTA, the total costs increased due to the need for more intensive follow-up and repeat intervention.

The benefits of the available techniques for surgical renal artery reconstruction have been documented in recently reported series.‘,2,4-7*‘8 The surgical reconstructions used in this series included a mix of aortorenal bypass, renal endar- terectomy, and extra-anatomic reconstructions (hepatorenal or splenorenal bypass). Each of these techniques was equally efficacious, sug- gesting that the procedure should be tailored to the individual patient. Although aortorenal by- pass remains the gold standard,4-7 renal endarter- ectomy is particularly useful in patients who also require aortic reconstruction or have orificial le- sions, ‘* while extra-anatomic bypass avoids crossclamping a diffusely diseased aorta.7

Dean et al have the largest reported experience with aortorenal bypass.” The mortality rate of their last 136 procedures was 1.4%, and the rates of improvement in blood pressure control and renal function were 76% and 68%, respectively. Similar exemplary results were noted by Stanley et al, who reported a failure rate of only 3% in a contemporary series of aortorenal bypasses.4

Renal endarterectomy is an excellent option in patients with bilateral disease, particularly of the renal orifices. It also can be combined with aortic reconstructions with gratifying results. Extra-an- atomic bypass has been championed by Cambria et al, who recently reported a 5% early failure rate and a 5-year patency of 82% in 121 extra- anatomic renal reconstructions.7

In the present study, the vast majority (94%) of our patients had atherosclerotic renovascular disease, and salvage of renal function was at least a partial indication for intervention in 70% of patients. Concomitant aortic replacement was necessary in 57% of the surgically treated pa- tients. Furthermore, three of our patients had un- dergone cardiac transplantation for end-stage ischemic cardiomyopathy prior to requiring in- tervention for renovascular disease. In this mod-

502 ERDOES ET AL

em series, the results of surgical renal revascu- larization were excellent and offered more durable patency and functional improvement than percutaneous transluminal angioplasty. The morbidity and mortality rates for surgical and percutaneous procedures were similar.

This study demonstrates that anatomy and pathophysiology are the key determinants in acheiving successful functional outcome and that surgical reconstruction in patients with diffuse atherosclerotic disease needing renal revascular- ization offers a superior outcome. The operation should be tailored to fit the individual patient’s disease, since the results of endarterectomy and bypass procedures are equivalent.

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