From the Eastern Vascular Society

Endovascular revascularization of renal arterystenosis in the solitary functioning kidneyMark G. Davies, MD, PhD, MBA, Wael E. Saad, MD, Jean X. Bismuth, MD, Joseph J. Naoum, MD,Eric K. Peden, MD, and Alan B. Lumsden, MD, Houston, Tex

Background: Endovascular therapy for symptomatic atherosclerotic renal artery stenosis (ARAS) is considered effective.This study evaluates the factors that impact long term anatomic and functional outcomes of endovascular therapy ofARAS in patients with a solitary functioning kidney.Methods: We performed a retrospective analysis of records from patients who underwent endovascular intervention forARAS and identified patients with a solitary functioning kidney (absent or nonfunctioning contralateral kidney) andpatients with contralateral normal kidney (for comparison) between January 1990 and January 2008. Indications forintervention in the solitary functioning kidney were poorly controlled hypertension (diastolic blood pressure [BP] >90mm Hg on >3 antihypertensive medications) and/or elevated creatinine (Cr >1.5 mg/dL). Clinical benefit was definedas freedom from composite recurrent symptoms (recurrent hypertension or renal-related morbidity-increase in persistentcreatinine >20% of baseline, progression to hemodialysis, and death from renal-related causes), anatomic patency andpatient survival were measured.Results: A total of 242 patients (56% male, average age 69 years, range, 45-90) underwent angioplasty (23%) orprimary stenting (77%) of a single renal artery with a normal contralateral renal vessel and kidney and 73 patients(58% male, average age 70 years, range, 52-89) underwent angioplasty (37%) or primary stenting (63%) for a solitaryfunctioning kidney. There were no significant differences in mortality or morbidity between the groups. There wasa significant difference in the long-term survival with 55 � 8% patients with a normal contralateral kidney vs 27 �7% patients with a solitary functioning kidney alive at 10 years. Clinical benefit was 67 � 6% and 67 � 4% at 5 yearsand 63 � 8% and 62 � 4% at 10 years for solitary functioning kidney and normal contralateral groups, respectively.Using proportional hazard analysis, the predictors of long-term clinical benefit were ipsilateral kidney size (>9 cm),no immediate deterioration in function, and an estimated Glomerular Filtration Rate (eGFR) >30 mL/min/1.73m2.Neither control of diabetes nor the administration of statins was shown to influence outcomes in the solitary functioningkidney.Conclusion: Intervention in patients with a solitary functioning kidney is a safe procedure and improves or stabilizes renalfunction in 82% of patients. Clinical benefit is dictated by preoperative GFR, renal size, and the occurrence of acute

functional injury after the procedure. (J Vasc Surg 2009;49:953-60.)

While controversy remains on the endovascular therapyfor symptomatic atherosclerotic renal artery stenosis (ARAS),it is considered effective and appears to have significantbenefits in the well-selected patient.1-7 Acute functionalinjury associated with renal intervention for atheroscleroticdisease is now recognized as an important clinical problemand has led to a growing realization that embolic protectiondevices may be required to protect the renal parenchymaduring renal interventions.8-10 We have recently shownthat acute functional renal injury occurs in approximately20% of patients undergoing percutaneous renal artery in-tervention, is more likely in the presence of an unrepairedabdominal aortic aneurysm (AAA), diabetes, with pre-existing renal disease, is a negative predictor of survival, is

From the Department of Cardiovascular Surgery, Methodist DeBakey Heartand Vascular Center, The Methodist Hospital.

Competition of interest: none.Presented at the Annual Meeting of the Easter Vascular Society, September,

2008 (Boston, Mass).Reprint requests: Mark G. Davies, MD, PhD, MBA, Methodist DeBakey

Heart and Vascular Center, Department of Cardiovascular Surgery, TheMethodist Hospital, 6550 Fannin Street, Smith Tower - Suite 1401,Houston, TX 77030 (e-mail: MDavies@tmhs.org).

0741-5214/$36.00Copyright © 2009 by The Society for Vascular Surgery.

doi:10.1016/j.jvs.2008.11.042

associated with subsequent renal failure, need for dialysis,and death.11 We did find that the status of the contralateralrenal artery was important. Additionally, the advent of renalembolic devices and the proposed indication of interven-tion for use in atherosclerotic disease in a solitary kidney toprevent functional injury added impetus for us to addressthe outcomes of intervention in patients with a solitarykidney. Thus, this study evaluates the factors that impactlong term anatomic and functional outcomes of endovas-cular therapy of ARAS in patients with a solitary function-ing kidney.

METHODS

Study design. We performed a retrospective analysisof records from patients who underwent endovascular in-tervention for ARAS and identified patients with a solitaryfunctioning kidney (definition: absent or nonfunctioningcontralateral kidney) and patients with a contralateral nor-mal kidney between January 1990 and January 2008. Pa-tients with bilateral ARAS were excluded from the study.Indications for intervention were poorly controlled hyper-tension (diastolic blood pressure [BP] �90 mm Hg on �3antihypertensive medications) and/or with elevated creat-

inine (�1.5 mg/dL). For each patient, demographics,

953

JOURNAL OF VASCULAR SURGERYApril 2009954 Davies et al

existing comorbid conditions, and risk factors for athero-sclerosis were identified. We evaluated the early and lateoutcomes of endovascular renal interventions in 73 patientswith solitary kidneys and compared them with results of169 patients with normal contralateral kidneys who under-went renal interventions during the same period.

Treatment algorithm. Patients with hypertensionand/or elevated serum creatinine levels had a diagnosticstudy to identify the presence of renal artery stenosis. Thisstudy consisted of standard angiography, magnetic reso-nance angiography, renal isotope scan, or duplex ultra-sound scan. Duplex ultrasound scan criteria to identifyrenal artery stenosis have been previously described.12 Inthe presence of clinical criteria defined by Rundback et al13

and a �60% stenosis on ultrasound scan or �50% stenosison magnetic resonance angiography/computerized tomo-graphic angiography or a positive renal isotope scan, an-giography was performed. Interventions were performed inpatients with renal artery stenosis �50% by angiographyregardless of comorbidities. The majority of these interven-tions were transfemoral and no distal protection deviceswere used. Patients not categorized into the clinicalcriteria referenced were managed medically. Occludedrenal arteries and nonfunctioning kidneys were nottreated. Patients with creatinine �1.5 mg/mL werehydrated overnight with normal saline and in the last 5years received Mucomyst (Acetylcysteine, Bristol-MyersSquibb Company, Princeton, NJ) 600 mg twice a day(BID) prescribed orally (PO) 24 hours preoperativelyand 48 hours postoperatively. Patients were followed at6-month intervals after the procedure. Blood pressure,serum creatinine, and the number of antihypertensivemedications were identified during these intervals. Eachpatient had at least one duplex ultrasound scan within 6months of the procedure and an ultrasound scan every 6months thereafter to assess patency. If the duplex ultra-sound scan showed �60% stenosis and the patient hadrecurrent symptoms, angiography was performed and re-stenosis was treated if the arterial diameter was �50%.

Definitions. Coronary artery disease was defined as ahistory of angina pectoris, myocardial infarction, conges-tive heart disease, or prior coronary artery revasculariza-tions. Cerebrovascular disease included a history of stroke,transient ischemic attack, or carotid artery revascularization.Hypercholesterolemia was defined as fasting cholesterol�200 mg/dL. Diabetes was defined as a fasting plasmaglucose �110 mg/dL or an HbA1c �7%. Diabetics werecharacterized as insulin dependent diabetes mellitus(IDDM) or non-insulin dependent diabetes mellitus(NIDDM). Hypertension was defined as diastolic BPgreater than 90 mm Hg on �3 antihypertensive medica-tions. Metabolic syndrome was defined as previously de-scribed14 (insulin resistance or impaired glucose tolerance,hypertension, dyslipidemia, and abdominal obesity), withthe exception of abdominal circumference, which was notroutinely recorded. We substituted a body mass index score�30.0 as a positive score instead of an abdominal circum-

ference �102 cm or �88 cm for male or female patients,

respectively. An elevated creatinine was defined as �1.5mg/dL on two consecutive values during a 3-month pe-riod. Chronic renal insufficiency was defined as a persistentserum creatinine �1.5 mg/dL for greater than 6 months.Estimated glomerular filtration rate (eGFR) was defined as186.3 * serum creatinine�1.154 * age�0.203 * 0.742 (iffemale) *1.212 (if African American). The baseline serumcreatinine was the value recorded closest to the procedure.Patients were considered to have a “nonfunctioning kid-ney” if any two of the following local criteria used at ourinstitution over the time of the study were met: (1) a duplexultrasound scan identified a pole-to-pole length of less than9 cm with no renal flow in the main renal artery andparenchymal peak systolic velocity �10 cm/second; (2)surgically or congenitally absent kidney; (3) no visiblenephrogram on contrast arteriogram. A normal contralat-eral kidney was considered a kidney without evidence of�50% renal artery stenosis and not fulfilling criteria for a“nonfunctioning kidney”. Renal Resistive Index was de-fined from duplex scan imaging as 1-end-diastolic velocity/peak systolic velocity (1-EDV/PSV)*100. Nephrosclerosiswas defined as grade 1: normal intrarenal vessels, orderlyprogression of branching patterns (no pruning), normalnephrogram with distinct corticomedullary junction; grade 2:ectasia of arcuate and distal interlobular arteries, peripheralpruning, reduced arterial volume with normal renal mass,normal nephrogram; grade 3: marked ectasia extendingcentrally, total pruning with abrupt interlobar artery termi-nations, marked reduced arterial volume with decreasedrenal mass, and faint absent nephrogram. An endoluminalprocedural success was a residual stenosis of �30%; failureswere residual stenosis �30%, by angiographic measure-ment, including lesions unable to be dilated or crossed, andocclusion within 30 days. A death within 30 days of theprocedure was considered procedure-related. Acute func-tional renal injury was defined as a persistent increase in theserum creatinine of �0.5 mg/dL at 1 month after theprocedure. Acute anatomic renal injury was defined as renalartery dissection, perforation, acute occlusion, renal paren-chymal infarction, and renal parenchymal perforation. Ac-cess site complication was defined as hematoma, pseudoa-neurysms, arteriovenous fistula, or a vessel injury requiringeither percutaneous or open intervention. Systemic com-plications were any new cardiac pulmonary infectious ornon-renal systemic complication that required intervention orhalted discharge within 24 hours of the procedure. Responsein the hypertensive patient was defined as follows: “cured”patients were normotensive (diastolic BP �90 mm Hg andsystolic BP �140 mm Hg) without medications; “improved”patients were normotensive (diastolic BP �90 mm Hgand/or systolic BP �140 mm Hg) on the same (or re-duced) number of medications, or had a diastolic BP 15mm Hg below baseline with the same or reduced numberof medications. “No effect” patients had no change orinability to meet these criteria for cure or improvement andwere considered a treatment failure. Early renal functionresponses to angioplasty were defined as follows: “cured”

renal function required a serum creatinine concentration

JOURNAL OF VASCULAR SURGERYVolume 49, Number 4 Davies et al 955

�1.5 mg/dL; “improvement” in renal function required a�20% reduction in the serum creatinine concentration;“stable” renal function required a �20% increase or reduc-tion in the serum creatinine concentration; “deterioration”in renal function required a �20% increase in the serumcreatinine concentration.13 Stable renal function and dete-rioration were considered treatment failures. Freedomfrom renal-related morbidity was defined as a persistentincrease in creatinine �20% of baseline, progression tohemodialysis, and death from renal-related causes.13

Statistical analysis. We performed our analysis on an“intention-to-treat” basis. Measured values are reported aspercentages or means � 1 standard deviation. Mann-Whitneytests were used to test the difference between means. Fis-cher’s or �2 tests were performed to test the significancebetween proportions in each group. Survival and clinicalbenefit rates are calculated using life table analysis andreported using the Society for Vascular Surgery (SVS)criteria. Standard errors are reported in actuarial analyses.The log rank test was used to determine differences be-tween life tables. Analyses were performed using JMP soft-ware version 7.0 (SAS Institute, Cary, NC). Cox propor-tional hazards models were employed for time-dependentoutcomes by preprocedural variables and periproceduralvariables.

RESULTS

Patient population. Over the time period, 242 pa-tients (56% male, average age 69 years, range, 45-90)underwent angioplasty (23%) or primary stenting (77%) ofa single renal artery with a normal contralateral renal vesseland kidney, and 73 patients (58% male, average age 70years, range, 52-89) underwent angioplasty (37%) or pri-mary stenting (63%) for a solitary functioning kidney. Onehundred thirty-two patients with bilateral ARAS were ex-cluded from the analysis. Hypertension was a much morecommon presentation in the normal group compared tothe solitary functioning group where presentation withrenal insufficiency predominated (Table I). There was nosignificant difference in the majority of the co-morbiditiesbetween the two groups except that there were significantlymore patients with congestive heart failure and a history ofcerebrovascular disease in the solitary functioning kidneygroup (Table I). When the status of renal insufficiency isspecifically examined, there was no significant difference inthe mean serum creatinine concentration and eGFR be-tween the groups. However, the distribution of patientswith an eGFR �30 mL/min/1.73m2 was significantlygreater in the group with a solitary functioning kidney(Table II). The intrinsic measures of the treated kidney (size,resistive index, and nephrosclerosis grade) were equivalent inboth groups (Table II). The range of kidney size in the solitarygroup was 13.7 to 7.0 cm pole-to-pole length.

Immediate outcomes (<3 months). Of the 242planned interventions for a single renal artery with a normalcontralateral renal vessel, there was a 5% technical failurerate (�30% residual stenosis) but no periprocedural or

90-day mortalities. The procedure-related complication

rate for this group was 9% (all minor). Of the 73 plannedinterventions for solitary functioning kidney, there was a 4%technical failure rate (�30% residual stenosis). There wereno periprocedural or 90-day mortalities. The procedure-related complication rate (access and anatomic related) was12% (all minor). There were no significant differencesbetween the two groups. The nature of the renal interven-tions and categories of complications in both groups areshown in Table III. Immediate renal clinical benefit wassuperior in the solitary kidney group compared to thenormal contralateral group (Table IV). In the presence of anormal contralateral kidney, only 6% of patients treateddemonstrated immediate clinical benefit of improved orcured renal dysfunction and 86% showed no change within3 months of procedure. In comparison, in the presence of asolitary functioning kidney, 12% of patients treated dem-onstrated immediate clinical benefit of improved or curedrenal dysfunction and 69% showed no change within 3months of procedure (Table IV). However, there was asignificant difference in acute functional injury in the soli-tary functioning kidney group (Table III) which was trans-lated into a greater number of patients who were consid-ered to have had a deterioration in their renal function at 3months (Table IV). A preprocedure eGFR �30 mL/min/1.73m2 was associated with immediate clinical benefit inthose patients with a solitary kidney (relative risk [RR]0.66, 95% confidence interval [CI] 0.45 to 0.95, P �.0094). With respect to hypertension, there was a signifi-cant clinical benefit in 60% of the normal contralateralkidney group and 20% of the solitary functioning kidneygroup (Table IV). The differences in the respective clinicalbenefits achieved likely reflect the differences in presentingsymptoms between the groups.

Outcomes (>3 months). There was a significant dif-

Table I. Patients’ characteristics, presenting symptoms,and co-morbidities

Normal Solitary P value

DemographicsPatients 242 73 —Kidneys treated 242 73 —Male 56% 58% .88Average age (mean � SD,

years) 69 � 11 70 � 9 .47Symptoms

Hypertension 70% 38% .001Elevated creatinine 12% 21%Hypertension with

elevated creatinine 18% 41%Co-morbidities

Smoking history 60% 64% .56Coronary artery disease 46% 53% .32Congestive heart failure 24% 44% .003Diabetes mellitus 28% 23% .41Hyperlipidemia 65% 67% .77Metabolic syndrome 70% 74% .52Cerebrovascular 23% 33% .12

SD, Standard deviation.

ference in the long-term survival between the normal con-

JOURNAL OF VASCULAR SURGERYApril 2009956 Davies et al

tralateral kidney and solitary functioning kidney groupswith patients with a solitary functioning kidney having alower life expectancy (Fig, A). In patients with a normalcontralateral kidney, survival was 76 � 4% and 55 � 8% at5 and 10 years, while in patients with a solitary functioningkidney survival was 62 � 6% and 27 � 7% at 5 and 10 years.

Table II. Kidney disease, creatinine levels, estimatedGFR, ipsilateral and contralateral hemodynamic, andanatomy parameters

Normal Solitary P value

Kidney disease stage1 8% 0% .052 27% 12% .053 51% 53% .14 11% 29% .055 3% 5% .09

Functional parametersCreatinine (mg/dL) 1.5 � 1.0 1.9 � 1.0 .5Mean eGFR mL/

min/1.73m2 55 � 24 40 � 18 .5eGFR �30mL/

min/1.73m2 13% 35% .05eGFR 30-60mL/

min/1.73m2 51% 53% .1eGFR �60mL/

min/1.73m2 36% 12% .05Ipsilateral kidney

anatomyKidney size 10.1 � 0.1 11.0 � 1.5 .1Resistive index 0.73 � 0.1 0.75 � 0.11 .2Nephrosclerosis 1.30 � 0.47 1.42 � 0.02 .3

Contralateral kidneyanatomy

Normal 100% 0% —Stenosis (�60%) 0% 0% —Nonfunctioning 0% 23% —Surgically absent 0% 15% —Atrophy 0% 21% —Occlusion 0% 42% —

Contralateral kidneyparameters

Kidney size 10.2 � 1.1 7.4 � 1.4 .05Resistive index 0.73 � 0.09 — —Nephrosclerosis 1.23 � 0.42 2.67 � 0.70 .01

eGFR, Estimated glomerular filtration rate.

Table III. Interventions and periproceduralcomplications

Normal Solitary P value

InterventionsAngioplasty 23% 27% .51Stent placement 77% 73% —Predilation 45% 44% .88Contralateral intervention 0% 0% —

ComplicationsAcute functional injury 14% 30% .006Anatomic injury 4% 4% 1.0Access site 5% 8% .38Systemic 0% 0% —

The eGFR �30 (hazard ratio [HR] 8.18, 2.61-20.4;

95% CI; P � .03), dialysis dependency (HR 4.1, 1.92-8.65;P � .003) and smoking (HR 2.5, 1.15-5.38; P � .02) wereassociated with decreased survival in the solitary function-ing kidney group. Cumulative patency rates determined byserial duplex scan imaging were 81 � 5% vs 87 � 6% at 5years and 68% vs 83% at 10 years for normal contralateraland solitary functioning kidney groups respectively (Fig, B).By Cox proportional hazard analysis, hyperlipidemia(HR 5.16, 1.40-20.1, P � .012) and metabolic syn-drome (HR 3.62, 1.74-7.43, P � .014) were associatedwith decreased patency. Restenosis rates were equivalentat 5 years (85 � 4% vs 87 � 6%, normal contralateral vssolitary functioning) and 10 years (78 � 9% vs 84 � 10%,normal contralateral vs solitary functioning) (Fig, C).Hyperlipidemia (HR 10.4, 2.1-64.7, P � .003) and anelevated fasting blood sugar (HR 7.3, 1.9-30.8, P �.004) were associated with increased rate of restenosis insolitary functioning kidneys. Freedom from renal-relatedmorbidity (persistent increase in creatinine �20% ofbaseline, progression to hemodialysis, and death fromrenal-related causes) was 59 � 10% and 73 � 7% at 5years for solitary functioning kidney and normal con-tralateral groups, respectively (Fig, D). Recurrent symp-toms and restenosis were highly correlated. Clinical ben-efit from hypertension (84 � 9% at 10 years) was superiorto clinical benefit from renal-related morbidity (59 � 9%at 10 years) (Fig, E). Using proportional hazard analysis,the predictors of long-term clinical benefit were ipsilat-eral kidney size (�9 cm) (HR �0.24, �0.36 to �0.12,P � .001), no immediate deterioration in function (HR0.47, 0.01 to 0.88, P � .004) and a eGFR �30 mL/min/1.73m2 (HR �0.44, �0.72 to �0.14, P � .02).Neither control of diabetes (HR 1.2, 0.88 to 1.94, P �.41) nor the administration of statins (HR 1.34, 0.86 to2.14, P � .30) was shown to influence outcomes in the

Table IV. Outcomes

Normal Solitary P value

Immediate hypertensionoutcomes

Deterioration 1% 0%

.0001No change 39% 80%Improved 52% 17%Cured 8% 3%

Long-term hypertensionoutcomes

Deterioration 10% 7% .44No change 90% 93%Immediate renal outcomes

Deterioration 8% 19%

.03No change 86% 69%Improved 5% 11%Cured 1% 1%

Long Term Renal OutcomesIncrease in creatinine 21% 22% .86Progression to hemodialysis 7% 15% .07Death from renal cause 2% 3% .65

solitary functioning kidney.

JOURNAL OF VASCULAR SURGERYVolume 49, Number 4 Davies et al 957

Fig. A, Survival: Kaplan-Meier analysis of survival of the patients with a solitary kidney or a normal contralateral kidney. Thenumber at risk at each time interval is shown below each panel. Values are mean � standard error of the mean. Standard errorsexceeding 10% are not shown. B, Patency: Kaplan-Meier analysis of cumulative patency with a solitary kidney or a normalcontralateral kidney. The number at risk at each time interval is shown below each panel. Values are mean � standard errorof the mean. Standard errors exceeding 10% are not shown. C, Restenosis: Kaplan-Meier analysis of freedom from restenosisof the patients with a solitary kidney or a normal contralateral kidney. The number at risk at each time interval is shown beloweach panel. Values are mean � standard error of the mean. Standard errors exceeding 10% are not shown. D, Recurrentsymptoms: Kaplan-Meier analysis of freedom from renal-related morbidity (persistent increase in creatinine �20% ofbaseline, progression to hemodialysis, death from renal-related causes) of the patients with a solitary kidney or a normalcontralateral kidney. The number at risk at each time interval is shown below each panel. Values are mean � standard errorof the mean. Standard errors exceeding 10% are not shown. E, Retained clinical benefit from recurrent hypertension andrenal-related morbidity in the solitary kidney: Kaplan-Meier analysis of freedom from recurrent hypertension and renal-related morbidity (increase in persistent creatinine �20% of baseline, progression to hemodialysis, death from renal-relatedcauses) of the patients with a solitary kidney. The number at risk at each time interval is shown below each panel. Values are

mean � standard error of the mean. Standard errors exceeding 10% are not shown.

JOURNAL OF VASCULAR SURGERYApril 2009958 Davies et al

DISCUSSION

This series represents one of the largest reports ontreatment of ARAS in the solitary functioning kidney.Intervention in patients with a solitary functioning kidneyand appropriate symptoms is a safe procedure and comparesfavorably with those interventions performed for ARAS anda normal contralateral kidney. Intervention did improve orstabilize renal function in 82% of the patients presentingwith ARAS in a solitary kidney. Although overall survival inthese patients is much lower than if a normal contralateralkidney were present, the recurrence of symptoms wasequivalent (59 � 10% and 73 � 7%) at 5 years supportingthe longer term clinical efficacy of interventions in thesepatients. Clinical benefit appeared to be dictated by preop-erative eGFR, renal size, and the occurrence of acute func-tional injury after the procedure.

At the present time, there are no unique establishedcriteria for endovascular treatment of renal artery stenosis ina solitary functioning kidney. One criterion suggested hasbeen kidney size, as it is reported that a pole-to-pole lengthof less than 8 cm is a significant predictor that revascular-ization will not help in improving renal function.15 Thiswas also taken into consideration in our patient selectionwith a mean kidney size of 11 cm, but we did performprocedures in kidneys with a minimum renal size of 7 cmduring the early part of the series. A second criterion oftenemployed is the anatomic location of the stenosis, as anostial localization has a more favorable outcome than aperipheral lesion.16,17 A third criterion is the degree ofstenosis present. While it has been shown that stenosis lessthan 60% have a 48% chance of progressing into significantstenosis in 3 years.12 A stenosis greater than 75% becomesan occlusion in 13 months in 39% of cases.18 A finalcriterion is the state and rate of decline of the renal insuffi-ciency. Hanson et al have clearly demonstrated that interven-ing in a patient who is in the declining phase of renal insuffi-ciency is far superior than intervening in the patient where thedeterioration is established and long standing.19-22

Renal artery stenosis is an independent predictor ofmortality. At 7 years, 73% of patients with renal arterystenosis are dead.23 The 7-year mortality in this study forpatients with a solitary kidney was 66%, which is equivalentto untreated disease and was significantly higher than thosepatients with two kidneys (32% at 7 years). Similar to thecurrent study, immediate and long-term postprocedurecreatinine deterioration and dialysis-dependency have beenassociated with increased mortality.1,2,24 We have alsoshown that acute functional injury (ie, a rise in creatinine�0.5 mg/dL) also has a significant impact on survival.11

There was a significant incidence in acute functional injuryin the solitary kidney group that likely impacted the sur-vival. Elevated creatinine has already been shown to affectsurvival after therapy for renal artery stenosis despite ade-quate revascularization.1,2,24 Intervention in the solitarykidney did not appear to influence survival.

Technical success defined as �30% residual stenosis at

the end of the procedure has been reported to be between

93-100% for endovascular interventions in the solitary kid-ney. Cumulative patency rates in this series determined byserial duplex scan imaging were 81 � 5% vs 87 � 6% at 5years and 68% vs 83% at 10 years for normal and solitarykidney groups. In a series of 15 patients by Sahin et al,25

primary patency rates were 100% for 6 months, 92.3% for12 months, and 69.2% for 24 months. The secondarypatency rate at 24 months was 100%. In another series of 16patients by Cioni et al,26 cumulative primary patency ratewas 81% at 12 months and 75% at 24 months. We had a 0%mortality rate and an all-cause morbidity rate of 12%, all ofwhich were minor. Other reports have shown mortalityrates ranging from 0% to 4% and all-cause morbidity ratesranging from 27% to 43%.25-27 These data compared veryfavorably to open surgery where perioperative mortalitywas 6%, and major morbidity was 43%, including the needfor permanent (9%) and temporary (9%) dialysis.28 It thusappears that intervention in the solitary kidney has a rela-tively low mortality and morbidity compared to historicaldata on endoluminal intervention and open surgery.

After simple angioplasty in all comers, improvement orcure of BP has been reported as 66-100%, and improve-ment or stabilization of the renal functions was reported as38-100%.29-32 In contrast, after primary stent placement,improvement or cure of BP was reported as 44-100% andimprovement or stabilization of the renal functions wasreported as 24-100%.17,26,33-37 While the immediate clin-ical outcomes in patients with a normal contralateral kidneydemonstrated numbers in these ranges (hypertension 60%and renal 92%) those with a solitary kidney were much lesslikely for hypertension (20%) and equivalent for renal(81%). Bush et al27 reported improvement in renal functionin 46% of patients, no change in 28%, and deterioration in25% while Shannon et al38 reported 43%, 29%, and 29%,respectively. In comparison, only 12% of patients treated inthis study demonstrated immediate clinical benefit of im-proved or cured renal dysfunction and 69% showed nochange within 3 months of procedure. This data was equiv-alent to the control group except we saw a greater propor-tion of patients showing deterioration in renal function.While the improvement rates were lower than previousreports, a lower proportion of deterioration than in thoseprevious reports balanced this. Only 19% of patientsshowed deterioration in their renal function with 3 monthsof intervention lower than the reports by Bush (25%) andShannon (29%), however, twofold greater than our controlgroup. We did find that a preprocedure eGFR �30 mL/min/1.73m2 was associated with immediate renal benefitin those patients with a solitary kidney. Long-term clinicalbenefit from renal-related morbidity was 59% at 5 years andwas predicted by ipsilateral kidney size (�9 cm), no imme-diate deterioration in renal function and a eGFR �30mL/min/1.73m2. In contrast to these percutaneous re-sults, Reilly et al28 reported the outcomes of open surgicalinterventions in 35 patients and showed that 91% of pa-tients had stable or improved renal function and that hy-pertension was cured or improved in 85%. The current data

suggests that a quantification of residual function through

JOURNAL OF VASCULAR SURGERYVolume 49, Number 4 Davies et al 959

both biochemical and functional assessments in the solitarykidney will predict success and will allow better stratifica-tion of indications for intervention.

CONCLUSION

Intervention in patients with a solitary functioningkidney is a safe procedure and in the short term improves orstabilizes renal function in 82% of patients. Clinical benefitis dictated by preoperative eGFR, renal size, and the occur-rence of acute functional injury after the procedure.

AUTHOR CONTRIBUTIONS

Conception and design: MDAnalysis and interpretation: WS, MDData collection: EP, JB, JN, WS, AL, MDWriting the article: WS, AL, MDCritical revision of the article: EP, JB, JN, WS, AL, MDFinal approval of the article: EP, JB, JN, WS, AL, MDStatistical analysis: WS, MDObtained funding: MDOverall responsibility: MD

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Submitted Sep 19, 2008; accepted Nov 11, 2008.