- Email: [email protected]
Transplant Renal Artery Stenosis: Outcome after Percutaneous Intervention
Transplant Renal Artery Stenosis: Outcome after Percutaneous Intervention J. Robert Beecroft, MD, FRCPC, Dheeraj K. Rajan, MD, FRCPC, Timothy W.I. Clark, MSc, MD, FRCPC, Michael Robinette, MD, FRCSC, and S. William Stavropoulos, MD PURPOSE: To assess the outcome of percutaneous transluminal angioplasty (PTA) and stent placement as the primary treatment for transplant renal artery stenosis (TRAS). MATERIALS AND METHODS: A retrospective review of PTA and stent placement procedures performed for TRAS from April 1997 to July 2003 was conducted. Reviewed parameters included technical success, date of transplantation, dates of percutaneous intervention, mean arterial blood pressure, number of blood pressure medications, and serum creatinine level before and after intervention. Twenty-one interventions were performed in 18 allografts. The primary clinical indication for imaging and treatment was increased creatinine level in 12 allografts and hypertension in six allografts. Patency rates were estimated with use of the Kaplan-Meier method. RESULTS: The technical success rate of PTA/stent placement was 100% and the clinical success rate was 94% (17 of 18 allografts). Thirteen interventions involved PTA alone, with eight combined PTA and stent insertions. The mean preintervention serum creatinine level among 12 allografts presenting with elevated creatinine levels was 2.8 mg/dL ⴞ 1.4 (SD), compared with a 1-month postintervention mean of 2.2 mg/dL ⴞ 0.7 (P ⴝ .03). Of six allografts that presented with hypertension, significant improvement was seen between the preintervention and 1-month postintervention mean systolic (174 mm Hg vs 135 mm Hg, P ⴝ .003) and diastolic (99 mm Hg vs 82 mm Hg, P ⴝ .02) pressures. These patients required a mean of 2.3 medications for blood pressure control before intervention, compared with a mean of 1.0 medications at 1 month after intervention (P ⴝ .002). Primary patency rates at 3, 6, and 12 months (ⴞ95% CI) were 94% ⴞ 6%, 72% ⴞ 12%, and 72% ⴞ 12%, respectively. Secondary patency rates at 3, 6, and 12 months (ⴞ95 CI) were 100%, 85% ⴞ 10%, and 85% ⴞ 10%, respectively. Mean follow-up time was 27 months. Of the eight allografts that underwent stent placement, all eight remained patent at last follow-up (mean, 18.3 months ⴞ 9.2). One major complication of a puncture site pseudoaneurysm occurred (5%). CONCLUSION: Primary treatment of TRAS with PTA with or without stent placement has good intermediate-term patency and is associated with significant early improvement in blood pressure and creatinine level. J Vasc Interv Radiol 2004; 15:1407–1413 Abbreviations:
PTA ⫽ percutaneous transluminal angioplasty, TRAS ⫽ transplant renal artery stenosis
TRANSPLANT renal artery stenosis (TRAS) is the most frequent vascular From the Division of Vascular and Interventional Radiology, Department of Medical Imaging (J.R.B., D.K.R.), and Division of Urology (M.A.R.), Toronto General Hospital, University Health Network–University of Toronto, 585 University Avenue, NCSB 1C-560, Toronto, ON M5G 2N2, Canada; and Section of Interventional Radiology (T.W.I.C., S.W.S.), Department of Radiology, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania. Received April 21, 2004; revision requested May 18; final revision received and accepted July 12. From the 2004 SIR Annual Meeting. Address correspondence to J.R.B.; E-mail: [email protected] None of the authors have identified a conflict of interest. © SIR, 2004 DOI: 10.1097/01.RVI.0000141338.62574.F4
complication in renal transplantation, with an incidence varying from 1% to 23% (1–5). TRAS can present clinically with hypertension and/or increased serum creatinine levels. Noninvasive imaging can detect an underlying stenosis, and color-flow duplex ultrasound (US) and magnetic resonance (MR) angiography have now become the primary noninvasive imaging modalities for the diagnosis of TRAS (6). However, catheter-based angiography remains the gold standard for evaluation of TRAS. Angiography provides a definitive diagnosis and allows the option for treatment with subsequent endovascular therapy. Percutaneous transluminal angioplasty (PTA) is recognized as the ini-
tial treatment of choice in TRAS, with studies having demonstrated its efficacy. Initial technical success of PTA in the treatment of TRAS has been reported to be greater than 80% (1,3,4,7– 11). Reported rates of clinical success are 63%– 83% for hypertension (3,7,8, 10 –12), 67% for treatment of elevated serum creatinine levels (10), 82% for hypertension and/or elevated serum creatinine levels (4), and 76% for long-term allograft survival (7). Metallic stents in TRAS have been used for treatment of recurrent and/or ostial stenosis, but there are limited studies performed to date. Stent placement has been associated with high initial technical success rates and good patency rates, with minimal complications (13–16).
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In this study, we retrospectively examined our institutions’ outcomes of percutaneous interventions in the treatment of TRAS to assess the efficacy of endovascular therapy with PTA with or without stent placement.
MATERIALS AND METHODS Patient Group A retrospective analysis of all patients who underwent angiography and percutaneous intervention for the treatment of TRAS from April 1997 to July 2003 was conducted. Patients were identified with use of radiology and renal transplantation databases maintained at the two participating institutions. Reviewed parameters included type of renal allograft, date of transplantation, clinical presentation of TRAS, dates of intervention, type of intervention(s) performed, technical success, and length of follow-up. Mean arterial blood pressure, number of blood pressure medications, and serum creatinine levels were also recorded before the intervention and at follow-up visits to assess clinical outcome. Institutional review boards granted approval at one institution and an exemption at the other institution for this retrospective study. Eighteen renal allografts were identified in which a total of 21 interventions were performed (angioplasty with or without stent placement). Nine allografts were cadaveric, seven allografts were living related, and two allografts were living nonrelated. Seventeen anastomoses were end-to-side to the external iliac artery, and a single anastomosis (for a living nonrelated allograft) was end-to-end to the internal iliac artery. The mean age of the patient cohort was 57 years (range, 19 – 68 years). Fourteen patients were men and four were women. Renal allografts with TRAS were initially identified by increased blood pressure or increasing serum creatinine level compared with baseline at clinical visits to the transplant clinic. All cases of TRAS were identified by color-flow Doppler US or MR angiography. No allografts had renal biopsies within 3 months before endovascular intervention.
Treatment Method In each intervention, diagnostic renal arteriography was performed via a femoral arterial approach; an ipsilateral or contralateral femoral approach was chosen based on the type of surgical anastomosis of transplant renal artery (end-to-side with use of the external iliac artery or end-to-end with use of the internal iliac artery) and the angle of anastomosis. Nonselective ipsilateral iliac arteriography was performed to exclude an inflow/preanastomotic lesion, often referred to as pseudo-renal transplant artery stenosis in the literature (4,17). The transplant renal artery and anastomosis were then assessed angiographically in an optimal projection to profile the anastomosis. If there was concern for contrast material–induced nephrotoxicity, alternative contrast agents (eg, CO2, gadolinium) were used for preliminary angiography in selected patients. The volumes of iodinated contrast material were kept to a minimum to reduce the risk of nephrotoxicity. Hemodynamically significant stenosis was considered as narrowing of the luminal diameter greater than 50% (5,18). Additionally, in all cases, pressure measurements across the stenosis were obtained to assess for a significant hemodynamic gradient, considered as greater than 10% peak systolic blood pressure gradient. In all cases, heparin sodium was administered intravenously (3,000 – 5,000 IU). The stenoses were traversed with a guide wire, followed by the use of 4-F catheters to obtain pressure measurements across the stenosis. Nitroglycerin (100 –200 g intraarterially into the transplant renal artery) and/or nifedipine (10 mg sublingual) were administered to prevent vasospasm on an operator preference basis. After appropriate calibration of images, measurement of stenosis was made by measuring the ratio between the diameter of the stenosed segment of the artery and the diameter of a normal segment of renal artery (18). TRAS was then treated initially with an angioplasty balloon catheter; the size of the balloon was chosen to oversize the measured diameter of the normal segment of the renal artery by no more than 10% (range, 4 – 8 mm diameter).
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If results obtained with angioplasty were suboptimal (determined angiographically or by pressure gradient measurements), balloon-expandable stents (range, 4 – 8 mm diameter) were then placed. Indications for stent use at our institutions include greater than 30% residual stenosis after PTA, persistent peak systolic pressure gradient greater than 10% after angioplasty, flow-limiting dissection, and early recurrent clinically significant stenosis within 3 months of angioplasty (5,18). An example of the treatment method described earlier involving PTA with or without stent placement is demonstrated in the Figure. Follow-up was performed during routine visits to the transplant clinic every 3 months with measurement of blood pressure and serum creatinine. Repeat color-flow Doppler US and/or MR angiography was performed when restenosis was suggested by increasing serum creatinine level or increasing blood pressure. With color-flow Doppler US, criteria for significant stenosis include (i) peak systolic velocities greater than 2 m/sec, (ii) velocity gradient between stenotic and prestenotic segments of more than 2:1, and (iii) marked distal turbulence (spectral broadening) (19). With MR angiography, a stenosis of greater than 50% luminal diameter was interpreted as an anatomic criterion for possible TRAS. Allografts meeting these criteria underwent subsequent investigation with angiography for diagnosis and percutaneous therapy. Definitions and Endpoints Definitions of hypertension and renal insufficiency provided by Rundback et al (18) were used as indications for angiographic investigation and endovascular therapy of TRAS. Hypertension was considered if (i) blood pressure increased from baseline, (ii) accelerated hypertension (sudden worsening of previously controlled hypertension) occurred, or (iii) refractory hypertension (hypertension resistant to treatment with at least three medications of different classes) occurred. Elevated creatinine levels necessitating intervention for renal salvage was defined as (i) sudden unexplained worsening of renal function (our criteria included an increased serum creatinine level greater then 10% over baseline) and (ii) impair-
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Figure. Images from a patient who presented with increasing blood pressure relative to baseline and required use of one blood pressure medication. Color-flow Doppler US and MR angiography findings were consistent with TRAS. (a) Initial arteriogram demonstrates greater than 50% stenosis at the origin of the transplant renal artery to the external iliac artery. Pressure measurements demonstrated a 17% peak systolic pressure gradient. (b) Arteriogram after PTA with a 7-mm ⫻ 2-cm balloon indicates improvement in the degree of the stenosis. However, a hemodynamically significant pressure gradient (12%) persisted. (c) A Palmaz Genesis 154 balloon-expandable stent was deployed and dilated to 7 mm. Arteriogram after stent placement demonstrates a widely patent transplant renal artery with no residual stenosis. The peak systolic pressure gradient decreased to 6%. Postintervention blood pressure decreased to 110/80 mm Hg with no hypertensive medication.
ment of renal function secondary to antihypertensive treatment. Technical and clinical successes have been previously defined (4,5,18). Technical success after percutaneous intervention was defined as residual stenosis less than 30%, no flow-limiting dissection, and a residual peak systolic pressure gradient less than 10% systolic blood pressure across the
lesion. Clinical success was assessed at 1 month after intervention and was defined as (i) more than a 15% reduction in serum creatinine level (stabilization of serum creatinine levels was also considered to constitute success), (ii) more than 15% reduction in mean diastolic blood pressure with the number of antihypertensive medications equal to that before angioplasty, or (iii)
more than 10% reduction in mean diastolic blood pressure with a reduction in number of antihypertensive medications. Complications were considered procedure-related if they occurred within 30 days of percutaneous intervention (20). Complication events were classified as major or minor based on criteria established by the
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Standards of Practice Committee of the Society of Interventional Radiology (21).
The technical success rate of all percutaneous interventions was 100% (21 of 21 interventions), and the clinical success rate of intervention on allografts was 94% (17 of 18 allografts). Thirteen interventions were PTA alone and eight interventions involved PTA and stent placement. Stents used included four Palmaz Genesis 154 stents (Cordis, Miami, FL) dilated to diameters of 5 mm in two allografts and 7 mm in two allografts, two Herculink stents (Guidant, Santa Clara, CA) dilated to diameters of 4.5 mm and 6.5 mm, one Palmaz Corinthian stent (Cordis) dilated to a diameter of 6 mm, and one Perflex stent (Cordis) dilated to 6 mm in diameter.
vated serum creatinine level; this was technically successful, and there was maintained clinical success until the date of last follow-up 18 months after second intervention. The other two patients who required repeat intervention underwent technically and clinically successful PTA initially, with decreased serum creatinine at 1 month after PTA. At routine follow-up, elevated serum creatinine levels were noted. The two patients underwent repeat color-flow Doppler US, which demonstrated findings consistent with restenosis. Both underwent repeat PTA of TRAS at 11 and 14 months, respectively. The repeat interventions were technically and clinically successful. Clinical success was achieved in 11 of 12 allografts presenting with elevated creatinine levels. In the single intervention that was not clinically successful, the patient underwent technically successful PTA and stent placement of TRAS. However, the 1-month postintervention serum creatinine value increased 8% from preintervention values (3.2 mg/dL after intervention vs 3.0 mg/dL before intervention). The allograft was lost to chronic failure 10 months after intervention. In the group of patients who presented with elevated serum creatinine levels, the mean serum creatinine value before PTA/stent placement was 2.8 mg/dL ⫾ 1.4 (range, 1.4 –5.7 mg/dL), versus a 1-month PTA value of 2.2 mg/dL ⫾ 0.7 (range, 1.5–3.4 mg/dL). The observed decrease in serum creatinine was statistically significant, with a P value of .03.
Allografts Presenting with Elevated Creatinine
Allografts Presenting with Hypertension
Twelve patients who presented with elevated creatinine levels underwent a total of 15 percutaneous interventions: 11 with PTA alone and four with PTA and stent placement. Three patients each underwent two interventions. In one patient, the initial intervention was PTA alone followed by a second intervention 6 months later with PTA and stent placement. The first intervention was technically and initially clinically successful, with decreased serum creatinine level at 1 month after the intervention. The second intervention was performed 6 months after the first, again for ele-
Six allografts presented with hypertension and underwent a total of six interventions. Three allografts underwent percutaneous intervention with PTA alone and three underwent PTA and stent placement (Figure). All interventions were technically and clinically successful. Statistically significant improvements were seen in the preintervention versus 1-month postintervention mean systolic (174 mm Hg vs 135 mm Hg, P ⫽ .003) and diastolic (99 mm Hg vs 82 mm Hg, P ⫽ .02) pressures. A significant decrease in the mean number of required medications for blood pressure control after percuta-
Statistical Analysis The differences in preintervention and 1-month postintervention blood pressure and serum creatinine levels were compared with paired two-sample Student t tests. The number of blood pressure medications was compared with use of the Wilcoxon ranksum test. Patency rates were calculated with use of the Kaplan-Meier method with 95% confidence intervals. The software used for statistical analysis was SAS version 8.02 (SAS, Cary, NC). A probability value of .05 was considered the threshold of statistical significance.
RESULTS
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neous intervention was also demonstrated (2.3 medications before intervention vs 1.0 at 1 month after intervention, P ⫽ .002). Patency Primary patency rates at 3, 6, and 12 months (⫾95% CI) were 94% ⫾ 6%, 72% ⫾ 12%, and 72% ⫾ 12%, respectively. Secondary patency rates at 3, 6, and 12 months (⫾95% CI) were 100%, 85% ⫾ 10%, and 85% ⫾ 10%, respectively. As described earlier, three allografts required repeat intervention, and in one allograft, the single intervention was clinically unsuccessful, with that allograft lost to chronic rejection at 10 months. One additional allograft failed at 11 months after intervention as a result of chronic failure. Follow-up The mean follow-up interval for patients after percutaneous intervention was 27 months (range, 5– 64 months). Of the eight allografts that underwent stent placement, all eight remained patent as assessed by clinical and noninvasive imaging follow-up with color-flow Doppler US at last follow-up (mean, 18.3 months; range, 4 –29 months). Complications Complications occurred in 10.5% of interventions (two of 19), with one major complication and one minor complication. The single major complication among 19 interventions (5%) was a puncture site pseudoaneurysm successfully treated with percutaneous thrombin injection. The single minor complication was a puncture site hematoma, which resolved with conservative treatment.
DISCUSSION Three different treatment methods for TRAS are available. Medical management may be performed to control hypertension, with unknown effect on kidney function. Surgical intervention with revascularization may be performed, which is considered a major operation, with graft loss after vascular reconstruction reported in as many as 20% of cases (22), and with recurrence rates ranging from 7% (22) to
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Table 1 Results of Studies Investigating Treatment of TRAS with PTA
Year
No. of Pts.
Technical Success (%)
Patel et al (4) Halimi et al (9) Wong et al (1) Sankari et al (3) Fauchald et al (10)
2001 1999 1996 1996 1992
17 26 77 16 25
94 92.3 – 94 88
Matalon et al (12)
1992
18*
75
Benoit et al (23) Greenstein et al (11) Raynaud et al (8)
1990 1987 1986
49 39 43
69 88 81
Grossman et al (7)
1982
17
88
Study
Clinical Success (%) 82 – – 75 67† 63‡ 83§ 63㛳 40.8¶ 83# 74** 67†† 76‡‡ 87§§
Follow-up (months) 26.9 (mean) 68 (mean) – 44.7 24 (median) 23 (median) 23.3 (mean) 32 30 (mean) 1 12 ⬃15.6
Complications – 1/26 (minor) – 5/16 5/25 2 (major) 28% “morbidity” 7/39 – 3/17 (minor)
* 24 PTA procedures. † Long-term clinical success rate based on renal function. ‡ Long-term clinical success rate based on blood pressure. § 10% or greater reduction in mean blood pressure 1 week after PTA. 㛳 Persistent 10% or greater decrease in mean blood pressure on long-term follow-up (average, 11.5 months; range, 2–32 months). ¶ Long-term success rate, follow-up of 32 months ⫾ 28. # Rate of cure or improvement among patients with functioning kidneys at a mean follow-up period of 30 months. ** Improvement at 1 month after a primary successful PTA. †† Improvement at 1 year after a primary successful PTA. ‡‡ Calculated via 13 of 17 total patients who had long-term allograft survival, and in all of these instances blood pressure was decreased after PTA. §§ Reported as 13 of 15 patients who had successful dilation and long-term allograft survival, and in all of these instances blood pressure was decreased after PTA.
15% (23). Finally, percutaneous endovascular management with use of PTA and/or stent placement may be undertaken. Percutaneous management is now considered the treatment of choice if medical treatment fails, and does not preclude subsequent surgical correction (3,4,8,10,11,23,24). Initial technical success of PTA in the treatment of TRAS has been reported to be greater than 80% (1,3,4,7– 11). Long-term clinical success defined as either improvement in blood pressure control or stabilization/improvement in renal function is reported to be 63%– 82% at 1 year (3,4,8,10), with the restenosis rate after PTA to be in the range of 10%–36% (1,3,4,8 –10,23). The methods of reporting technical success and the parameters used to assess clinical outcome vary widely in the literature. Summarized results of previous studies with endpoints and methods similar to those used in this retrospective review evaluating outcome of PTA for TRAS are presented in Table 1.
The efficacy of endovascular therapy for TRAS in this retrospective study is suggested by the statistically significant decrease in mean systolic and diastolic blood pressure, serum creatinine level, and number of antihypertensive medications used by patients after intervention. Our results, with 100% technical and 94% clinical success rates for therapy of TRAS with PTA with or without stent placement, are similar to those reported in the literature with use of PTA alone (Table 1). However, our reported experience does add to the existing literature. Although Halimi et al (9) and Grossman et al (7) (in a subset of their patient population in which 13 of 15 patients had successful dilation) demonstrated efficacy of treating TRAS with PTA with statistically significant decreases after PTA in systolic and diastolic blood pressure and serum creatinine levels, no mention is made regarding use of blood pressure medications. In a study by Wong et al (1), 77 allografts treated with PTA showed
a significant decrease in plasma creatinine level after therapy, but did not demonstrate statistically significant decreases in mean blood pressure or number of antihypertensive medications after PTA. Reasons for this discrepancy in our study compared with others could be related to the supplemental use of stents in the treatment of TRAS when PTA is unsuccessful or when complications arise from PTA. Endovascular stents have been used for the treatment of recurrent and/or ostial stenosis and in cases of suboptimal results with PTA. In addition, serious complications of PTA can be salvaged with stents. There have been limited studies performed to date to assess stent placement for TRAS, primarily in the clinical scenario of recurrent or resistant TRAS; results from these studies are summarized in Table 2. Insertion of stents has been demonstrated to have a high initial technical success rate and reasonable patency, with minimal complications (13–16). In our experience, of the eight allo-
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Table 2 Summary of Results of Studies Involving Stents for Treatment of TRAS Technical Success (%)
Clinical Success (%) NR 71.4 83† 100‡ 100§
Study
Year
No. of Stents
Bertoni et al (13) Nicita et al (16) Sierre et al (15)
2000 1998 1998
9 8* 6
100 100 100
Newman-Sanders et al (14)
1995
4
100
Follow-up (months)
Complications
33.5 (Mean) 14.8 (Mean) 34 (Mean)
0 0 0
4–24
1/4 (acute stent thrombosis)
* In seven patients. † At last follow-up (mean, 34 months); clinical success was determined at last follow-up (mean, 34 months) with regard to systolic blood pressure. ‡ At last follow-up (mean, 34 months); clinical success was determined at last follow-up (mean 34 months) with regard to serum creatinine level. § Defined as all patients who had stable allograft function and stable blood pressure control at last follow-up (range, 4 –24 months).
grafts treated with stents, there was a 100% technical success rate and an 88% clinical success rate (seven of eight), with continued patency and no instances of recurrent graft dysfunction at a mean follow-up interval of 18.3 months. The total of eight allografts treated with stents for TRAS in this study is similar to the largest reported numbers in the literature, by Nicita et al (16) (n ⫽ 7) and Bertoni et al (13) (n ⫽ 9). We preferred to use balloon-expandable stents for greater radial strength and accurate placement compared with self-expanding stents. Previous technical limitations of balloon-expandable stents have now been largely resolved with the introduction of multiple new stent platforms by a variety of medical device companies. Recently introduced premounted balloon-expandable stents have a reduced profile and will pass over 0.014 – 0.021inch guide wires and through 5-F introducers. Reduced shortening after expansion, good trackability over the aortic bifurcation, and premounting of stents to prevent migration of the stent off the deployment balloon are additional benefits of the newer stent platforms. These may allow for improved technical success. Complication rates are low in the treatment of TRAS with PTA and/or stent placement (Tables 1, 2), with the rate of graft loss lower for PTA than for surgery (7–9,12,22,24). Our experience supports previously reported low complication rates of endovascular therapy in the setting of TRAS, with a
major complication rate of 5% (one of 19) related to femoral arterial puncture and no instances of allograft loss during intervention. Several limitations are present in this study. These include the retrospective nature of the study and multiple operators performing the procedures. The relatively small patient population is another weakness in the paper; however, the number of interventions was sufficient to demonstrate significant decreases in systolic and diastolic arterial pressures, serum creatinine levels, and number of antihypertensive medications after endovascular therapy in this patient population. The relatively small number of interventions precludes meaningful comparison of the efficacy of PTA versus stent placement in the treatment of TRAS. The presence of other underlying pathology that may have contributed to increased blood pressure or increasing serum creatinine levels in renal transplant recipients was not definitively excluded in our patient population. References 1. Wong W, Fynn SP, Higgins RM, et al. Transplant renal artery stenosis in 77 patients— does it have an immunological cause? Transplantation 1996; 61: 215–219. 2. Sutherland RS, Spees EK, Jones JW, Fink DW. Renal artery stenosis after renal transplantation: the impact of the hypogastric artery anastomosis. J Urol 1993; 149:980 –985. 3. Sankari BR, Geisinger M, Zelch M,
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Brouhard B, Cunningham R, Novick AC. Post-transplant renal artery stenosis: impact of therapy on long-term kidney function and blood pressure control. J Urol 1996; 155:1860 –1864. Patel NH, Jindal RM, Wilkin T, et al. Renal arterial stenosis in renal allografts: retrospective study of predisposing factors and outcome after percutaneous transluminal angioplasty. Radiology 2001; 219:663– 667. Fervenza FC, Lafayette RA, Alfrey EJ, Petersen J. Renal artery stenosis in kidney transplantation. Am J Kidney Dis 1998; 31:142–148. Spinosa DJ, Isaacs RB, Matsumoto AH, Angle JF, Hagspiel KD, Leung DA. Angiographic evaluation and treatment of transplant renal artery stenosis. Curr Opin Urol 2001; 11:197–205. Grossman RA, Dafoe DC, Shoenfeld RB, et al. Percutaneous transluminal angioplasty treatment of renal transplant artery stenosis. Transplantation 1982; 34:339 –343. Raynaud A, Bedrossian J, Remy P, Brisset JM, Angel CY, Gaux JC. Percutaneous transluminal angioplasty of renal transplant arterial stenoses. AJR Am J Roentgenol 1986; 146:853– 857. Halimi JM, Al-Najjar A, Buchler M, et al. Transplant renal artery stenosis: potential role of ischemia/reperfusion injury and long-term outcome following angioplasty. J Urol 1999; 161:28 –32. Fauchald P, Vatne K, Paulsen D, et al. Long-term clinical results of percutaneous transluminal angioplasty in transplant renal artery stenosis. Nephrol Dial Transplant 1992; 7:256 –259. Greenstein SM, Verstandig A, McLean GK, et al. Percutaneous transluminal angioplasty. The procedure of choice in the hypertensive renal allograft recipi-
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ent with renal artery stenosis. Transplantation 1987; 43:29 –32. Matalon TA, Thompson MJ, Patel SK, Brunner MC, Merkel FK, Jensik SC. Percutaneous transluminal angioplasty for transplant renal artery stenosis. J Vasc Interv Radiol 1992; 3:55–58. Bertoni E, Zanazzi M, Rosat A, et al. Efficacy and safety of Palmaz stent insertion in the treatment of renal artery stenosis in kidney transplantation. Transpl Int 2000; 13(suppl 1):S425– S430. Newman-Sanders AP, Gedroyc WG, al-Kutoubi MA, Koo C, Taube D. The use of expandable metal stents in transplant renal artery stenosis. Clin Radiol 1995; 50:245–250. Sierre SD, Raynaud AC, Carreres T, Sapoval MR, Beyssen BM, Gaux JC. Treatment of recurrent transplant renal artery stenosis with metallic stents. J Vasc Interv Radiol 1998; 9:639 – 644.
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16. Nicita G, Villari D, Marzocco M, Li Marzi V, Trippitelli A, Santoro G. Endoluminal stent placement after percutaneous transluminal angioplasty in the treatment of post-transplant renal artery stenosis. J Urol 1998; 159:34 –37. 17. Becker BN, Odorico JS, Becker YT, et al. Peripheral vascular disease and renal transplant artery stenosis: a reappraisal of transplant renovascular disease. Clin Transpl 1999; 13:349 –355. 18. Rundback JH, Sacks D, Kent C, et al. Guidelines for the reporting of renal artery revascularization in clinical trials. J Vasc Interv Radiol 2003; 14(suppl): S477–S492. 19. de Morais RH, Muglia VF, Mamere AE, et al. Duplex Doppler sonography of transplant renal artery stenosis. J Clin Ultrasound 2003; 31:135–141. 20. Goodwin SC, Bonilla SM, Sacks D, et al. Reporting standards for uterine artery embolization for the treatment
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of uterine leiomyomata. J Vasc Interv Radiol 2001; 12:1011–1120. Drooz AT, Lewis CA, Allen TE, et al. Quality improvement guidelines for percutaneous transcatheter embolization. J Vasc Interv Radiol 1997; 8:889 – 895. Merkus JW, Huysmans FT, Hoitsma AJ, Buskens FG, Skotnicki SH, Koene RA. Renal allograft artery stenosis: results of medical treatment and intervention: a retrospective analysis. Transpl Int 1993; 6:111–115. Benoit G, Moukarzel M, Hiesse C, Verdelli G, Charpentier B, Fries D. Transplant renal artery stenosis: experience and comparative results between surgery and angioplasty. Transpl Int 1990; 3:137–140. Sniderman KW, Sprayregen S, Sos TA, et al. Percutaneous transluminal dilation in renal transplant arterial stenosis. Transplantation 1980; 30:440 – 444.
PTA ⫽ percutaneous transluminal angioplasty, TRAS ⫽ transplant renal artery stenosis
TRANSPLANT renal artery stenosis (TRAS) is the most frequent vascular From the Division of Vascular and Interventional Radiology, Department of Medical Imaging (J.R.B., D.K.R.), and Division of Urology (M.A.R.), Toronto General Hospital, University Health Network–University of Toronto, 585 University Avenue, NCSB 1C-560, Toronto, ON M5G 2N2, Canada; and Section of Interventional Radiology (T.W.I.C., S.W.S.), Department of Radiology, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania. Received April 21, 2004; revision requested May 18; final revision received and accepted July 12. From the 2004 SIR Annual Meeting. Address correspondence to J.R.B.; E-mail: [email protected] None of the authors have identified a conflict of interest. © SIR, 2004 DOI: 10.1097/01.RVI.0000141338.62574.F4
complication in renal transplantation, with an incidence varying from 1% to 23% (1–5). TRAS can present clinically with hypertension and/or increased serum creatinine levels. Noninvasive imaging can detect an underlying stenosis, and color-flow duplex ultrasound (US) and magnetic resonance (MR) angiography have now become the primary noninvasive imaging modalities for the diagnosis of TRAS (6). However, catheter-based angiography remains the gold standard for evaluation of TRAS. Angiography provides a definitive diagnosis and allows the option for treatment with subsequent endovascular therapy. Percutaneous transluminal angioplasty (PTA) is recognized as the ini-
tial treatment of choice in TRAS, with studies having demonstrated its efficacy. Initial technical success of PTA in the treatment of TRAS has been reported to be greater than 80% (1,3,4,7– 11). Reported rates of clinical success are 63%– 83% for hypertension (3,7,8, 10 –12), 67% for treatment of elevated serum creatinine levels (10), 82% for hypertension and/or elevated serum creatinine levels (4), and 76% for long-term allograft survival (7). Metallic stents in TRAS have been used for treatment of recurrent and/or ostial stenosis, but there are limited studies performed to date. Stent placement has been associated with high initial technical success rates and good patency rates, with minimal complications (13–16).
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Percutaneous Intervention for Transplant Renal Artery Stenosis
In this study, we retrospectively examined our institutions’ outcomes of percutaneous interventions in the treatment of TRAS to assess the efficacy of endovascular therapy with PTA with or without stent placement.
MATERIALS AND METHODS Patient Group A retrospective analysis of all patients who underwent angiography and percutaneous intervention for the treatment of TRAS from April 1997 to July 2003 was conducted. Patients were identified with use of radiology and renal transplantation databases maintained at the two participating institutions. Reviewed parameters included type of renal allograft, date of transplantation, clinical presentation of TRAS, dates of intervention, type of intervention(s) performed, technical success, and length of follow-up. Mean arterial blood pressure, number of blood pressure medications, and serum creatinine levels were also recorded before the intervention and at follow-up visits to assess clinical outcome. Institutional review boards granted approval at one institution and an exemption at the other institution for this retrospective study. Eighteen renal allografts were identified in which a total of 21 interventions were performed (angioplasty with or without stent placement). Nine allografts were cadaveric, seven allografts were living related, and two allografts were living nonrelated. Seventeen anastomoses were end-to-side to the external iliac artery, and a single anastomosis (for a living nonrelated allograft) was end-to-end to the internal iliac artery. The mean age of the patient cohort was 57 years (range, 19 – 68 years). Fourteen patients were men and four were women. Renal allografts with TRAS were initially identified by increased blood pressure or increasing serum creatinine level compared with baseline at clinical visits to the transplant clinic. All cases of TRAS were identified by color-flow Doppler US or MR angiography. No allografts had renal biopsies within 3 months before endovascular intervention.
Treatment Method In each intervention, diagnostic renal arteriography was performed via a femoral arterial approach; an ipsilateral or contralateral femoral approach was chosen based on the type of surgical anastomosis of transplant renal artery (end-to-side with use of the external iliac artery or end-to-end with use of the internal iliac artery) and the angle of anastomosis. Nonselective ipsilateral iliac arteriography was performed to exclude an inflow/preanastomotic lesion, often referred to as pseudo-renal transplant artery stenosis in the literature (4,17). The transplant renal artery and anastomosis were then assessed angiographically in an optimal projection to profile the anastomosis. If there was concern for contrast material–induced nephrotoxicity, alternative contrast agents (eg, CO2, gadolinium) were used for preliminary angiography in selected patients. The volumes of iodinated contrast material were kept to a minimum to reduce the risk of nephrotoxicity. Hemodynamically significant stenosis was considered as narrowing of the luminal diameter greater than 50% (5,18). Additionally, in all cases, pressure measurements across the stenosis were obtained to assess for a significant hemodynamic gradient, considered as greater than 10% peak systolic blood pressure gradient. In all cases, heparin sodium was administered intravenously (3,000 – 5,000 IU). The stenoses were traversed with a guide wire, followed by the use of 4-F catheters to obtain pressure measurements across the stenosis. Nitroglycerin (100 –200 g intraarterially into the transplant renal artery) and/or nifedipine (10 mg sublingual) were administered to prevent vasospasm on an operator preference basis. After appropriate calibration of images, measurement of stenosis was made by measuring the ratio between the diameter of the stenosed segment of the artery and the diameter of a normal segment of renal artery (18). TRAS was then treated initially with an angioplasty balloon catheter; the size of the balloon was chosen to oversize the measured diameter of the normal segment of the renal artery by no more than 10% (range, 4 – 8 mm diameter).
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If results obtained with angioplasty were suboptimal (determined angiographically or by pressure gradient measurements), balloon-expandable stents (range, 4 – 8 mm diameter) were then placed. Indications for stent use at our institutions include greater than 30% residual stenosis after PTA, persistent peak systolic pressure gradient greater than 10% after angioplasty, flow-limiting dissection, and early recurrent clinically significant stenosis within 3 months of angioplasty (5,18). An example of the treatment method described earlier involving PTA with or without stent placement is demonstrated in the Figure. Follow-up was performed during routine visits to the transplant clinic every 3 months with measurement of blood pressure and serum creatinine. Repeat color-flow Doppler US and/or MR angiography was performed when restenosis was suggested by increasing serum creatinine level or increasing blood pressure. With color-flow Doppler US, criteria for significant stenosis include (i) peak systolic velocities greater than 2 m/sec, (ii) velocity gradient between stenotic and prestenotic segments of more than 2:1, and (iii) marked distal turbulence (spectral broadening) (19). With MR angiography, a stenosis of greater than 50% luminal diameter was interpreted as an anatomic criterion for possible TRAS. Allografts meeting these criteria underwent subsequent investigation with angiography for diagnosis and percutaneous therapy. Definitions and Endpoints Definitions of hypertension and renal insufficiency provided by Rundback et al (18) were used as indications for angiographic investigation and endovascular therapy of TRAS. Hypertension was considered if (i) blood pressure increased from baseline, (ii) accelerated hypertension (sudden worsening of previously controlled hypertension) occurred, or (iii) refractory hypertension (hypertension resistant to treatment with at least three medications of different classes) occurred. Elevated creatinine levels necessitating intervention for renal salvage was defined as (i) sudden unexplained worsening of renal function (our criteria included an increased serum creatinine level greater then 10% over baseline) and (ii) impair-
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Figure. Images from a patient who presented with increasing blood pressure relative to baseline and required use of one blood pressure medication. Color-flow Doppler US and MR angiography findings were consistent with TRAS. (a) Initial arteriogram demonstrates greater than 50% stenosis at the origin of the transplant renal artery to the external iliac artery. Pressure measurements demonstrated a 17% peak systolic pressure gradient. (b) Arteriogram after PTA with a 7-mm ⫻ 2-cm balloon indicates improvement in the degree of the stenosis. However, a hemodynamically significant pressure gradient (12%) persisted. (c) A Palmaz Genesis 154 balloon-expandable stent was deployed and dilated to 7 mm. Arteriogram after stent placement demonstrates a widely patent transplant renal artery with no residual stenosis. The peak systolic pressure gradient decreased to 6%. Postintervention blood pressure decreased to 110/80 mm Hg with no hypertensive medication.
ment of renal function secondary to antihypertensive treatment. Technical and clinical successes have been previously defined (4,5,18). Technical success after percutaneous intervention was defined as residual stenosis less than 30%, no flow-limiting dissection, and a residual peak systolic pressure gradient less than 10% systolic blood pressure across the
lesion. Clinical success was assessed at 1 month after intervention and was defined as (i) more than a 15% reduction in serum creatinine level (stabilization of serum creatinine levels was also considered to constitute success), (ii) more than 15% reduction in mean diastolic blood pressure with the number of antihypertensive medications equal to that before angioplasty, or (iii)
more than 10% reduction in mean diastolic blood pressure with a reduction in number of antihypertensive medications. Complications were considered procedure-related if they occurred within 30 days of percutaneous intervention (20). Complication events were classified as major or minor based on criteria established by the
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Standards of Practice Committee of the Society of Interventional Radiology (21).
The technical success rate of all percutaneous interventions was 100% (21 of 21 interventions), and the clinical success rate of intervention on allografts was 94% (17 of 18 allografts). Thirteen interventions were PTA alone and eight interventions involved PTA and stent placement. Stents used included four Palmaz Genesis 154 stents (Cordis, Miami, FL) dilated to diameters of 5 mm in two allografts and 7 mm in two allografts, two Herculink stents (Guidant, Santa Clara, CA) dilated to diameters of 4.5 mm and 6.5 mm, one Palmaz Corinthian stent (Cordis) dilated to a diameter of 6 mm, and one Perflex stent (Cordis) dilated to 6 mm in diameter.
vated serum creatinine level; this was technically successful, and there was maintained clinical success until the date of last follow-up 18 months after second intervention. The other two patients who required repeat intervention underwent technically and clinically successful PTA initially, with decreased serum creatinine at 1 month after PTA. At routine follow-up, elevated serum creatinine levels were noted. The two patients underwent repeat color-flow Doppler US, which demonstrated findings consistent with restenosis. Both underwent repeat PTA of TRAS at 11 and 14 months, respectively. The repeat interventions were technically and clinically successful. Clinical success was achieved in 11 of 12 allografts presenting with elevated creatinine levels. In the single intervention that was not clinically successful, the patient underwent technically successful PTA and stent placement of TRAS. However, the 1-month postintervention serum creatinine value increased 8% from preintervention values (3.2 mg/dL after intervention vs 3.0 mg/dL before intervention). The allograft was lost to chronic failure 10 months after intervention. In the group of patients who presented with elevated serum creatinine levels, the mean serum creatinine value before PTA/stent placement was 2.8 mg/dL ⫾ 1.4 (range, 1.4 –5.7 mg/dL), versus a 1-month PTA value of 2.2 mg/dL ⫾ 0.7 (range, 1.5–3.4 mg/dL). The observed decrease in serum creatinine was statistically significant, with a P value of .03.
Allografts Presenting with Elevated Creatinine
Allografts Presenting with Hypertension
Twelve patients who presented with elevated creatinine levels underwent a total of 15 percutaneous interventions: 11 with PTA alone and four with PTA and stent placement. Three patients each underwent two interventions. In one patient, the initial intervention was PTA alone followed by a second intervention 6 months later with PTA and stent placement. The first intervention was technically and initially clinically successful, with decreased serum creatinine level at 1 month after the intervention. The second intervention was performed 6 months after the first, again for ele-
Six allografts presented with hypertension and underwent a total of six interventions. Three allografts underwent percutaneous intervention with PTA alone and three underwent PTA and stent placement (Figure). All interventions were technically and clinically successful. Statistically significant improvements were seen in the preintervention versus 1-month postintervention mean systolic (174 mm Hg vs 135 mm Hg, P ⫽ .003) and diastolic (99 mm Hg vs 82 mm Hg, P ⫽ .02) pressures. A significant decrease in the mean number of required medications for blood pressure control after percuta-
Statistical Analysis The differences in preintervention and 1-month postintervention blood pressure and serum creatinine levels were compared with paired two-sample Student t tests. The number of blood pressure medications was compared with use of the Wilcoxon ranksum test. Patency rates were calculated with use of the Kaplan-Meier method with 95% confidence intervals. The software used for statistical analysis was SAS version 8.02 (SAS, Cary, NC). A probability value of .05 was considered the threshold of statistical significance.
RESULTS
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neous intervention was also demonstrated (2.3 medications before intervention vs 1.0 at 1 month after intervention, P ⫽ .002). Patency Primary patency rates at 3, 6, and 12 months (⫾95% CI) were 94% ⫾ 6%, 72% ⫾ 12%, and 72% ⫾ 12%, respectively. Secondary patency rates at 3, 6, and 12 months (⫾95% CI) were 100%, 85% ⫾ 10%, and 85% ⫾ 10%, respectively. As described earlier, three allografts required repeat intervention, and in one allograft, the single intervention was clinically unsuccessful, with that allograft lost to chronic rejection at 10 months. One additional allograft failed at 11 months after intervention as a result of chronic failure. Follow-up The mean follow-up interval for patients after percutaneous intervention was 27 months (range, 5– 64 months). Of the eight allografts that underwent stent placement, all eight remained patent as assessed by clinical and noninvasive imaging follow-up with color-flow Doppler US at last follow-up (mean, 18.3 months; range, 4 –29 months). Complications Complications occurred in 10.5% of interventions (two of 19), with one major complication and one minor complication. The single major complication among 19 interventions (5%) was a puncture site pseudoaneurysm successfully treated with percutaneous thrombin injection. The single minor complication was a puncture site hematoma, which resolved with conservative treatment.
DISCUSSION Three different treatment methods for TRAS are available. Medical management may be performed to control hypertension, with unknown effect on kidney function. Surgical intervention with revascularization may be performed, which is considered a major operation, with graft loss after vascular reconstruction reported in as many as 20% of cases (22), and with recurrence rates ranging from 7% (22) to
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Table 1 Results of Studies Investigating Treatment of TRAS with PTA
Year
No. of Pts.
Technical Success (%)
Patel et al (4) Halimi et al (9) Wong et al (1) Sankari et al (3) Fauchald et al (10)
2001 1999 1996 1996 1992
17 26 77 16 25
94 92.3 – 94 88
Matalon et al (12)
1992
18*
75
Benoit et al (23) Greenstein et al (11) Raynaud et al (8)
1990 1987 1986
49 39 43
69 88 81
Grossman et al (7)
1982
17
88
Study
Clinical Success (%) 82 – – 75 67† 63‡ 83§ 63㛳 40.8¶ 83# 74** 67†† 76‡‡ 87§§
Follow-up (months) 26.9 (mean) 68 (mean) – 44.7 24 (median) 23 (median) 23.3 (mean) 32 30 (mean) 1 12 ⬃15.6
Complications – 1/26 (minor) – 5/16 5/25 2 (major) 28% “morbidity” 7/39 – 3/17 (minor)
* 24 PTA procedures. † Long-term clinical success rate based on renal function. ‡ Long-term clinical success rate based on blood pressure. § 10% or greater reduction in mean blood pressure 1 week after PTA. 㛳 Persistent 10% or greater decrease in mean blood pressure on long-term follow-up (average, 11.5 months; range, 2–32 months). ¶ Long-term success rate, follow-up of 32 months ⫾ 28. # Rate of cure or improvement among patients with functioning kidneys at a mean follow-up period of 30 months. ** Improvement at 1 month after a primary successful PTA. †† Improvement at 1 year after a primary successful PTA. ‡‡ Calculated via 13 of 17 total patients who had long-term allograft survival, and in all of these instances blood pressure was decreased after PTA. §§ Reported as 13 of 15 patients who had successful dilation and long-term allograft survival, and in all of these instances blood pressure was decreased after PTA.
15% (23). Finally, percutaneous endovascular management with use of PTA and/or stent placement may be undertaken. Percutaneous management is now considered the treatment of choice if medical treatment fails, and does not preclude subsequent surgical correction (3,4,8,10,11,23,24). Initial technical success of PTA in the treatment of TRAS has been reported to be greater than 80% (1,3,4,7– 11). Long-term clinical success defined as either improvement in blood pressure control or stabilization/improvement in renal function is reported to be 63%– 82% at 1 year (3,4,8,10), with the restenosis rate after PTA to be in the range of 10%–36% (1,3,4,8 –10,23). The methods of reporting technical success and the parameters used to assess clinical outcome vary widely in the literature. Summarized results of previous studies with endpoints and methods similar to those used in this retrospective review evaluating outcome of PTA for TRAS are presented in Table 1.
The efficacy of endovascular therapy for TRAS in this retrospective study is suggested by the statistically significant decrease in mean systolic and diastolic blood pressure, serum creatinine level, and number of antihypertensive medications used by patients after intervention. Our results, with 100% technical and 94% clinical success rates for therapy of TRAS with PTA with or without stent placement, are similar to those reported in the literature with use of PTA alone (Table 1). However, our reported experience does add to the existing literature. Although Halimi et al (9) and Grossman et al (7) (in a subset of their patient population in which 13 of 15 patients had successful dilation) demonstrated efficacy of treating TRAS with PTA with statistically significant decreases after PTA in systolic and diastolic blood pressure and serum creatinine levels, no mention is made regarding use of blood pressure medications. In a study by Wong et al (1), 77 allografts treated with PTA showed
a significant decrease in plasma creatinine level after therapy, but did not demonstrate statistically significant decreases in mean blood pressure or number of antihypertensive medications after PTA. Reasons for this discrepancy in our study compared with others could be related to the supplemental use of stents in the treatment of TRAS when PTA is unsuccessful or when complications arise from PTA. Endovascular stents have been used for the treatment of recurrent and/or ostial stenosis and in cases of suboptimal results with PTA. In addition, serious complications of PTA can be salvaged with stents. There have been limited studies performed to date to assess stent placement for TRAS, primarily in the clinical scenario of recurrent or resistant TRAS; results from these studies are summarized in Table 2. Insertion of stents has been demonstrated to have a high initial technical success rate and reasonable patency, with minimal complications (13–16). In our experience, of the eight allo-
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Table 2 Summary of Results of Studies Involving Stents for Treatment of TRAS Technical Success (%)
Clinical Success (%) NR 71.4 83† 100‡ 100§
Study
Year
No. of Stents
Bertoni et al (13) Nicita et al (16) Sierre et al (15)
2000 1998 1998
9 8* 6
100 100 100
Newman-Sanders et al (14)
1995
4
100
Follow-up (months)
Complications
33.5 (Mean) 14.8 (Mean) 34 (Mean)
0 0 0
4–24
1/4 (acute stent thrombosis)
* In seven patients. † At last follow-up (mean, 34 months); clinical success was determined at last follow-up (mean, 34 months) with regard to systolic blood pressure. ‡ At last follow-up (mean, 34 months); clinical success was determined at last follow-up (mean 34 months) with regard to serum creatinine level. § Defined as all patients who had stable allograft function and stable blood pressure control at last follow-up (range, 4 –24 months).
grafts treated with stents, there was a 100% technical success rate and an 88% clinical success rate (seven of eight), with continued patency and no instances of recurrent graft dysfunction at a mean follow-up interval of 18.3 months. The total of eight allografts treated with stents for TRAS in this study is similar to the largest reported numbers in the literature, by Nicita et al (16) (n ⫽ 7) and Bertoni et al (13) (n ⫽ 9). We preferred to use balloon-expandable stents for greater radial strength and accurate placement compared with self-expanding stents. Previous technical limitations of balloon-expandable stents have now been largely resolved with the introduction of multiple new stent platforms by a variety of medical device companies. Recently introduced premounted balloon-expandable stents have a reduced profile and will pass over 0.014 – 0.021inch guide wires and through 5-F introducers. Reduced shortening after expansion, good trackability over the aortic bifurcation, and premounting of stents to prevent migration of the stent off the deployment balloon are additional benefits of the newer stent platforms. These may allow for improved technical success. Complication rates are low in the treatment of TRAS with PTA and/or stent placement (Tables 1, 2), with the rate of graft loss lower for PTA than for surgery (7–9,12,22,24). Our experience supports previously reported low complication rates of endovascular therapy in the setting of TRAS, with a
major complication rate of 5% (one of 19) related to femoral arterial puncture and no instances of allograft loss during intervention. Several limitations are present in this study. These include the retrospective nature of the study and multiple operators performing the procedures. The relatively small patient population is another weakness in the paper; however, the number of interventions was sufficient to demonstrate significant decreases in systolic and diastolic arterial pressures, serum creatinine levels, and number of antihypertensive medications after endovascular therapy in this patient population. The relatively small number of interventions precludes meaningful comparison of the efficacy of PTA versus stent placement in the treatment of TRAS. The presence of other underlying pathology that may have contributed to increased blood pressure or increasing serum creatinine levels in renal transplant recipients was not definitively excluded in our patient population. References 1. Wong W, Fynn SP, Higgins RM, et al. Transplant renal artery stenosis in 77 patients— does it have an immunological cause? Transplantation 1996; 61: 215–219. 2. Sutherland RS, Spees EK, Jones JW, Fink DW. Renal artery stenosis after renal transplantation: the impact of the hypogastric artery anastomosis. J Urol 1993; 149:980 –985. 3. Sankari BR, Geisinger M, Zelch M,
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