- Email: [email protected]
Renal Revascularization: Who Benefits?
difficult to visualize against the background of high signal in overlaying subcutaneous and marrow fat.
Pitfalls InterpretaLion of peripheral vascular MRA studies must be done with care to avoid number pitfalls that can mimic or mask stenoses and occlusions. When a tortuous vessel drifts out of the imaging volume it will falsely appear occluded. Always check vessels in multiple orthogonal obliques to ensure that the vessel stays within the imaging volume along its entire course. Metallic clips and stents can also give the signal dropout that can be lnterpreted falsely as stenosis or occlusion. Stents have a characteristic region o~ signal dropout and adjacent bright spot that is easily identlAed on source images. Viewing the source images is also important for avoiding MIP artifacts which can occur when a bright structure overlaps the vessel of interest on the MIP. In general, the MIPs are best when made as narrow as possible yet still contain the vessel of interest. There can also be stair stepping artifact that resembles FMD when the MIPed images are too thick. This can be reduced by use of zero-interpolation. Finally, it is important to realize that ,\~ RA tends to overestimate the severity of stenoses in the pelVis and underestimate the severity of stenoses in the infrainguinal region.
Accuracy of MRA Technique for Evaluating Peripheral VascuJar Disease No. Investigator Year Patients Technique
Owen
1992 1993 Baum 1995 Prince 1995 Snidow 1998 Hmy 1997 Ho 1998 Meaney 1998 Yamashita 1998 I.e 1998 WincheSler 1998 Link 1999
155 43 32 39 2S 20 20 23 22 67
2000 2000 2000
39 61 5
23
Sensitivity
Specificity
ZOTOF "Superior to DSA" 2DTOF
Yucel
ZOTOF 3DGd 3DGJ 3DGd Bolus clla5e Bolus chase
3DGd ZOGd ZOGd 3DGJ
82 94 1m 93-96 93 81-89 96 94 90 100
98 96-100 98 91-95 83 91 98 83
81-94 92 98
73-92 97 96
84
98
(post swot) Lundin
Ruehm Fellner
Note.-l'OF
=
3DGd Bolus chase Bolus chase
time of flight.
Renal Revascularization (Part I)
Monday, March 5, 2001 7:30 a.m.-9:30 a.m. Moderator: Terence A.S. Matalon, MD
Literature There have now been numerous investigations on the accuracy of !'v'IRA techniques for evaluating patients suspected of haVing peripheral vascular disease. 2D timeof-flight has been shown to be accurate for evaluating infrapoplileal al1eries however the examination is cumbersome to perform because of the requirement of multiple coil placements for each leg. More proximally in the pelVis, 2D TOF has been more limited because of artifactual signal loss from vessel tortuosity, pulsatile flow, and susceptibility from bowel gas. Gd-enhanced 3D MRA, on the other hand, is highly accurate in the pelvis and thigh. Comparative studies have established a high level of accuracy in this region (Table 1). However, visualization of the smaller vessels below the knee can often be less reliable using bolus chase technique. For this reason, some centers have advocated performing 2D time-of-flight initially on the symptomatic leg below the knee before a three-station bolus chase 3D MRA. Alternative, the infra popliteal vessels can be evaluated with the 2D projection MRA technique, which also proVide bolus timing information as described here. In this lecture, I will describe in a step-by-step fashion the procedure for performing 3D bolus chase MRA using the fast bolus-sharing method. In addition, all of these protocol details arc available at www.m1prvtocols.com. These sequences are already in beta testing or product form for many magnet manufacturers.
P92
7:30 a.m. Renal Revascularization: Who Benefits? Steve I Schwab, MD David W. Btttterly, /vfD Duke University Medical Center Dw-bam, North Carolina Atherosclerotic renal disease has emerged as a relatively coounon condition in older patients. This atherosclerotic renal vascular disease is associated with cwo primalY pathophysiologic outcomes. The better-described of these is renal vascular hypertension. Renal Vascular Hypertension
Recent estimates suggest that renal vascular hypertension accounts for <1% of serious hypertension. Indications for treatment of renal artery stenosis and the treatment of renal vascular hypertension have been well developed (1). These include an appropriately severe renal vascular stenosis and appropriate lateralization of hormonal activity characterized by significant increases in renin secretion from the involved kidney. The emergence of angiotensin converting enzyme inhibitors have made surgical and endovascular treatment of this condition much less important than previous. Treatment of renal vascular disease, when the renins have nor been shown to clearly lateralize, improves hypeltension in only a minority of cases. Thus renal vascular hyperten-
sion, while a weJl-defined clinical entity, is relatively uncommon compared to the prevalence of renal artery stenosis. Renal Ischemic Disease In 1992, we initially characterized the prevalence of renal vascular disease in a group of patients referred for diagnostic cardiac catheterization (2). A total of 1,235 patients were enrolled in this study and underwent aortography at the time of cardiac catheterization to assess for the presence for renal vascular disease. Renal vascular disease was identified in a full 30% of patients being studied. Stenoses of <50% were noted in 15% of the patients and severe renal vascular disease characterized by >50% stenosis in another 15% of patients. The extent of coronary artery disease, peripheral vascular disease, and congestive heart failure predicted the likelihood of renal vascular disease. Surprisingly, the presence of hypertension was not predictive of renal vascular stenosis occurring in fewer than half the patients. Therefore, renal artery stenosis was usually clinicaJly silent and only rarely clinically associated with hypertension and, even more rarely, associated with clearly defined renal vascular hypertension. Therefore, renal artery stenosis is relatively common in this patient population while welldefined and treatable, renal vascular hypertension is uncommon. The important issue that has emerged has been the treatment of these stenotic lesions to preserve renal mass and slow the loss of renal function (3,4). This concept has been termed renal ischemic disease. Up until recently these questions with regard to treatment of renal ischemia were moot because the techniques involved for correcting renal artery stenosis involved significant risks in patients who already had Significant peripheral vascular, cardiovascular, and cerebrovascular risks factors. Novic and coJleagues and other investigators pioneered concepts of hepatorenal and splenic renal surgical bypass to avoid the significant morbidity and mortality of entering the aorta (5). Nonetheless, even in a highly selected group of patients, the risks of this procedure were Significant and it was performed relatively rarely. Percutaneous transluminal angioplasty of stenotic atherosclerotic lesions was relatively unsuccessful. The osteal nature of the majority of these lesions led to a high rate of failure and a high rate of restenosis (6-8). More recently, endovascular angioplasty when combined with endovascular stent placement has been shown to have a dramatically superior rate of technical success along with a relatively low rate of complication. Recently, van de Yen and associates reported a randomized trial comparing percutaneous transluminal angioplasty with stent deployment to percutaneous transluminal angioplasty alone. Primary success was 88% versus 70% and 6-month patency was 75% versus 29% (6). Blum et al (7) described 75 patients with renal artery stents and a mean [ollow-up of 27%. The procedure was technically successful in all with minor complications occurring in rel-
atively few and major complications in none (7). Frequency of restenosis in this study was <10%. Dorros et al (8) reported similar success with percutaneous transluminal angioplasty, stent placement, and stenosis. Therefore, technical advances, including the use of transluminal angioplasty with endovascular stent placement combined with antiplatelet therapy has significantly diminished the risks in patients undergoing percutaneous treatment of renal artery stenosis. Indeed, not only is the risks relatively low but the likelihood of restenosis is also acceptably low at one and two year follow-up. The key question is what is the benefit of these interventions. Fortunately two large studies dealing with the natural history of treated and untreated renal artelY stenosis is now available for evaluation. Conlon and associates from Duke University and Chabova and associates from the Mayo Clinic have reported their longterm foJlow-up (9-10). These studies have evaluated the natural history as a risk of 290/0-71% for progression of a 50% stenosis progressing to total occlusion. Caps et al reported a duplex ultrasonography foJlow-up in 295 kidneys and 177 patients with 33 months of follow-up. Progression based on duplex determination was 35% at three years and 51% at five years. Nine renal artery occlusions or 3% occurred over the course of the study (11). Thus occlusion was a relatively uncommon event. AdditionaJly, all occlusions occurred in patients with >600/0-70% stenosis on the study prior to the occlusion. At our institution, disease progression was assessed in 1,189 patients undergoing follow-up cardiac catheterization with aortography. Mean duration between angio'grams was was 2.6 years. Eleven% had severe progression. Not surprisingly, these vessels tended to progress in a time-dependent fashion with 25% of the patients demonstrating progressive disease by the five year mark. Although radiographic progression was demonstrable, there was little clinical change. [n this study, four year mortality was 35%. The patients with renal artery stenosis were more likely to have severe coronary artery disease and a depressed ejection fraction. Renal artery stenosis was a strong independent predictor of mortality. The major cause of death with or without renal artery stenosis was cardiovascular disease. Indeed, the presence or absence of renal artery stenosis did not influence the likelihood of progression to end-stage renal disease even though the presence of renal artery stenosis was a strong predictor of mortality. Correction of the renal artery stenosis not only did not effect overall renal outcome but had no effect on mortality compared to patients with similar disease whose renal arteries were not prospectively corrected Chabova and associates at the Mayo Clinic arrived at similar findings. They evaluated 68 patients with high grade renal artery stenosis, >70% unilateral or bilateral, who were followed medically without vascular percutaneous intelvention. Over the course of follow-up in this patient population there was some decline in renal function with a creatinine level
P93
rising from 1.4 mg/dI. to 2 mg/dL. Interestingly there was no significant difference in blood pressure, although slightly more medications were required for blood pressure control. Eighty-five percent had stable renal function at three years of follow-up. Remarkably, even patients with significant bilateral renal artery stenosis had no significant decrement in renal function. TIle risks of progressive renal failure in this high risk group was only 12.8% in the group with unilateral renal disease and 190/0 in the group with bilateral renal disease. Only two of the 68 patients advanced to end-stage renal disease from progressive renal artery stenosis. Mortality over the course of follow-up in this group was high with 28% dying mostly from either cardiovascular or cerebrovas~ cular event. In conclusion, the studies of both Conlon et al and Chabova et al offer long-term follow-up in a large group of patients with and without renal vascular intervention. The level of disease in both these populations was relatively severe and the population was older than in previous reports. The renal outcome was surprisingly good in those patients in whom intervention did not occur. The overall mortality seems related to cardiovascular and cerebrovascular disease. Thus, intervention on renal artery stenosis yield at best a very modest benefit in prevention of renal failure. Controversy exits when a technique is available for which the risk is modest but the benefits are likewise modest. This appears to be the case with atherosclerotic renal artery stenosis. A rational approach would be careful follow-up of patients with Significant renal artery stenosis with percutaneous intervention in those patients who show clear-cut loss of renal function and progression of renal artery stenosis. In the majority of other patients, intervention can probably be avoided.
References 1. Albers F, Svetkey 1. Screening and diagnosis in renal vascular hyperten,sion. In: Novik, Scobie, Hamilton, eds. Renal Vascular Disease. London: \VB Saunders, 1996,205-223. 2. Harding MB, Smith LR, Himmelstein SI, et al. Renal artery stenosis: prevalence and associated risk factors in patients undergoing routine carcUac catheterization. J Am Soc Nephrol 1992;2,1608-1616. 3. facobson HR. Ischemic renal disease: an overlooked clinical entity. Kidney 1nt 1988,34,729-743. 4. Rirruner ]M, Gennari FJ. Atherosclerotic renovascular disease and progressive renal failure. Ann Intern MedI993,118,712-719. 5. Novick AC, Straffon RA, Stewart BH, Gifford RW, Vidt D. Diminished operative morbidity and mortality in renal revascularization. JAMA 1981;246:749753. 6. van de 'len PJ, Kaatee R, Beutler JJ, et a1. Arterial stenting and balloon angioplasty in ostial athcroscle-
P94
rotic renovascular disease: a randomised trial. Lancet 1999;353,282-286. 7. Blum U, Krumme B, flugel P, et a1. Treatment of ostial renal-arrery stenosis with vascular endoprostheses after unsuccessful balloon angioplasty. N Engl J Med 1997;336,159-465. 8. Dorros G, Jaff ,',1, Mathiak L, Lowe A, Murphy K, He T. four-year follow-up of Palmaz-Schatz stent revascularization as treatment for atherosclerotic renal artery stenosis. Circulation 1998;998:642-647. 9. Conlon PJ, Athirakul K, Kovalik E, et a!. Survival in renal vascular disease. J Am Soc Nephrol 1998;9: 252-256. 10. Chabova V, Schirger A, Stanson AW, McKusick ivtA, Textor Sc. Outcomes of atherosclerotic renal artery stenosis managed without revascularization. Mayo Clin Proc 2000;75,137-444. 11. Caps MT, lieder RE, Polissar NL, et a!. Risk of atro-
phy in kidneys with atherosclerotic renal artelY stenosis. Kidney lnt 1998;53,735-742.
7:50 a.m. Screening for Renal Artery Artery Stenosis W. Dennis Foley, AID Froedtert Memon'al Lutheran Hospital Milwaukee, Wisconsin
Systemic hypertension is said to affect 20% of the adult population. It is estimated that 1%-2% of adult hypertensive patients have renovascular disease as the underlying etiology. Clinical predictors of renovascular hypertension include severe or accelerating hypertension difficult to control with medical therapy. In these patients, ACE inhibitors may control hypertension but result in signilicant renal functional impairment. A flank bruit mayor may not be present. Renovascular hypertension is the association of a hemodynamically Significant renal artery stenosis (6
Pitfalls InterpretaLion of peripheral vascular MRA studies must be done with care to avoid number pitfalls that can mimic or mask stenoses and occlusions. When a tortuous vessel drifts out of the imaging volume it will falsely appear occluded. Always check vessels in multiple orthogonal obliques to ensure that the vessel stays within the imaging volume along its entire course. Metallic clips and stents can also give the signal dropout that can be lnterpreted falsely as stenosis or occlusion. Stents have a characteristic region o~ signal dropout and adjacent bright spot that is easily identlAed on source images. Viewing the source images is also important for avoiding MIP artifacts which can occur when a bright structure overlaps the vessel of interest on the MIP. In general, the MIPs are best when made as narrow as possible yet still contain the vessel of interest. There can also be stair stepping artifact that resembles FMD when the MIPed images are too thick. This can be reduced by use of zero-interpolation. Finally, it is important to realize that ,\~ RA tends to overestimate the severity of stenoses in the pelVis and underestimate the severity of stenoses in the infrainguinal region.
Accuracy of MRA Technique for Evaluating Peripheral VascuJar Disease No. Investigator Year Patients Technique
Owen
1992 1993 Baum 1995 Prince 1995 Snidow 1998 Hmy 1997 Ho 1998 Meaney 1998 Yamashita 1998 I.e 1998 WincheSler 1998 Link 1999
155 43 32 39 2S 20 20 23 22 67
2000 2000 2000
39 61 5
23
Sensitivity
Specificity
ZOTOF "Superior to DSA" 2DTOF
Yucel
ZOTOF 3DGd 3DGJ 3DGd Bolus clla5e Bolus chase
3DGd ZOGd ZOGd 3DGJ
82 94 1m 93-96 93 81-89 96 94 90 100
98 96-100 98 91-95 83 91 98 83
81-94 92 98
73-92 97 96
84
98
(post swot) Lundin
Ruehm Fellner
Note.-l'OF
=
3DGd Bolus chase Bolus chase
time of flight.
Renal Revascularization (Part I)
Monday, March 5, 2001 7:30 a.m.-9:30 a.m. Moderator: Terence A.S. Matalon, MD
Literature There have now been numerous investigations on the accuracy of !'v'IRA techniques for evaluating patients suspected of haVing peripheral vascular disease. 2D timeof-flight has been shown to be accurate for evaluating infrapoplileal al1eries however the examination is cumbersome to perform because of the requirement of multiple coil placements for each leg. More proximally in the pelVis, 2D TOF has been more limited because of artifactual signal loss from vessel tortuosity, pulsatile flow, and susceptibility from bowel gas. Gd-enhanced 3D MRA, on the other hand, is highly accurate in the pelvis and thigh. Comparative studies have established a high level of accuracy in this region (Table 1). However, visualization of the smaller vessels below the knee can often be less reliable using bolus chase technique. For this reason, some centers have advocated performing 2D time-of-flight initially on the symptomatic leg below the knee before a three-station bolus chase 3D MRA. Alternative, the infra popliteal vessels can be evaluated with the 2D projection MRA technique, which also proVide bolus timing information as described here. In this lecture, I will describe in a step-by-step fashion the procedure for performing 3D bolus chase MRA using the fast bolus-sharing method. In addition, all of these protocol details arc available at www.m1prvtocols.com. These sequences are already in beta testing or product form for many magnet manufacturers.
P92
7:30 a.m. Renal Revascularization: Who Benefits? Steve I Schwab, MD David W. Btttterly, /vfD Duke University Medical Center Dw-bam, North Carolina Atherosclerotic renal disease has emerged as a relatively coounon condition in older patients. This atherosclerotic renal vascular disease is associated with cwo primalY pathophysiologic outcomes. The better-described of these is renal vascular hypertension. Renal Vascular Hypertension
Recent estimates suggest that renal vascular hypertension accounts for <1% of serious hypertension. Indications for treatment of renal artery stenosis and the treatment of renal vascular hypertension have been well developed (1). These include an appropriately severe renal vascular stenosis and appropriate lateralization of hormonal activity characterized by significant increases in renin secretion from the involved kidney. The emergence of angiotensin converting enzyme inhibitors have made surgical and endovascular treatment of this condition much less important than previous. Treatment of renal vascular disease, when the renins have nor been shown to clearly lateralize, improves hypeltension in only a minority of cases. Thus renal vascular hyperten-
sion, while a weJl-defined clinical entity, is relatively uncommon compared to the prevalence of renal artery stenosis. Renal Ischemic Disease In 1992, we initially characterized the prevalence of renal vascular disease in a group of patients referred for diagnostic cardiac catheterization (2). A total of 1,235 patients were enrolled in this study and underwent aortography at the time of cardiac catheterization to assess for the presence for renal vascular disease. Renal vascular disease was identified in a full 30% of patients being studied. Stenoses of <50% were noted in 15% of the patients and severe renal vascular disease characterized by >50% stenosis in another 15% of patients. The extent of coronary artery disease, peripheral vascular disease, and congestive heart failure predicted the likelihood of renal vascular disease. Surprisingly, the presence of hypertension was not predictive of renal vascular stenosis occurring in fewer than half the patients. Therefore, renal artery stenosis was usually clinicaJly silent and only rarely clinically associated with hypertension and, even more rarely, associated with clearly defined renal vascular hypertension. Therefore, renal artery stenosis is relatively common in this patient population while welldefined and treatable, renal vascular hypertension is uncommon. The important issue that has emerged has been the treatment of these stenotic lesions to preserve renal mass and slow the loss of renal function (3,4). This concept has been termed renal ischemic disease. Up until recently these questions with regard to treatment of renal ischemia were moot because the techniques involved for correcting renal artery stenosis involved significant risks in patients who already had Significant peripheral vascular, cardiovascular, and cerebrovascular risks factors. Novic and coJleagues and other investigators pioneered concepts of hepatorenal and splenic renal surgical bypass to avoid the significant morbidity and mortality of entering the aorta (5). Nonetheless, even in a highly selected group of patients, the risks of this procedure were Significant and it was performed relatively rarely. Percutaneous transluminal angioplasty of stenotic atherosclerotic lesions was relatively unsuccessful. The osteal nature of the majority of these lesions led to a high rate of failure and a high rate of restenosis (6-8). More recently, endovascular angioplasty when combined with endovascular stent placement has been shown to have a dramatically superior rate of technical success along with a relatively low rate of complication. Recently, van de Yen and associates reported a randomized trial comparing percutaneous transluminal angioplasty with stent deployment to percutaneous transluminal angioplasty alone. Primary success was 88% versus 70% and 6-month patency was 75% versus 29% (6). Blum et al (7) described 75 patients with renal artery stents and a mean [ollow-up of 27%. The procedure was technically successful in all with minor complications occurring in rel-
atively few and major complications in none (7). Frequency of restenosis in this study was <10%. Dorros et al (8) reported similar success with percutaneous transluminal angioplasty, stent placement, and stenosis. Therefore, technical advances, including the use of transluminal angioplasty with endovascular stent placement combined with antiplatelet therapy has significantly diminished the risks in patients undergoing percutaneous treatment of renal artery stenosis. Indeed, not only is the risks relatively low but the likelihood of restenosis is also acceptably low at one and two year follow-up. The key question is what is the benefit of these interventions. Fortunately two large studies dealing with the natural history of treated and untreated renal artelY stenosis is now available for evaluation. Conlon and associates from Duke University and Chabova and associates from the Mayo Clinic have reported their longterm foJlow-up (9-10). These studies have evaluated the natural history as a risk of 290/0-71% for progression of a 50% stenosis progressing to total occlusion. Caps et al reported a duplex ultrasonography foJlow-up in 295 kidneys and 177 patients with 33 months of follow-up. Progression based on duplex determination was 35% at three years and 51% at five years. Nine renal artery occlusions or 3% occurred over the course of the study (11). Thus occlusion was a relatively uncommon event. AdditionaJly, all occlusions occurred in patients with >600/0-70% stenosis on the study prior to the occlusion. At our institution, disease progression was assessed in 1,189 patients undergoing follow-up cardiac catheterization with aortography. Mean duration between angio'grams was was 2.6 years. Eleven% had severe progression. Not surprisingly, these vessels tended to progress in a time-dependent fashion with 25% of the patients demonstrating progressive disease by the five year mark. Although radiographic progression was demonstrable, there was little clinical change. [n this study, four year mortality was 35%. The patients with renal artery stenosis were more likely to have severe coronary artery disease and a depressed ejection fraction. Renal artery stenosis was a strong independent predictor of mortality. The major cause of death with or without renal artery stenosis was cardiovascular disease. Indeed, the presence or absence of renal artery stenosis did not influence the likelihood of progression to end-stage renal disease even though the presence of renal artery stenosis was a strong predictor of mortality. Correction of the renal artery stenosis not only did not effect overall renal outcome but had no effect on mortality compared to patients with similar disease whose renal arteries were not prospectively corrected Chabova and associates at the Mayo Clinic arrived at similar findings. They evaluated 68 patients with high grade renal artery stenosis, >70% unilateral or bilateral, who were followed medically without vascular percutaneous intelvention. Over the course of follow-up in this patient population there was some decline in renal function with a creatinine level
P93
rising from 1.4 mg/dI. to 2 mg/dL. Interestingly there was no significant difference in blood pressure, although slightly more medications were required for blood pressure control. Eighty-five percent had stable renal function at three years of follow-up. Remarkably, even patients with significant bilateral renal artery stenosis had no significant decrement in renal function. TIle risks of progressive renal failure in this high risk group was only 12.8% in the group with unilateral renal disease and 190/0 in the group with bilateral renal disease. Only two of the 68 patients advanced to end-stage renal disease from progressive renal artery stenosis. Mortality over the course of follow-up in this group was high with 28% dying mostly from either cardiovascular or cerebrovas~ cular event. In conclusion, the studies of both Conlon et al and Chabova et al offer long-term follow-up in a large group of patients with and without renal vascular intervention. The level of disease in both these populations was relatively severe and the population was older than in previous reports. The renal outcome was surprisingly good in those patients in whom intervention did not occur. The overall mortality seems related to cardiovascular and cerebrovascular disease. Thus, intervention on renal artery stenosis yield at best a very modest benefit in prevention of renal failure. Controversy exits when a technique is available for which the risk is modest but the benefits are likewise modest. This appears to be the case with atherosclerotic renal artery stenosis. A rational approach would be careful follow-up of patients with Significant renal artery stenosis with percutaneous intervention in those patients who show clear-cut loss of renal function and progression of renal artery stenosis. In the majority of other patients, intervention can probably be avoided.
References 1. Albers F, Svetkey 1. Screening and diagnosis in renal vascular hyperten,sion. In: Novik, Scobie, Hamilton, eds. Renal Vascular Disease. London: \VB Saunders, 1996,205-223. 2. Harding MB, Smith LR, Himmelstein SI, et al. Renal artery stenosis: prevalence and associated risk factors in patients undergoing routine carcUac catheterization. J Am Soc Nephrol 1992;2,1608-1616. 3. facobson HR. Ischemic renal disease: an overlooked clinical entity. Kidney 1nt 1988,34,729-743. 4. Rirruner ]M, Gennari FJ. Atherosclerotic renovascular disease and progressive renal failure. Ann Intern MedI993,118,712-719. 5. Novick AC, Straffon RA, Stewart BH, Gifford RW, Vidt D. Diminished operative morbidity and mortality in renal revascularization. JAMA 1981;246:749753. 6. van de 'len PJ, Kaatee R, Beutler JJ, et a1. Arterial stenting and balloon angioplasty in ostial athcroscle-
P94
rotic renovascular disease: a randomised trial. Lancet 1999;353,282-286. 7. Blum U, Krumme B, flugel P, et a1. Treatment of ostial renal-arrery stenosis with vascular endoprostheses after unsuccessful balloon angioplasty. N Engl J Med 1997;336,159-465. 8. Dorros G, Jaff ,',1, Mathiak L, Lowe A, Murphy K, He T. four-year follow-up of Palmaz-Schatz stent revascularization as treatment for atherosclerotic renal artery stenosis. Circulation 1998;998:642-647. 9. Conlon PJ, Athirakul K, Kovalik E, et a!. Survival in renal vascular disease. J Am Soc Nephrol 1998;9: 252-256. 10. Chabova V, Schirger A, Stanson AW, McKusick ivtA, Textor Sc. Outcomes of atherosclerotic renal artery stenosis managed without revascularization. Mayo Clin Proc 2000;75,137-444. 11. Caps MT, lieder RE, Polissar NL, et a!. Risk of atro-
phy in kidneys with atherosclerotic renal artelY stenosis. Kidney lnt 1998;53,735-742.
7:50 a.m. Screening for Renal Artery Artery Stenosis W. Dennis Foley, AID Froedtert Memon'al Lutheran Hospital Milwaukee, Wisconsin
Systemic hypertension is said to affect 20% of the adult population. It is estimated that 1%-2% of adult hypertensive patients have renovascular disease as the underlying etiology. Clinical predictors of renovascular hypertension include severe or accelerating hypertension difficult to control with medical therapy. In these patients, ACE inhibitors may control hypertension but result in signilicant renal functional impairment. A flank bruit mayor may not be present. Renovascular hypertension is the association of a hemodynamically Significant renal artery stenosis (6