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Staged Endovascular Occlusion of Giant Idiopathic Renal Arteriovenous Fistula with Platinum Microcoils and Silk Suture Threads
Staged Endovascular Occlusion of Giant Idiopathic Renal Arteriovenous Fistula with Platinum Microcoils and Silk Suture Threads B. J. Gralino, Jr, MD, and Deborah L. Bricker, BSN, CRN, RVT Large symptomatic aneurysmal renal arteriovenous (AV) fistulas usually present with a flank bruit, uncontrolled hypertension, and high-output cardiac failure. Traditionally, these have been treated surgically because of the risk of inadvertent pulmonary embolism with use of embolization techniques. The authors report a case of a giant renal AV fistula successfully treated with staged embolization with use of metallic coils and silk suture. This resulted in a graded reduction in the extreme flow through the fistula, followed by delayed thrombosis and cure of the patient’s symptoms. Index terms:
Arteries, embolization
•
Embolization
•
Fistula, arteriovenous
J Vasc Interv Radiol 2002; 13:747–752 Abbreviation:
AV ⫽ arteriovenous
IDIOPATHIC renal arteriovenous (AV) fistulas are aneurysmal with a single cavernous communication between the artery and the venous outflow (1). Symptomatic AV fistulas are usually large and are traditionally treated with total or partial nephrectomy because of the risk of inadvertent pulmonary embolism of embolic materials when endovascular techniques are used (2,3). The literature contains reports of successful embolic treatment of fistulas with use of conventional coils or detachable balloons (1,4,5,6), but these are limited by the diameter of the fistula. We report the successful embolic occlusion of a giant fistula by flow obstruction with custom giant coils and standard filler coils followed by staged thrombosis with platinum microcoils, used to exclude cerebral aneurysms (7), and silk suture threads.
From the Section of Vascular and Interventional Radiology, Harris Methodist Hospital, Fort Worth, Texas. Received November 26, 2001; revision requested January 28, 2002; final revision received February 26; accepted February 27. Address correspondence to B.J.G., Radiology Associates of Tarrant County, 816 W. Cannon St., Ft. Worth, TX 76104; E-mail: [email protected] © SIR, 2002
CASE REPORT A 61-year-old man was referred to our service with a history of uncontrolled hypertension, high-output cardiac failure, loud right flank bruit with thrill, and magnetic resonance (MR) findings of a large vascular malformation of the right kidney with huge outflow vessels obscuring the renal hilum and inflow vessels (Fig 1a). There was no history of flank trauma or surgery. The patient had been evaluated by the vascular surgery and urology services but was considered to be at excessive risk for nephrectomy because of anticipated technical difficulties in controlling inflow and hemorrhage. Arteriography (Fig 1b) confirmed a huge aneurysmal right renal AV fistula with extremely high flow as evidenced by simultaneous arterial and venous opacification. It is difficult to describe the magnitude of flow encountered with this fistula. The right renal artery was the same size as the patient’s lower abdominal aorta (17 mm in diameter). There was poor filling of intrarenal branch arteries as a result of the massive shunting of the fistula and very little nephrogram, but some fusiform aneurysmal dilation involving the proximal segmental divi-
sions of the renal artery was visualized. Aneurysmal tortuous venous outflow ranged in diameter from 25 to 50 mm and obscured the central part of the kidney and the actual fistula site. Marked dilation of the suprarenal inferior vena cava was present. However, an eccentric stenosis was noted of the main renal vein adjacent to the distal end of the fistula as a result of compression by adjacent aneurysmal fistula outflow (Fig 1c). The main renal vein measured 15 mm in diameter at its narrowest point. We believed that this stenosis, along with the long, tortuous fistula conduit and balloon occlusion of fistula inflow, would allow safe flow direction of large embolization coils. The main renal vein would, in effect, offer a capture point for any coil that might go astray. Risk of abrupt renal outflow obstruction by initial coil migration, although potentially catastrophic, would be highly unlikely because of the extreme flow present. The proximity to the inferior vena cava would also provide access for percutaneous retrieval. All vessel diameters used in treatment planning were carefully measured with use of the software provided by our equipment manufacturer (Siemens Medical Systems, Iselin, NJ).
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Staged Endovascular Occlusion of Giant Renal AV Fistula
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JVIR
Figure 1. (a) MR image shows giant idiopathic right renal AV fistula obscuring the kidney and its hilar vessels. Note cardiomegaly. (b) Aortography shows marked dilation of the right renal artery inflow of the fistula. (c) Huge redundant venous outflow with eccentric stenosis of the main renal vein (arrow) is also shown.
The patient returned 1 month later for endovascular treatment. General anesthesia was administered, and a Swan-Ganz VIP catheter (Edwards Lifesciences, Irvine, CA) was placed for continuous pulmonary artery pressure monitoring. Cardiac output was severely elevated at 17.8 L/min. After femoral placement of a 9-F sheath, a 20-mm-diameter balloon occlusion
catheter (Boston Scientific, Natick, MA) was placed into the distal right main renal artery and advanced to the proximal outflow region of the fistula. A balloon-occlusion selective renal arteriogram was obtained to localize the origin of the AV fistula (Fig 2a). The exact origin of the fistula was difficult to determine because of arterialization of the venous outflow. However, we
considered this irrelevant as long as the most distal renal artery branch origin was identified to spare renal perfusion after fistula embolization. Careful review of the balloon-occlusion angiogram revealed no renal artery branch filling distal to the tip of the balloon catheter. In addition, slight narrowing was noted at the fistula origin. This can be seen in Figure 2a,
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Figure 2. (a) Balloon occlusion right renal arteriogram demonstrates the origin of the fistula. (b) Selective right renal arteriogram after placement of standard coil nest shows some decrease in arterial steal with demonstrable renal artery branch filling. (c) After completion of the coil nest with platinum microcoils, silk suture threads were deposited and are visible on the control arteriogram proximal to the coils (arrow).
where there is some tapering of the proximal part of the balloon. Traction had to be applied to pull the proximal end of the balloon into the renal artery so that sufficient plugging of flow could
be achieved. We initially tried a 30-mmdiameter balloon-occlusion catheter, but this was too stiff for distal advancement. The apparent foreshortening of the course of the balloon occlusion catheter
in Figure 2a is caused by the oblique projection used. We did not consider arterial inflow occlusion as an acceptable treatment option because the fistula was too close to renal branch origins.
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The distal end of the balloon catheter was then maintained within the proximal outflow segment of the fistula distal to the renal artery origins and where the diameter measured greater than 25 mm. This was used subsequently for flow control. Custom 0.038-inch, 30-mm-diameter embolization coils (Cook, Bloomington, IN) were deployed into the fistula during balloon occlusion and then allowed to migrate under careful flow control by slight balloon deflation and inflation into the venous outflow, where the diameter measured less than 30 mm. After the coils became stabilized in the outflow vein, the balloon was deflated. Balloon occlusion times were maintained for no longer than 15 minutes to minimize renal ischemia. We did not use heparinization during balloon occlusions because slight flow was maintained around the balloon. An increase in systolic blood pressure to 180 mm Hg was controlled during the balloon occlusion part of the procedure with nitroprusside infusion. Transient hypotension was also observed at other times and was controlled with balloon deflation or medically by the anesthesiologist. Additional 20-mm-diameter coils were deployed in the same manner, forming a framework for introduction of smaller filler coils. The balloon-occlusion catheter was then exchanged for a selective catheter, which was advanced just proximal to the coil nest. Smaller standard coils (Cook) were then deployed to form a more uniform nest. A total of 50 coils were placed. Only slight reduction in fistula flow was noted, but the procedure was terminated because of lack of availability of additional coils. The patient returned in 1 month for additional coil embolization. A 5-F guiding catheter with a 0.038-inch internal diameter (Boston Scientific) was placed in the right renal artery. This was followed by coaxial placement of a 3-F microcatheter with 0.021-inch lumen (Cordis, Miami Lakes, FL) advanced to the coil nest. A total of 69 additional 0.018inch platinum coils (Cordis or Target Therapeutics/Boston Scientific) were used to pack the nest. Further reduction of flow through the fistula with improved intrarenal arterial perfusion was noted (Fig 2b) and the procedure was terminated. One month later, the patient re-
turned with persistent right flank bruit and Doppler sonographic evidence of persistent patency of the fistula. Additional embolization was performed with deployment of 54 softer platinum microcoils (Micrus, Mountain View, CA), filling residual spaces between coils and forming a true solid coil mass. We favored this type of cerebral aneurysm coil because it has a quick thermal, rather than electrolytic (7), detachment mechanism that is not affected by the presence of an adjacent large metallic coil nest. Further decrease in fistula flow was noted, but flow was still considered too brisk to allow safe use of a liquid occlusive agent such as cyanoacrylate or absolute alcohol. Instead, approximately 50 silk suture threads (Ethicon/Johnson & Johnson, Somerville, NJ) 4 cm in length were injected at the proximal edge of the coil nest with use of 3-mL syringes. These can be quickly prepared and delivered by a simple loading technique (8). Little change in fistula flow was seen on the completion arteriogram 30 minutes later (Fig 2c). The procedure was terminated with the expectation of delayed thrombosis of the fistula. One week after the completion of embolization, the patient developed mild right flank pain and a low-grade fever. Nuclide lung scan results were negative for pulmonary embolism. Color Doppler evaluation and computed tomography (CT) demonstrated partial thrombosis of the renal AV fistula. Blood culture results were negative. The patient’s fever and flank pain resolved over the course of the next several days. Two weeks later, the right flank bruit ceased. The patient returned 2 months later for follow-up right renal arteriography. This confirmed occlusion of the renal AV fistula (Fig 3a). There was delayed central segmental vessel filling from the residual aneurysmal inflow (not shown) but uniform preservation of renal perfusion (Fig 3b). Follow-up of the fusiform aneurysmal dilation of the renal artery adjacent to the thrombosed AV fistula was planned. Cardiac output had decreased to 9 L/min. The patient no longer reported exertional dyspnea. His blood pressure was now controlled with less medication, and chest radiographs showed resolution of cardiomegaly. Follow-up renal Doppler sonography
JVIR
performed 10 months after completion of embolization showed persistent occlusion and thrombosis of the AV fistula.
DISCUSSION AV fistulas of the kidney can be classified as congenital, acquired, or idiopathic (2,9,10). Congenital renal malformations constitute approximately 20% of the total. They are described as cirsoid with multiple AV communications located near the collecting system and commonly present with gross hematuria. Malformations of this type have been successfully treated with embolization (11,12). Acquired malformations represent approximately 75% of cases and result from iatrogenic causes (biopsy, surgery), blunt or penetrating trauma, or neoplasm (renal cell carcinoma, metastatic disease). These can also be managed with percutaneous embolization, although 70% of those caused by closed renal biopsy will heal spontaneously (9). Idiopathic malformations are unusual, representing only approximately 5% of renal AV malformations. These are characterized as single cavernous channels with well-defined aneurysmal arterial and venous elements. The larger are usually symptomatic and commonly associated with abdominal bruit, hypertension, and high-output cardiac failure. Noninvasive evaluation reflects the high flow rate associated with this type of malformation. Color Doppler images characteristically show aliasing and color saturation. Spectral analysis is associated with increased flow velocity, decreased arterial resistance, and arterial wave forms in the outflow vein (13). Contrast-enhanced CT shows the hypervascular nature of the lesion with the aneurysmal component and the dilated renal vein and suprarenal inferior vena cava (14). Arteriography demonstrates the detailed anatomy of the feeding and draining vessels. Identification of the exact location of the fistula may be difficult because of the extremely high flow and superimposition of tortuous dilated vessels. This may require use of proximal occlusion balloon control as in our case, but localization is important in planning embolic occlu-
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751
Figure 3. (a) Follow-up postembolization right renal arteriogram shows occlusion of the renal AV fistula. (b) Parenchymal phase of arteriogram demonstrates preservation of right renal perfusion.
sion treatment sparing the renal parenchymal perfusion. There are a number of options now available for embolization of renal AV fistula. However, particulate emboli (absorbable gelatin sponge, polyvinyl alcohol, gelatin spheres) are not suitable for large-vessel fistulas unless used in combination with other occlusive devices such as metallic coils. We believe that use of particles would not likely result in occlusion of such an advanced fistula as reported here even with a tight coil nest and would have the potential for embolization to the lungs. Commercially available detachable balloons are not large enough for treatment of our patient. Perhaps a custom balloon could have been made, but risk of premature detachment would be high because of the extreme flow. In addition, possible distal balloon migration could cause abrupt outflow occlusion, which would be catastrophic in our patient. We also considered a dual arterial and venous approach recently reported by Mansueto et al (15). However, the size of the fistula reported is not comparable to that present in our patient, requiring only a 10-mm occlusion balloon. In addition, the technique is dependent on
distal outflow occlusion of the fistula. An abrupt venous occlusive technique without inflow control would be disastrous in our case if inadvertent iatrogenic vessel perforation were to occur. Embolization of a large renal AV fistula has been previously reported with use of vascular occlusion devices as large as 13 mm in diameter (1). The diameter of the proximal fistula outflow in our patient approached 25 mm and measured up to 50 mm in the more distal aneurysmal venous outflow segments. This precluded use of standard occlusive devices, which are generally limited to diameters smaller than 20 mm (16). Larger coils can be made from guide wire fragments with the inner core removed. However, we preferred larger commercial custom framing coils with curve memory and with greater hoop strength to begin a coil nest. Large platinum coils for treatment of aneurysms of the vein of Galen are also available. However, we did not think they would offer enough radial force for stability nor enough softness as filler coils for complete packing. Even after filling the initial coils with a fairly dense assortment of standard embolization coils, there was
no significant decrease in fistula flow. This required deployment of soft platinum microcoils used to pack cerebral aneurysms to obtain a true solid nest of coils. Decreased flow through the fistula was noted, but we still did not think this was sufficient to allow safe use of a liquid occlusive agent. Thrombin would probably have passed through even our “solid” coil nest and may have caused serious systemic thromboembolic complications. We believed the residual flow after completion of coil embolization in our case was enough to make the risk of showering the lungs with cyanoacrylate or possible cardiopulmonary arrest with ethanol too high. Hot contrast medium would be another consideration, but we have no experience with this agent. It likely would also require more stasis of flow to be effective. Potentially, the coils themselves could serve as a nidus for pulmonary embolism, but this has not been evident with our patient or in our previous clinical experience. Silk suture has long been known to be highly thrombogenic and has been used in neurointerventions for em-
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Staged Endovascular Occlusion of Giant Renal AV Fistula
bolic occlusions of vascular malformations, including high-flow lesions (17,18). Silk suture in combination with platinum microcoils has been shown to provide closure of solitary cerebral AV fistulas (19). Closure of post-nephrectomy renal AV fistulas has also been reported with use of a combination of metallic coils and silk emboli (20). Effective vessel occlusions have been demonstrated with silk as the sole embolic agent or in combination with particulate emboli, microcoils, or liquid occlusive agents. Histologic analysis of vessels occluded with silk may show a nonspecific inflammatory response (18), possibly adding to the durability of the thrombosis. Fever has been reported to occur in 24% of patients without infection, usually 5– 8 days after silk embolization (18). The major disadvantage of silk as an embolic agent is its lack of radiopacity. Threads of silk suture could be safely deposited proximal to the solid coil nest in our patient without risk of pulmonary embolism. We believe that our technique provided a graded step down in fistula flow with delayed thrombosis of the AV fistula and was beneficial in avoiding any potential adverse cardiac or sustained hemodynamic effects by such a massive AV shunt. We noted brief but significant changes in systemic pressures during initial balloon occlusion of the fistula. Our patient tolerated endovascular occlusion quite well, experiencing only postembolization symptoms of mild flank pain and low-grade fever. In conclusion, our case demonstrates that even a giant renal AV fistula with extreme flow can be successfully occluded with percutaneous embolization.
Acknowledgments: The authors thank Joseph A. Horton, MD (Department of Radiology, University of Alabama), Wayne Yakes, MD (Vascular Malformation Center, Englewood, CO), and James Harper, MD (Department of Anesthesiology, Harris Methodist Hospital), for their helpful suggestions. References 1. Kearse WS Jr, Joseph AE, Sabanegh ES. Transcatheter embolization of large idiopathic renal arteriovenous fistula. J Urol 1994; 151:967–969. 2. Taketera H, Nakamura M, Nakano E, et al. Renal arteriovenous fistula associated with a huge renal vein dilatation. J Urol 1987; 137:722–724. 3. Takaha M, Matsumoto A, Ochi K, Takeuchi M, Takemoto M, Sonoda T. Intrarenal arteriovenous malformation. J Urol 1980; 124:315–318. 4. Djellouli N, Boyer L, Ravel A, et al. Cure of renovascular hypertension by percutaneous occlusion of a large idiopathic renal arteriovenous fistula. Int Angiol 1997; 16:255–257. 5. Kadir S, Marshall FF, White RI, Kaufman SL, Barth K. Therapeutic embolization of the kidney with detachable silicone balloons. J Urol 1983; 129:11–13. 6. Saliou C, Raynaud A, Blanc F, Azencot M, Fabiani J. Idiopathic renal arteriovenous fistula: treatment with embolization. Ann Vasc Surg 1998; 12:75–77. 7. Byrne JV, Guglielmi G. The Guglielmi detachable coil. In: Endovascular Treatment of Intracranial Aneurysms. Heidelberg, Germany: Springer-Verlag, 1998;136 –157. 8. Connors JJ III, Wojak JC. Tricks of the trade. In: Connors JJ III, Wojak JC, ed. Interventional Neuroradiology Strategies and Practical Techniques. Philadelphia: WB Saunders, 1999;44. 9. Messing E, Kessler R, Kavaney PB. Renal arteriovenous fistulas. Urology 1976; 8:101–107. 10. Kopchick JH, Bourne NK, Fine SW, Jacobsohn HA, Jacobs SC, Lawson RK. Congenital renal malformations. Urology 1981; 27:13–17.
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11. Clouse ME, Levin DC, Desautels RE. Transcatheter embolotherapy for congenital renal arteriovenous malformations. Urology 1983; 22:360 –365. 12. Banks B, Pfister RC, Wholey M, Ferral H. Interventional case of the day. AJR Am J Roentgenol 1998; 171:851. 13. Takebayashi S, Aida N, Matsui K. Arteriovenous malformations of the kidneys: diagnosis and follow-up with color Doppler sonography in six patients. AJR Am J Roentgenol 1991; 157: 991–995. 14. Honda H, Onitsuka H, Naitou S, et al. Renal arteriovenous malformations: CT features. J Comput Assist Tomogr 1991; 15:261–264. 15. Mansueto G, D’Onofrio M, Minniti S, Ferrara RM, Procacci C. Therapeutic embolization of idiopathic renal arteriovenous fistula using the “stop-flow” technique. J Endovasc Ther 2001; 8: 210 –215. 16. Castaneda-Zuniga WR, Tadavarthy SM, Galliani CA, Laerum F, Schwarten DE, Amplatz K. Experimental venous occlusion with stainless-steel spiders. Radiology 1981; 141:238 –242. 17. Eskridge JM, Hartling RP. Preoperative embolization of brain AVMs using surgical silk and polyvinyl alcohol [abstract]. Am J Neuroradiol 1989; 10:882. 18. Dehdashti AR, Muster M, Reverdin A, De Tribolet N, Ruefenacht A. Preoperative silk suture embolization of cerebral and dural arteriovenous malformations. Neurosurg Focus [online]. Nov 2001; 11(5). Accessed January 31, 2002. Available at: http://www.neurosurgery.org/focus/nov01/11–5-nsftoc.html. 19. Halbach VV, Higashida RT, Hieshima GB, Hardin CW, Dowd CF, Barnwell SL. Transarterial occlusion of solitary intracerebral arteriovenous fistulas. Am J Neuroradiol 1989; 10:747–752. 20. Castaneda-Zuniga WR, Tadavarthy SM, Murphy W, Beranek I, Amplatz K. Nonsurgical closure of large arteriovenous fistulas. JAMA 1976; 236:2649 – 2650.
Arteries, embolization
•
Embolization
•
Fistula, arteriovenous
J Vasc Interv Radiol 2002; 13:747–752 Abbreviation:
AV ⫽ arteriovenous
IDIOPATHIC renal arteriovenous (AV) fistulas are aneurysmal with a single cavernous communication between the artery and the venous outflow (1). Symptomatic AV fistulas are usually large and are traditionally treated with total or partial nephrectomy because of the risk of inadvertent pulmonary embolism of embolic materials when endovascular techniques are used (2,3). The literature contains reports of successful embolic treatment of fistulas with use of conventional coils or detachable balloons (1,4,5,6), but these are limited by the diameter of the fistula. We report the successful embolic occlusion of a giant fistula by flow obstruction with custom giant coils and standard filler coils followed by staged thrombosis with platinum microcoils, used to exclude cerebral aneurysms (7), and silk suture threads.
From the Section of Vascular and Interventional Radiology, Harris Methodist Hospital, Fort Worth, Texas. Received November 26, 2001; revision requested January 28, 2002; final revision received February 26; accepted February 27. Address correspondence to B.J.G., Radiology Associates of Tarrant County, 816 W. Cannon St., Ft. Worth, TX 76104; E-mail: [email protected] © SIR, 2002
CASE REPORT A 61-year-old man was referred to our service with a history of uncontrolled hypertension, high-output cardiac failure, loud right flank bruit with thrill, and magnetic resonance (MR) findings of a large vascular malformation of the right kidney with huge outflow vessels obscuring the renal hilum and inflow vessels (Fig 1a). There was no history of flank trauma or surgery. The patient had been evaluated by the vascular surgery and urology services but was considered to be at excessive risk for nephrectomy because of anticipated technical difficulties in controlling inflow and hemorrhage. Arteriography (Fig 1b) confirmed a huge aneurysmal right renal AV fistula with extremely high flow as evidenced by simultaneous arterial and venous opacification. It is difficult to describe the magnitude of flow encountered with this fistula. The right renal artery was the same size as the patient’s lower abdominal aorta (17 mm in diameter). There was poor filling of intrarenal branch arteries as a result of the massive shunting of the fistula and very little nephrogram, but some fusiform aneurysmal dilation involving the proximal segmental divi-
sions of the renal artery was visualized. Aneurysmal tortuous venous outflow ranged in diameter from 25 to 50 mm and obscured the central part of the kidney and the actual fistula site. Marked dilation of the suprarenal inferior vena cava was present. However, an eccentric stenosis was noted of the main renal vein adjacent to the distal end of the fistula as a result of compression by adjacent aneurysmal fistula outflow (Fig 1c). The main renal vein measured 15 mm in diameter at its narrowest point. We believed that this stenosis, along with the long, tortuous fistula conduit and balloon occlusion of fistula inflow, would allow safe flow direction of large embolization coils. The main renal vein would, in effect, offer a capture point for any coil that might go astray. Risk of abrupt renal outflow obstruction by initial coil migration, although potentially catastrophic, would be highly unlikely because of the extreme flow present. The proximity to the inferior vena cava would also provide access for percutaneous retrieval. All vessel diameters used in treatment planning were carefully measured with use of the software provided by our equipment manufacturer (Siemens Medical Systems, Iselin, NJ).
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Staged Endovascular Occlusion of Giant Renal AV Fistula
July 2002
JVIR
Figure 1. (a) MR image shows giant idiopathic right renal AV fistula obscuring the kidney and its hilar vessels. Note cardiomegaly. (b) Aortography shows marked dilation of the right renal artery inflow of the fistula. (c) Huge redundant venous outflow with eccentric stenosis of the main renal vein (arrow) is also shown.
The patient returned 1 month later for endovascular treatment. General anesthesia was administered, and a Swan-Ganz VIP catheter (Edwards Lifesciences, Irvine, CA) was placed for continuous pulmonary artery pressure monitoring. Cardiac output was severely elevated at 17.8 L/min. After femoral placement of a 9-F sheath, a 20-mm-diameter balloon occlusion
catheter (Boston Scientific, Natick, MA) was placed into the distal right main renal artery and advanced to the proximal outflow region of the fistula. A balloon-occlusion selective renal arteriogram was obtained to localize the origin of the AV fistula (Fig 2a). The exact origin of the fistula was difficult to determine because of arterialization of the venous outflow. However, we
considered this irrelevant as long as the most distal renal artery branch origin was identified to spare renal perfusion after fistula embolization. Careful review of the balloon-occlusion angiogram revealed no renal artery branch filling distal to the tip of the balloon catheter. In addition, slight narrowing was noted at the fistula origin. This can be seen in Figure 2a,
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Figure 2. (a) Balloon occlusion right renal arteriogram demonstrates the origin of the fistula. (b) Selective right renal arteriogram after placement of standard coil nest shows some decrease in arterial steal with demonstrable renal artery branch filling. (c) After completion of the coil nest with platinum microcoils, silk suture threads were deposited and are visible on the control arteriogram proximal to the coils (arrow).
where there is some tapering of the proximal part of the balloon. Traction had to be applied to pull the proximal end of the balloon into the renal artery so that sufficient plugging of flow could
be achieved. We initially tried a 30-mmdiameter balloon-occlusion catheter, but this was too stiff for distal advancement. The apparent foreshortening of the course of the balloon occlusion catheter
in Figure 2a is caused by the oblique projection used. We did not consider arterial inflow occlusion as an acceptable treatment option because the fistula was too close to renal branch origins.
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July 2002
Staged Endovascular Occlusion of Giant Renal AV Fistula
The distal end of the balloon catheter was then maintained within the proximal outflow segment of the fistula distal to the renal artery origins and where the diameter measured greater than 25 mm. This was used subsequently for flow control. Custom 0.038-inch, 30-mm-diameter embolization coils (Cook, Bloomington, IN) were deployed into the fistula during balloon occlusion and then allowed to migrate under careful flow control by slight balloon deflation and inflation into the venous outflow, where the diameter measured less than 30 mm. After the coils became stabilized in the outflow vein, the balloon was deflated. Balloon occlusion times were maintained for no longer than 15 minutes to minimize renal ischemia. We did not use heparinization during balloon occlusions because slight flow was maintained around the balloon. An increase in systolic blood pressure to 180 mm Hg was controlled during the balloon occlusion part of the procedure with nitroprusside infusion. Transient hypotension was also observed at other times and was controlled with balloon deflation or medically by the anesthesiologist. Additional 20-mm-diameter coils were deployed in the same manner, forming a framework for introduction of smaller filler coils. The balloon-occlusion catheter was then exchanged for a selective catheter, which was advanced just proximal to the coil nest. Smaller standard coils (Cook) were then deployed to form a more uniform nest. A total of 50 coils were placed. Only slight reduction in fistula flow was noted, but the procedure was terminated because of lack of availability of additional coils. The patient returned in 1 month for additional coil embolization. A 5-F guiding catheter with a 0.038-inch internal diameter (Boston Scientific) was placed in the right renal artery. This was followed by coaxial placement of a 3-F microcatheter with 0.021-inch lumen (Cordis, Miami Lakes, FL) advanced to the coil nest. A total of 69 additional 0.018inch platinum coils (Cordis or Target Therapeutics/Boston Scientific) were used to pack the nest. Further reduction of flow through the fistula with improved intrarenal arterial perfusion was noted (Fig 2b) and the procedure was terminated. One month later, the patient re-
turned with persistent right flank bruit and Doppler sonographic evidence of persistent patency of the fistula. Additional embolization was performed with deployment of 54 softer platinum microcoils (Micrus, Mountain View, CA), filling residual spaces between coils and forming a true solid coil mass. We favored this type of cerebral aneurysm coil because it has a quick thermal, rather than electrolytic (7), detachment mechanism that is not affected by the presence of an adjacent large metallic coil nest. Further decrease in fistula flow was noted, but flow was still considered too brisk to allow safe use of a liquid occlusive agent such as cyanoacrylate or absolute alcohol. Instead, approximately 50 silk suture threads (Ethicon/Johnson & Johnson, Somerville, NJ) 4 cm in length were injected at the proximal edge of the coil nest with use of 3-mL syringes. These can be quickly prepared and delivered by a simple loading technique (8). Little change in fistula flow was seen on the completion arteriogram 30 minutes later (Fig 2c). The procedure was terminated with the expectation of delayed thrombosis of the fistula. One week after the completion of embolization, the patient developed mild right flank pain and a low-grade fever. Nuclide lung scan results were negative for pulmonary embolism. Color Doppler evaluation and computed tomography (CT) demonstrated partial thrombosis of the renal AV fistula. Blood culture results were negative. The patient’s fever and flank pain resolved over the course of the next several days. Two weeks later, the right flank bruit ceased. The patient returned 2 months later for follow-up right renal arteriography. This confirmed occlusion of the renal AV fistula (Fig 3a). There was delayed central segmental vessel filling from the residual aneurysmal inflow (not shown) but uniform preservation of renal perfusion (Fig 3b). Follow-up of the fusiform aneurysmal dilation of the renal artery adjacent to the thrombosed AV fistula was planned. Cardiac output had decreased to 9 L/min. The patient no longer reported exertional dyspnea. His blood pressure was now controlled with less medication, and chest radiographs showed resolution of cardiomegaly. Follow-up renal Doppler sonography
JVIR
performed 10 months after completion of embolization showed persistent occlusion and thrombosis of the AV fistula.
DISCUSSION AV fistulas of the kidney can be classified as congenital, acquired, or idiopathic (2,9,10). Congenital renal malformations constitute approximately 20% of the total. They are described as cirsoid with multiple AV communications located near the collecting system and commonly present with gross hematuria. Malformations of this type have been successfully treated with embolization (11,12). Acquired malformations represent approximately 75% of cases and result from iatrogenic causes (biopsy, surgery), blunt or penetrating trauma, or neoplasm (renal cell carcinoma, metastatic disease). These can also be managed with percutaneous embolization, although 70% of those caused by closed renal biopsy will heal spontaneously (9). Idiopathic malformations are unusual, representing only approximately 5% of renal AV malformations. These are characterized as single cavernous channels with well-defined aneurysmal arterial and venous elements. The larger are usually symptomatic and commonly associated with abdominal bruit, hypertension, and high-output cardiac failure. Noninvasive evaluation reflects the high flow rate associated with this type of malformation. Color Doppler images characteristically show aliasing and color saturation. Spectral analysis is associated with increased flow velocity, decreased arterial resistance, and arterial wave forms in the outflow vein (13). Contrast-enhanced CT shows the hypervascular nature of the lesion with the aneurysmal component and the dilated renal vein and suprarenal inferior vena cava (14). Arteriography demonstrates the detailed anatomy of the feeding and draining vessels. Identification of the exact location of the fistula may be difficult because of the extremely high flow and superimposition of tortuous dilated vessels. This may require use of proximal occlusion balloon control as in our case, but localization is important in planning embolic occlu-
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Gralino and Bricker
•
751
Figure 3. (a) Follow-up postembolization right renal arteriogram shows occlusion of the renal AV fistula. (b) Parenchymal phase of arteriogram demonstrates preservation of right renal perfusion.
sion treatment sparing the renal parenchymal perfusion. There are a number of options now available for embolization of renal AV fistula. However, particulate emboli (absorbable gelatin sponge, polyvinyl alcohol, gelatin spheres) are not suitable for large-vessel fistulas unless used in combination with other occlusive devices such as metallic coils. We believe that use of particles would not likely result in occlusion of such an advanced fistula as reported here even with a tight coil nest and would have the potential for embolization to the lungs. Commercially available detachable balloons are not large enough for treatment of our patient. Perhaps a custom balloon could have been made, but risk of premature detachment would be high because of the extreme flow. In addition, possible distal balloon migration could cause abrupt outflow occlusion, which would be catastrophic in our patient. We also considered a dual arterial and venous approach recently reported by Mansueto et al (15). However, the size of the fistula reported is not comparable to that present in our patient, requiring only a 10-mm occlusion balloon. In addition, the technique is dependent on
distal outflow occlusion of the fistula. An abrupt venous occlusive technique without inflow control would be disastrous in our case if inadvertent iatrogenic vessel perforation were to occur. Embolization of a large renal AV fistula has been previously reported with use of vascular occlusion devices as large as 13 mm in diameter (1). The diameter of the proximal fistula outflow in our patient approached 25 mm and measured up to 50 mm in the more distal aneurysmal venous outflow segments. This precluded use of standard occlusive devices, which are generally limited to diameters smaller than 20 mm (16). Larger coils can be made from guide wire fragments with the inner core removed. However, we preferred larger commercial custom framing coils with curve memory and with greater hoop strength to begin a coil nest. Large platinum coils for treatment of aneurysms of the vein of Galen are also available. However, we did not think they would offer enough radial force for stability nor enough softness as filler coils for complete packing. Even after filling the initial coils with a fairly dense assortment of standard embolization coils, there was
no significant decrease in fistula flow. This required deployment of soft platinum microcoils used to pack cerebral aneurysms to obtain a true solid nest of coils. Decreased flow through the fistula was noted, but we still did not think this was sufficient to allow safe use of a liquid occlusive agent. Thrombin would probably have passed through even our “solid” coil nest and may have caused serious systemic thromboembolic complications. We believed the residual flow after completion of coil embolization in our case was enough to make the risk of showering the lungs with cyanoacrylate or possible cardiopulmonary arrest with ethanol too high. Hot contrast medium would be another consideration, but we have no experience with this agent. It likely would also require more stasis of flow to be effective. Potentially, the coils themselves could serve as a nidus for pulmonary embolism, but this has not been evident with our patient or in our previous clinical experience. Silk suture has long been known to be highly thrombogenic and has been used in neurointerventions for em-
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bolic occlusions of vascular malformations, including high-flow lesions (17,18). Silk suture in combination with platinum microcoils has been shown to provide closure of solitary cerebral AV fistulas (19). Closure of post-nephrectomy renal AV fistulas has also been reported with use of a combination of metallic coils and silk emboli (20). Effective vessel occlusions have been demonstrated with silk as the sole embolic agent or in combination with particulate emboli, microcoils, or liquid occlusive agents. Histologic analysis of vessels occluded with silk may show a nonspecific inflammatory response (18), possibly adding to the durability of the thrombosis. Fever has been reported to occur in 24% of patients without infection, usually 5– 8 days after silk embolization (18). The major disadvantage of silk as an embolic agent is its lack of radiopacity. Threads of silk suture could be safely deposited proximal to the solid coil nest in our patient without risk of pulmonary embolism. We believe that our technique provided a graded step down in fistula flow with delayed thrombosis of the AV fistula and was beneficial in avoiding any potential adverse cardiac or sustained hemodynamic effects by such a massive AV shunt. We noted brief but significant changes in systemic pressures during initial balloon occlusion of the fistula. Our patient tolerated endovascular occlusion quite well, experiencing only postembolization symptoms of mild flank pain and low-grade fever. In conclusion, our case demonstrates that even a giant renal AV fistula with extreme flow can be successfully occluded with percutaneous embolization.
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