TECHNICAL NOTE Renal Arteriovenous Fistula with Rapid Blood Flow Successfully Treated by Transcatheter Arterial Embolization: Application of Interlocking Detachable Coil as Coil Anchor Takeki Mori, Koji Sugimoto, Takanori Taniguchi, Masakatsu Tsurusaki, Kenta Izaki, Junya Konishi, Carlos A. Zamora, Kazuro Sugimura Department of Radiology, Kobe University, School of Medicine, 7-5-2, Kusunoki-cho, Chuo-Ku, Kobe, Hyogo, 650-0017, Japan Abstract A 70-year-old woman presented to our outpatient clinic with a large idiopathic renal arteriovenous fistula (AVF). Transcatheter arterial embolization (TAE) using interlocking detachable coils (IDC) as an anchor was planned. However, because of markedly rapid blood flow and excessive coil flexibility, detaching an IDC carried a high risk of migration. Therefore, we first coiled multiple loops of a microcatheter and then loaded it with an IDC. In this way, the coil was well fitted to the arterial wall and could be detached by withdrawing the microcatheter during balloon occlusion (“pre- framing technique”). Complete occlusion of the afferent artery was achieved by additional coiling and absolute ethanol. This technique contributed to a safe embolization of a high-flow AVF, avoiding migration of the IDC. Key words: Arteriovenous fistula—Kidney—Transcatheter arte- rial embolization—Interlocking detachable coil Recently, transcatheter arterial embolization (TAE) has become the treatment of choice for renal arteriovenous fistulas (AVF), replac- ing surgical intervention [1]. However, TAE of an AVF with markedly rapid blood flow is sometimes difficult as it carries the risk of coil migration, which may result in pulmonary embolism. We present the case of a high-flow idiopathic renal AVF success- fully treated with TAE, using an interlocking detachable coil (IDC) as an anchor. Case Report In July 2001, a 70-year-old woman with a right renal AVF was sent to our department for TAE. She had been diagnosed with cardiomegaly since she was 30 but had remained asymptomatic. There was no past history of surgical interventions and/or abdominal trauma. Her chest radiograph showed mild cardiomegaly, with a cardio-thoracic ratio of 0.59 (normal  0.5). Blood tests and biochemical examinations were unremarkable. After explaining the benefits and risks of the ranscatheter arterial embolization, she consented to the procedure. First, a 5-F pigtail catheter was inserted via the right femoral artery and abdominal aortography was performed. There was a marked degree of infrarenal aortic tortuosity, and a large AVF was depicted through a dilated branch of the right renal artery with aneurysmal change and early venous drainage (Fig. 1). There was a single afferent artery, 12 mm in diameter, originating from the right renal artery at the renal hilum. A retrograde right renal venography revealed that the aneurysmal portion (3025 mm in size) directly penetrated to the main right renal vein through a large fistula. Although we attempted to occlude the drainage vein to prevent possible pulmonary embolism caused by coil migration, rapid venous return made it difficult to wedge the balloon. Therefore, an access route via the right femoral vein was kept for immediate insertion of a snare catheter. Although we tried to place an IDC (20 mm in diameter/22 cm long) as a coil anchor under balloon occlusion, it could not be pushed out from the coaxial microcatheter because of high intracatheter resistance. This poor pushability seemed to have resulted from the arterial tortuosity and nar- rowed catheter lumen caused by over-inflation of the balloon. Subsequently, we tried to place the IDC after deflating the balloon catheter. However, the flexibility of the coil made it impossible to fix it to the arterial wall, since it was continuously straightened under the markedly high flow. As a next attempt, we coiled multiple loops of a microcatheter into the afferent artery while the balloon catheter was deflated. There was a small branch near the balloon catheter tip and these loops could be formed by pushing and rotating the microcatheter so as to wedge the microcatheter tip to this branch’s orifice. This spiraled microcatheter kept its form even without balloon occlusion and seemed to be fixed to the arterial wall tightly enough to avoid migration of the IDC. An IDC was then loaded into this coil-shaped microcatheter tip and the balloon was inflated. The first IDC was carefully detached by withdrawing the microcatheter while controlling blood flow (Figs. 2,3). After one more IDC was added with the same technique, the balloon was deflated. Two complicated IDCs were fixed securely enough with the coil anchor. Fifteen microcoils and 3 ml of ethanol were used for the complete TAE. A follow-up right renal arteriography obtained 1 week after the proce- dure indicated complete occlusion of the AVF (Fig. 4). Partial renal infarc- tion, temporary right back pain, and temporary elevation of serum lactate dehydrogenase level were observed as minor complications. No major complication was observed. A chest X-ray obtained 5 months after the procedure showed a slight improvement of cardiomegaly (cardiothoracic ratio of 0.52). Correspondence to: Takeki Mori; email: mori-t@iris.eonet.ne.jp Cardio V ascular and Interventional Radiology © Springer-Verlag New York, LLC. 2004 Cardiovasc Intervent Radiol (2004) 27:374 –376 Published Online: 8 June 2004 DOI: 10.1007/s00270-004-0068-7