Complex Renal Artery Aneurysm: Successful Exclusion With Balloon-Expandable Covered Stent

Abstract: We report an incidentally noted aneurysm in the left renal artery in a 60-year-old woman. Repair was recommended due to the size of the aneurysm and the patient’s history of hypertension. The aneurysm was located in a bifurcation lesion, and angulation at the site was approximately 90 degrees. We were able to successfully exclude the aneurysm, however, with a balloon-expandable covered stent. This suggests that balloon-expandable covered stents offer excellent delivery and precise deployment, even in cases where complex anatomical issues are involved.

J INVASIVE CARDIOL 2013;25(11):612-614

Key words: renal artery aneurysm repair, balloon-expandable covered stent

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Renal artery aneurysms (RAAs) are uncommon, occurring in approximately only 0.09% of the population,¹ and diagnosis is often made incidentally. Hypertension is a commonly associated disease. The main complication is rupture, and repair is recommended for RAAs of >1.0 cm if hypertension is present and of >1.5 to 2.0 cm if it is not.² Operative strategies include aneurysmorrhaphy, bypass, or both. According to a previous report, however, these procedures carry a 1.6% mortality and 12% morbidity rate.³ Being minimally invasive, endovascular therapy offers the most favored approach. Case studies involving such therapy have reported use of stent grafts and catheter-directed embolization.^1,4,5 Endovascular therapy is controversial, however, where complex anatomical issues are involved, such as in angulated or bifurcation lesions. Recently, the efficacy and safety of endovascular therapy with balloon-expandable covered stents for peripheral artery disease and coarctation of the aorta has been reported.^6,7 Balloon-expandable covered stents have a low crossing profile, allowing for precise delivery. This suggests that such stents would also be effective where complex anatomical issues were involved. 

We report successful aneurysm therapy with a balloon-expandable covered stent, the Advanta V12 (Atrium Medical Corporation).

Case Report

An aneurysm was incidentally noted in the left renal artery of a 60-year-old woman with a history of hypertension. Computed tomography (CT) revealed the diameter of the aneurysm to be 16 x 18 mm (Figure 1). The aneurysm was located proximal to the ventral branch of the renal artery. The dorsal branch was observed to arise just proximal to the ventral branch (Figure 2A), suggesting that it would be difficult to position the stent without crossing the former. Moreover, the renal artery had an angulation of approximately 90 degrees at the aneurysm site. The patient’s serum creatinine level was 0.8 mg/dL.

Covered stents are not yet commercially available in Japan, so prior approval from the ethics committee of this institute was required for their use. After obtaining informed consent, endovascular therapy was performed. Under local anesthesia, percutaneous access to the right common femoral artery was achieved with an 8 Fr sheath by the Seldinger technique and 5000 units of heparin were administered. An 8 Fr RDC1 guiding catheter (Cordis Corporation) was delivered to the renal artery ostium. After stabilizing the guiding catheter, the buddy-wire technique was employed with two 0.014˝, 300 cm Deja-vu support wires (Cordis Corporation) (Figure 2B). A 5 x 22 mm Advanta V12 stent was smoothly delivered to the aneurysm site (Figure 2C) and deployed at 8 atm. Final angiography demonstrated successful exclusion of the aneurysm without dorsal branch occlusion (Figure 2D). There were no procedure-related complications, and the patient was discharged 2 days later. One hundred mg aspirin was continued indefinitely and 200 mg ticlopidine per day was administered for 3 months. At discharge, the patient’s creatinine level was 0.8 mg/dL.

 At 2-month follow-up, computed tomography angiography demonstrated persistent exclusion of the aneurysm (Figure 3). Six months later, exclusion of the aneurysm was confirmed by renal duplex sonography. 

Discussion

This case demonstrated the feasibility and efficacy of the Advanta V12 stent in successfully excluding a renal aneurysm with precise delivery. This balloon-expandable stent is covered with a microporous polytetrafluoroethylene coating to maximize cellular biocompatibility. Film-cast encapsulation technology prevents the stainless-steel struts from coming into contact with the luminal wall and tissue from prolapsing through the expandable stent. The patented film-cast covering helps distribute radial expansion stress during balloon deployment.⁸ Although endovascular therapy is the most favored approach in cases such as the present one, here it would have been difficult to use a stent graft, since the aneurysm was located on an angulated artery. However, the low crossing profile of this balloon-expandable covered stent allowed precise delivery, even with such a complex lesion. Moreover, the aneurysm was located near a bifurcation site. However, this balloon-expandable covered stent displays minimal foreshortening. Therefore, it could be precisely positioned, allowing us to avoid crossing the dorsal branch. Balloon-expandable covered stents thus appear to provide excellent delivery and precise deployment in complex anatomical lesions. Fortunately, there was no major branch in the aneurysm. It is difficult to avoid covering the major branch if it originates within the aneurysm. Coil embolization could be another approach. However, it is important to minimize the embolized area. The Advanta V12 stent is 0.035˝-wire compatible. However, we seldom use a 0.035˝ wire in order to treat the renal artery due to the risk of perforation. It is sometimes difficult to deliver the stent with a 0.014˝ wire. In such cases, we use a support wire, and the buddy-wire technique may also be employed to provide extra support.

Renal artery aneurysms are a well-recognized complication of fibromuscular dysplasia (FMD), and the rate of RAA in patients with FMD is 9.6%.⁹ In the present case, the bilateral renal artery had a “string of beads” appearance on an arteriogram, consistent with FMD. Fibromuscular dysplasia is a non-atherosclerotic, non-inflammatory vascular disease, which frequently involves the mid and/or distal segment of the renal artery, and is bilateral in two-thirds of patients.¹⁰ Destruction and replacement of the smooth muscle cells in the tunica media and external elastic lamella by fibrotic lamina produces localized areas of aneurysmal dilatation.⁹ Treatment for aneurysms with FMD has included endovascular therapy with detachable coils^9,11,12 and surgery with nephrectomy.¹⁰ Indications for repair are similar to those for other renal aneurysms; however, the appropriate therapy for aneurysms with FMD should be considered with care, as a dysplastic aneurysm may have a very thin wall, increasing the risk of rupture.

The major complication after covered-stent implantation is leakage into the aneurysm. Moreover, in-stent restenosis is a considerable problem in renal artery stenting as the diameter of the renal artery is smaller than that of the iliac artery. Giles et al reported the treatment of renal artery disease employing Atrium’s covered stents.¹³ In their study, 16 stents were deployed in cases of renal artery disease including in-stent restenosis. The primary patency rate in the renal artery stent was 72%, and assisted primary patency was 92% at 12 months. Although the sample of this earlier study was small and long-term data are still required, treatment with balloon-expandable covered stents for the renal artery appears to be acceptable with regard to in-stent restenosis. 

Endovascular therapy has the advantage of being minimally invasive compared to open surgery. Furthermore, balloon-expandable covered stents appear to offer potential in the treatment of RAAs, even in cases where complex anatomical issues are involved. Further study and long-term follow-up are required, however, to confirm the efficacy and safety of this device in the treatment of RAAs.

References

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From the Cardiovascular Center, Sendai Kousei Hospital, Miyagi, Japan.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Manuscript submitted April 21, 2013, provisional acceptance given April 29, 2013, final version accepted May 16, 2013.

Address for correspondence: Mio Musashi, MD, 4-15 Hirosemachi, Aoba-ku, Sendai, Miyagi 980-0873, Japan. Email: mio.musashi@gmail.com