Embolization Therapy: Principles and Clinical Applications, 1 Ed.

Renal Artery Aneurysms

Carlos Abath • Romero Marques • Marcos Barbosa de Souza Júnior

Primary renal artery aneurysms (RAAs) are relatively rare, contributing to 1% of all aneurysms and 15% to 22% of visceral aneurysms.1 They have an estimated incidence of 0.09% in the general population, 0.1% to 2.5% in angiographic series, and up to 9.7% in autopsy series.24 However, the trend for more widespread investigation of the renal arteries with noninvasive methods has resulted in an increasing number of cases receiving medical attention.5

In most cases, the clinical relevance of the aneurysm is uncertain as the patient has no symptoms directly related to the aneurysm. Some patients may present arterial hypertension, renal ischemia, hematuria, or flank pain, but the cause-and-effect relationship is hardly established.4,6,7 The natural history of RAA is poorly documented. Although rupture is rare, with an incidence reported at 5% to 10%, it may be associated with mortality rates as high as 80%. The risk of RAA rupture is significantly increased in pregnancy and polyarteritis nodosa (PAN) and is also related to the aneurysm size.4,810

The accepted indications for RAA treatment include symptomatic patients, women who are pregnant or in those contemplating pregnancy, PAN, and enlarging lesions. Currently, no consensus exists for the size at which an RAA should be repaired in an asymptomatic patient. It is recommended that the lesion should be treated when greater than 1.5 to 3 cm, although most use 2 cm as the reference size for treatment.4,6,7,10,11

The surgical management of RAA is relatively safe, with a low mortality rate ranging from 0% to 4%. Otherwise, in complex lesions, intentional nephrectomy occurs in up to 20% of cases and unplanned nephrectomy in 5% of cases.1,6 With the progress of endovascular techniques and development of new devices, even very complex lesions can be selectively treated, sparing the normal vascular tree. Therefore, this less invasive procedure carries a much lower morbidity and mortality rate, assuring that a complete understanding of aneurysm angioarchitecture is achieved and a proper endovascular strategy is planned. In this chapter, we will describe our endovascular management of RAA, discussing the patient and endovascular technique selection criteria and determining the immediate and long-term anatomic results.

TECHNIQUE

Atherosclerosis and fibrous dysplasia are the most common causes of aneurysm formation. This can also be associated with some systemic diseases, such as PAN, neurofibromatosis, and tuberous sclerosis. Traumatic and iatrogenic renal artery pseudoaneurysms are frequent vascular lesions but represent another pathophysiologic entity.

Over the last decade, we have treated 21 cases of nontraumatic RAA. There were 16 females and 5 males, with a mean age of 51.2 years (range, 19 to 79 years). Six patients had hypertension, 2 of them with a solitary kidney. Five other patients presented flank pain related to the side where the aneurysms were located. Two other patients had hematuria. In the 8 remaining patients, the aneurysms were found incidentally.

Atherosclerosis, fibromuscular dysplasia, and tuberous sclerosis coexisted in 4, 14, and 3 patients, respectively. The mean aneurysm diameter was 26 mm (range, 15 to 38 mm). For the purposes of endovascular treatment strategy, the RAAs were classified according to their location12,13 as type I, main renal artery (3 cases); type II, arterial bifurcations (14 cases); and type III, distal intrarenal (3 cases) (Fig. 47.1).

The endovascular treatment of RAA must be precise, safe, and durable, achieving complete aneurysm exclusion from the blood circulation and preserving, as much as possible, the arterial tree and renal parenchyma. To achieve these goals, the lesions can be treated by stent graft implant or selective embolization of the aneurysm sac. Unfortunately, both of these techniques have limitations and cannot be applied to every case. It is sometimes necessary to perform a parent vessel occlusion to treat the aneurysm, with some grade of renal parenchyma compromise. A full understanding of the arterial anatomy is needed for the recognition of challenging technical difficulties that will guide the choice of the best strategy and proper tools for each specific case. Complex and large lesions, broad-necked aneurysms, and bifurcation-located aneurysms, with arterial branch involvement, must be well identified and studied before the endovascular treatment. The noninvasive diagnostic methods, mainly the multidetector computed tomography, can provide valuable information regarding the aneurysm size, mural thrombus, wall calcification, and relationship with the parent vessel. Digital angiography with three-dimensional (3-D) reconstruction remains the best method for a pretreatment anatomic evaluation.

Angiography

As usual, the diagnostic angiography, via a femoral approach, begins with an aortography, unless there is an abnormal renal function. This initial study may show additional aneurysms or other lesions in the contralateral kidney, which can change the original treatment plan. It also can show the presence of accessory renal arteries. A selective renal angiography is then performed, in anteroposterior and oblique views, to demonstrate the aneurysm neck on profile. The distances from the aneurysm to renal artery ostium and renal artery bifurcation must be shown and are essential to the decision of placing a stent graft. The involvement of arterial branches by the aneurysm must also be disclosed. If the aneurysm is large or close to the renal bifurcation, it can be extremely difficult to obtain adequate visualization of the structures because the aneurysm sac is superposed over the renal vascular tree. Therefore, it is very useful to do a rotational angiography for 3-D image reconstruction. With the aid of a workstation, it is possible to play with the 3-D images to get the best views and to find the ideal working projection, where the neck is visualized on true profile. Once the working projection is found, the arch is positioned according to the angulations displayed in the workstation. Another advantage is the possibility of obtaining the vessel and aneurysm measurements with a minimal error margin. In our practice, we use Allura (Philips Healthcare, The Netherlands) or Artis zeego (Siemens Corporation, Malvern, Pennsylvania) equipment, doing the rotational angiography with 20 mL of nonionic contrast at a flow rate of 4 mL per second.

Stent Graft

Despite the development of new, more flexible, low-profile devices, the stent graft has restricted use in the treatment of RAA. It should not be applied in type II aneurysms because it would cover an important branch at the bifurcation, leading to a major renal infarction. It is not useful in type III distal lesions either because it does not have enough flexibility and low profile to navigate in tiny and tortuous vessels. The stent graft is a treatment option only in selected type I aneurysms, when the main renal artery is straight and the edges of the aneurysm neck are located at least 15 mm away from the renal ostium and hilar bifurcation. If these limits are not respected, there is a risk of technical failure, resulting in endoleak and persistent flow inside the aneurysm pouch. This occurred in the only case in which we tried to use a stent graft to seal a type I aneurysm, and the procedure had to be complemented by Onyx (Covidien, Irvine, California) embolization (Fig. 47.2).

Thromboembolism is another problem related to the use of stent graft in small-sized vessels such as the renal arteries, demanding a long-term administration of double antiplatelet therapy with acetylsalicylic acid and clopidogrel.

Flow-Diverter Stents

Flow-diverters stents have been developed for endovascular treatment of intracranial aneurysms, and today, two such stents are available: the Pipeline (Covidien, Plymouth, Minnesota) stent and the Silk stent (Balt Extrusion, Montmorency, France). Although they represent a safe, durable, and curative treatment of selected wide-necked, large, and giant intracranial aneurysms, important complications such as stent thrombosis, side branch occlusion, or postimplantation bleeding have been reported.14

The Cardiatis multilayer stent (Cardiatis, Isnes, Belgium) is a new type of flow-diverter stent consisting of two interconnected layers without any coverage, leading to decreased turbulent flow velocity in the aneurysm sac while improving laminar flow in the main artery and its branches. The stent is made of a biocompatible cobalt alloy wire, is available in diameters from 2 to 50 mm, and can be loaded in small (6-Fr) delivery systems.15 Even though it is a promising tool for the endovascular treatment of some selected visceral and peripheral aneurysms, only few case reports and small series have been published.15At the moment, this technology should be restricted to the rare cases where the other options are not applicable until its clinical effectiveness and safety is proved in further studies with longer follow-up.

Selective Coil Embolization

The advent of microcatheter and guidewire systems and new embolic agents allowed a selective occlusion of the most RAAs regardless of the topographic localization. The best lesions for this endovascular approach are saccular aneurysms with a well-defined narrow neck, measuring less than 4 mm or presenting a dome-to-neck proportion equal or superior to 2:1, without arterial branches arising from the aneurysm.

Preference is given to perform the procedure under general anesthesia for controlled apnea and generous use of road mapping. The embolization is safer and quicker and contrast volume is reduced. After digital subtraction aortography, selective renal artery catheterization is done with a double curve guiding catheter 6-Fr (Mach 1, Boston Scientific Corporation, Natick, Massachusetts). Thereafter, superselective catheterization of the aneurysm is performed with the Excelsior 14 microcatheter (Boston Scientific Corporation, Natick, Massachusetts) over a platinum tip 0.0014-in steerable guidewire (Transcend; Boston Scientific Corporation, Natick, Massachusetts) under road mapping fluoroscopy. The microcatheter is advanced coaxially through the guiding catheter, which is fitted proximally with a rotating hemostatic valve. The coaxial system is continuously flushed with heparinized saline solution to prevent thrombus formation in between the catheters.

Once the microcatheter tip is inside the aneurysm, the cavity is progressively filled with multiple detachable microcoils. Currently, there are many types of detachable microcoils in the market from different manufacturers. In most of our cases, the Guglielmi detachable coil (GDC; Boston Scientific Corporation, Natick, Massachusetts) is used. GDCs are circular or multishaped soft platinum coils, varying in size and length. The coil is attached to a Teflon-coated stainless steel delivery wire by a short portion of uninsulated stainless steel. After the correct position of the implanted coil is confirmed angiographically, a positive direct electrical current is applied to the proximal end of the stainless delivery wire. The negative pole is connected to a needle positioned in the patient’s skin. Within 1 minute, the current dissolves the uninsulated stainless steel section proximal to the platinum coil by electrolysis and the delivery wire is then withdrawn. The size of the first coil should equal the aneurysm size, achieving a basketlike configuration within the sac (Fig. 47.3B). The remaining cavity is filled with smaller coils, which are placed within the network of the first GDC, until the whole cavity of the aneurysm is densely packed with coils (Fig. 47.3C). Unfortunately, this technique alone cannot be applied to more complex lesions, such as large-neck aneurysms or when arterial branches arise from the aneurysm sac. In these cases, it is essential to perform associated remodeling techniques to protect the neck and avoid parent vessel or branch occlusion. This complication was observed early in our experience, when we did not protect the wide aneurysm neck in a type II lesion (Fig. 47.4).

REMODELING TECHNIQUES

Until the development of remodeling techniques, wide-necked aneurysms could not be treated by selective embolization without a significant risk of parent vessel occlusion caused by coil migration into the unprotected parent artery. In the remodeling technique, a temporary balloon is inflated intermittently at the aneurysmal neck while the microcoil or other embolic agents are deposited. Alternatively, a stent can be delivered to protect the neck, acting as a scaffold in the parent artery, while coils or other embolic materials are deposited into the aneurysmal lumen.

Balloon-Assisted Coiling

The balloon remodeling technique, first described by Moret and coworkers16 in 1997, was the initial alternative to surmount the problem of wide-necked brain aneurysms. In this technique, a soft semicompliant or conformable balloon is positioned across the neck of an aneurysm and inflated during coiling. The balloon works as a mechanical barrier that allows tighter packing of the aneurysm while preventing coil herniation into the parent artery during coil delivery. Also, the balloon stabilizes the microcatheter during coil delivery and forces the coils to conform to the 3-D shape of the aneurysm. The best balloons, specially designed for this technique, are the flexible, very low profile, compliant balloons: HyperGlide and HyperForm (Covidien, Plymouth, Minnesota). We routinely use the HyperGlide, leaving the HyperForm for some aneurysms located in bifurcations. Unfortunately, in some cases, the size of these balloons, which reaches only 4 mm in diameter, does not fit the main renal artery diameter, which ranges from 5 to 7 mm. So, they must be replaced by regular peripheral balloons with the desired diameters (Aviator plus; Cordis Corporation, Somerville, New Jersey).

When the balloon remodeling technique is performed, it is necessary to use a larger 7-Fr guiding catheter (Mach 1, Boston Scientific Corporation, Natick, Massachusetts) or a 6-Fr renal sheath introducer (Flexor® Cook Medical, Inc., Bloomington, Indiana), allowing passage for a balloon and a microcatheter at same time. Alternatively, we can do bilateral femoral puncture, introducing one 6-Fr guiding catheter in each side for the balloon and microcatheter, respectively. Special attention must be paid to the heparinization, keeping the activated coagulation time (ACT) three times the basal level. With the guiding catheter selectively placed in the main renal artery, the deflated balloon is positioned in the parent vessel, across the aneurysm neck. Selective microcatheterization of the aneurysm is then performed. Inflation of the balloon across the aneurysm neck temporarily occludes the neck and the parent vessel. Under balloon protection, coils are then delivered into the aneurysm. After placement of each coil into the aneurysm but before detachment, the balloon is deflated to test the stability of the coil. If no displacement of the coil is observed, the coil is detached. If movement is detected after balloon deflation, the coil is considered unstable and repositioned or removed. The procedure is repeated to obtain a dense and stable packing (Fig. 47.3).

Sometimes, when both branches are involved by a large-neck aneurysm located at the bifurcation, a double balloon protection technique is required to avoid occlusion of one of the branches by coil herniation (Fig. 47.5).

Stent-Assisted Coiling

Although the balloon technique constitutes an important method for the endovascular treatment of wide-necked aneurysms, the adjunctive use of stents may be an appealing alternative in RAA.

The implantation of a stent across the neck area serves as a buttress to the coil mass and contributes to changing the hemodynamic parameters locally by redirecting the flow and providing a substrate for endothelialization in that area, decreasing the chance of long-term aneurysm recanalization.

Similarly to the balloon-assisted embolization technique, the stent is positioned and deployed in front of the aneurysmal neck. Thereafter, selective microcatheterization of the aneurysmal lumen is done through the stent mesh or on parallel to it. The microcoils then are successively positioned and detached to achieve good packing.

Liquid Embolic Agents

Even when an aneurysm looks densely packed, there is a lot of space between the coils that may contribute to a significant number of recurrences after embolization, especially in large and giant wide-necked aneurysms. The use of a liquid agent that would be able to obliterate the aneurysm sac completely and seal the neck has significant advantages and has been examined for several years. The liquid nonadhesive embolic agent for this application is Onyx. Specifically designed for endovascular use, Onyx is an ethylene vinyl alcohol copolymer dissolved in an organic solvent, dimethyl sulfoxide (DMSO). When this liquid embolic agent comes in contact with an aqueous solution, it precipitates and initially forms an outer soft and spongy polymer cast with a semiliquid center. As further material is injected into the cast, it fills the space into which it is injected, and additional material then breaks out through the outer layer of the existing cast.

Despite the fact that Onyx has been developed to deal with cerebral aneurysm and that almost all scientific literature is related to neurointerventional procedures,17,18 we think that the concepts can also be applied to RAA. We have performed Onyx renal artery embolization in patients with type I and type II aneurysms, under general anesthesia, via a right femoral approach.

A 7-Fr guiding catheter or a 6-Fr renal sheath introducer is selectively placed in the main renal artery. The technique of Onyx embolization begins with the placement of a highly compliant DMSO-compatible occlusion balloon (HyperGlide or HyperForm) within the parent vessel over the aneurysm neck. As the maximum sizes for these balloons are 5 × 20 mm and 7 × 7 mm, respectively, they may not fit to the main renal artery diameter in every case. In this case, we have to use a bigger regular peripheral balloon (Aviator plus), without any problem related to DMSO compatibility. The balloon is left deflated while a DMSO-compatible microcatheter (Rebar; Covidien, Plymouth, Minnesota) is placed within the aneurysm. A slow test injection of contrast material through the microcatheter is made with the balloon inflated to ensure that the neck is controlled and a satisfactory seal is achieved with stasis of contrast material within the aneurysm. The microcatheter is then purged with saline to clear any contrast residue and primed with DMSO with a volume to match the dead space within the microcatheter. Onyx (HD 500) is then injected through the microcatheter. After a volume of approximately 0.2 mL, the Onyx approaches the end of the microcatheter and the balloon is inflated to a predetermined volume (measured when testing the seal between the aneurysm neck and parent vessel, as mentioned previously). The balloon temporarily occludes the parent vessel during the procedure while the aneurysm is filled with the Onyx, which forms a cast that seals off the aneurysm from the circulation and, in effect, reconstructs the parent vessel wall (Fig. 47.6).

The Onyx is injected at a rate of approximately 0.1 mL per minute, during approximately 5 minutes, by using a special syringe, which operates by means of a screw thread. Because Onyx is a viscous material, it accumulates around the microcatheter tip and gradually enlarges to form a kernel that remains attached to the end of the microcatheter. After each injection, the balloon is left inflated for another 2 minutes and is then deflated to allow renal reperfusion for 2 additional minutes, and the cycle is repeated. With each injection, new portions of the aneurysm fill (Fig. 47.7); eventually, the material flows down to the margins of the balloon and occludes the aneurysm neck. When the material comes into contact with the balloon, the injection is slowed or stopped, with brief 15- to 30-second pauses, to minimize the risk of leakage into the parent artery and beyond the balloon. At this point, it is advisable to follow the Onyx injection by subtracted fluoroscopy, under apnea, for better visualization of the embolic agent. It is important to ensure that material covers the aneurysm neck to achieve complete and durable occlusion and reduce the risk of aneurysm regrowth. The microcatheter position is not adjusted once the injection has begun. After angiographic confirmation of complete or satisfactory occlusion of the aneurysm occurs, the catheter syringe is decompressed by aspiration of 0.2 mL of the material and a 10-minute pause is taken to allow complete solidification of the polymer with the balloon deflated. The balloon is then reinflated, and the microcatheter is removed by gentle traction.

Another liquid embolic agent used to treat RAA is the tissue adhesive agent N-butyl cyanoacrylate (NBCA) (Histoacryl; B Braun Melsungen AG, Melsungen, Germany), which immediately polymerizes when it contacts ionic fluids, such as blood, forming a cast within vessel lumen resulting in occlusion. The glue is used in mixture with the oil dye Lipiodol (Guerbet, Aulnay-sous-Bois, France) to become visible under x-ray and delay the polymerization time. We use a concentration of 20% to 50% of NBCA in the treatment of renal vascular lesions. Unlike the embolic agent Onyx, the polymerization behavior of the NBCA/Lipiodol mixture is something unforeseeable and can lead to inadvertent parent vessel occlusion. So we reserve this embolic agent to treat only distal type III renal aneurysms when it is possible to occlude the parent vessel, provoking an acceptable small area of renal parenchyma infarction (Fig. 47.8).

ASSOCIATION OF TECHNIQUES AND MATERIALS

The management of complex RAA sometimes demands association of different techniques and embolic agents to be successful and safe. If one technique or material fails to completely exclude an aneurysm from the circulation, another strategy is performed for total obliteration of the lesion. In our series, a type I renal aneurysm was initially treated with a stent graft (Jograft; Jomed, Rangendingen, Germany), but the lesion continued to be patent due to a leakage at the distal end of the stent graft. Therefore, the tip of a microcatheter was positioned within the aneurysm and Onyx was injected while a balloon was inflated over the aneurysm neck, achieving a complete occlusion of the aneurysm sac (Fig. 47.2).

On other occasions, different materials are associated to obtain better and durable results or expand the safety margin of the procedure. This was the case of a huge type I renal aneurysm, whose neck encompassed the parent vessel wall. First, we deployed a bare stent across the neck and then a microcatheter was placed within the aneurysm lumen through the mesh of the stent. A peripheral balloon was inflated in front of the aneurysm neck and 7.5 mL of Onyx were injected inside the lesion. As a small leakage of Onyx was noticed through the aneurysm neck and beyond the balloon, we stopped the liquid agent injection and finished the neck occlusion with detachable microcoils. This way, a complete aneurysm occlusion was achieved, reconstructing and keeping the parent vessel patent. Besides the dense compaction of the aneurysm lumen, the stent changed the local hemodynamic parameters, redirecting the flow and decreasing the chance of a long-term recanalization (Fig. 47.9).

In another complex lesion, a type III intrarenal aneurysm ruptured, leading to an arteriovenous fistula (AVF), associated with a venous dilation. Initially, a detachable microcoil was delivered within the arterial aneurysm to decrease the flow. Then, the embolization was concluded by injecting glue (⅔ lipiodol + ⅓ cyanoacrylate: 33%) to obliterate the AVF and fill the aneurysm cavity (Fig. 47.8).

RESULTS

Twenty-one large or giant RAAs were submitted to endovascular treatment in 21 patients, with complete occlusion of the aneurysm cavity in all of them (100% technical success). Two aneurysms were classified as type I lesions and 16 as type II. All of them but one were treated with remodeling technique coil or Onyx embolization. Unintentional branch occlusion occurred just in one type II lesion in which we did not use the remodeling technique, resulting in a small but clinically asymptomatic renal infarction (Fig. 47.4). In one large type I aneurysm, an association of techniques and materials was used, leading to a significant patient x-ray exposure. Clinical follow-up demonstrated a localized actinic dermatitis at the skin over the affected kidney (Fig. 47.7).

Three aneurysms were classified as type III lesions and were embolized with glue after distal superselective catheterization. Despite the occlusion of the tiny parent vessels, none or minimal renal parenchyma infarction was noted, with no clinical significance.

A clinical and diagnostic Doppler ultrasonography follow-up was performed in all patients (mean, 32.6 months; range, 9 to 75 months). Digital angiography was available in only one patient a year after the endovascular treatment. In two patients with hematuria, the bleeding disappeared immediately after embolization. The patients with arterial hypertension and flank pain presented total or partial improvement of their signs and symptoms. In all patients, the serum creatinine levels were normal, remaining unchanged after the procedure. Ultrasonography and angiography follow-up examinations confirmed successful and durable occlusion of all aneurysms, without any recurrence (Figs. 47.2 and 47.9).

DISCUSSION

The rare occurrence of RAAs has created a debate regarding the threshold for repair. There is general consensus that repair should be performed when meeting the following criteria: RAAs exceeding 2 or 2.5 cm, or documented enlarging aneurysm; symptomatic RAAs with flank pain, hematuria, or hypertension; RAAs with documented distal embolization; RAAs in pregnancy or in women of childbearing age; and RAAs with associated significant stenosis or renal malperfusion.4,6,7,10,11,13

Although surgical mortality of elective operation in experienced institutions is essentially nonexistent, morbidity and long recovery periods persist. Aortorenal bypass graft occlusions and unplanned nephrectomy occur even in the largest series.6,19 With the advent of covered stents, lower profile endovascular devices, and new embolic agents, the technical feasibility of treating a larger number of RAA is now increased. Currently, the endovascular techniques allow the successful treatment of complex RAA despite of having complicating factors such as large size, wide neck, location near or at the bifurcation, branch involvement by the aneurysm, and association with AVF.

Rundback and coworkers12 proposed an angiographic classification of RAAs that helps to establish treatment strategies. Type I lesions are saccular aneurysms that arise from the main artery or a large segmental branch and can be excluded with stent grafts. At the moment, the stent grafts present some limitations because the devices available are still rigid and high profile and have poor endovascular navigability.20 Besides, the aneurysm neck is often situated close to the renal artery bifurcation, even in type I aneurysms, precluding a satisfactory seal. If the distance from the aneurysm to the renal artery bifurcation is less than 15 mm, the stent graft may not exclude the aneurysm sac from the circulation, as happened in one case of this series (Fig. 47.2). Another problem related to the stent graft is the need of long-term double antiplatelet therapy after the procedure. Selective coil or Onyx embolization, associated or not to remodeling technique, is a valuable alternative to treat type I RAA.

Type II RAAs are either fusiform or adjacent to a bifurcation and were generally treated with surgery or nephrectomy if required. These challenging lesions accounted for the most of our cases and were dealt with only endovascular approach. In this particular group of aneurysms, the use of remodeling technique, as an adjunct to selective coil or Onyx embolization, is strongly recommended to avoid inadvertent branch or parent vessel occlusion.

Type III RAA lesions arise from small segmental arteries that supply a small portion of the kidney and can be embolized by occlusion. Several embolic agents, such as microcoils and glue, can be used to obliterate these distal aneurysms.

Because of the reduced number of RAA cases, it is impossible to make a definitive comparison between coils and Onyx.1728 Being a liquid agent, the Onyx is able to better obliterate the aneurysm sac and, theoretically, would avoid aneurysm recurrence or regrowth. On the other hand, even with remodeling technique, it is difficult to avoid leakage of Onyx beyond the protection balloon at the end of the procedure, which could be responsible for thromboembolic events or late parent vessel occlusion. Certainly, it is much safer and easier to occlude the remnant aneurysm neck using microcoils instead of Onyx. Finally, the Onyx embolization procedure lasts longer and exposes the patient to more radiation.

However, it is important to say that the different embolic agents, such as coils and Onyx, should be used as complementary tools, and the interventional radiologist must take advantage of both to offer the best benefit for the patient. In very large aneurysms, it is possible to almost completely fill the aneurysm cavity with Onyx and finish the residual neck occlusion safely with microcoils. 3-D angiography is a very important technique for better understanding of the renal vascular anatomy. A complete comprehension of the renal aneurysm angioarchitecture is essential to choose the best therapeutic strategy planning.

TIPS AND TRICKS

• The selective embolization of complex RAA is a challenging procedure, demanding high-quality image, done on apnea, for a better understanding of the aneurysm angioarchitecture. So, do the cases under general anesthesia.

• To better control the embolic material deposition inside the aneurysm sac, it is essential to see the aneurysm neck on profile and to identify the origin of secondary branches involved by the aneurysm. This is not easy with plain angiography. Then, begin the procedure with a rotational angiography and 3-D reconstruction for a better definition of the working projections.

• Give preference for a preshaped sheath (Flexor® Ansel 6-Fr from Cook) instead of a preshaped guide catheter. The sheath has a larger internal lumen, with more space available for the microcatheter and remodelling balloon.

• Always use continuous pressurized heparinized saline solution on the guide sheath to avoid thromboembolic complications.

• When using Onyx to embolize RAAs, be sure to choose a microcatheter brand compatible with the Onyx solution because the DMSO can dissolve the microcatheter wall. You may use any of the DMSO-compatible microcatheters produced by Covidien.

• To deal with complex renal aneurysm, try to be familiar with the neurointervention tools, such as microcatheters, microwires, remodelling balloons, detachable microcoils, and Onyx.

CONCLUSION

The endovascular treatment of RAA is a feasible, safe, and effective procedure, which seems durable, even in complex lesions. Despite the good results, larger series with long-term follow-up are necessary to establish the real role of the endovascular techniques.

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