DOI: 10.1148/rg.25si055517
RadioGraphics 2005;25:S213-S227
© RSNA, 2005
Endovascular Treatment of Iliac Artery Aneurysms1
Ichiro Sakamoto, MD,
Eijun Sueyoshi, MD,
Shiro Hazama, MD,
Kenji Makino, MD,
Akifumi Nishida, MD,
Tetsuji Yamaguchi, MD,
Kiyoyuki Eishi, MD and
Masataka Uetani, MD
1 From the Departments of Radiology (I.S., E.S., K.M., A.N., T.Y., M.U.) and Cardiovascular Surgery (S.H., K.E.), Nagasaki University School of Medicine, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan. Presented as an education exhibit at the 2004 RSNA Annual Meeting. Received April 1, 2005; revision requested May 6 and received July 5; accepted July 12. All authors have no financial relationships to disclose.
Address correspondence to I.S. (e-mail: ichiro-s{at}net.nagasaki-u.ac.jp).
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Abstract
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Endovascular treatment is now an alternative to surgery for the treatment of iliac artery aneurysms (IAAs). A variety of minimally invasive therapeutic options are available (eg, coil embolization, stent-graft placement), and choosing an appropriate option is essential for achieving excellent long-term results and reducing potential complications. Preprocedural imaging with multi–detector row computed tomography or magnetic resonance imaging is necessary for evaluating patient eligibility and planning the interventional procedure. An imaging classification system for IAAs that is based on anatomic features and endovascular treatment options has been developed and may help determine therapeutic strategies for affected patients. Early experience indicates that endovascular treatment is safe and effective in treating IAAs, and it is expected that various devices that will make endovascular treatment easier to perform will soon become commercially available. However, large, long-term follow-up studies will be needed to determine whether this approach is a practical alternative to open surgery.
© RSNA, 2005
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Introduction
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The natural course of an iliac artery aneurysm (IAA) consists of progressive expansion with eventual rupture. With advances in catheter technology, transcatheter embolization and endovascular stent-graft placement have become possible alternatives to surgery in the treatment of IAAs (1–3).
These minimally invasive methods include a variety of therapeutic options, and choosing an appropriate option on the basis of the imaging characteristics of IAAs is essential for achieving excellent long-term results and reducing potential complications (4). In this article, we describe IAAs and therapeutic strategies for the treatment of IAAs without compressive symptoms, IAAs with compressive symptoms, and infected aneurysms. We also discuss and illustrate preprocedural imaging and various endovascular treatment options. In addition, we describe a new imaging classification system for IAAs that is based on anatomic features and endovascular treatment options. Finally, we discuss follow-up imaging and possible complications of endovascular treatment for IAAs, including postimplantation syndrome and postembolization syndrome, iliac artery injury, stent-graft thrombosis, colonic mucosal ischemia, and buttock claudication.
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Iliac Artery Aneurysms
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Involvement of the iliac arteries is seen in 10%–20% of patients with abdominal aortic aneurysms (AAAs) (5). On the other hand, isolated IAAs are relatively rare, with an estimated prevalence of 0.008%–0.03% based on large autopsy series (6,7). Like AAAs, IAAs most commonly occur in elderly men. IAAs occur much more frequently in the common and internal iliac arteries than in the external iliac arteries. The most common cause of IAA is atherosclerosis. Other causes include trauma, infection, dissection, excessive athletic effort (eg, bicycle racing), paraanastomotic graft failure, and connective tissue disorders such as Marfan syndrome and Ehlers-Danlos syndrome (8). Like AAAs, IAAs can mimic neurologic, genitourologic, and gastrointestinal symptoms due to external compression (9,10). In addition, at clinical examination or conventional angiography, IAAs with luminal narrowing secondary to aneurysmal thrombosis may mimic arteriosclerosis obliterans (Fig 1). Hence, it is desirable that iliac artery stenosis be routinely evaluated with CT or magnetic resonance (MR) imaging prior to angioplasty, even if the entity appears to be a simple stenosis. In some studies, IAA is defined as enlargement of the artery to a diameter of more than 1.5 cm. As mentioned earlier, the natural course of an IAA consists of progressive expansion with eventual rupture, and the risk of rupture increases with aneurysm size (11). A review of the literature reveals that surgical repair should be recommended for isolated IAAs greater than 3.0–3.5 cm in diameter, since the smallest reported ruptured IAA was 3 cm (6,9,12). However, this procedure is associated with mortality rates of 7%–11% for elective surgery and 50% for emergency surgery (9).
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Figure 1a. Aneurysm of the right common iliac artery in a 66-year-old man with an initial symptom of intermittent claudication. (a) Angiogram shows severe to moderate stenoses in the right common iliac artery that mimic arteriosclerosis obliterans. (b) Coronal computed tomographic (CT) scan shows an aneurysm of the right common iliac artery with severe narrowing of the vessel lumen due to a large volume of mural thrombus. (c) Angiogram obtained immediately after stent-graft placement in the right common and external iliac arteries shows complete exclusion of the aneurysm and restoration of the luminal diameter.
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Figure 1b. Aneurysm of the right common iliac artery in a 66-year-old man with an initial symptom of intermittent claudication. (a) Angiogram shows severe to moderate stenoses in the right common iliac artery that mimic arteriosclerosis obliterans. (b) Coronal computed tomographic (CT) scan shows an aneurysm of the right common iliac artery with severe narrowing of the vessel lumen due to a large volume of mural thrombus. (c) Angiogram obtained immediately after stent-graft placement in the right common and external iliac arteries shows complete exclusion of the aneurysm and restoration of the luminal diameter.
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Figure 1c. Aneurysm of the right common iliac artery in a 66-year-old man with an initial symptom of intermittent claudication. (a) Angiogram shows severe to moderate stenoses in the right common iliac artery that mimic arteriosclerosis obliterans. (b) Coronal computed tomographic (CT) scan shows an aneurysm of the right common iliac artery with severe narrowing of the vessel lumen due to a large volume of mural thrombus. (c) Angiogram obtained immediately after stent-graft placement in the right common and external iliac arteries shows complete exclusion of the aneurysm and restoration of the luminal diameter.
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Therapeutic Strategies for IAAs
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IAAs without Compressive Symptoms
IAAs without compressive symptoms can be treated with either open surgery or endovascular treatment. In poor surgical candidates, endovascular treatment is usually favored, and selection of the appropriate endovascular technique should be based on the morphologic features of IAAs on preprocedural images. On the other hand, in good surgical candidates, there is controversy regarding which patients should undergo stent-graft placement and which should undergo surgery because the long-term results of endovascular treatment are still unknown.
IAAs with Compressive Symptoms
IAAs with compressive symptoms (eg, neurologic or urologic symptoms) should be treated with open surgery because endovascular treatment cannot rapidly reduce aneurysm size (Fig 2). In our experience, aneurysms that are thrombosed with endovascular treatment show a gradual reduction in size over a long period of time (3).
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Figure 2a. Gradual shrinkage of an IAA treated with coil embolization. (a) Preembolization CT scan shows an aneurysm of the right internal iliac artery. (b) CT scan obtained 22 months after coil embolization shows gradual interval shrinkage of the thrombosed aneurysm.
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Figure 2b. Gradual shrinkage of an IAA treated with coil embolization. (a) Preembolization CT scan shows an aneurysm of the right internal iliac artery. (b) CT scan obtained 22 months after coil embolization shows gradual interval shrinkage of the thrombosed aneurysm.
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Infected Aneurysms
Infected aneurysms generally progress to rupture if they are left untreated. The first surgical treatment option for such aneurysms involves in situ placement of an aortic graft but carries a high risk of graft infection. The second surgical treatment option is resection of the aneurysm followed by arterial ligation and creation of an extraanatomic bypass. However, this option involves two major procedures and also carries a risk of infectious aortic stump rupture. Stent-graft placement is not a first-line option for the treatment of infected aneurysms because of a high risk of stent-graft infection (Fig 3). However, there have been several reports of favorable outcome after stent-graft repair of infected aneurysms (13,14). Therefore, in poor surgical candidates, stent-graft placement may be used to gain time to improve the patient’s condition prior to open surgery and, in certain patients, may even become the definitive treatment.
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Figure 3a. Stent-graft placement for an infected aneurysm of the right common iliac artery in a 78-year-old man with a serious case of pneumonia. (a) Pelvic angiogram shows a saccular aneurysm of the right common iliac artery. (b) Angiogram obtained immediately after stent-graft placement shows complete exclusion of the aneurysm. (c) Coronal CT scan obtained 2 months later shows revascularization and interval enlargement of the treated aneurysm. In addition, a newly developed infected aneurysm is seen in the lower abdominal aorta (arrow). Treatment of an infected aneurysm with stent-graft placement is controversial because of the risk of stent-graft infection and the fragility of the affected artery. Therefore, the use of stent-grafts should be restricted to patients for whom open surgery poses a high risk.
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Figure 3b. Stent-graft placement for an infected aneurysm of the right common iliac artery in a 78-year-old man with a serious case of pneumonia. (a) Pelvic angiogram shows a saccular aneurysm of the right common iliac artery. (b) Angiogram obtained immediately after stent-graft placement shows complete exclusion of the aneurysm. (c) Coronal CT scan obtained 2 months later shows revascularization and interval enlargement of the treated aneurysm. In addition, a newly developed infected aneurysm is seen in the lower abdominal aorta (arrow). Treatment of an infected aneurysm with stent-graft placement is controversial because of the risk of stent-graft infection and the fragility of the affected artery. Therefore, the use of stent-grafts should be restricted to patients for whom open surgery poses a high risk.
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Figure 3c. Stent-graft placement for an infected aneurysm of the right common iliac artery in a 78-year-old man with a serious case of pneumonia. (a) Pelvic angiogram shows a saccular aneurysm of the right common iliac artery. (b) Angiogram obtained immediately after stent-graft placement shows complete exclusion of the aneurysm. (c) Coronal CT scan obtained 2 months later shows revascularization and interval enlargement of the treated aneurysm. In addition, a newly developed infected aneurysm is seen in the lower abdominal aorta (arrow). Treatment of an infected aneurysm with stent-graft placement is controversial because of the risk of stent-graft infection and the fragility of the affected artery. Therefore, the use of stent-grafts should be restricted to patients for whom open surgery poses a high risk.
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Preprocedural Imaging
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Preprocedural imaging is essential in evaluating patient eligibility for endovascular treatment and planning the intervention. The proximal and distal necks and the body of the aneurysm as well as the device delivery route should be assessed prior to endovascular treatment. Multi–detector row CT is the most effective diagnostic tool, providing exact information regarding the presence, location, diameter, and extension of the aneurysm. In particular, the exact length of the proximal and distal necks should be evaluated with CT and three-dimensional (3D) reformation because these measurements have the greatest influence on the choice of therapeutic option. MR imaging is advantageous in patients with renal failure (15). MR imaging protocol usually includes electrocardiographically-gated spin-echo T1-weighted sequences and MR angiography with a gadolinium-enhanced 3D gradient-echo sequence. Catheter angiography with a calibrated catheter may be necessary to measure the exact length of the proximal and distal necks of the aneurysm. However, interventional radiologists should keep in mind that, in IAAs with mural thrombus, the exact length of the proximal and distal necks may be overestimated with catheter angiography alone (Fig 4).
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Figure 4a. Limitations of catheter angiography in aneurysm evaluation. (a) Catheter angiogram shows an aneurysm of the left internal iliac artery, the proximal neck of which (arrow) appears to be long enough to allow safe embolization. (b) Coronal CT scan demonstrates a short distance between the aneurysm and the iliac artery bifurcation, indicating that proximal coil embolization would be technically unfeasible. In aneurysms with a large volume of mural thrombus, the exact length of the proximal and distal necks is difficult to evaluate with catheter angiography alone.
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Figure 4b. Limitations of catheter angiography in aneurysm evaluation. (a) Catheter angiogram shows an aneurysm of the left internal iliac artery, the proximal neck of which (arrow) appears to be long enough to allow safe embolization. (b) Coronal CT scan demonstrates a short distance between the aneurysm and the iliac artery bifurcation, indicating that proximal coil embolization would be technically unfeasible. In aneurysms with a large volume of mural thrombus, the exact length of the proximal and distal necks is difficult to evaluate with catheter angiography alone.
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The diameter, tortuosity, and atherosclerotic changes of the iliofemoral arteries should be assessed with CT or MR angiography prior to stent-graft placement to determine which side is most appropriate for the device delivery route, thus decreasing the risk of iliac artery injury (Fig 5). This preprocedural imaging work-up for endovascular treatment of IAAs is similar in most respects to that for stent-graft placement in AAAs.
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Figure 5a. MR angiographic evaluation of the iliac arteries. (a) Maximum-intensity-projection image allows accurate measurement of the luminal diameters of the bilateral iliac arteries. (b, c) On left (b) and right (c) anterior maximum-intensity-projection images, the tortuosity of the iliac arteries is clearly displayed.
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Figure 5b. MR angiographic evaluation of the iliac arteries. (a) Maximum-intensity-projection image allows accurate measurement of the luminal diameters of the bilateral iliac arteries. (b, c) On left (b) and right (c) anterior maximum-intensity-projection images, the tortuosity of the iliac arteries is clearly displayed.
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Figure 5c. MR angiographic evaluation of the iliac arteries. (a) Maximum-intensity-projection image allows accurate measurement of the luminal diameters of the bilateral iliac arteries. (b, c) On left (b) and right (c) anterior maximum-intensity-projection images, the tortuosity of the iliac arteries is clearly displayed.
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In Japan, there is currently no commercially available stent-graft; consequently, the stent-graft must be custom fabricated for each patient on the basis of findings at multi–detector row CT with 3D reformation or MR imaging. Generally, it is necessary to create stent-grafts that are 10%–15% larger than normal to prevent migration and provide good attachment to the aortic wall.
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Endovascular Treatment for IAAs
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Coil Embolization
All coil embolization procedures are performed in the angiography suite with use of a local anesthetic. Heparin (3000–5000 U) is administered intraarterially at the start of the procedure. After insertion of a 4- or 5-F introducer sheath via the ipsilateral or contralateral femoral artery, a 4- or 5-F shepherd hook catheter (Clinical Supply, Tokyo, Japan) is inserted into the target iliac artery and the size and extension of the IAA is evaluated with angiography. In cases in which the orifice of the inferior mesenteric artery (IMA) was ligated during prior AAA repair, angiography of the superior mesenteric artery (SMA) is necessary prior to exclusion of the internal iliac artery with embolotherapy or stent-graft placement to evaluate collateral pathways to distal branches of the IMA. IAAs are usually embolized with 0.035-inch stainless-steel coils 5–20 mm in diameter (Cook, Bloomington, Ind), 0.035-inch platinum coils 5–10 mm in diameter (Cook), or 0.016-inch platinum coils 5–10 mm in diameter (Tornado, Cook).
Endovascular Stent-Graft Placement
Endovascular stent-graft placement is performed in the angiography suite with the patient under local or general anesthesia. It is performed with a custom-made stent-graft composed of a Z or Spiral Z stent with woven polyester (Cook) or a 12-mm-diameter Passager stent (Meadox Medicals, Oakland, NJ). Heparin (5000 U) is administered at the beginning of the procedure. After ipsilateral femoral arteriotomy, the stent-graft is introduced through a 10–18-F introducer sheath. Initially, the tip of the stent delivery system is positioned slightly beyond the lesion and the stent-graft is pushed up to the distal extremity of the delivery system. Once the stent-graft has been positioned correctly, the sheath is gently retracted over the pusher and the stent freely expands, adhering to the arterial wall. If attachment to the vessel wall is insufficient, a balloon catheter is used to expand the stent-graft, thereby ensuring good contact with the wall at both ends. Ideally, stent-grafts should cover the lesion and at least 1.5–2.0 cm of the normal artery proximal and distal to the lesion. Patients receive long-term anticoagulant therapy (unless contraindicated) after undergoing stent-graft placement.
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Classification Scheme for IAAs
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We have developed an imaging classification system for IAAs that is based on the anatomic features of the aneurysm and the relevant endovascular treatment option. Type I IAAs are internal IAAs that are far enough (>2 cm) from the origin of the internal iliac artery to allow proximal embolization, whereas type II IAAs are internal IAAs that are not sufficiently distant to allow this procedure. Type III IAAs are common IAAs that are far enough from the aortoiliac bifurcation to allow placement of a straight stent-graft, whereas type IV IAAs are common IAAs that are not sufficiently distant to allow such placement. Type V IAAs are common or internal IAAs that develop after AAA repair with a bifurcated graft.
Type I IAAs
Proximal and distal embolization is the first-line treatment option for internal IAAs because it is minimally invasive and can prevent revascularization due to cross-filling by pelvic collateral vessels (1,2). In particular, this technique is advised for internal IAAs that are sufficiently distant (>2 cm) from the origin of the internal iliac artery to allow proximal embolization (Figs 6, 7). Catheterization of a site distal to the aneurysm can be technically difficult and time consuming. In such cases, coil packing of the aneurysm sac followed by proximal embolization can also be performed, although doing so usually requires a large number of coils, especially in large aneurysms (Fig 8). Proximal embolization alone is an undesirable option because it necessarily involves the risk of aneurysm revascularization due to abundant pelvic collateral vessels (2,3,8).
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Figure 6. Drawings illustrate the two treatment options that are available for a type I IAA: proximal and distal embolization (left) and coil packing and proximal embolization (right). The aneurysm is far enough from the origin of the internal iliac artery to allow proximal embolization.
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Figure 7a. Proximal and distal embolization of an aneurysm of the left internal iliac artery in an 80-year-old man. (a) Preembolization angiogram shows an aneurysm of the left internal iliac artery and dilatation of the left common iliac artery. (b) Postembolization angiogram shows that the aneurysm has been completely excluded. An aneurysm of the left common iliac artery was treated with stent-graft placement 12 months later.
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Figure 7b. Proximal and distal embolization of an aneurysm of the left internal iliac artery in an 80-year-old man. (a) Preembolization angiogram shows an aneurysm of the left internal iliac artery and dilatation of the left common iliac artery. (b) Postembolization angiogram shows that the aneurysm has been completely excluded. An aneurysm of the left common iliac artery was treated with stent-graft placement 12 months later.
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Figure 8a. Coil packing and proximal embolization of a ruptured aneurysm of the left internal iliac artery in an 86-year-old man. (a) Pretherapeutic angiogram shows an aneurysm of the left internal iliac artery and extravasated contrast material (arrow). (b) Posttherapeutic angiogram of the left internal iliac artery shows complete exclusion of the ruptured aneurysm.
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Figure 8b. Coil packing and proximal embolization of a ruptured aneurysm of the left internal iliac artery in an 86-year-old man. (a) Pretherapeutic angiogram shows an aneurysm of the left internal iliac artery and extravasated contrast material (arrow). (b) Posttherapeutic angiogram of the left internal iliac artery shows complete exclusion of the ruptured aneurysm.
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Type II IAAs
In internal IAAs that are less than 2 cm from the origin of the internal iliac artery, proximal embolization is occasionally challenging because the embolization coils may migrate into the common or external iliac artery. In such cases, stent-graft placement across the origin of the IAA is functionally equivalent to proximal embolization (Fig 9). Therefore, distal embolization of the aneurysm followed by stent-graft placement is thought to be an effective alternative treatment for IAAs that are a short distance from the iliac artery bifurcation (Fig 10). However, stent-graft insertion can be technically unfeasible if the common or external iliac artery is extremely tortuous or small. In such circumstances, distal embolization of the aneurysm, placement of a bare stent across the origin of the IAA, and proximal embolization through the wire mesh of the stent are possible alternatives (Fig 11). The bare stent is positioned to prevent migration of coils into the common or external iliac artery (16).
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Figure 9. Drawings illustrate treatment of a type II IAA with a stent-graft (left) and a bare stent (right). Such an aneurysm is not far enough from the origin of the internal iliac artery to allow proximal embolization.
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Figure 10a. Embolization and stent-graft placement in an ipsilateral internal iliac artery for an aneurysm of the left internal iliac artery in a 73-year-old woman. (a) Sagittal multiplanar reformatted CT image shows an aneurysm of the left internal iliac artery located a short distance from the iliac artery bifurcation. The aneurysm was treated with embolization of distal branches of the left internal iliac artery followed by stent-graft placement in the left common and external iliac arteries. (b) Angiogram obtained immediately after the procedure shows complete exclusion of the aneurysm. (c) Coronal multiplanar reformatted CT image obtained 2 months later shows complete thrombosis of the aneurysm.
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Figure 10b. Embolization and stent-graft placement in an ipsilateral internal iliac artery for an aneurysm of the left internal iliac artery in a 73-year-old woman. (a) Sagittal multiplanar reformatted CT image shows an aneurysm of the left internal iliac artery located a short distance from the iliac artery bifurcation. The aneurysm was treated with embolization of distal branches of the left internal iliac artery followed by stent-graft placement in the left common and external iliac arteries. (b) Angiogram obtained immediately after the procedure shows complete exclusion of the aneurysm. (c) Coronal multiplanar reformatted CT image obtained 2 months later shows complete thrombosis of the aneurysm.
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Figure 10c. Embolization and stent-graft placement in an ipsilateral internal iliac artery for an aneurysm of the left internal iliac artery in a 73-year-old woman. (a) Sagittal multiplanar reformatted CT image shows an aneurysm of the left internal iliac artery located a short distance from the iliac artery bifurcation. The aneurysm was treated with embolization of distal branches of the left internal iliac artery followed by stent-graft placement in the left common and external iliac arteries. (b) Angiogram obtained immediately after the procedure shows complete exclusion of the aneurysm. (c) Coronal multiplanar reformatted CT image obtained 2 months later shows complete thrombosis of the aneurysm.
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Figure 11a. Placement of a bare stent and proximal embolization through its wire mesh for an aneurysm of the right internal iliac artery in a 72-year-old man. (a) Pelvic angiogram shows an aneurysm of the right internal iliac artery with a wide mouth and a short neck. An aneurysm of the left common iliac artery is also seen. Insertion of a stent-graft was considered to be unfeasible because of the extreme tortuosity of the right external iliac artery (arrow). Therefore, treatment consisted of placement of a bare stent (Wallstent; Boston Scientific, Natick, Mass) in the right common and external iliac arteries, followed by embolization with a catheter inserted through the wire mesh of the stent into a proximal part of the internal IAA. (b) Fluoroscopic image obtained immediately after stent placement shows the catheter (black arrows). Coil embolization was subsequently performed via the catheter. White arrows indicate distal embolization coils. (c) Posttreatment angiogram shows complete exclusion of the right internal IAA. The left common IAA was treated with stent-graft placement 1 month later.
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Figure 11b. Placement of a bare stent and proximal embolization through its wire mesh for an aneurysm of the right internal iliac artery in a 72-year-old man. (a) Pelvic angiogram shows an aneurysm of the right internal iliac artery with a wide mouth and a short neck. An aneurysm of the left common iliac artery is also seen. Insertion of a stent-graft was considered to be unfeasible because of the extreme tortuosity of the right external iliac artery (arrow). Therefore, treatment consisted of placement of a bare stent (Wallstent; Boston Scientific, Natick, Mass) in the right common and external iliac arteries, followed by embolization with a catheter inserted through the wire mesh of the stent into a proximal part of the internal IAA. (b) Fluoroscopic image obtained immediately after stent placement shows the catheter (black arrows). Coil embolization was subsequently performed via the catheter. White arrows indicate distal embolization coils. (c) Posttreatment angiogram shows complete exclusion of the right internal IAA. The left common IAA was treated with stent-graft placement 1 month later.
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Figure 11c. Placement of a bare stent and proximal embolization through its wire mesh for an aneurysm of the right internal iliac artery in a 72-year-old man. (a) Pelvic angiogram shows an aneurysm of the right internal iliac artery with a wide mouth and a short neck. An aneurysm of the left common iliac artery is also seen. Insertion of a stent-graft was considered to be unfeasible because of the extreme tortuosity of the right external iliac artery (arrow). Therefore, treatment consisted of placement of a bare stent (Wallstent; Boston Scientific, Natick, Mass) in the right common and external iliac arteries, followed by embolization with a catheter inserted through the wire mesh of the stent into a proximal part of the internal IAA. (b) Fluoroscopic image obtained immediately after stent placement shows the catheter (black arrows). Coil embolization was subsequently performed via the catheter. White arrows indicate distal embolization coils. (c) Posttreatment angiogram shows complete exclusion of the right internal IAA. The left common IAA was treated with stent-graft placement 1 month later.
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Type III IAAs
Common IAAs that are more than 2 cm from the aortoiliac bifurcation can be treated with stent-graft placement in the ipsilateral common and external iliac arteries (Fig 12). However, embolization of the distal portion of the ipsilateral internal iliac artery must be performed prior to stent-graft placement to avoid retrograde flow to the aneurysms (type 2 endoleaks according to the conventional terminology used in aortic stent-graft placement) (Fig 13) (5).
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Figure 12. Drawing illustrates treatment of a type III aneurysm of the common iliac artery. The aneurysm is far enough from the aortoiliac bifurcation to allow placement of a straight stent-graft.
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Figure 13a. Embolization and stent-graft placement in an ipsilateral internal iliac artery for an aneurysm of the left common iliac artery in a 78-year-old man. (a) CT angiogram shows a large aneurysm extending from the left common iliac artery to the internal iliac arteries. The aneurysm was treated with embolization of distal branches of the left internal iliac artery followed by stent-graft placement in the left common and external iliac arteries. (b) Angiogram obtained immediately after the procedure shows complete exclusion of the aneurysm. (c) Coronal multiplanar reformatted CT image obtained 2 months later shows complete thrombosis of the aneurysm and patency of the stent-graft.
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Figure 13b. Embolization and stent-graft placement in an ipsilateral internal iliac artery for an aneurysm of the left common iliac artery in a 78-year-old man. (a) CT angiogram shows a large aneurysm extending from the left common iliac artery to the internal iliac arteries. The aneurysm was treated with embolization of distal branches of the left internal iliac artery followed by stent-graft placement in the left common and external iliac arteries. (b) Angiogram obtained immediately after the procedure shows complete exclusion of the aneurysm. (c) Coronal multiplanar reformatted CT image obtained 2 months later shows complete thrombosis of the aneurysm and patency of the stent-graft.
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Figure 13c. Embolization and stent-graft placement in an ipsilateral internal iliac artery for an aneurysm of the left common iliac artery in a 78-year-old man. (a) CT angiogram shows a large aneurysm extending from the left common iliac artery to the internal iliac arteries. The aneurysm was treated with embolization of distal branches of the left internal iliac artery followed by stent-graft placement in the left common and external iliac arteries. (b) Angiogram obtained immediately after the procedure shows complete exclusion of the aneurysm. (c) Coronal multiplanar reformatted CT image obtained 2 months later shows complete thrombosis of the aneurysm and patency of the stent-graft.
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Type IV IAAs
Common IAAs that are less than 2 cm from the aortoiliac bifurcation are difficult to treat with stent-graft placement because of the high risk of endoleaks (type 1 endoleaks according to the conventional terminology used in aortic stent-graft placement), which result from incomplete sealing of the stent-graft at the proximal attachment site. Therefore, such common IAAs can be treated with stent-graft placement in the aorta and a single iliac artery, although this technique necessitates a subsequent femorofemoral crossover bypass procedure to preserve blood flow to the contralateral leg (Fig 14). Generally, stent-graft placement in the aorta and an ipsilateral iliac artery is selected as a first-line option. Stent-graft placement in the aorta and a contralateral iliac artery is advised when the ipsilateral iliac artery is exceedingly tortuous or small (Fig 15). In addition, bifurcated aortoiliac stent-graft placement is an alternative for type IV aneurysms. However, this technique may not be a first-line option because it necessitates sufficient diameter of the lower abdominal aorta for placement of the bifurcated graft and sufficient diameter of the iliac arteries for insertion of the large delivery devices. The technique may be preferred for IAAs with coexisting AAAs.
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Figure 14. Drawings illustrate treatment of a type IV aneurysm of the common iliac artery. The aneurysm is not far enough from the aortoiliac bifurcation to allow proximal embolization.
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Figure 15a. Stent-graft placement in the aorta and a single iliac artery and femorofemoral crossover bypass grafting for an aneurysm of the right common iliac artery in a 78-year-old man. (a, b) Angiogram (a) and coronal multiplanar reformatted CT image (b) show an aneurysm of the right common iliac artery located a short distance from the aortoiliac bifurcation. Mural thrombus is also seen in the aneurysm (arrows in b). The patient underwent stent-graft placement in the lower abdominal aorta and the left common iliac artery and embolization of the right common and internal iliac arteries. Femorofemoral bypass grafting was subsequently performed to preserve blood flow to the right leg. (c) Angiogram obtained immediately after the procedure shows complete exclusion of the common IAA and patency of the femorofemoral bypass graft.
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Figure 15b. Stent-graft placement in the aorta and a single iliac artery and femorofemoral crossover bypass grafting for an aneurysm of the right common iliac artery in a 78-year-old man. (a, b) Angiogram (a) and coronal multiplanar reformatted CT image (b) show an aneurysm of the right common iliac artery located a short distance from the aortoiliac bifurcation. Mural thrombus is also seen in the aneurysm (arrows in b). The patient underwent stent-graft placement in the lower abdominal aorta and the left common iliac artery and embolization of the right common and internal iliac arteries. Femorofemoral bypass grafting was subsequently performed to preserve blood flow to the right leg. (c) Angiogram obtained immediately after the procedure shows complete exclusion of the common IAA and patency of the femorofemoral bypass graft.
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Figure 15c. Stent-graft placement in the aorta and a single iliac artery and femorofemoral crossover bypass grafting for an aneurysm of the right common iliac artery in a 78-year-old man. (a, b) Angiogram (a) and coronal multiplanar reformatted CT image (b) show an aneurysm of the right common iliac artery located a short distance from the aortoiliac bifurcation. Mural thrombus is also seen in the aneurysm (arrows in b). The patient underwent stent-graft placement in the lower abdominal aorta and the left common iliac artery and embolization of the right common and internal iliac arteries. Femorofemoral bypass grafting was subsequently performed to preserve blood flow to the right leg. (c) Angiogram obtained immediately after the procedure shows complete exclusion of the common IAA and patency of the femorofemoral bypass graft.
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Type V IAAs
AAA repair often necessitates placement of a bifurcated graft because involvement of the common iliac arteries is not an infrequent occurrence. The limbs of a bifurcated graft are usually anastomosed end-to-end with the common iliac arteries (Fig 16). Paraanastomotic IAAs that develop after such AAA repair can be treated with embolization of the distal portion of the ipsilateral internal iliac artery followed by stent-graft placement. When the common iliac arteries are affected with aneurysmal or severe atherosclerotic change, the graft limbs may be anastomosed end-to-side with the external iliac or femoral arteries, followed by oversewing of the orifice of the common iliac arteries (Fig 16). This surgical procedure can help preserve retrograde flow to the internal iliac arteries and prevent ischemia of pelvic organs. However, continued perfusion of "cul-de-sac"–shaped common iliac arteries may induce progressive dilatation (Fig 17). Surgical treatment of such IAAs is technically demanding owing to postoperative adhesions. On the other hand, in patients with IAAs that developed after AAA repair performed with distal end-to-side anastomosis to the external iliac or femoral artery, proximal embolization can be safely performed because the proximal portion is long enough to permit embolization (Fig 18) (3,17).
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Figure 17. Drawings illustrate AAA repair in which a bifurcated graft is implanted with the graft limbs anastomosed end-to-side with the external iliac arteries. In cases treated with this method, pelvic circulation is retrograde via the bilateral external iliac arteries, and continued perfusion of cul-de-sac–shaped common iliac arteries may induce progressive dilatation.
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Figure 18a. Proximal and distal embolization for an aneurysm of the right common iliac artery in a 78-year-old man. The patient had a history of AAA repair in which a bifurcated graft was implanted with the graft limbs anastomosed end-to-side with the external iliac arteries. (a) MR angiogram obtained 10 years after AAA repair shows an aneurysm of the right common iliac artery. (b) Angiogram obtained after the injection of contrast material into the right external iliac artery shows the fusiform aneurysm and retrograde enhancement of the right graft limb. (c) Immediate postembolization angiogram shows complete exclusion of the aneurysm.
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Figure 18b. Proximal and distal embolization for an aneurysm of the right common iliac artery in a 78-year-old man. The patient had a history of AAA repair in which a bifurcated graft was implanted with the graft limbs anastomosed end-to-side with the external iliac arteries. (a) MR angiogram obtained 10 years after AAA repair shows an aneurysm of the right common iliac artery. (b) Angiogram obtained after the injection of contrast material into the right external iliac artery shows the fusiform aneurysm and retrograde enhancement of the right graft limb. (c) Immediate postembolization angiogram shows complete exclusion of the aneurysm.
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Figure 18c. Proximal and distal embolization for an aneurysm of the right common iliac artery in a 78-year-old man. The patient had a history of AAA repair in which a bifurcated graft was implanted with the graft limbs anastomosed end-to-side with the external iliac arteries. (a) MR angiogram obtained 10 years after AAA repair shows an aneurysm of the right common iliac artery. (b) Angiogram obtained after the injection of contrast material into the right external iliac artery shows the fusiform aneurysm and retrograde enhancement of the right graft limb. (c) Immediate postembolization angiogram shows complete exclusion of the aneurysm.
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Follow-up Imaging
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Contrast material–enhanced CT is routinely performed 1 week, 1 month, 3 months, and 6 months after endovascular treatment and at 6-month intervals thereafter. In most cases, immediate and long-term thrombosis of IAAs can be achieved with endovascular treatment. However, regardless of the therapeutic option used, the treated aneurysm usually shows a gradual reduction in size over time. Therefore, regular imaging follow-up is essential, not only after stent-graft placement but also after embolotherapy alone.
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Complications of Endovascular Treatment for IAAs
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In a minority of cases, complications will occur after endovascular treatment for IAAs. Most of these complications can be accurately diagnosed and afterward managed with minimally invasive techniques. Therefore, interventional radiologists should be aware of possible complications, which will help in preventing or precisely treating these complications.
Postimplantation Syndrome and Postembolization Syndrome
After undergoing stent-graft insertion or coil embolization, patients may experience postimplantation syndrome or postembolization syndrome, consisting of low-grade fever, abdominal pain, mild leukocytosis, and elevation of the C-reactive protein level (18,19). These syndromes are usually self limiting and resolve within 1 week without special treatment.
Iliac Artery Injury
Iliac artery injury is a complication that may occur when the delivery system for stent-graft placement is advanced through a small or tortuous iliac artery (20). According to Tillich et al (21), a high degree of tortuosity is a risk factor for the development of iliac artery injuries in patients undergoing transfemoral delivery of endovascular devices, whereas there is no statistically significant difference between the mean diameter of dissected iliac arteries and that of nondissected arteries. Therefore, the minimum diameter of iliac arteries that is required for the transport of the stent-graft seems to be difficult to determine. The need for iliac angioplasty prior to stent-graft insertion may best be determined on the basis of several predisposing factors such as the size, calcification, and tortuosity of the iliac arteries and the size of the delivery device.
Iliac artery injury should be managed promptly because of the risk of subsequent arterial thrombosis and distal ischemia. Most iliac artery injuries can be treated with stent placement (Fig 19), although some cases may necessitate surgery (endarterectomy or bypass procedure) (22).
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Figure 19a. Iliac artery injury with subsequent stent-graft thrombosis. (a) Angiogram obtained immediately after stent-graft placement for an aneurysm of the right common iliac artery shows acute thrombosis of the stent-graft. The patient subsequently underwent thrombectomy. (b) Angiogram obtained immediately after thrombectomy shows recanalization of the stent-graft and severe stenosis of the right external iliac artery (arrow) caused by insertion of the delivery system. (c) Angiogram obtained after stent placement in the stenosed lesion shows restoration of the luminal diameter.
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Figure 19b. Iliac artery injury with subsequent stent-graft thrombosis. (a) Angiogram obtained immediately after stent-graft placement for an aneurysm of the right common iliac artery shows acute thrombosis of the stent-graft. The patient subsequently underwent thrombectomy. (b) Angiogram obtained immediately after thrombectomy shows recanalization of the stent-graft and severe stenosis of the right external iliac artery (arrow) caused by insertion of the delivery system. (c) Angiogram obtained after stent placement in the stenosed lesion shows restoration of the luminal diameter.
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Abstract
Introduction
