Asian Cardiovasc Thorac Ann 2007;15:280-284
© 2007 Asia Publishing EXchange Ltd
Strategy for Isolated Iliac Artery Aneurysms
Shinichi Hiromatsu, MD,
Yukio Hosokawa, MD,
Noriko Egawa, MD,
Hiroko Yokokura, MD,
Keiichi Akaiwa, MD,
Shigeaki Aoyagi, MD
Department of Surgery, Kurume University School of Medicine, Fukuoka-ken, Japan
For reprint information contact: Shinichi Hiromatsu, MD Tel: 81 94 235 3311 Fax: 81 94 235 8967 Email: kaeru{at}med.kurume-u.ac.jp, Department of Surgery Kurume University School of Medicine, 67 Asahi-machi, Kurume-shi, Fukuoka-ken, 830-0011 Japan.
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ABSTRACT
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We retrospectively reviewed 41 patients with isolated iliac artery aneurysms presenting over a 21-year period. The mean age was 72 years. Mean aneurysmal diameter was 6.0 cm (range, 3.2–13 cm). The aneurysms were located in the common iliac artery in 31 patients, internal iliac artery in 7, and both arteries in 3. Rupture occurred in 20 patients (49%). The frequency of rupture of isolated iliac artery aneurysms was significantly higher than that of abdominal aortic aneurysms (8%) during the same period. The 30-day mortality was 9.8%; death in all 4 patients was due to rupture of the aneurysm. The surgical procedure was aneurysmectomy and replacement with a bifurcated prosthetic graft in 24 patients (59%), closure of the common iliac artery with a femorofemoral crossover in 7, minilaparotomy in 3, thromboexclusion in 6, and endoluminal stent-graft repair in one. In contrast to abdominal aortic aneurysms, isolated iliac artery aneurysms can be treated by various methods other than replacement with a bifurcated prosthetic graft. When selecting a strategy for such aneurysms, it is important to choose an approach appropriate to the location and risk, because of the frequency of rupture.
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INTRODUCTION
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Isolated iliac artery aneurysm (IAA) has been encountered infrequently in the past, comprising 0.9% to 4.7% of all intra-abdominal aneurysms in a review of older studies, whereas in recent times, many asymptomatic IAAs have been detected incidentally as a result of the widespread use of abdominal ultrasonography and computed tomography.1–3 The relative frequency of isolated IAA compared to abdominal aortic aneurysm (AAA) ranges from 5.1% to 19.4%.4 Isolated IAA can be treated by choosing a suitable method based on the risk or location of the aneurysm because there are more surgical procedures for IAA than AAA. The aim of this study was to develop a strategy for isolated IAA by reviewing our experience of the disease over a 21-year period.
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PATIENTS AND METHODS
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We retrospectively reviewed 41 patients with a diagnosis of isolated IAA who were seen at the Kurume University School of Medicine Hospital during a 21-year period extending from January 1983 to December 2003. Only patients with aneurysms limited to the common, external, or internal iliac arteries were included. Those with iliac artery aneurysms associated with AAA were excluded. The relative and absolute surgical indications for isolated IAA were diameters of at least 3 cm and 4 cm, respectively. The mean age of the patients was 73.0 ± 7.9 years (range, 53–85 years); 35 were men and 6 were women. The medical records of each patient were reviewed to determine the location of the aneurysm, symptoms, physical findings, and the surgical procedures employed. The incidence of ruptured IAA according to location was calculated. A comparison was made between ruptured AAA and ruptured IAA. The results of our series were compared with reported series of isolated IAA with regard to hospital mortality.
The groups were compared by Student’s t test or the chi-squared test, using Stat-View software (SAS Institute, Cary, NC, USA). A p value < 0.05 was considered statistically significant.
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RESULTS
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Forty-one patients had 53 isolated IAAs; 31 had common iliac artery aneurysms (CIAAs), 7 had internal iliac artery aneurysms (IIAAs), and 3 had both CIAA and IIAA. Twenty-nine (71%) patients had unilateral isolated IAAs and 12 (29%) had bilateral IAAs. There were 25 aneurysms on the right side and 28 on the left. Forty aneurysms (75%) were located in the common iliac artery and 13 (25%) were in the internal iliac artery. There were no aneurysms in the external iliac artery.
Twenty-nine patients (71%) had symptoms, 8 of whom had an unruptured aneurysm. The most frequent presenting symptom was lower abdominal pain due to rupture in 17 patients and without rupture in 2, while 2 patients with lower abdominal pain due to rupture presented with leg pain. Three patients without rupture presented with leg pain resulting from pressure on nerve roots. One patient without rupture presented with a swollen leg from iliofemoral thrombosis secondary to pressure from an expanding CIAA, and one who complained of a swollen leg presented with an arteriovenous fistula. Three patients with rupture presented with subcutaneous hematoma, hematuria, or bloody stools. Eleven of the 20 patients (52%) with unruptured aneurysms had no symptoms, and only 4/20 had a palpable abdominal mass.
The IAAs ruptured in 20 (49%) patients; 13 of 31 CIAAs and all 7 IIAAs ruptured. The maximum IAA diameters ranged from 3.2 to 13 cm (mean, 6.0 ± 1.9 cm). The diameters of those that ruptured ranged from 5.0 to 13.0 cm (mean, 6.8 ± 2.1 cm), whereas the unruptured IAAs had diameters of 3.2 to 7.5 cm (mean, 4.8 ± 1.1 cm; p = 0.0002). During the same period, 658 patients with AAA underwent surgery, of which 53 had a ruptured aneurysm (8%). The frequency of rupture of IAAs was significantly greater than that of AAAs (p = 0.0008). The median maximum diameters measured by preoperative computed tomography were 7.2 ± 1.6 cm for ruptured AAAs and 6.8 ± 2.1 cm for ruptured IAAs. There was no significant difference between the two groups; however, compared to the diameter of the normal artery, IAAs became relatively larger than AAAs when rupture occurred. The emergency room at our facility is equipped for computed tomography so that even if a patient is in shock, providing they are not in cardiac arrest, we can quickly obtain a scan while giving a blood transfusion or administering a hypertensive agent, so it was possible to measure the diameters of the aneurysms and make an accurate diagnosis before surgery in all patients, even in those whose aneurysm had ruptured.
The surgical strategy was tailored to the general health status of the patient and specific arterial aneurysmal anatomy. All 6 patients with bilateral CIAAs underwent open resection. In 25 patients with a unilateral CIAA, open resection was performed in 18 and thromboexclusion in 7. Endoaneurysmorrhaphy was carried out in 3 of the 7 patients with bilateral IIAAs; the other 4 had thromboexclusion. To shorten the operation time, thromboexclusion of IIAA was applied in 3 patients in shock due to rupture or with impending rupture. The incidences of reconstructive and combined procedures are depicted in Figure 1
. For CIAA, a bifurcated graft was placed in 21 patients, with re-implantation of the inferior mesenteric artery in 3 and left internal iliac artery bypass grafting using a Dacron graft in 2. Femorofemoral artery bypass grafting with coil embolization or ligation of the neck of the aneurysm was performed in 7 patients. Aorta-external iliac artery bypass or aortofemoral bypass grafting with minimally invasive vascular surgical techniques was undertaken in 3 patients. Reconstruction was carried out in 3 cases of IIAA. Aortobifemoral bypass was instituted in one patient, and aorta-external iliac bypass in 2. Thromboexclusion without reconstruction of the internal iliac artery was conducted in 4 cases. Thromboexclusion was performed in 6 of 7 IIAAs.
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Figure 1. Surgical procedures for isolated iliac artery aneurysms in our clinic. CIA = common iliac artery, F-F = femorofemoral, IIA = internal iliac artery.
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The 30-day mortality rate for CIAA was 4.89% (2/41) and 6.45% (2/31) for IIAA. All 21 patients who underwent elective surgery survived the operation. Four (20%) of the 20 patients who underwent emergency surgery for rupture died postoperatively. The cause of death was multiple organ failure due to continued shock in one case, sepsis due to rupture into the sigmoid colon in one, and hemorrhagic shock due to recurrent rupture in the patient who underwent only ligation of IIA. One patient died after 2 weeks due to sepsis caused by perforation of the ileum. The 30-day mortality rate for all isolated IAAs was 9.8% (4/41). The 30-day mortality rate was 20% for ruptured isolated IAA and 26.4% for ruptured AAA; there was no significant difference between the two groups.
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DISCUSSION
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A total of 198 patients with isolated iliac aneurysms described in the Japanese literature were compared with our series (Table 1).5–8 It is generally agreed that the most common cause of an aneurysm is arteriosclerosis. If an aortic bifurcation becomes an obtuse angle in arteriosclerosis, rather than an acute angle, which is not morbid, the pulsation waves will be reflected more strongly.9 This may account for the high incidence of abdominal aneurysms. Common iliac artery aneurysm and IIAA may easily arise because waves forming at the bifurcation due to shortening of the distance to the reflection of the pulse bifurcation of the CIA and IIA are generated more strongly. However, since the external iliac artery does not have any branches until it becomes the common femoral artery, reflection of a pulsation wave does not readily occur, which is believed to be the reason external iliac artery aneurysms do not easily form. Furthermore, since the distance to a branch of the CIA or IIA is short, an aneurysm uses the branch as a fulcrum, making extension in the direction of the long axis difficult for isolated IAAs, thereby further expanding the short axis diameter of isolated IAAs more easily. We believe that this is the cause of rupture in many cases.
The incidence of ruptured isolated IAA was significantly higher than that of ruptured AAA in our series and previous studies.10 There was no significant difference in the mortality rates between our series and previous studies (9.6% and 9.8%, respectively). Except for the one patient treated by elective surgical repair who died of a pulmonary embolism, those with ruptured isolated IAAs who underwent emergency repair died perioperatively both in our series and in previous series. Due to the risk of rupture, we recommend surgical repair as early as possible when an isolated IAA is diagnosed.
Most physicians recommend that patients with an isolated IAA larger than 3 cm in diameter, who are otherwise good operative risks (no neurologic disorder, not bedridden, and not in the terminal stage of a malignant disease), should undergo elective repair.10 We believe that the presence of an isolated IAA has a significant impact on life-expectancy because of the high rate of rupture and associated high mortality rate. The prognosis of isolated IAA is not clearly understood. The strategy differs for CIAA and IIAA. Furthermore, each type has two categories: high risk and low risk. Figure 2 presents the strategy for the treatment approach of CIAA. High-risk patients with a unilateral CIAA are managed by thromboexclusion with a coil or ligation of the proximal aneurysm neck requiring femorofemoral bypass, while those at low risk are treated by aneurysmectomy with a bifurcated interposition prosthetic graft or local interposition graft.11 For bilateral CIAAs, high-risk patients are managed by thromboexclusion with a bifurcated interposition prosthetic graft, while low-risk patients are treated by aneurysmectomy with a bifurcated interposition prosthetic graft. Figure 3 illustrates the strategy for the treatment approach of IIAA. High-risk patients with an unilateral IIAA are managed by thromboexclusion with a coil or ligation of the proximal neck of the aneurysm, and those at low risk are treated by endoaneurysmorrhaphy without re-implantation of the IIA. For bilateral IIAAs, high-risk patients are managed by thromboexclusion with a coil or ligation of the proximal aneurysm neck, while those at low risk are treated by endoaneurysmorrhaphy with a bifurcated interposition prosthetic graft requiring unilateral IIA re-implantation.
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Figure 2. Strategy for treatment of common iliac artery aneurysms (CIAA). F-F = femorofemoral, MIVS = minimally invasive vascular surgery.
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As described previously, various procedures for treating IIAAs are available.12 Internal iliac artery aneurysms may be misdiagnosed because nonspecific symptoms of IAA result from pressure or erosion on adjacent structures, such as hydroureteronephrosis, hematuria, femoral or obturator neurological symptoms, and bloody stool, especially in the absence of a pulsatile mass.5–7 Iliac aneurysms will be discovered early if the orthopedic surgeon, urologist, or gynecologist suspects an aneurysm, so it is important for them to suspect the presence of this disease. As isolated IAAs can be treated by percutaneous techniques under local anesthesia, older patients at high risk may also be candidates for treatment.6 In addition, as none of the patients who were waiting for surgery died during the perioperative period, we believe our treatment policy was correct.
Recently, great enthusiasm has been expressed for percutaneous endovascular stent-graft repair of isolated IAAs.13–17 In one patient in our series who underwent such a repair, the size of the aneurysm remained decreased and stable 5 years after the procedure. Casana and colleagues13 reported that all patients underwent successful endovascular treatment of isolated IAA, although the median follow-up period was only 18 months. However, Krupski and colleagues18 suggested that surgical repair might be more durable and effective than percutaneous techniques because the long-term result is still uncertain. We believe that placement of stent-grafts may become the treatment of choice for isolated IAAs in the future, assuming improvements in equipment and good long-term results. When performing endovascular aortic repair for CIAA in our department, we insert a taper-type device from the abdominal aorta to the diseased external iliac artery, while for the iliac artery on the opposite side, we fenestrate a stent graft to maintain blood flow. Thus, the indications for endovascular aortic repair are: a unilateral CIAA, neck of the aneurysm 
1 cm, diameter of external iliac artery where stent graft will be inserted 8 mm, and the possibility that the contralateral IIA can be preserved. Patients who met all 4 of these criteria were included in the study. Recently, we have considered treating IIAA also with a stent graft; a surgical procedure that is the same as inserting a stent graft for CIAA and involves adding coil embolectomy peripherally in the IIAA.
We recommend surgery even if the patient is at high risk, because various procedures are available for the treatment of isolated IAAs, depending on the condition of the patient and the location of the aneurysm. Surgery should be performed as early as possible when an isolated IAA is diagnosed, because of the possibility of rupture. We undertake surgery even if the patient has a concomitant disease, because treatment of isolated IAAs can be performed by minimally invasive vascular surgery, other than replacement with a bifurcated prosthetic graft. Any strategy for isolated IAA should be tailored to the health status of the patient and specific arterial aneurysmal anatomy.
Presented by poster at the 13th Annual Meeting of the Asian Society for Cardiovascular Surgery, Chiang Mai, Thailand, February 5–8, 2005.
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ABSTRACT
INTRODUCTION
