Surgical treatment of aorto-iliac occlusive disease without preoperative arteriography
(Portuguese PDF version)

Ricardo C. Rocha Moreira1

1. Chief of Prof. Dr. Elias Abrão Service of Vascular Surgery - Hospital Nossa Senhora das Graças and University Hospital Cajuru - PUC-PR, Curitiba PR.

Correspondence:
Ricardo C. Rocha Moreira
Rua Pedro Muraro, 50 casa 24
CEP : 82030-620 - Curitiba - PR

ABSTRACT

Aortoiliac occlusive disease (AIOD) is one of the most frequent clinical problems faced by vascular surgeons in terms of assessment and treatment. Traditionally, contrast arteriography (CA) has been the diagnostic exam of choice for AIOD. However, CA has several disadvantages as a diagnostic method: it is invasive, uncomfortable, expensive and associated with the risk of severe complications. The present article reviews the new imaging exams used for the assessment of AIOD, and their application in surgical practice. Four imaging exams are presented: contrast arteriography (CA), Doppler ultrasound (DUS), computed axial tomography angiography (angio-CT) and magnetic resonance angiography (angio-MRI). In addition, the author analyzes these methods, by using his extensive experience in surgery of the extracranial carotids without preoperative arteriography. The author concludes that the future of the diagnosis of patients with AIOD lies in minimally invasive exams. The role of traditional catheter arteriography would be restricted to interventional procedures.

Key words: Doppler ultrasonography, magnetic resonance angiography, surgery, angiography
 Palavras-chave: ultra-sonografia doppler, angiografia por ressonância magnética, cirurgia, arteriografia.

J Vasc Br 2002;1(1):47-54.

INTRODUCTION

The distal abdominal aorta and the iliac arteries are amongst the arterial segments most commonly affected by atherosclerosis.1,2 The resulting clinical entity, known as aorto-iliac atherosclerosis obliterans or aorto-iliac occlusive disease (AIOD), is one of the most frequent clinical problems confronted by vascular surgeons.3

Clinically, AIOD presents as lower limb ischemia. The characteristic clinical picture of advanced AIOD is known as Leriche syndrome, which consists of a triad of symptoms: intermittent claudication, absent femoral pulses and sexual impotence. However, the vast majority of patients with aorto-iliac occlusive disease do not have the classical Leriche syndrome; instead, they have chronic lower-extremity ischemia, of variable severity.4

The clinical presentation and natural history of aorto-iliac occlusive disease are influenced by the location of the atheromatous plaques and by the degree of stenosis. Brewster4 has proposed an anatomo-pathological classification of aorto-iliac occlusive disease into three types: type I: the disease is limited to the infrarenal aorta and the common iliac arteries; type II: diffuse disease of the aorto-iliac segment, from the aorta to the femoral artery; type III: multisegmentar occlusive disease, including the aorto-iliac segment and the infrainguinal arteries. Usually, patients with type I and II lesions are relatively young and present with intermittent claudication. Patients with occlusive disease in multiple arterial segments (type III) have severe lower-extremity ischemia. In these cases, the lesions of the aorto-iliac segment can be the sole cause of ischemia or have a secondary role, by reducing the inflow to the femoral artery and its branches, that are also extensively damaged by atherosclerosis.

Contrast arteriography (CA) is the traditional diagnostic exam for AIOD. CA clearly shows the morphological changes caused by atherosclerosis in the abdominal aorta and in the arteries of the lower limbs, thus allowing for proper planning of treatment.5 Although traditionally acclaimed, CA has several disadvantages as a diagnostic method: it is invasive, uncomfortable, expensive and associated with the risk of severe complications. Over the last 20 years, technological advances have provided other methods to assess the aorto-iliac segment. The present article reviews those new imaging methods for the diagnosis of AIOD, as well as their application in surgical practice.

DIAGNOSTIC EXAMS IN AORTOILIAC OCCLUSIVE DISEASE (AIOD)

The initial diagnosis of patients with lower-limb occlusive arterial disease is based on clinical examination. Imaging exams should be used to confirm the clinical diagnosis and to locate exactly the pathological process, thus allowing better treatment planning. At present, four imaging methods are used for evaluation of suspected AIOD: contrast arteriography (CA), Doppler ultrasound (DUS), computed axial tomographic angiography (angio-CT) (Figure 1) and magnetic resonance angiography (angio-MRI) (Figure 2). The latter three methods are regarded as alternative exams to traditional CA and are discussed individually.

click hereFigure 1 - Angio-CT of aorto-iliac segment showing AIDO.

click hereFigure 2 - Angio-MRI showing AIDO.

In the present review, the emphasis is placed upon DUS, for three reasons: a) the literature is richer in clinical experience with DUS than with the other two methods; b) DUS is available in almost all Vascular Surgery Services in Brazil, but angio-CT and angio-MRI are not; and c) the author has personal experience with DUS, and is conducting a line of research on its application in the management of patients with arterial diseases.

DOPPLER ULTRASOUND (DUS)

Ultrasound technology began to be applied in the evaluation of the cardiovascular system in the 60's. At that time, devices called Doppler flowmeters were developed. Those devices employed continuous ultrasound waves and the so-called Doppler effect to detect flow in blood vessels with a transducer. In the 70's, the first ultrasound imaging systems were developed. These systems used pulsed ultrasound waves that, reflected heterogeneously through several tissues, formed a real-time two-dimensional image. This type of ultrasonography, called mode B (which stands for Brightness) was used for studying venous and arterial anatomy and for detecting pathological processes, such as venous thrombosis and aneurysms. The next step was to combine the two types of ultrasound (mode B imaging and pulsed Doppler flowmeter) into a single device. The result of this association was called Doppler ultrasound or duplex scanning.6 This new technology allowed imaging the anatomic changes in a vascular segment and, at the same time, obtaining information about the blood flow in that segment. Throughout the 1980's, Doppler ultrasound devices were improved, and a major breakthrough was the introduction of color flow imaging or color-coded echo-Doppler. Color-flow techniques made it much easier to image deep arteries, such as the aorta and its branches, and vessels with slow blood flow, such as the veins and arteries distal to occluded segments.

DUS has the following advantages, when compared with CA: it is noninvasive; it provides images of arterial anatomy, as well as physiological information; it is much less expensive; and the risk of complications risk is zero. DUS presents only one disadvantage as a diagnostic method :it is an exam that completely depend on the skills and experience of the examiner. Since it became popular at the end of the 1980's, DUS has completely changed the diagnosis of several vascular disorders. DUS has partially replaced arteriography in the assessment of extracranial carotid and it has been increasingly used for the diagnosis of lower-limb arterial occlusive disease.7,8

With the advent of DUS in the early 1980's, several studies were conducted with the objective of comparing this new method with arteriography for the evaluation of the aorto-iliac segment. In 1984, Rubba et al. published the first comparative study between CA and DUS, and concluded that DUS seemed to be a promising method for the evaluation of the aorto-iliac segment.9 From 1985 on, Strandness and his team at the University of Washington, in Seattle, USA, have popularized DUS as an accurate method for the initial investigation of patients with suspected lower-limb arterial occlusive disease.10,11

In 1989, Cossmann et al. reported the first study on the use of color-flow imaging for the detection of lower-limb arterial occlusive disease.12 The authors concluded that the color imaging exam was not only more accurate, but also easier to perform than its black-and-white counterpart. Those authors for the first time suggested that DUS could potentially replace arteriography in the assessment of selected cases of lower-extremity ischemia.

Starting in 1989, Legemate et al. published a series of studies on Doppler ultrasound exam of the aorto-iliac segment. The studies conducted by this Dutch group were crucial for the development and popularization of DUS as a method of evaluation of the aorto-iliac segment.13,14,15,16,17 In 1991, they published two studies, which showed a good correlation between DUS and CA with digital subtraction. However, the correlation of these methods with arterial manometry was only fair, when the latter was regarded as the "gold standard". The authors concluded that DUS could replace conventional arteriography in most cases. The role of arterial manometry consisted in clarifying the hemodynamic significance of some borderline lesions detected by DUS or CA.14,15

In 1992, Moneta et al. compared arterial ultrasonographic "mapping" of lower limbs with arteriography in a series of 150 consecutive patients.18 The authors concluded that Doppler ultrasound was excellent for the assessment of the aorto-iliac segment and good for the femoro-popliteal segment.

Currie et al. compared several methods of evaluation of the aorto-iliac segment: clinical examination, DUS, CA, arterial manometry, and angio-MRI (Figure 3).19 Two findings of this study are noteworthy: the clinical examination was only reliable when there was occlusion proximal to the femoral artery and DUS was more accurate than angio-MRI in the detection of significant stenosis. Their conclusion was that the best noninvasive evaluation method for the aorto-iliac segment was DUS. The same authors report a modification in the DUS exam for the evaluation of the aorto-iliac segment: post-occlusive hyperemic duplex scanning.20 The modification consisted of temporary interruption of blood flow to the limb with an sphygmomanometer inflated above the systolic pressure, which was then released in order to cause reactive hyperemia. The augmented blood flow thus induced increased the accuracy of DUS in the detection of stenosis.

click hereFigure 3 - Stenosis of the iliac artery shown on DUS and CA.

Despite the methodological differences among the several studies, the extensive review of comparative studies allows for some conclusions regarding the value of DUS in the assessment of AIOD.21,22

1. the exam can be performed in practically all patients, provided that a fasting period of 8 to 12 hours is followed before the exam. In some patients, it is necessary to administer substances that reduce the amount of intestinal gases;

2. color flow imaging makes it much easier to perform the exam and improves its accuracy;

3. the accuracy rate in the detection of hemodynamically significant lesions of the aorto-iliac segment is consistently greater than 90%, in studies that set CA as the "gold standard";

4. accuracy increases when the exam is carried out in conditions of augmented blood flow, such as in post-occlusive reactive hyperemia.

In Brazil, the use of DUS for the diagnosis of AIOD seems to be quite limited. Except for an abstract published in the annals of a congress,23 there are no clinical studies published in Brazil on the use of Doppler ultrasound for the evaluation of the aorto-iliac segment.

COMPUTED TOMOGRAPHIC ANGIOGRAPHY (Angio-CT)

AComputed axial tomography (CAT scan) was developed in England in the 1970's. Initially used for imaging the skull and encephalon, CAT scan's use was later extended to other regions, such as the trunk and limbs. The development of helical (or spiral) CT has greatly reduced the time for the acquisition of images and has allowed its application to imaging the aorta and other vessels with rapid blood flow.24 Since the early 1990's, computed axial tomography (CAT-angiography) has been widely used for vascular evaluation and is currently considered the exam of choice for planning the surgical or endovascular treatment of aortic aneurysms. Comparative studies clearly show that CAT-angiography is as accurate as CA for the evaluation of the aorto-iliac segment.25,26,27 Nevertheless, CAT-angiography has been little used for the management of AIOD, when the patient does not have an associated aneurysm.24

Raptopoulos et al. and Ricker et al. studied angio-CT in patients with AIOD, comparing it to digital subtraction CA.25,26 They concluded that angio-C had perfect accuracy in severe occlusions and stenosis (> 80%). In intermediate stenosis and in very calcified iliac arteries, angio-CT showed strong limitations, even with help of sophisticated CT reformatting techniques.

More recently, Tins, Oxtoby and Patel studied 35 patients with AOID, comparing angio-CT with CA.27 The authors found excellent correlation between both exams, except in patients with short iliac stenosis. Those results were confirmed by Rubin et al., by means of an ultrafast CT scanner.28 In all those studies, the authors emphasize the advantages of CAT-angiography: it is minimally invasive, ii is performed with intravenous injection of contrast, thus not requiring arterial puncture, and it is not time-consuming (less than 5 min duration).

Angio-CT has yet been routinely used as an exam for the investigation of AIOD, but its advantages make it an excellent option in special situations, such as: patients in whom arterial catheterization is difficult; patients with both aortic aneurysms and AIOD; patients with a pacemaker or metallic prostheses (who should not undergo MRI); and claustrophobic patients.24

MAGNETIC RESONANCE ANGIOGRAPHY (Angio-MRI)

Magnetic resonance is a physical phenomenon that has been used for obtaining images of tissues without exposing the patient to ionizing radiation, as it occurs with CA and CAT angiography. Magnetic resonance imaging (MRI) has revolutionized diagnosis in several medical specialties, such as Neurology. The continuous improvement of MRI equipment has made it possible to obtain images of blood vessels, with the use of a special, noniodinated contrast agent. This new form of MR, which uses sophisticated 3D image reformatting techniques, is known as magnetic resonance angiography (angio-MRI).29

Pioneer investigative studies of angio-MRI in patients with lower-limb arterial occlusive disease date back to the early 1990's.30,31,32 Toese studies showed that the new technique was highly accurate to show arterial occlusions and stenosis from the abdominal aorta down to the arteries of the foot. An important aspect is that MRA is able to image small-diameter arteries distal to occluded arteries, which can be missed in conventional angiography. Over the past 10 years, a series of studies using a wide variety of MR imaging techniques have been performed on patients with AIOD, associated or not with aortic aneurysms. The systematic review of those studies allows some conclusions on the importance of angio-MRI in the investigation of lower-limb arterial occlusive disease:33,34,35

1. most patients tolerate angio-MRI very well (except for some claustrophobic patients);

2. the accuracy is practically the same of CA;

3. the risk of complications is null;

4. the cost of angio-MRI is lower than the cost of CA.

In short, angio-MRI can advantageously replace CA in the vast majority of patients with lower-limb arterial occlusive disease, both in the aorto-iliac and in infrainguinal segments.

SURGERY OF THE AORTOILIAC SEGMENT WITHOUT PREOPERATIVE ARTERIOGRAPHY: clinical experience

The improvement of other imaging exams notwithstanding, CA continues to be the exam of choice in the vast majority of services that treat patients with AIOD in Brazil. The preference for CA can be explained by several factors, including: widespread availability and familiarity with the exam, the fact that most vascular surgeons still perform their own arteriographies and, certainly, the tradition of nearly 50 years of clinical practice.3,5

Over the last decade, the pioneer studies described in the previous sections have changed many vascular surgeons' decision-making to the new imaging exams. That change especially occurred in the treatment of aortic aneurysms and of occlusive extracranial carotid disease. More recently, patients with lower-limb occlusive disease have also been undergoing surgical or endovascular treatment, based exclusively on the new imaging methods analyzed in the previous section.

SURGERY FOR AIOD BASED ON DUS

Arterial "mapping" with DUS can be done from the aorta (at the level of renal arteries) to the arteries of the foot. The studies discussed in the previous section have clearly shown that DUS can safely replace CA in almost all patients. However, only in the last decade surgeons have been making decisions started based on DUS .

Vashisht et al. and van der Heidjen et al. reported the first studies in which DUS was used to select patients with AIOD for percutaneous angioplasty.36,37 Both studies concluded that an adequate DUS could avoid diagnostic CA in almost all cases of AIOD amenable to treatment with percutaneous angioplasty. Thus, it would not be necessary to subject the patients to two arteriographies.

Over the past few years, investigators from different countries have reported series of patients with AIOD treated by open surgery or percutaneous angioplasty, in whom clinical decisions were exclusively based on DUS.38,39,40,41,42,43 From those reports, it is possible to conclude that DUS can be used as the sole pre-operative exam in patients with AIOD, provided that the surgical service has highly qualified personnel to perform vascular DUS.

SURGERY FOR AIOD BASED ON CAT ANGIOGRAPHY

TAs mentioned above, CAT angiography has been widely used for the evaluation of abdominal aortic aneurysms. In patients with aneurysms associated with AIOD, angio-CT can be used as the sole preoperative exam, because the surgical treatment of aneurysm includes the correction of associated occlusive lesions.

No study on the use of CAT angiography as the sole preoperative exam in patients with isolated AIOD could be found in literature. Nevertheless, in some special situations that were previously described, CAT angiography can be used for this purpose. An example would be a patient with missing femoral pulses, admitted to a center or clinic where MRI equipment is not available. In this case, CAT angiography could be advantageously used, since it is noninvasive, quicker and less expensive than CA.

SURGERY FOR AIOD BASED ON MRA

The experience with angio-MRI as the sole preoperative exam in patients with AIOD has increased over the past decade. The first series of patients undergoing surgery for AIOD with angio-MRI as the only preoperative exam was published by Cambria et al. in 1993.30 The following year, Carpenter et al. reported a large series of arterial reconstructions of the lower limbs, using angio-MRI as the sole preoperative exam.32 Among 80 patients, 11 underwent reconstruction of the aorto-iliac segment. The authors concluded that angio-MRI was adequate in all cases, except for two claustrophobic patients who could not complete the exam. The authors concluded that the use of angio-MRI resulted in reduced costs, besides avoiding CA, with its known disadvantages.

Since then, several studies on the use of MRA as the only preoperative imaging technique for patients with AIOD have been published.44,45,46,47,48,49 The overall conclusion is that angio-MRI can safely replace CA in the preoperative investigation of most patients with AIOD.

AUTHOR'S EXPERIENCE

The author, at the Prof. Dr. Elias Abrão Division of Vascular Surgery (Hospital Nossa Senhora das Graças and University Hospital Cajuru, PUC-PR), in the city of Curitiba, in southern Brazil, has a large of performing surgery for extracranial carotid artery without the use of preoperative arteriography. Out of that experience, the author had the idea to investigate DUS in the evaluation of patients with lower-limb arterial occlusive disease. The initial study was focused on patients with suspected AIOD. From 1996 to 2000, a total of 125 patients were prospectively studied with DUS and CA, comparing the two exams in 552 segments of the infrarenal aorta and of the common and external iliac arteries. The conclusion is that DUS had a high level of validity and optimal correlation coefficients with CA in the investigation of suspected AIOD.50

Based on that study, the author decided to perform surgery in the aorto-iliac segment in selected patients, without preoperative arteriography. Over the past two years, 13 patients with AIOD underwent surgical intervention in the aorto-iliac segment, based on DUS (11 cases) and on angio-MRI (two cases). Those 13 cases represent 18% of the patients with AIOD surgically treated at the Service during that period. The indications not to perform pre-operative arterography were difficult arterial puncture in five cases and allergy to iodinated contrast in one case. In the remaining cases, the surgeon considered the imaging exam (DUS or MRA) to be sufficient for clinical decision, thus eliminating the need for arteriography. In all 13 cases, the intraoperative findings correlated with DUS or angio-MRI. No postoperative complication could be attributed to the accuracy (or lack thereof) of the preoperative exams.

CONCLUSIONS

The present study allows for some conclusions about the management of AIOD without preoperative arteriography

1. at present, the vascular surgeon has excellent alternatives to CA when deciding on diagnostic exams of patients with AIOD ;

2. DUS is an excellent exam for initial investigation, since it is noninvasive, risk-free and relatively inexpensive;

3. DUS can be used as the definitive exam in two situations:

a) to rule out the presence of hemodynamically significant AIOD, proximal to infrainguinal occlusive disease; and,

b) in cases of total abdominal aortic occlusion (Figure 4), with normal infrainguinal arteries. In both situations, CA is not required, since it does not add to the surgical decision-making process.

click hereFigure 4 - Abdominal aortic occlusion, shown through color DUS.

4. CAT angiography can be used as an alternative to CA in patients whose arterial puncture is difficult (ex.: occlusion of two iliac and/or femoral arteries);

5. Angio-MRI is the best imaging method currently available for the investigation of patients with suspected AIOD. However, due to its scarce availability in Brazil and to its high cost, it should be reserved for patients in whom satisfactory aorto-iliac DUS cannot be performed.

The overall conclusion is that the future of the diagnosis of patients with AIOD is based on minimally invasive exams. The role of CA - conventional catheter arteriography - should be restricted to interventional procedures, such percutaneous angioplasty and implantation of endoprosthesis.

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