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Surgical Management of Aortoiliac Occlusive Disease
In the Western world, atherosclerotic occlusive disease of the abdominal aorta and iliac arteries is a common cause of lower extremity ischemia in middle-aged and elderly patients. Although not as common as occlusive disease of the femoropopliteal arterial system, with which it may be combined, aortoiliac occlusive disease may be more disabling because of the greater number of muscle groups subjected to diminished perfusion. The initial manifestation of occlusive disease of the distal aorta or iliac arteries is intermittent claudication of the buttock, hip, thigh, and/or calf. Because the calf muscles are usually the only muscle groups affected by intermittent claudication caused by superficial femoral artery occlusion, the involvement of more proximal muscles in the symptom complex may help to distinguish aortoiliac occlusive disease from femoropopliteal occlusive disease. However, relatively few patients with aortoiliac disease complain of only calf claudication; male patients with aortoiliac occlusive disease often complain of impotence because of pelvic ischemia with inadequate perfusion of the internal pudendal arteries. In addition to impotence, these men may develop buttock claudication, atrophy of the leg muscles, lower extremity pallor, and absent femoral pulses, a constellation of symptoms first described by Rene Leriche in the 1940s.
Patients with aortoiliac occlusive disease can develop ischemic rest pain or tissue loss; however, this presentation is uncommon, because patients develop a rich collateral circulation reconstituting the infrainguinal system, thereby providing adequate tissue perfusion at rest. Collaterals often form between the hypogastric and lumbar arteries to the circumflex iliac, femoral, and profunda vessels as well as between the mesenteric arteries and hemorrhoidal vessels. Arteriosclerotic plaque in the aorta and iliac arteries can also embolize, causing the so-called blue toe syndrome (i.e., microembolization of arteriosclerotic debris to the terminal vessels in the foot). Such symptoms can occur in a patient who otherwise appears to have adequate distal perfusion, including palpable pedal pulses. Under these circumstances, a workup should ensue with a computed tomography (CT) angiogram, looking for a proximal source of microembolization. When there is concomitant femoropopliteal occlusive disease in the setting of aortoiliac disease—a combination more prevalent in elderly patients with diabetes and hypertension—rest pain or tissue loss may ensue. As in any arterial system, tandem lesions in the periphery are more significant than single lesions.
Aortoiliac occlusive disease usually afflicts older patients who have a history of tobacco use, hypertension, and hyperlipidemia. In our experience, patients reporting symptoms of claudication caused by aortoiliac occlusive disease are on average nearly a decade younger than those complaining of claudication from superficial femoral artery occlusion. However, patients with rest pain from concomitant multisegmental occlusive disease are usually older (i.e., in the seventh decade of life) than those who present with rest pain from isolated femoropopliteal disease.
The initial lesions of aortoiliac occlusive disease usually begin at the terminal aorta and the proximal portions of the common iliac arteries or at the bifurcations of the common iliac arteries ( Fig. 23.1 ). The lesions then progress proximally and distally. Approximately 33% of patients treated for symptomatic aortoiliac disease have disease at the origin of the deep femoral arteries, and more than 40% have superficial femoral artery occlusions. The natural history of aortoiliac occlusive disease is one of slow progression. The ultimate anatomic result of aortoiliac atherosclerosis is variable, as occlusion of the distal abdominal aorta can occur with progression of the thrombus up to the level of the renal arteries ( Fig. 23.2 ). Although occlusion of the terminal aorta may remain stable for years, it does not always have a benign course. Starrett and Stoney observed that more than one-third of patients with aortic occlusion went on to develop thrombosis of the renal arteries over a period of 5 to 10 years ( Fig. 23.3 ). However, many years later, authors from the same institution found no evidence of renal thrombosis in 21 patients who were followed with arteriography after a mean of 27.7 months.
The earliest manifestations of aortoiliac occlusive disease are evident in the terminal aorta and proximal common iliac vessels.
Aortoiliac occlusive disease results in a variable degree of collateralization, shown as a discrete channel from a lumbar artery to the deep iliac circumflex artery (A) and as a multiplicity of small vessels that supply the hemorrhoidal and gluteal arteries that reconstitute the femoral vessels via iliac and femoral circumflex arteries (B).
The end result of aortoiliac occlusive disease consists of total aortic thrombosis, which may include the origins of the renal arteries.
Variants in the pattern of aortoiliac occlusive disease can occur, including relatively circumscribed occlusive lesions of the midabdominal aorta described in early to middle-aged female smokers ( Fig. 23.4 ). Although the upper abdominal aorta is ordinarily spared in patients with aortoiliac occlusive disease, a minority of these patients have marked involvement of this aortic segment, with occlusive disease at the origins of the major visceral vessels and renal arteries ( Fig. 23.5 ).
Aortoiliac occlusive disease may consist of a short-segment circumferential lesion, especially common in younger women. Such a lesion may be amenable to localized endarterectomy.
A large meandering mesenteric artery associated with total superior mesenteric artery celiac occlusion, renal artery stenosis, complete occlusion of the right common iliac artery, and distal left external iliac stenoses with a single patent hypogastric artery. End-to-side proximal anastomosis may best preserve both the mesenteric and pelvic circulation.
Diagnosis
The diagnosis of aortoiliac occlusive disease should be made after a thorough history and physical exam. Complaints of thigh claudication, with or without accompanying sexual dysfunction in males, suggest this disease process. Claudication symptoms, however, must be differentiated from symptoms of nerve root irritation caused by spinal stenosis or intervertebral disk herniation, which may be associated with activity and relieved by rest. Patients with spinal disease can ordinarily be distinguished from patients with vasculogenic claudication because of the typical sciatic distribution of their pain, which is equally reproducible with standing and walking. An even more sensitive finding in patients with lumbar spinal stenosis is that prolonged standing in an erect posture will exacerbate symptoms.
Over time, a patient with intermittent claudication may develop atrophy of the lower extremity muscles from chronic disuse; however, the soft tissue of the extremities will usually appear healthy and well perfused at rest. Diminished or absent femoral pulses is a critical physical exam finding that can indicate the level of the occlusive disease. Bruits heard in the groin can also call attention to proximal occlusive lesions. However, stenotic lesions at the origins of the superficial or deep femoral arteries can also cause femoral bruits. Palpable pedal pulses at rest may be found in patients with severe claudication from aortoiliac occlusive disease even when the femoral pulses are barely discernible. This reflects a rich collateral circulation that can develop over time.
Segmental Doppler pressures at all levels in the lower extremity are lower than the brachial pressure; in the absence of concomitant superficial femoral occlusive disease, no significant gradient between the upper thigh pressure and the ankle pressure will be present. However, disabling symptoms can occur in patients with aortoiliac disease who have near-normal resting ankle pressures and a normal ankle-brachial pressure index at rest. Therefore it can be helpful to repeat pressure measurements after a period of graded exercise, because a marked decrease will occur in patients with significant aortoiliac disease. More sophisticated Doppler waveform analysis or the use of a pulse-volume recorder may reveal patterns suggestive of proximal occlusive lesions. We have found, however, that resting and postexercise Doppler pressure measurements are satisfactory for the evaluation of most patients.
Indications for intervention include disabling claudication despite optimal medical therapy, ischemic rest pain, or tissue loss. For those with lifestyle-limiting claudication, emphasis should initially be placed on optimal medical therapy of hypertension, elevated cholesterol, and glucose control as well as risk factor modification with smoking cessation and weight loss. In addition, exercise therapy may relieve symptoms adequately to allow a lifestyle acceptable to the patient; intervention is then not needed or recommended, particularly in elderly patients or those with cardiac, pulmonary, neurologic, or other comorbidities. In contrast, patients with critical limb ischemia should be more aggressively and expeditiously treated by open or endovascular means as long as their medical risk and life expectancy warrant such intervention.
Preoperative Evaluation
The preoperative evaluation of a patient with aortoiliac occlusive disease includes a careful evaluation of any accompanying cardiopulmonary disease. In the authors' experience, approximately 40% of patients with symptomatic aortoiliac occlusive disease have clear clinical and electrocardiographic evidence of coronary artery disease. Symptomatic unstable coronary artery disease in such individuals demands investigation, including stress testing and cardiac catheterization in many cases. If coronary revascularization is indicated, this procedure should take precedence; the aortoiliac occlusive disease can be repaired later. Patients with mild or stable coronary artery disease can ordinarily undergo aortoiliac reconstruction without great risk. Older patients with severe cardiopulmonary disease who are not candidates for coronary artery intervention are probably best managed with an extraanatomic bypass as opposed to direct reconstruction. Patients with severe restrictive pulmonary disease may require a period of preoperative preparation that includes bronchodilators, broad-spectrum antibiotics, and abstinence from cigarette smoking.
Angiography, most often performed through a retrograde femoral approach, has historically been deemed the “gold standard” in the preoperative evaluation of patients with symptomatic aortoiliac disease. However, axial imaging with CT angiography (CTA) or magnetic resonance angiography (MRA) is now the most common diagnostic imaging study. CTA and MRA are well suited for evaluating the aorta and the mesenteric, renal, and iliac arteries, affording careful operative planning. Faster acquisition techniques and high-quality three-dimensional postprocessing capabilities make MRA an attractive, noninvasive modality. However, the question of which is the most cost-effective imaging modality remains controversial. Regardless of the imaging technique, the goal of the radiographic examination is to provide views of the entire abdominal aorta in two planes and to look for unexpected lesions of the celiac axis or superior mesenteric artery origins, to provide anteroposterior and oblique views of the pelvis to define any iliac artery lesions in more than one plane, and to demonstrate possible lesions at the origins of the deep femoral arteries. It is critical to preoperatively identify and ultimately preserve a large inferior mesenteric artery in the setting of severe superior mesenteric artery disease in order to prevent bowel ischemia (see Fig. 23.5 ). Views of the distal runoff vessels should also be obtained to demonstrate associated femoropopliteal occlusive disease. If catheter angiography is used, at the time of angiography, obtaining pull-back pressures across iliac artery lesions of unclear significance can help to elucidate the clinical significance of such lesions. Measurements should be taken at rest and after papaverine injection or during a period of reactive hyperemia after tourniquet ischemia to mimic the hemodynamic situation that occurs with exercise.
Open surgical reconstruction and percutaneous balloon angioplasty with or without stenting are the main treatment options for aortoiliac occlusive disease. The choice of treatment approach should be based on the durability of the intervention for the occlusive lesion or lesions as well as the patient's ability to safely tolerate a particular intervention. The TransAtlantic Intersociety Consensus (TASC) II guidelines delineated which anatomic lesions are best served by percutaneous versus open surgical therapy. In general, TASC A and B lesions (focal, short-segment lesions [≤3 to 10 cm], unilateral or bilateral) are best treated with endovascular options. Conversely, TASC D lesions (long-segment occlusions and diffuse, severe long-segment disease, particularly bilateral) are best treated with open surgery. Intermediate TASC C lesions can be treated appropriately with either technique; however, these lesions and even some TASC D lesions are increasingly being treated by percutaneous stenting.
Aortofemoral Bypass Graft
The aortofemoral bypass graft, given its long-term durability, remains the gold standard for the treatment of severe symptomatic aortoiliac occlusive disease. This procedure's 30-day operative mortality rate of 5% to 8% in the early 1970s has been reduced to less than 2% over the past two decades, a level similar to that observed in patients undergoing elective abdominal aortic aneurysm repair. Much of the reduction in operative mortality is due to the prevention of early cardiac deaths in patients with heart disease through improvements in perioperative care. These advances include selective utilization of preemptive cardiac surgery, sophisticated pharmacologic management of the damaged myocardium, continuation of certain antiplatelet agents, and more precise perioperative fluid management tailored to the myocardial reserve.
Surgical Technique
After the administration of appropriate antibiotics, the femoral vessels are often exposed first through bilateral groin incisions to reduce the time of an open abdomen and the insensible fluid loss and hypothermia that occur with an exposed abdomen. The proximal extent of the dissection should be carried to the inguinal ligament. Often, partial division of the inguinal ligament is necessary to identify a soft segment of vessel that will be suitable for clamping. Control of the epigastric and circumflex iliac vessels with Silastic tapes is often necessary, as these vessels are often enlarged from years of receiving collateral flow. Distally, the superficial femoral and deep femoral arteries are also controlled. The extent of their exposure depends on the extent of concomitant femoropopliteal disease. Once the femoral dissection is complete, the inferior aspect of a retroperitoneal tunnel in each groin is bluntly created, ensuring that this tunnel remains directly anterior to the external iliac artery.
Next, the aorta is exposed through a midline transperitoneal incision, although some prefer a transverse incision. Others expose the infrarenal aorta through a left retroperitoneal exposure, which is an attractive alternative for patients with multiple prior intraabdominal procedures. Once the duodenum and small bowel have been mobilized and retracted to the right, a self-retaining retractor is placed and the infrarenal aorta is exposed from the left renal vein down to the inferior mesenteric artery and until soft areas for clamping are identified. The softest part of the aorta is often located right below the renal arteries. Dissection of the distal aorta and iliac arteries should be minimized to prevent injury to the iliac veins and hypogastric plexus. Injury to the nerve plexus can cause men to have difficulty achieving an erection and ejaculating. Once all vessels are exposed, tunnels are created bluntly from the peritoneal cavity toward each groin incision using the anterior surface of the common and external iliacs arteries as a guide. By doing so, the tunnels will be behind the ureters, and they will not be mistakenly incorporated into the tunnel passage. Note that the tunnel on the left side is created deep to the sigmoid mesentery and lateral to the nerve plexus overlying the terminal aorta. Systemic heparin sodium is administered prior to the application of atraumatic vascular clamps. It may be necessary to apply the clamp in an anteroposterior configuration in the event of severe posterior calcification in order to prevent traumatic clamp injury.
A bifurcated, knitted Dacron prosthetic graft, usually impregnated with collagen or gelatin, is used by most surgeons, although polytetrafluoroethylene (PTFE) grafts are used by some. There is some evidence that a knitted graft may provide a more stable pseudointima than a woven prosthesis. The graft size—typically 18 by 9 mm, 16 by 8 mm, or 14 by 7 mm—is selected to best match the native aorta and femoral arteries. The graft is trimmed accordingly and then the proximal anastomosis is constructed either end to end or end to side, using a running 3-0 polypropylene or PTFE suture, just inferior to the renal arteries. After completion of the proximal anastomosis, the limbs are flushed with heparinized saline, clamped, and then passed through the retroperitoneal tunnels to the groin. In the groin, end-to-side anastomoses are fashioned onto the distal common femoral artery with a running 5-0 polypropylene suture. Often, the anastomoses are carried down onto the deep femoral arteries for a short distance. Prior to completing the anastomoses, graft flushing maneuvers are used; then the clamps are removed, one side at a time, while monitoring the blood pressure as reperfusion can result in hypotension.
An important factor contributing to improved outcomes has undoubtedly been recognizing the role of the deep femoral artery in providing sustained patency of the aortofemoral graft limb. The current practice of extending the distal anastomosis onto the origin of the deep femoral artery to ensure an adequate outflow tract is critical in patients with tandem superficial femoral occlusions or stenosis of deep femoral origin. If a profundaplasty or endarterectomy is necessary, the vessel should be closed with a patch of saphenous vein, bovine pericardium, or endarterectomized superficial femoral artery as opposed to creating a long deep femoral patch with the distal end of the aortofemoral prosthesis.
The incidence of graft infection has been minimized with perioperative antibiotic administration. Aortoenteric fistulas can be minimized by closing the retroperitoneal tissue and posterior parietal peritoneum over the graft and proximal suture line, thereby preventing erosion of the graft into the duodenum. In thin patients, it may be difficult to primarily close the retroperitoneum over the graft; an omental flap can be utilized in such scenarios.
Controversy remains over the proper configuration of the proximal anastomosis as it has several ramifications. Most favor an end-to-end configuration, during which the aorta is transected between clamps approximately 1 to 2 inches below the renal arteries and the distal stump is oversewn or stapled ( Fig. 23.6 ). This technique permits a comprehensive endarterectomy or thrombectomy of the proximal native aorta under direct vision before constructing the anastomosis. Excluding flow from a heavily diseased distal aorta, which may have had plaque or thrombus dislodge during clamp application, may prevent intraoperative emboli to the lower extremities. Additionally, this configuration theoretically creates a better inflow pattern with less turbulence.
Furthermore, the end-to-end technique does not project anteriorly, thereby affording easier closure of the retroperitoneum, which arguably results in lower rates of aortoduodenal fistulas. However, this configuration relies on patent external iliac arteries in order for the pelvis to receive retrograde perfusion. In comparison, an end-to-side configuration ( Fig. 23.7 ) is best suited for those with heavily diseased external iliac arteries, such that preservation of antegrade aortic flow is necessary to supply the hypogastric or inferior mesenteric artery. In addition, an end-to-side anastomosis should be constructed in those with a critically large inferior mesenteric artery (IMA) or accessory renal arteries to preserve flow in these crucial vessels. With this technique, a longitudinal aortotomy is made on a nondiseased segment of aorta just below the renal arteries. Great care is taken to remove all loose debris and mural thrombus from the segment of clamped aorta. At completion of an end-to-side anastomosis, adequate backflushing of all loosened debris and clot from the distal aorta is essential before forward flow is reestablished. Unfortunately controlled studies have not been conducted to substantiate that the results of one technique is superior to the other. Arteriographic studies in patients with indications for an end-to-side anastomosis are shown in Figs. 23.5 and 23.8 .
Despite significant advances in laparoscopic and robotic surgery, applications of these techniques to vascular surgery have been limited. Nonetheless, several authors have applied laparoscopic techniques to aortofemoral reconstruction. Whether performed completely via the laparoscopic approach or through limited incisions with laparoscopy-assisted dissection, the procedure has proved to be time-consuming and technically challenging. As the technology evolves and intracorporeal anastomotic techniques are refined, the future role of laparoscopic or robotic aortofemoral bypass will become defined.
In patients with focal aortoiliac lesions, aortoiliac endarterectomy is a suitable albeit uncommon treatment option. This tedious operation, even in the hands of enthusiasts, is confined to patients whose aortic disease ends distally near the bifurcation of the common iliac arteries ( Fig. 23.9 ; see also Fig. 23.4 ). This group of patients characteristically consists of middle-aged women with small aortas and occlusive disease of the midabdominal aorta that ends at the aortic bifurcation or in the proximal portions of the common iliac arteries. Aortoiliac endarterectomy is typically avoided in males because such a technique will interfere with the autonomic nerve plexus at the terminal aorta. There is little evidence to suggest that endarterectomy is superior to a properly performed aortofemoral bypass graft in terms of early or late results. Furthermore, in the current endovascular era, most patients will focal lesions are treated with percutaneous balloon angioplasty with or without stenting.
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