Repair of Iliac Artery Aneurysms by Endoluminal Grafting: The Systematic Approach of One Institution

Abstract

Isolated iliac artery aneurysms are rare lesions that are difficult to detect and treat. Prompt diagnosis and timely intervention are essential, because the incidence of rupture is as high as 50%. The reported mortality rate for patients who undergo surgery for ruptured iliac artery aneurysm ranges from 50% to 70%. The recommended therapy remains surgical excision, although percutaneous techniques are effective alternatives in selected cases. Early intervention, carried out in a systematic fashion, can reduce the high morbidity and mortality.

We report 4 cases of isolated iliac artery aneurysms managed over a period of 8 years by means of endoluminal grafting, with only 1 death. In our experience, prompt diagnosis by use of less invasive methods, such as duplex Doppler imaging, and timely intervention led to a reduction in the overall mortality.

Isolated iliac artery aneurysms are rare clinical conditions. They are difficult to detect and treat and consequently have been associated with a high rate of mortality. ¹ Rupture of iliac artery aneurysms is reported to carry a 50% to 70% mortality rate, and because the incidence of rupture is as high as 50%, it is imperative that diagnosis be early and intervention prompt. ^1,2 The recommended therapy for this condition is still surgical excision, ³ although newer treatments such as intravascular stenting are being performed. Early intervention with the proper surgical technique can reduce the morbidity and mortality associated with this condition.

We report 4 cases of isolated iliac artery aneurysm managed in our hospital over a period of 8 years; only 1 of these patients died. Although our number of cases is small, we believe that this low mortality figure is the consequence of early diagnosis and prompt surgical intervention.

Materials and Methods

In this retrospective study, we analyzed all cases of aneurysm of the aorta and its branches from the 1st of January 1991 to the 31st of March 1999. All cases of traumatic pseudoaneurysm and aortic dissection were excluded from this analysis.

During the 8-year period, 31 patients underwent operation in our center to treat these aneurysms. The patients were predominantly male (n = 29) and ranged in age from 25 to 72 years. Most aneurysms (48%) occurred in the 51-to-70-year-old age group. Eight aneurysms affected the iliac arteries, and 4 of these (12.9% of the 31) were confined to the iliac arteries.

We would like to focus on the presentation and management of these rare but dangerous conditions.

Case Reports

Patient 1

In April 1996, a 64-year-old man presented at another institution with acute onset of abdominal pain of 24 hours' duration. The pain was mainly in the lower quadrants and flanks. He also had anuria at the time of presentation. Fullness was present in the right lower quadrant, and an ultrasound scan of the abdomen revealed a 6-cm aneurysm of the right common iliac artery. The patient was then transferred to our hospital.

Immediately after admission, he collapsed and was resuscitated with volume expanders. On the basis of the ultrasonographic abdominal findings, we made a diagnosis of ruptured common iliac artery aneurysm and operated on an emergency basis without further vascular study.

Surgery revealed a ruptured common iliac artery aneurysm with no clots in the aneurysmal cavity. Proximal control of the aorta and distal control of the common femoral artery was achieved. We opened the sac completely and performed inlay grafting between the aorta and the common femoral artery, using a Cooley Veri-Soft graft (Meadox Medical Inc; now a division of Boston Scientific Meditech, Wayne, NJ).

Recovery in the postoperative period was complicated by abdominal wound dehiscence on the 15th postoperative day. Now on regular follow-up, the patient has good graft flow and normal peripheral pulses 3 years after surgery.

Patient 2

In September 1997, a 65-year-old man presented with pain in the right iliac fossa of 6 months' duration. He was on medication for hypertension, and 25 years earlier he had undergone surgery for an ulcer that was possibly peptic, but about which very few details were known. Clinically, he was found to have a pulsatile mass in the right lower quadrant with no bruit. A computed tomographic (CT) scan of the abdomen revealed a large common iliac artery aneurysm and dilatations of the celiac trunk and the hepatic artery. Angiography revealed a large right common iliac artery aneurysm at a distance of 2 cm from the aortic bifurcation. At laparotomy, we saw a 10-cm right common iliac artery aneurysm with an opening of 2 cm. A Cooley Veri-Soft graft (Meadox Medical Inc) was used for inlay grafting. After surgery, the patient's peripheral pulses could be palpated normally, and he is now on regular follow-up.

Patient 3

In November 1998, a 61-year-old man presented with swelling in the right iliac fossa of 3 years' duration. His right hip was painful. He had undergone surgery for his hip pain 4 years before, at which time a partial hip replacement had been done. On evaluation, he had edema of the right leg and a non-pulsatile swelling over the right iliac fossa with bruit. Ultrasonic examination of the abdomen was inconclusive. A duplex Doppler study revealed a right external iliac artery distorted by a huge clot-filled mass that appeared to arise from a leak in the posterior wall of the artery. Because this information was incomplete, a peripheral angiogram was done, which revealed an external iliac artery aneurysm with clots in it. The distal femoral artery was well defined.

At laparotomy, the common iliac artery was seen to be normal to the point of its bifurcation, below which there was a large aneurysm of the right external iliac artery. The aneurysm was excised and a Cooley Veri-Soft graft (Meadox Medical Inc) was placed endoluminally in the external iliac artery for its entire length, with anastomosis between the common iliac artery proximally and the deep femoral artery distally.

Postoperatively, the patient has continued to have some fullness of his lower abdomen. However, during regular follow-up we have observed that his peripheral pulses are normal, the swelling of his leg has decreased, and he is ambulant.

Patient 4

In February 1999, a 55-year-old man was referred to us in a clinical state of shock, after an initial treatment elsewhere for his acute onset of abdominal pain. He was resuscitated with volume expanders and then evaluated. Doppler ultrasonographic imaging of the abdomen revealed a 6-cm aneurysm of the left common iliac artery, with evidence of extraperitoneal fluid collection. The aorta was of normal size. Distally, the external iliac artery could not be discerned. A presumptive diagnosis of ruptured aortoiliac aneurysm involving the bifurcation of the aorta was made, and the patient was taken up for emergency surgery.

At laparotomy, there was a large aneurysmal sac protruding from the common iliac artery, surrounded by an extraperitoneal hematoma. There was no involvement of the aortic bifurcation. Proximal control of the aorta and distal control of the common femoral artery at the groin was achieved. Endoluminal grafting was done between the bifurcation of the aorta and the external iliac artery using a Cooley Veri-Soft graft (Meadox Medical Inc).

Because of the turbulent preoperative presentation and substantial loss of blood, which could be replaced only late, the patient did not tolerate declamping. He died in the immediate postoperative period as a result of declamping shock.

Discussion

Isolated iliac artery aneurysms are uncommon and difficult to treat. Autopsy series have yielded an estimated prevalence of 0.008% to 0.03%. ^2,4 A wide variety of conditions—such as atherosclerosis, infection, pregnancy, trauma, and collagen vascular diseases like Marfan syndrome—have been reported as causal factors. The condition is found more often in men than in women and is generally seen in elderly patients. This is in accord with our experience: all of our patients were male and were over 60 years old, except for 1 man who was 55. Early diagnosis is critical because the rate of rupture increases with aneurysmal size, especially if the diameter exceeds 5 cm. ⁵

Most of these aneurysms are caused by atherosclerosis. ⁶ However, 1 of our patients developed symptoms associated with aneurysm after having undergone hip surgery. Operative trauma is an established cause of aneurysms, and in this instance the rupture was at the posterior aspect of the artery, which increases the likelihood that the injury was iatrogenic. ^7,8

The signs and symptoms of an iliac artery aneurysm are usually caused by compression upon, or erosion into, adjacent structures. ¹ The usual course of events is one of progressive expansion, which of course can lead to rupture. The rate of rupture of an isolated iliac artery aneurysm depends on its size at the time of evaluation. Although reported rates vary widely (from 14% to 70%, according to the study ^1,2), Richardson and Greenfield reported a 31% rate of rupture in iliac artery aneurysms that had a mean diameter of 5.6 cm. ¹

In managing these aneurysms, there is a very high perioperative mortality rate (33% to 50% in emergency surgery; 7% to 11% in elective procedures). ^1,2 Even so, the appropriate treatment for any iliac artery aneurysm larger than 3 cm is surgical repair, the currently recommended therapy. ³ The surgical procedure of choice is endoluminal grafting, with exclusion or excision of the aneurysmal sac. ^3,9,10 Emphasis is on early diagnosis and referral: indeed, 1 of our patients died of late resuscitation, as a consequence of late referral to a tertiary care hospital. A systematic, planned operative approach is necessary to reduce morbidity and mortality.

In selected cases, percutaneous techniques such as coil occlusion or stent grafting may be effective alternatives to surgical procedures. ^11–13 These procedures offer the advantage of immediate isolation of the aneurysm from the circulation without general anesthesia, thus reducing the amount of blood loss and decreasing postoperative recovery time. Hence they are of particular value in treating patients who are at high surgical risk because of concomitant illnesses. ¹⁴