Introduction

To our knowledge this is the first case described with aortoiliac aneurysmal disease and PSA. PSA is a rare vascular congenital abnormality, which may present with ischemic or aneurysmal symptoms in adult life. Age at presentation ranges from 6 months to 89 years, mean age is 54 years (1). The incidence is 0.025-0.04% in angiographic series (1). The PSA arises from the internal iliac artery (IIA) and is believed to be a remnant of the dorsal arch of the lower limb bud (2). Two types of PSA have been described. Our case was the complete type. This , involves the PSA being the main arterial supply of the lower extremity. It continues as the popliteal artery below the knee level, while the superficial femoral artery tapers off blindly in the anterior thigh (figure 1). In the incomplete type the superficial femoral artery is the main supply of the lower extremity. Here the PSA tapers off blindly in the deep posterior part of the thigh. There may be anastomosis with the superficial femoral artery. Twenty-two percent of PSAs are bilateral (1).

Figure 1

Figure 1: Normal vascular anatomy of the lower extremity on the left and persistent sciatic artery illustrated on the right

The PSA can cause lower extremity ischemia during procedures such as hip replacement (3), renal transplant (4), embolization of pelvic traumatic bleeding (5), and for pelvic surgery in general. As our case shows, PSA also has the potential to cause ischemic complications during endovascular repair of aortoiliac aneurysms.

Case report

A 57 year-old female, with a history of hypertension and alcohol abuse presented to us with aortoiliac aneurysmal disease. The aneurysm was found incidentally during a physical exam for hypertension. Femoral pulses were present bilaterally. There was no family history of abdominal aortic aneurysm. A computerized axial tomography showed a 50mm fusiform abdominal aortic aneurysm with extensive atherosclerosis, intramural thrombus and a short neck (figure 2). The distal neck of the aneurysm was poorly defined and measured 35mm. The right common iliac artery was tortuous and measured 17mm at its maximum point of dilatation distally. Multi-focal right internal iliac artery aneurysms were also noted, measuring 17mm at the maximal point of dilatation.

Figure 2

Figure 2: CT scan of short neck of aneurysm. Arrow marking right renal artery.

Due to the suboptimal visualization of the IIA aneurysm on the CT scan the patient was admitted for an aortogram. The possibility to perform coiling of the potential IIA aneurysms was also entertained. The aortogram showed a 6mm neck of the abdominal aortic aneurysm inferior to the left renal artery. The run off series showed a tortuous aneurysmal PSA replacing the IIA and coursing inferiorly into the pelvis. It passed posterior to the femoral artery and posterior to the right hip joint (figure 3). The artery coursed distally as the main arterial supply of the lower extremity. Below the knee it continued as the popliteal artery. The superficial femoral artery ended blindly at the mid thigh level. Anatomy was normal below the right knee. Normal anatomy was found on the left side.

Figure 3

Figure 3: Angiogram of right-sided persistent sciatic artery. The SFA marked with large arrow above and the PSA marked with small arrow below.

The short neck of the aortic aneurysm necessitated an open approach for the aortoiliac repair. Poor compliance was expected due to a significant alcohol intake. The patient was deemed to be in good general health. This combined with multiple borderline sized PSA aneurysms determined us to proceed with a simultaneous isolation of the PSA and a femoropopliteal bypass. Resecting the aneurysm was not considered necessary or possible. The young age of the patient and the bypass location above the knee level made us choose a Gore-Tex graft as a conduit for the femoropopliteal bypass.

At operation the right popliteal artery was isolated and so was the common femoral artery. The aortoiliac aneurysm was repaired using a bifurcated Gore-Tex graft. The left distal graft anastomosis was made with the common iliac artery. On the right side there was considerable atherosclerotic disease and also dilatation of the PSA. An end-to-side anastomosis was made with the common femoral artery. The common iliac artery, the IIA/PSA and the external iliac artery were ligated. The popliteal artery was isolated above the knee. We then performed a femoropopliteal bypass using a Gore-Tex graft. The proximal anastomosis was on the femoral limb of the previously placed aortic graft.

The proximal portion of the popliteal artery was ligated. The patient had palpable pulses at the conclusion of the procedure.

The patient met in our clinic with significant alcohol intoxication on multiple occasions. On all occasions she had palpable pulses in the popliteal artery and distal to this. There were no symptoms to suggest enlarging aneurysmal disease. After two years the patient was lost to follow up. No further imaging was obtained.

Discussion

Of the case reports on persistent sciatic artery that were found, only one described a case associated with abdominal aortic aneurysm (6). This case did not involve the common iliac vessels. It is likely that many patients with persistent sciatic arteries remain asymptomatic and do not require treatment. The incidence on angiogram series seems to be much higher than the number of case reports. This is however a rare disease and not enough is known about the pathophysiology and the natural course.

Desired therapeutic endpoints for our case were 1) prevention of aortoiliac rupture 2) avoidance of leg ischemia and embolism 3) avoidance of rupture of persistent sciatic artery aneurysms. There seems to be agreement on the treatment of the isolated PSA. The main determinant of surgical treatment is the type of PSA present. It has been shown that the incomplete PSA can be ligated without complementary procedures (7). The complete type requires arterial reconstruction (1). If the patient has no symptoms and no aneurysms are present the PSA can be followed.

Treatment of aortoiliac aneurysm and PSA in combination has not been described before, that we know of. We suggest that the four major determinants affecting management would be 1) incomplete or complete type PSA 2) uni- or bilateral PSA 3) unilateral or bilateral Iliac artery aneurysms. 4) the presence of PSA aneurysms. Endovascular repair of the aortic aneurysm and the PSA should be feasible in most instances. If any doubts about the anatomy and feasibility of the procedure would occur, one should perform an open procedure. An asymptomatic, unilateral and non-aneurysmal persistent sciatic artery that would not be occluded by an endovascular graft could be spared and followed expectantly.

To avoid ischemic complications in AAA management, all incidental internal iliac artery aneurysms or abnormalities should be evaluated for the possibility of PSA before ligation or embolization is considered.

Despite its rarity, persistent sciatic artery with aortoiliac aneurysmal disease can be treated with excellent results once it is recognized. Endovascular treatment should be evaluated in all cases.