Case of persistent sciatic artery in a dialysis patient with critical limb ischemia

Abstract

Persistent sciatic artery is a rare congenital malformation (incidence rate, 0.03%–0.06%). We report the case of a 72-year-old male patient with persistent sciatic artery suffering from pain at rest and an ulcer on the left first toe. Angiography findings showed 90% stenosis in the distal persistent sciatic artery. Endovascular therapy was considered difficult because of a long stenotic lesion from the persistent sciatic artery to the popliteal artery and extremely high calcification of the whole body. Because of poor blood flow to the lower leg, vascular prosthesis would have increased the risk of thrombotic occlusion. Therefore, below-knee femoropopliteal bypass using the great saphenous vein graft was performed, which led to the healing of the ulcer on the left first toe. Contrast-enhanced computed tomography of the lower limbs was performed to confirm that the bypass blood flow was good. The patient was discharged on postoperative day 5.

Introduction

A persistent sciatic artery (PSA) is an extremely rare congenital anomaly that occurs when the sciatic artery that nourishes the lower limbs during the embryonic period fails to regress on embryonic development. A complete PSA is continuous with the popliteal artery and may be complicated by hypoplasia of the femoral artery. We report the case of a patient with critical limb ischemia undergoing hemodialysis; the patient underwent femoropopliteal arterial bypass from the hypoplastic femoral artery to the popliteal artery below the knee for complete PSA with severe stenosis.

Case report

The patient was a 72-year-old man who was receiving maintenance dialysis at our hospital. He was introduced to dialysis 14 years ago because of chronic renal failure due to nephrosclerosis. His medical history included hypertension, percutaneous coronary intervention for angina, pacemaker placement for complete atrioventricular block, and endovascular therapy (EVT) for decreased arteriovenous fistula blood flow due to stenosis of the left subclavian artery. Computed tomography findings indicated the presence of left complete and right incomplete residual sciatic arteries and extremely high calcified arteries (Figure 1). He started complaining of worsening left foot pain occurring even at rest, and developed an ulcer on his left first toe, which restricted his walking ability. Arterial pulsation below the left popliteal artery was not palpable, the ankle-brachial index (ABI) was 0.41 on the left, and the skin perfusion pressure (SPP) was unmeasurable due to pain. Lower limb angiography was performed by retrograde puncture of the left femoral artery, which revealed left PSA. It originated from the internal iliac artery and directly communicated with the popliteal artery. The superficial femoral artery was hypoplastic and did not directly communicate with the popliteal artery. There was 90% stenosis of the distal PSA (Figure 2). We decided to perform femoropopliteal (FP) bypass to reestablish blood flow to the lower limb. Peripherally, high degree of calcification was observed in the popliteal artery; however, a potential site for vascular anastomosis was identified and deemed suitable because of less calcification in the popliteal artery below the knee. The common femoral artery was 12 mm in diameter and had good pulsation; therefore, it was judged that the blood flow was sufficient. The great saphenous vein was collected from the left thigh, a vein cutter was used to create a non-reversed vein graft, and FP bypass was performed. Postoperatively, the ABI improved from 0.41 on the left to 0.58, and the SPP for the dorsal and plantar aspects of the left foot were 60 and 45 mmHg, respectively. The pulsation of the dorsalispedis artery also became palpable. On postoperative day 4, contrast-enhanced computed tomography of the lower limbs was performed, and it was confirmed that the blood flow through the bypass was satisfactory (Figure 3). The patient’s ulcer had also healed, and he was discharged on postoperative day 5.

Figure 1.

(a) The bilateral common iliac arteries presented high calcification. (b) The left complete persistent sciatic artery was highly calcified (arrow). The right persistent sciatic artery was incomplete.

Figure 2.

(a) Angiography findings showed a hypoplastic superficial femoral artery (white arrow). A persistent sciatic artery was directly continuous with the popliteal artery (black arrow). (b) A highly stenotic lesion was observed in the popliteal artery from the distal persistent artery (arrow). (c) A chronic obstructive lesion was observed distal to the popliteal artery below the knee.

Figure 3.

The left persistent sciatic artery directly communicated with the popliteal artery. The left superficial femoral artery was hypoplastic. The right persistent sciatic artery was incomplete and hypoplastic. The great saphenous vein graft presented good patency, with an average minor axis of approximately 6 mm (arrow).

Discussion

The incidence of PSA was reported to be 0.03%–0.06%. ¹ Approximately 70% of cases are classified as having a complete PSA, as described by Bower et al. ² A complete PSA is continuous with the popliteal artery and may be complicated by hypoplasia of the femoral artery. In the incomplete type, PSA is not continuous with the popliteal artery, and the superficial femoral artery is continuous with the popliteal artery as usual. ² Although approximately 40% of patients with PSA are asymptomatic, arteriosclerosis and aneurysms may develop early due to the congenital hypoplasia of elastic fibers in the arterial wall or the anatomical position of the artery, which subjects it to repeated external forces during standing and flexion/extension. Acute ischemia, gangrene, pulsatile mass, and sciatica have been reported as symptoms, but aneurysm formation is the most common complication and is thought to occur in approximately 44% of patients with PSA. Approximately 8% of such patients undergo lower limb amputations.^1,3 In cases of acute ischemia, EVT can be performed instead of surgery. d’Adamo et al. ⁴ placed peripheral endgrafts on the PSA pseudoaneurysm, which was caused by a fractured stent, and obtained satisfactory results. However, in this case, it was a long stenotic lesion with high calcification from the PSA to the popliteal artery and was accompanied by high calcification of the whole body. Therefore, EVT was considered unsuitable in this case. Revascularization may be unsuccessful in cases where the femoral artery is hypoplastic; therefore, it is necessary to examine whether its caliber is large enough for sufficient blood flow to the lower limbs before performing FP bypass. In one case, obturator foramen bypass was performed from the internal iliac artery to the distal PSA and the proximal PSA aneurysm was resected. ⁵ In other cases, satisfactory results were obtained when FP bypass was performed using the hypoplastic femoral artery as the inflow vessel.^6–8 Regarding bypass graft selection, the blood flow below the knee was poor, and the risk of thrombotic obstruction with vascular prosthesis was considered high because of its inferior patency rates. Therefore, good blood flow was established by selecting the great saphenous vein graft and performing FP bypass. The common femoral artery was 12 mm in diameter and had a good pulsation; therefore, it was judged that the blood flow was sufficient. The patient has remained asymptomatic in the year following the operation and continues visiting the outpatient clinic on his own. We could rescue his left lower limb by performing FP bypass.

Conclusion

In this case, the patient with a complete left PSA presented with critical limb ischemia. Great saphenous vein graft was used to perform FP bypass, and satisfactory blood flow was obtained, which led to the healing of the ulcer of the first toe.