Imaging description

A persistent sciatic artery can easily be identified using CT angiography of the pelvis and lower extremities. Sequential enhanced axial images through the pelvis demonstrate a vascular structure in the left hemipelvis that courses along the left acetabulum (Figure 89.1) before diving inferolaterally along the anterior aspect of the gluteus maximus into the left thigh (Figure 89.2). The vessel is of greater caliber than the ipsilateral external iliac, superficial femoral, and profunda femoris arteries. Its course is better appreciated on three-dimensional volume renderings (Figure 89.3), where the associated enlargement of the ipsilateral internal iliac artery can also be well appreciated. While this persistent left sciatic artery is mildly tortuous proximally, it is relatively uniform in caliber throughout its visualized course and does not contain any thrombus.

Importance

The persistent sciatic artery is a very rare vascular variant that can become clinically significant if complicated by aneurysm or thrombosis. In such cases, patients often present with a pulsatile or enlarging gluteal mass or new onset of decreased pedal pulses, and surgical bypass (femoropopliteal or femorotibial) becomes necessary to restore blood flow to the leg.

Typical clinical scenario

The embryologic sciatic artery begins as a branch of the umbilical artery and perfuses the entire lower limb bud. By about the sixth week of gestation, the iliofemoral system begins to form and the sciatic artery begins to regress. Segments of the sciatic artery normally remain in the adult to form portions of the popliteal and peroneal arteries.

In cases where the sciatic artery persists, it arises from the internal iliac artery and follows the course of the inferior gluteal artery. After passing through the sciatic foramen into the thigh, it may run adjacent to the posterior cutaneous or sciatic nerves. This course can predispose patients to sciatic neuropathy if the vessel becomes enlarged due to aneurysm or thrombus. In cases where the superficial femoral artery is hypoplastic, patency of the sciatic artery becomes critical to preserve limb perfusion.