Teaching Case

The patient was admitted clinically due to arterial ischaemia of the right lower limb, with apparent irreversible ischaemia of 2nd and 3rd right foot toe ("blue toe syndrome").

Conventional aorto-iliac angiography was performed (left v approach).

Conventional aorta-iliac angiography showed a normal diameter and luminal contour of the aorta, and common and external iliac arteries.
The femoral artery (both the common and superficial branch) were permeable, despite early termination of the right superficial femoral branch.
It is noteworthy that the right popliteal artery (which is the origin of all three lower leg main blood vessels) is connected to a large arterial branch that originates from the right internal iliac artery. This large vessel has a large sacular dilation at the level of the right greater trochanter.

During the early embrionary period, the sciatic artery is the most important blood vessel of the lower limb. In most patients, while the external iliac artery develops, the sciatic artery involutes, except in a minority of patients (0, 001-0, 01%). [1]

Clinically, the classical finding for a sciatic artery is absence of femoral pulse with a palpable popliteal pulse, described by Cowie in 1960, also known as "Cowie sign". (Interestingly, to the authors knowledge, it is the only physical examination sign named after a radiologist). [2]

It is believed that these vessels given their paths are more susceptible to microtrauma and presumably due to wall dysplasia, and are more prone to develop aneurysms. In an article from 2009, about 200 cases of sciatic artery aneurism had been reported. [3]

In the end, about 50% of patients present clinically with an aneurysm in the trochanteric region, usually after the age of 40. [4]

At the time of the first assessment, the patient was immediately being considered for possible distal amputation (despite a palpable femoral and popliteal pulse), and at that time it was not entirely certain how proximal it would have to be done. As the patient had been referred from another institution (where aortic aneurysm had been excluded - images unavailable), after discussing with the on-call Interventional Radiologist, it was decided to go directly to angiography for 2 reasons: as the finding was unilateral, it was reasoned that the culprit lesion was likely also unilateral on that limb, so the earliest - and least invasive - possible treatment of an eventual cause of embolism was sought; catheter placement for continuous directed intra-arterial thrombolysis.

For this patient, it was decided to treat the aneurismatic dilation with a covered stent as has been suggested by other authors [5], in our case we used an antegrade approach. Usage of a covered stent allowed the elimination of athero-emboli source, achieved "anatomical" vascular permeability, and allowed intra-arterial thrombolysis to be performed in the lower limb.

The patient was then followed clinically (she improved). As she was left with a intra-arterial catheter in our institution, further angiography was performed. Given the presentation of the patient, 2nd and 3rd toe amputation were considered almost unavoidable, and the outcome of being able to avoid more proximal amputation was considered positive.

The patient was subsequently sent back to its original referral Hospital and failed to follow-up.