Atherosclerotic peripheral artery disease is a common finding in the elderly and can affect multiple arterial beds. With the onset of arterial occlusive disease, collateralization is also a common finding. In aorto-iliac arteries occlusion, collateralization via visceral-systemic and, most importantly, systemic-systemic pathways is observed and can be identified on imaging studies. Abdominal aortic occlusion can also be a result of spontaneous AAA thrombosis, and this usually presents with billateral acute limb ischemia, with a death rate up to 59%. There are also reports of chronically thrombosed AAA, which can present with symptoms of chronic ischemia and mimic peripheral artery disease.

We describe the case of a 71-year-old heavy smoker male with multiple comorbidities, such as heart failure, COPD, hypertension, hyperlipidemia and aortic valve replacement. He was previously treated for a contained rupture of a mycotic infrarrenal aneurysm (Brucella melitensis) with an aorto-uni-iliac endograft, due to a chronic occlusion of right common iliac artery and his extensive comorbidities. Early postoperative period was uneventful and, after that, he was lost to follow-up. Five-years later, a CT-angiography was performed, and thrombosis of the endograft was noted, with reconstitution of both external iliac arteries via collaterals. The patient was asymptomatic, and no surgical treatment was deemed necessary. Meanwhile, the patient is deceased due to unrelated causes.

Two dominant collateral pathways are observed in aortoiliac occlusive disease. Systemic-systemic pathways, derived from embryologic segments of the dorsal aorta include the intercostal, lumbar, internal thoracic, deep circumflex, inferior epigastric and obturator arteries. Visceral branches (superior mesenteric, celiac axis, inferior mesenteric, renals) can also develop important collaterals with systemic arteries. An important systemic-systemic collateralization pathway involves the intercostals-lumbars to deep circumflex iliac artery, which is well-developed on the patient right side (blue arrow). A more uncommon channel is the Winslow Pathway, that reroutes blood from the upper limb to the pelvis and lower limbs via the internal thoracic, superior and inferior epigastric to the distal external iliac arteries. In this patient, the bilateral external iliac reconstitution, and consequently bilateral lower limb arterial flow, is maintained predominantly through this uncommon pathway.

Surgeons should be aware of these uncommon collateralization pathways since they may be damaged during abdominal interventions, when harvesting internal thoracic artery for coronary artery bypass grafting or when using upper limb access with large devices in percutaneous interventions, as possibly disastrous limb-ischemic complications may ensue.

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