What does a surgical occlusion of the left internal iliac artery mean?

Surgical Occlusion of the Left Internal Iliac Artery: Definition and Clinical Implications

Surgical occlusion of the left internal iliac artery means intentionally blocking blood flow through this vessel, either by ligation (tying it off), embolization (using coils or plugs), or coverage with a stent-graft during endovascular procedures. 1

Anatomical Context

The internal iliac artery (also called the hypogastric artery) is the main arterial vessel supplying the pelvis, including:

• Pelvic organs (bladder, rectum, reproductive organs) 2
• Pelvic walls and perineum 2
• Gluteal region and buttock muscles 2
• Erectile tissue in men (via the internal pudendal artery branches) 3

Common Clinical Scenarios Requiring Occlusion

During Aortoiliac Aneurysm Repair

The most frequent indication is treatment of common iliac artery aneurysms during abdominal aortic aneurysm (AAA) repair, where the internal iliac artery must be sacrificed to achieve adequate seal zones for endovascular grafts. 1, 4

• Occurs in 20-40% of AAA patients who have concomitant iliac aneurysms 1
• Internal iliac artery occlusion is achieved through catheter-directed embolization or coverage with stent-grafts 4
• Success rate for achieving complete occlusion approaches 100% with modern techniques 4

During Obstetric or Gynecologic Hemorrhage

Internal iliac artery ligation serves as a lifesaving procedure for severe pelvic bleeding, though selective arterial embolization has increasingly replaced surgical ligation 2

Expected Clinical Consequences

Pelvic Ischemia Symptoms (Unilateral Occlusion)

Approximately 17-21% of patients develop pelvic ischemia symptoms after unilateral internal iliac artery occlusion, with most experiencing mild, self-limited claudication. 4, 5

The severity classification includes:

• Class 0 (79-83%): No symptoms 4
• Class I (12-17%): Non-limiting buttock claudication with exercise that often resolves within 6-12 months 4, 5
• Class II (9%): New-onset impotence or moderate-to-severe buttock pain causing physical limitation 4
• Class III (<1%): Buttock rest pain or colonic ischemia 4

Bilateral Occlusion Risks

Bilateral internal iliac artery occlusion carries substantially higher risks, with buttock claudication occurring in 36% of patients and erectile dysfunction in 10% of men. 1, 3

• Colonic ischemia risk increases significantly with bilateral occlusion 5
• Three documented cases of rectosigmoid ischemia occurred in patients with bilateral occlusions, with one requiring sigmoid resection 5
• One mortality from colon infarction has been reported after bilateral occlusion 4

Erectile Dysfunction

Bilateral internal iliac artery occlusion or stenosis produces the most severe erectile dysfunction because it eliminates collateral compensation from the contralateral side. 3

• Unilateral occlusion may cause erectile dysfunction when the contralateral internal iliac artery has pre-existing stenosis >70% 4
• The internal pudendal artery (branch of internal iliac) provides critical penile arterial perfusion 3

Predictors of Symptomatic Pelvic Ischemia

Two preoperative angiographic findings identify patients at highest risk for chronic pelvic claudication after internal iliac artery occlusion: 4

1. Stenosis >70% of the remaining (contralateral) internal iliac artery origin with non-opacification of more than 3 of the 6 internal iliac artery branches (63% of symptomatic patients) 4
2. Small caliber, diseased, or absent medial and lateral femoral circumflex arteries ipsilateral to the side of occlusion (25% of symptomatic patients) 4

Collateral Blood Flow Compensation

Despite occlusion, pelvic perfusion is maintained through five major collateral pathways: 6, 2

• Superior hemorrhoidal artery (from inferior mesenteric artery)
• Middle sacral artery (from aorta)
• Lumbar arteries
• Deep femoral artery branches (medial and lateral femoral circumflex arteries)
• Contralateral internal iliac artery

Bladder blood flow decreases to 52-75% of baseline after bilateral internal iliac artery occlusion but remains sufficient to prevent tissue necrosis in most cases. 6

Critical Management Principles

When Preservation is Recommended

Preservation of at least one hypogastric artery is strongly recommended when anatomically feasible during aortoiliac interventions to decrease the risk of pelvic ischemia. 1

• This is a Class 1, Level B recommendation from ACC/AHA guidelines 1
• Applies to both aneurysmal and occlusive aortoiliac disease 1

Ligation Technique Considerations

When bilateral ligation is unavoidable, ligating at the point below the takeoff of the superior gluteal artery (peripheral site) produces greater blood flow reduction to pelvic organs while maintaining gluteal perfusion. 6

• Central ligation (proximal to superior gluteal artery) reduces bladder blood flow to 73% of baseline 6
• Peripheral ligation reduces bladder blood flow to 52% of baseline 6

Important Clinical Caveats

• Acute bilateral internal iliac artery occlusion should be avoided whenever possible due to substantially higher complication rates 5
• Patients with pre-existing contralateral internal iliac artery stenosis require careful evaluation before planned unilateral occlusion 4
• Unintentional occlusion occurs in approximately 9% of endovascular AAA repairs due to iliac dissection or inadvertent graft coverage 5
• Most buttock claudication symptoms improve within 6-12 months as collateral circulation develops 4, 5
• Colonic ischemia risk appears small (<3%) after unilateral occlusion but increases substantially with bilateral occlusion 4, 5