Aortoiliac Occlusive Disease

Aortoiliac occlusive disease is atherosclerotic stenosis or occlusion of the infrarenal aorta and the common and external iliac arteries. It reduces inflow to the pelvis and legs.

It accounts for about a quarter to a third of symptomatic lower limb peripheral artery disease. Onset is usually in the sixth and seventh decades, and earlier in heavy smokers.

Leriche syndrome is the full picture: buttock and thigh claudication, erectile dysfunction, and absent or weak femoral pulses. Only a minority of patients show all three.

Smoking is the strongest risk factor. Others are diabetes, hypertension, dyslipidaemia and chronic kidney disease. Non-atherosclerotic causes are Takayasu arteritis, fibromuscular dysplasia, radiation arteritis and thrombosis of an aortic aneurysm.

Hypoplastic aortoiliac syndrome is early disease in a small calibre aorta, typically in women who smoke.

Lesions are grouped into four types. Type A is a short iliac stenosis. Type B is a short infrarenal aortic stenosis or a short unilateral occlusion. Type C is bilateral long lesions or occlusions. Type D is diffuse disease with aortic occlusion or aneurysm. The type directs the choice between endovascular and open repair.

Pathophysiology. Plaque narrows the inflow vessels, and collaterals (lumbar, internal mammary to epigastric, mesenteric to haemorrhoidal, circumflex iliac) compensate at rest but not on exercise. Plaque and thrombus can also embolise to the toes.

Nerves of the pelvis are ischaemic when both internal iliac arteries are poorly filled, which explains erectile dysfunction.

• Claudication of the buttock, hip and thigh, often also the calf, brought on by walking and relieved within minutes by rest.
• Erectile dysfunction in men.
• Weak or absent femoral pulses, femoral and abdominal bruits, cool pale feet, hair loss, dependent rubor and pallor on elevation.
• Chronic limb threatening ischaemia: rest pain in the forefoot at night that eases when the leg hangs down, ischaemic ulcers and gangrene.
• Atheroembolism (blue toe syndrome): painful discoloured toes with palpable pedal pulses, and livedo.
• Acute limb ischaemia from thrombosis: pain, pallor, pulselessness, paraesthesia, paralysis and coolness.

Red flags.

• Rest pain, tissue loss or gangrene
• Sudden onset of a cold, painful, pulseless leg
• Blue toes, or recurrent embolisation
• Pulsatile abdominal mass (coexisting aneurysm)
• Onset under 50 years, or an inflammatory picture with fever and raised ESR (arteritis)

• Ankle brachial index at rest: 0.91 to 1.30 is normal, 0.90 or less indicates peripheral artery disease, and 1.40 or more means non-compressible vessels (diabetes, kidney disease). Use the toe brachial index in that case (0.70 or less is abnormal). Chronic limb threatening ischaemia is likely with ankle pressure under 50 mm Hg, toe pressure under 30 mm Hg or transcutaneous oxygen pressure under 30 mm Hg.
• Exercise testing. Aortoiliac disease can give a normal resting index. A fall in ankle pressure of 30 mm Hg or more (or 20%) after treadmill walking confirms it.
• Duplex ultrasound. Monophasic, damped femoral waveforms. A peak systolic velocity ratio of 2.0 or more across a lesion indicates a stenosis of 50% or more, and 4.0 or more indicates 75% or more.
• CT angiography is the main planning test: lesion length, calcification, aneurysm, access vessels and runoff. MR angiography is an alternative (avoid gadolinium at eGFR under 30 mL/min/1.73 m2 unless a macrocyclic agent is chosen).
• Catheter angiography with pressure measurement. A peak-to-peak systolic gradient of 10 mm Hg or more at rest, or 15 to 20 mm Hg or more after a vasodilator, marks a significant lesion.
• Laboratory. Lipids, HbA1c, creatinine, full blood count, CRP and ESR when arteritis is suspected.
• Other vascular beds. Abdominal aortic ultrasound, carotid duplex, and assessment for coronary disease.

Differential diagnosis.

• Neurogenic claudication from lumbar canal stenosis (pain on standing, eased by sitting or flexion, pulses present)
• Hip and knee osteoarthritis
• Venous claudication, chronic compartment syndrome and popliteal entrapment
• Diabetic or other peripheral neuropathy
• Takayasu arteritis, mid-aortic syndrome and aortic coarctation
• Acute embolism or aortic dissection extending into the iliac arteries
• Other causes of erectile dysfunction

Risk factors and medical therapy (all patients).

• Stop smoking. Varenicline 0.5 mg orally once daily for days 1 to 3, 0.5 mg twice daily for days 4 to 7, then 1 mg twice daily for 11 weeks. At creatinine clearance under 30 mL/min start 0.5 mg once daily and do not exceed 0.5 mg twice daily. Avoid in pregnancy. Or nicotine patch 21 mg/24 h for 6 weeks, then 14 mg for 2 weeks, then 7 mg for 2 weeks (start at 14 mg for under 10 cigarettes daily).
• Atorvastatin 40 to 80 mg orally once daily. Liver enzymes at baseline and 3 months. Reduce the dose with clarithromycin or ciclosporin. Avoid in pregnancy. Aim for LDL cholesterol under 1.4 mmol/L (55 mg/dL) and a fall of at least 50%, adding ezetimibe 10 mg once daily when not at target.
• Aspirin 75 to 100 mg orally once daily (usual maximum 325 mg daily), or clopidogrel 75 mg once daily if aspirin is not tolerated. Use pantoprazole 40 mg daily for gastric protection and avoid omeprazole and esomeprazole with clopidogrel.
• Rivaroxaban 2.5 mg orally twice daily with aspirin 75 to 100 mg once daily for symptomatic disease or after revascularisation when bleeding risk is low. Use with caution at creatinine clearance 15 to 29 mL/min and avoid under 15 mL/min. Contraindicated in active bleeding, moderate or severe liver disease, and with strong dual CYP3A4 and P-glycoprotein inhibitors (ketoconazole, ritonavir).
• Blood pressure under 130/80 mm Hg. Ramipril 2.5 mg orally once daily, increased every 2 to 4 weeks to 10 mg once daily (maximum 10 mg daily, and 5 mg daily at creatinine clearance under 30 mL/min). Check potassium and creatinine 1 to 2 weeks after each change. Contraindicated in pregnancy and bilateral renal artery stenosis.
• HbA1c about 53 mmol/mol (7.0%) in diabetes, with daily foot inspection.
• Supervised exercise for 30 to 60 minutes, three times weekly for at least 12 weeks, walking to near maximal pain. Walking distance rises by 50 to 200%.
• Cilostazol 100 mg orally twice daily, 30 minutes before or 2 hours after food, maximum 200 mg daily. Assess benefit at 3 months and stop if none. Contraindicated in heart failure of any severity, creatinine clearance under 25 mL/min, moderate or severe liver impairment, unstable angina and myocardial infarction within 6 months. Use 50 mg twice daily with strong CYP3A4 or CYP2C19 inhibitors (ketoconazole, erythromycin, diltiazem, omeprazole).

Revascularisation. Indicated for lifestyle limiting claudication that fails 3 months of exercise and drugs, and urgently for chronic limb threatening ischaemia.

• Endovascular repair is first choice for types A and B and increasingly for C and D in experienced centres. Angioplasty with stenting, kissing balloon expandable stents at the bifurcation, and covered stents for long or calcified lesions. Technical success is 90 to 98%, with 5-year primary patency of about 70 to 85%.
• Open aortobifemoral bypass for diffuse disease in fit patients. Five year patency is about 85 to 90%, with perioperative mortality of about 2 to 4%. Risks are myocardial infarction, graft infection (1 to 2%), sexual dysfunction and colonic ischaemia.
• Axillobifemoral or femorofemoral crossover bypass for high risk patients or a hostile abdomen. Patency is lower.
• Prophylaxis: cefazolin 2 g intravenously as a single dose 30 to 60 minutes before incision (3 g if over 120 kg).
• After a stent: aspirin 75 to 100 mg plus clopidogrel 75 mg once daily for 1 to 3 months, then a single antiplatelet drug or aspirin with rivaroxaban 2.5 mg twice daily. After a bypass: aspirin long term.

Acute limb ischaemia. Unfractionated heparin 80 units/kg intravenous bolus, then 18 units/kg/h, adjusted to anti-Xa 0.3 to 0.7 IU/mL or an aPTT ratio of 1.5 to 2.5, no fixed maximum. Check platelets on days 5 to 14. Then urgent thrombectomy, catheter directed thrombolysis or bypass, with fasciotomy for reperfusion injury.

Chronic limb threatening ischaemia. Urgent revascularisation, wound care, treatment of foot infection by severity, and analgesia with paracetamol 1 g orally every 6 hours (maximum 4 g daily, 3 g in liver impairment or under 50 kg) with an opioid when needed.

Special groups.

• Women with hypoplastic aortoiliac syndrome have more complications with endovascular repair, so favour open repair.
• Takayasu arteritis: prednisolone 0.5 to 1 mg/kg orally once daily (maximum 60 mg) with a steroid sparing drug, and revascularise only after inflammation has been quiet for 3 to 6 months.
• Kidney disease and diabetes: limit contrast volume to under 3.7 times the creatinine clearance (mL/min).

Monitoring. Symptoms and ankle brachial index every 6 to 12 months. After intervention, duplex at 1, 6 and 12 months, then yearly. Lipids, HbA1c, blood pressure and smoking status at each visit.

Referral and escalation. Refer to vascular surgery for limiting claudication or any threatened limb. Emergency for acute limb ischaemia, rest pain with tissue loss, or rupture of an associated aneurysm.