What is the management approach for a patient with an infrarenal (below the kidney) aneurysm?

Management of Infrarenal Abdominal Aortic Aneurysms

The primary management approach for infrarenal abdominal aortic aneurysms (AAAs) is to prevent fatal rupture through appropriate surveillance for smaller aneurysms and timely intervention for those meeting size criteria, with open repair indicated for good surgical candidates and endovascular repair for high-risk patients. 1

Diagnosis and Surveillance

• Infrarenal AAAs are typically identified through physical examination or as incidental findings on abdominal imaging studies 1
• Ultrasound, CT, or MRI scanning should be used to determine aneurysm size and whether intervention is warranted 1
• Aneurysms measuring less than 4.0 cm in diameter should be monitored by ultrasound every 2-3 years 1
• Aneurysms measuring 4.0-5.4 cm should be monitored by ultrasound or CT scans every 6-12 months to detect expansion 1
• Risk factors for accelerated aneurysm growth include hypertension and smoking, which should be controlled during surveillance 1
• Patient compliance with surveillance is critical, as non-compliance has been associated with a 10% rupture rate compared to 0% in compliant patients 1

Indications for Intervention

• Repair is indicated for infrarenal AAAs measuring 5.5 cm or larger to eliminate rupture risk 1
• Repair can be beneficial for infrarenal AAAs measuring 5.0-5.4 cm in diameter 1
• Intervention is not recommended for asymptomatic infrarenal AAAs if they measure less than 5.0 cm in men or less than 4.5 cm in women 1
• Symptomatic AAAs warrant immediate repair regardless of diameter 1
• Patients with the clinical triad of abdominal/back pain, pulsatile abdominal mass, and hypotension require immediate surgical evaluation 1

Treatment Options

Open Surgical Repair

• Open repair is indicated as the primary treatment for patients who are good or average surgical candidates 1
• Open repair should be considered for patients who cannot comply with long-term surveillance required after endovascular repair 2
• Open repair has excellent early and mid-term outcomes in appropriately selected younger patients 3

Endovascular Aneurysm Repair (EVAR)

• Endovascular repair is reasonable in patients at high risk of complications from open operations due to cardiopulmonary or other associated diseases 1
• EVAR may be considered in patients at low or average surgical risk, though long-term outcomes are still being evaluated 1
• EVAR has become the primary treatment method for infrarenal AAAs due to improved short-term morbidity and mortality 4
• Caution is warranted when using large-diameter devices (34-36 mm) for EVAR, as they are associated with higher risk of proximal fixation failure 5

Post-Intervention Management

• Periodic long-term surveillance imaging is mandatory after endovascular repair to monitor for:
  • Endoleaks
  • Aneurysm sac stability or shrinkage
  • Stent graft patency
  • Stent migration or kinking 1, 6
• Annual duplex ultrasound with additional cross-sectional imaging every 5 years is recommended for stable EVAR repairs 6
• Immediate additional cross-sectional imaging is indicated if surveillance ultrasound detects endoleak, sac enlargement, stent migration, kinking, or decreased flow 6
• The risk of late aortic rupture after EVAR remains >5% through 8 years, emphasizing the need for continued surveillance 6

Risk Reduction Strategies

• Smoking cessation should be strongly advised for all patients with aneurysms to reduce expansion risk 1, 2
• Beta-adrenergic blocking agents may be considered to reduce the rate of aneurysm expansion 1, 2
• Hypertension should be controlled to reduce the risk of accelerated aneurysm growth 1

Common Pitfalls and Caveats

• Discontinuing surveillance prematurely after EVAR is dangerous as lifelong surveillance is necessary due to potential late complications 6
• Relying solely on ultrasound for the entire follow-up period after EVAR may miss stent migration, fracture, or non-contiguous aneurysms 6
• Patients with infrarenal AAAs should be evaluated for concomitant aneurysms in other vascular beds 2, 7
• Endovascular repair in patients with large infrarenal necks (≥29 mm) requiring 34-36 mm diameter endografts has higher rates of proximal fixation failure and may warrant consideration of fenestrated/branched devices or open repair 5