Abdominal Aortic Aneurysm

Diagnosis

A physical examination may reveal a pulsatile mass. The sensitivity of abdominal palpation ranges from 33% to 100%, while its specificity varies from 75% to 100%. The positive predictive value can also range from 14% to 100%. Detection rates are influenced by factors such as the diameter of the aorta, the clinician's experience, and the patient's body habitus.

Abdominal ultrasound

Abdominal ultrasound (US) and duplex ultrasound (DUS) are the primary imaging tools for detecting and managing small abdominal aortic aneurysms (AAAs), boasting high sensitivity and specificity rates (over 97%). The anteroposterior (AP) diameter is used as the main measurement plane. It's important to note that the diameter may measure 2 mm smaller during diastole compared to systole. The use of a standardised US protocol, including electrocardiogram gating and subsequent offline reading with minute calliper placement, reduces variability.

Calliper positioning determines which aortic boundaries are selected to define the diameter: outer to outer (OTO), leading edge to leading edge (LELE), or inner to inner (ITI). There is a lack of consensus on which method is preferable.

OTO

Advantage: More sensitive. Sub-aneurysmal diameters (25 to 29 mm) have a lower risk of becoming clinically relevant.

Disadvantage: OTO measurements cause the threshold for repair to be reached earlier.

ITI

Advantage: Fewer unnecessary operations on small AAAs.

Disadvantage: Requires a strict follow-up schedule for sub-aneurysmal aortic dilatation, as these cases may have a higher risk of developing into an AAA that requires repair.

Computed tomography angiography

Typically, this leads to a larger diameter on CTA compared to US, with studies reporting that the mean AP CTA diameter was 4.2 mm greater than the AP ultrasound diameter, and of 50 - 55 mm aortas, up to 70% of AAAs exceed 55 mm on CTA.

Screening

Male

A 65-year-old male who is either a current smoker or a former smoker. ++

Both male and female

First-degree relative with abdominal aortic aneurysm. +++

Other peripheral aneurysms. +++

Organ transplanted.++

+ indicates different degrees of suitability for screening.

Follow up

Every five years for a sub-aneurysmal aorta 25 - 29 mm in diameter
A three-year surveillance interval for AAAs measuring 30 - 39 mm.
Annually for 40 - 49 mm (Males), and 40 - 44 mm (Females).
Every six months for 50 - 54 mm (Males), and ≥ 45 mm (Females).

Risk of rupture

0.03% per annum for men with AAAs measuring 30 - 44 mm.
0.28% for those with AAA measurements of 45 -54 mm.
0.40% for men with AAAs just below the referral threshold (50 - 54 mm).

Medical management

Reduce Cardiovascular risk

Smoking cessation
Blood pressure control (systolic BP < 130 - 140 mmHg).
Low density lipoprotein (LDL) cholesterol reduction 50% and < 1.4 - 1.8 mmol/L (< 55 - 70 mg/dL) using high intensity statin therapy
Antiplatelet therapy
Lifestyle modification (including exercise and a healthy diet).

A study of over 12,000 UK patients with abdominal aortic aneurysm (AAA) revealed improved five-year survival rates among those taking specific medications. Patients on statins had a survival rate of 68%, compared to 42% for non-users. Those on antiplatelet therapy had a 64% survival rate versus 40%, and users of antihypertensive agents had a 62% survival rate compared to 39% for non-users. Further analysis suggested that diuretics may be less beneficial than other antihypertensive medications.

Reduce the rate of aneurysm growth and rupture.

No specific drug therapy for small AAAs.
There is a lack of randomized controlled trials (RCTs) specifically examining the effect of statins on the growth rates of abdominal aortic aneurysms (AAAs).
Patients with diabetes have a slower AAA growth rate than those without. Studies suggest that metformin, used for type II diabetes, may inhibit this growth.
Smoking cessation appears to be associated with an approximate 20% reduction in growth rate, as well as halving the risk of aneurysm rupture.

Indication for elective repair

Fusiform aneurysms < 55 mm in diameter should be managed conservatively.
In men, the annual risk of rupture for abdominal aortic aneurysms (AAAs) under 55 mm in diameter, measured by ultrasound, is low at 0.3% to 0.8%. When using computed tomography angiography, the corresponding diameters range from 55 mm to 62 mm, depending on the measurement method.
The RESCAN meta-analysis revealed that the rupture rate for women with a 42 mm abdominal aortic aneurysm (AAA) is comparable to that of men with a 55 mm AAA, suggesting that the diameter threshold for considering repair in women should be lowered. Closer to 50 mm, as measured with ultrasound.
There is evidence that rapid aneurysm growth (> 10 mm/year) is associated with a greater risk of rupture.

Consider a lower threshold for elective repair of a saccular aneurysm compared to a standard fusiform abdominal aortic aneurysm. The 2024 ESC Guidelines for managing peripheral arterial and aortic diseases recommend lowering the threshold for elective repair of saccular aneurysms to ≥ 45 mm.

Preoperative manangement

Beta-blocker: Initiation of beta-blockers is not recommended before abdominal aortic aneurysm repair.

Statin: Patients undergoing elective abdominal aortic aneurysm repair should start statin treatment pre-operatively (ideally at least four weeks before surgery) and continue indefinitely post-operatively.

Antiplatelet: Antiplatelet monotherapy with aspirin or thienopyridines (e.g., clopidogrel) does not significantly increase bleeding risk during abdominal aortic aneurysm (AAA) repair. The POISE-2 trial showed that withdrawing chronic aspirin therapy perioperatively did not raise the risk of cardiovascular or vascular complications. Experience with dual therapy using potent antiplatelet agents like prasugrel and ticagrelor during AAA repair is limited and likely increases the risk of serious bleeding, so it should be avoided.

OAC: Warfarin should be discontinued five days before surgery, and direct oral anticoagulants should be discontinued two days before surgery to minimize the risk of bleeding. Anticoagulation may be bridged using short-acting agents, such as low-molecular-weight heparin (LMWH) or unfractionated heparin.

References

Wanhainen A, Van Herzeele I, Bastos Goncalves F, Bellmunt Montoya S, Berard X, Boyle JR, et al. Editor’s Choice -- European Society for Vascular Surgery (ESVS) 2024 Clinical Practice Guidelines on the Management of Abdominal Aorto-Iliac Artery Aneurysms☆. European Journal of Vascular and Endovascular Surgery [Internet]. 2024 Feb 1 [cited 2025 Jul 31];67(2):192–331. Available from: https://doi.org/10.1016/j.ejvs.2023.11.002

Lucia Mazzolai, Gisela Teixido-Tura, Stefano Lanzi, Vinko Boc, Eduardo Bossone, Marianne Brodmann, Alessandra Bura-Rivière, Julie De Backer, Sebastien Deglise, Alessandro Della Corte, Christian Heiss, Marta Kałużna-Oleksy, Donata Kurpas, Carmel M McEniery, Tristan Mirault, Agnes A Pasquet, Alex Pitcher, Hannah A I Schaubroeck, Oliver Schlager, Per Anton Sirnes, Muriel G Sprynger, Eugenio Stabile, Françoise Steinbach, Matthias Thielmann, Roland R J van Kimmenade, Maarit Venermo, Jose F Rodriguez-Palomares, ESC Scientific Document Group , 2024 ESC Guidelines for the management of peripheral arterial and aortic diseases: Developed by the task force on the management of peripheral arterial and aortic diseases of the European Society of Cardiology (ESC) Endorsed by the European Association for Cardio-Thoracic Surgery (EACTS), the European Reference Network on Rare Multisystemic Vascular Diseases (VASCERN), and the European Society of Vascular Medicine (ESVM), European Heart Journal, Volume 45, Issue 36, 21 September 2024, Pages 3538–3700, https://doi.org/10.1093/eurheartj/ehae179