Arterial emergencies and aortic disease

Abdominal aortic aneurysm and rupture

Overview and approach

AAA surveillance/repair depends on size, growth, symptoms and patient risk; rupture is catastrophic.

  • Definition: an artery enlarged to more than 1.5 times its expected diameter; for the infrarenal aorta the accepted threshold is 3.0 cm (1).
  • Epidemiology: about 4-7% of men and 1-2% of women over 65 years. Risk factors: age, male sex, smoking, family history, atherosclerosis, hypertension, hypercholesterolaemia, other aneurysm. First-degree relatives have up to 20% lifetime risk (1).
  • Natural history: ongoing expansion, about 2-3 mm/year when under 5.5 cm and faster when larger. Annual rupture risk by diameter: 3.0-3.9 cm about 0%; 4.0-4.9 cm about 1%; 5.0-5.9 cm 1-10%; 6.0-6.9 cm 10-22%; 7 cm or more 30-50% (1).
  • Screening: no formal Australian screening program; ultrasound screening of men 65 years and over reduces aneurysm-related mortality in trials (including a Western Australian one), and is most cost-effective in smokers or those with a family history (1)(2).
Assessment and clinical features

Assess known aneurysm, abdominal/back pain, syncope and shock; a palpable mass is not always present.

  • Asymptomatic AAA is usually found incidentally on imaging or by targeted screening.
  • Symptomatic or rupture: abdominal, back or flank pain, tenderness over the aneurysm, syncope, hypotension, a pulsatile mass; distal embolisation can cause blue toe or acute limb ischaemia (1).
  • Retroperitoneal rupture may transiently tamponade and give a window for life-saving intervention; intraperitoneal rupture is usually rapidly fatal (1).
Differentials and investigations

Ultrasound for stable assessment; urgent CT angiography in suitable stable patients, with immediate vascular involvement for rupture concern.

  • Differentials for pain with a known or suspected AAA: renal colic, aortic dissection, mesenteric ischaemia, perforated viscus, pancreatitis, GI bleed, musculoskeletal back pain. Diagnosis in a shocked patient with a known AAA should not wait for imaging.
  • Ultrasound: modality of choice for detection, screening and surveillance. Measure the maximum transverse diameter perpendicular to flow (1).
  • CT angiography: investigation of choice to plan repair (morphology, neck, access vessels). Limits: iodinated contrast (renal impairment) and radiation (1).
  • Surveillance intervals (RACGP/ESVS-style, local protocols vary): 3.0-3.9 cm every 24 months; 4.0-4.5 cm every 12 months; 4.6-5.0 cm every 6 months; over 5.0 cm every 3 months (1). Newer SVS (RESCAN-based) intervals are longer (for example 3.0-3.9 cm every 3 years), and ANZSVS had not endorsed a guideline when RACGP published (3).
Management and follow-up

Vascular-directed surveillance/elective repair; suspected rupture follows emergency resuscitation and surgical pathways.

  • Small AAA: surveillance plus cardiovascular risk management: smoking cessation, statin, antiplatelet and antihypertensive therapy. No proven drug to slow growth. No evidence that exercise or travel causes rupture (1).
  • Indications for repair: male over 5.5 cm; female over 5.0 cm; growth over 1.0 cm/year; symptomatic AAA (pain, tenderness, distal embolisation). Trials show no survival benefit from repairing 4.0-5.5 cm aneurysms (1). Saccular aneurysms are often treated earlier (3).
  • EVAR vs open: operative mortality lower with EVAR (trials: EVAR-1 2.3% vs 6.0%; DREAM 1.2% vs 4.6%; OVER 0.5% vs 3.0%). EVAR needs suitable neck and access anatomy, can be done under local or regional anaesthetic, shorter stay, but needs lifelong (usually yearly) surveillance and more reinterventions, mostly for endoleak (type-based; endoleak is flow outside the graft but within the sac) (1).
  • Open repair: durable; ICU 1-2 days, hospital stay about 5-7 days; complications include cardiac (about 5%), pulmonary, renal, bowel ischaemia, graft infection, aorto-enteric fistula (1).
  • Ruptured AAA: immediate transfer to a vascular centre, activate massive transfusion, hypotensive resuscitation (avoid over-resuscitation). Overall mortality 80-90%; open repair mortality 30-40%; EVAR may improve survival (1).
Red flags and clinical pearls

Painful aneurysm or shock with concerning pain needs urgent escalation. Do not use a single elective size threshold for every patient.

  • Known AAA plus abdominal/back pain, syncope or tenderness = urgent vascular surgeon assessment (1).
  • Hypotensive resuscitation, not aggressive fluids, while en route to theatre (1).
  • Size alone is a crude surrogate of rupture risk; women rupture at smaller diameters, hence the lower 5.0 cm threshold (1)(3).
  • Viva: thresholds for repair, surveillance intervals, EVAR vs open, what an endoleak is.
References
  1. RACGP: Aortic aneurysms - screening, surveillance and referral (AFP 2013)
  2. Medicine Today: Abdominal aortic aneurysms (Cardiology Today 2016)
  3. RACGP AJGP 2018: AAA screening and surveillance

Last updated from Sen’s notes on 9 October 2026.