AKT · Cardiovascular/Vessels, aorta & venous

Abdominal aortic aneurysm

Permanent focal dilatation of the abdominal aorta (≥3 cm) from medial wall weakening

Overview

A focal dilatation of the abdominal aorta to ≥3 cm, usually infrarenal and degenerative. Most are asymptomatic and found on screening (the NHS offers a one-off ultrasound to men at 65); the catastrophe is rupture. Elective repair is offered above a size/growth threshold, balancing rupture risk against operative risk.

Recognise

Usually asymptomatic; a pulsatile, expansile central abdominal mass; back/abdominal pain if symptomatic/expanding
Ruptured AAA — the classic triad: sudden severe abdominal/back pain, hypotension/collapse, and a pulsatile mass
Risk factors: male sex, age, smoking, hypertension, family history, atherosclerosis

Red flags

Suspected rupture (pain + collapse + pulsatile mass) → immediate vascular surgery; do NOT delay a haemodynamically unstable patient for a CT
Tender or rapidly expanding aneurysm → symptomatic AAA → urgent repair

Differentials & how to tell them apart

Renal/ureteric colicloin-to-groin pain, haematuria — but never miss a ruptured AAA in an older patient labelled 'renal colic'

Pancreatitis / perforationdifferent examination/biochemistry, no pulsatile mass

Aortic dissectiontearing pain radiating to the back, pulse asymmetry, often thoracic

Abdominal aortic aneurysm — dilated aorta on contrast CT
James Heilman, MD / CC BY-SA 3.0 — Wikimedia Commons

Investigations

Ultrasound (screening and surveillance — the first-line test); CT angiography for surgical planning and suspected rupture (only if stable). Cardiovascular risk assessment before elective repair.

Management

Surveillance + risk factors for small AAA; elective repair (EVAR/open) at ≥5.5 cm or symptomatic

1Detect on screening/ultrasound; for small aneurysms enter surveillance and modify risk factors (smoking cessation, statin, BP control).Gate: Suspected rupture (sudden pain + hypotension + pulsatile mass) → straight to theatre/vascular surgery; an unstable patient should not be delayed for imaging.
2Refer for elective repair at ≥5.5 cm, if symptomatic/tender, or growing >1 cm/year — choosing EVAR or open repair based on anatomy and fitness.

Surveillance + risk-factor modification (stop smoking, statin, BP control) — for small aneurysms below the repair threshold

Elective repair (EVAR or open) at ≥5.5 cm, or symptomatic/rapidly growing (>1 cm/yr) or >4 cm growing fast — size/growth-based threshold balancing rupture vs operative risk

Emergency repair for rupture — open or emergency EVAR; permissive hypotension while transferring

Key points

Pulsatile expansile abdominal mass = AAA; screen men at 65 with ultrasound. Sudden abdominal/back pain + collapse + pulsatile mass = rupture → theatre, not CT, if unstable. Never accept 'renal colic' in an older arteriopath without excluding a ruptured AAA. Elective repair at ≥5.5 cm.

Monitor & prognosis

Ultrasound surveillance by size; cardiovascular risk optimisation; post-repair endoleak surveillance (EVAR).

Excellent if electively repaired; ruptured AAA has very high mortality.

Source: NICE NG156 (AAA); NHS AAA screening