guidelines

abdominal aortic aneurysm (aaa)

nice ng156 summary: who to screen/test, ultrasound diagnosis, referral thresholds by diameter, surveillance, and indications for repair (including growth rate).

last reviewed: 2026-02-14
based on: NICE NG156 (published 19 Mar 2020; last updated 19 Mar 2020)
reviewer: Dr Kola Tytler MBBS CertHE MBA MRCGP
view official NICE source

Executive summary

  • Screening focus: men aged 66+ should be informed about NHS AAA screening and can self-refer if not screened.
  • Ultrasound diagnosis: offer aortic ultrasound if AAA considered and not already in screening programme.
  • Referral thresholds:
    • AAA ≥5.5 cm → refer to regional vascular service to be seen within 2 weeks.
    • AAA 3.0–5.4 cm → refer to regional vascular service to be seen within 12 weeks.
  • Repair criteria (unruptured): consider repair if symptomatic, or if >4.0 cm and grows >1 cm in 1 year, or if ≥5.5 cm.
  • Surveillance frequency: use the same surveillance frequency as the NHS AAA screening programme (specialist-led).

Primary care actions (what to do on an incidental AAA report)

  • Document maximum anterior-posterior diameter and whether symptomatic.
  • Assess risk factors (smoking, CVD/PAD, COPD, hypertension, hyperlipidaemia, family history).
  • Refer to vascular service based on diameter threshold; do not “watch and wait” in primary care without specialist surveillance.
  • Optimise cardiovascular risk: smoking cessation, BP/lipid management, antiplatelets/statins where indicated (per overall risk and comorbidity).

When to consider repair (NICE NG156 in one screen)

  • Symptomatic AAA
  • Asymptomatic but:
    • >4.0 cm and growth >1 cm in 1 year (ultrasound inner-to-inner AP diameter)
    • or ≥5.5 cm

References (Harvard):

  • NICE (2020) Abdominal aortic aneurysm: diagnosis and management (NG156). https://www.nice.org.uk/guidance/ng156

FAQs

If the AAA is 5.6 cm but asymptomatic, how urgent is referral?
NICE recommends referral to a regional vascular service to be seen within 2 weeks when AAA is 5.5 cm or larger.
Do I arrange surveillance intervals myself?
No—NICE recommends surveillance using the NHS screening programme frequency, typically organised through vascular services/screening pathways.
What if the AAA grows quickly but is not 5.5 cm?
NICE advises considering repair if AAA is >4.0 cm and has grown by >1 cm in 1 year, even if below 5.5 cm.

Transparency

This page is an educational, clinician-written summary of publicly available NICE guidance intended for trained healthcare professionals. It uses original wording (not copied text) and should be used alongside the full NICE source, local pathways, and clinical judgement. Doses provided are for general reference; always check the BNF/SPC.