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  4. Abdominal Aortic Aneurysm (AAA)

Abdominal Aortic Aneurysm (AAA)

NICE guideline [NG156] Abdominal aortic aneurysm: diagnosis and management. Published Mar 2020. NICE CKS Abdominal aortic aneurysm screening. Last revised: May 2024.

Background Information

AAA is defined as a permanent localised dilatation of the abdominal aorta[ref]
  • Abdominal aortic diameter ≥3.0 cm, or
  • Artery diameter ≥1.5 times the normal diameter

Anatomical classification of AAA:[ref]
​​​
Location Description
Infrarenal (~85% cases) Located below the renal arteries
Juxtarenal Originates near but does not involve the renal arteries
Pararenal Involves origin of renal arteries
Suprarenal Located above the renal arteries, including the origins of visceral arteries
 

Major risk factors:[ref]
  • Male (6x more common than in women)
  • >65 y/o
  • Smoking

Other risk factors:[ref]
  • Hypertension
  • Cardiovascular disease and atherosclerosis
  • Peripheral aneurysm

Symptoms:
  • Mostly asymptomatic – most cases discovered incidentally
    • If symptomatic - usually abdominal / flank / back pain 
  • Features from distal embolisation
    • Acute limb ischaemia
    • Blue toe syndrome

Examination findings:
  • Aortic bruit
  • Pulsatile + expansile abdominal mass
 

Symptomatic AAA usually indicates aneurysm expansion or impending rupture.

Typical clinical features:
  • Sudden onset severe back and/or abdominal pain (+/- radiation to flank / buttocks / legs / groin)
  • Hypotension
  • Pulsatile abdominal mass
  • Grey Turner and/or Cullen sign

  

Be aware that features of a ruptured AAA may mimic those of renal colic.

Guidelines

Gold standard: CT angiography
  • Patient must be stable
  • Contrast extravasation from abdominal aorta indicates a ruptured AAA
  • Required for surgical planning

Point-of-care ultrasound maybe used in haemodynamically unstable patients to rapidly detect AAA.

 

Note that AAA is screened with an ultrasound but not CT angiography. See below for details on AAA screening.

Urgent repair (within 2 weeks) is indicated if:

  • Symptomatic​​​​​, or
  • Asymptomatic + 
    • ≥5.5 cm, or 
    • >4.0 cm + growing >1cm / year

If repair is not indicated → offer conservative care

1st line: open surgical repair

Endovascular aneurysm repair (EVAR) is preferred if:
  • Hostile abdomen (e.g. active intra-abdominal infection, adhesions, extensive prior abdominal surgery)
  • Anaesthetic risks

Main aim is to reduce the risk of progression:
  • Smoking cessation
  • Blood pressure control
 
  • Follow up and monitor with ultrasound (see screening section below for timing)

Absolute priority: immediate surgical repair / EVAREndovascular aneurysm repair


Hypotensive resuscitation (permissive hypotension) is recommended
  • RCEM recommends aiming for SBP 90-120 mmHg

 

Do NOT delay definitive surgical repair to stabilise the patient.

Routine screening for AAA:
  • Population: ALL ≥65 y/o men
  • Screening modality: one-off transabdominal ultrasound

Subsequent action depends on ultrasound findings:
 
Aortic diameter  Interpretation Re-scanning timeframe
<3.0cm No aneurysm Discharge, no further scanning
3.0 – 4.4 cm Small AAA 12-monthly scan
4.5 – 5.4cm Medium AAA 3-monthly scan
≥5.5cm Large AAA Refer to vascular surgery

References

Author: Konstantinos 
Reviewer: 
Last edited: 06/09/25