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Abdominal Aortic Aneurysm (AAA)

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

Background Information

  • Aneurysm: artery diameter ≥1.5 times the normal 
  • AAA: permanent pathological dilation of the abdominal aorta by 1.5 times the expected diameter based on person's sex and body size 
Conventional threshold for diagnosis of AAA is an abdominal aortic diameter of ≥3.0cm 

>90% of AAAs are infrarenal 

Important risk factors include: 
  • Male (6x more common than in women)
  • Advancing age 
  • Smoking 
  • Hypertension 

  • Mostly asymptomatic-most cases detected incidentally or on routine screening 
  • Abdominal / flank / back pain in minority of patients 

Possible examination findings:
  • Aortic bruit 
  • Pulsatile + expansile epigastric mass 

  • Sudden onset severe back and/or abdominal pain 
    • Possibly radiates to flank / buttocks / legs / groin 
  • Hypotension 
  • Grey Tuner and/or Cullen sign

The RCEM suggests considering ruptured AAA in the following patients:
  • >50 y/o with abdominal / back pain AND hypotension 
  • Known AAA with abdominal / back pain OR hypotension 
 

Features of ruptured AAA mimic those of renal colic.

Guidelines

1st line: bed-side abdominal ultrasound
  • Measure inner-to-inner maximum anterior-posterior aortic diameter 
  • Can confirm AAA but cannot definitively rule out rupture 
  • Abdominal aorta diameter ≥3.0cm indicates AAA 
  • Peri-aortic / free intraperitoneal / retroperitoneal fluid indicates ruptured AAA

Confirmatory: CT angiography (CTA)
  • Patient must be stable 
  • Abdominal aorta diameter  ≥3.0cm indiates AAA 
  • Contrast extravasation from abdominal aorta indicates ruptured AAA 

 
If unruptured AND asymptomatic 
  • Risk reduction of rupture 
    • Smoking cessation
    • Blood pressure control 
  • 2 week wait referral for repair if indicated: ≥5.5cm, OR >4cm + growing >1cm/year 
  • Conservative care if repair not indicated
 
If ruptured OR symptomatic unruptured:
  • A-E approach
  • Hypotensive resuscitation (permissive hypotension)
  • Involve senior + immediate imaging (bed side USS)
    • Referral for surgical intervention should NOT be delayed if imaging is not immediately available 
    • Clinical suspicion alone is an indication for surgery 
  • Definitive management: IMMEDIATE discussion with vascular surgeon for repair  

Indications for repair: 
  • Symptomatic 
  • Asymptomatic
    • ≥5.5cm, OR 
    • >4.0cm + growing >1cm / year 

Available approaches for repair: 
  • Open surgical repair (OSR) - laparotomy performed and a prosthetic graft is inserted into the dilated portion aorta, to alleviate pressure on the arterial wall 
  • Endovascular aneurysm repair (EVAR) - involves the placement of an intraluminal stent at the aneurysm site, through the femoral or iliac arteries, under fluoroscopic guidance 

Choice of repair approach: 
Scenario Recommendation
Unruptured + Asymptomatic  NICE recommends OSP, in the absence of contraindications
Unruptured + Symptomatic 
Ruptured  NICE recommends OSP or EVAR 
  • NICE recommends considering OSP for men <70 y/o, who have longer life expenctancy
  • For most patients, EVAR has been proven to be more beneficial than OSP 
 

Surgical management of unruptured AAA is an area of debate, with conflicting recommendations. For example, the European Society for Vascular Surgery recommends EVAR in most scenarios. 

Ultimately, it largely depends on local practice, surgeon's preference and patient's preference. 

Routine screening for AAA is offered to ALL ≥65 y/o men 

Screening modality: one-off transabdominal ultrasound
  • Measure inner-to-inner maximum anterior-posterior aortic diameter 

Subsequent action depends on ultrasound findings 
Aortic diameter Re-scanning timeframe
<3.0cm (no aneurysm) Discharge, no further scanning
3.0-4.4cm (small AAA) 12-monthly scan 
4.5-5.4cm (medium AAA) 3-monthly scan 
  ≥5.5.cm (large AAA) Refer to vascular surgery 

References

Author: Konstantinos 
Reviewer: TBC
Last Edited: