Abdominal aortic aneurysm

From Ganfyd

Abnormal, permanent dilatation of the abdominal portion of the aorta. Abdominal aortic aneurysms(AAA) affect mainly older, white men. Rupture of an AAA is often fatal. Of those that make it to hospital, many do badly following emergency repair.

Aetiology

Not fully understood. Some are inflammatory.

Prevalence

The frequency rate of asymptomatic AAA is 8.2% in the United Kingdom.

Risk Factors

• Smoking
• An 8 fold increase in risk for 1st degree relatives of a patient with an AAA.
• Other evidence of collagen deterioration: a male patient aged over 60 presenting with a hernia has a 6-8% risk of having an AAA

Natural History

Ruptured AAA.

• Biomechanics complicated, but essentially Laplace's law applies.
• The larger the AAA, the more likely it is to rupture.
• Can be asymptomatic.
• Can leak.
• Can rupture.
• Source of emboli.

Albert Einstein died of a rupture of his known and treated AAA

Investigations

Clinical examination

Competent clinical examination cannot exclude eventually lethal aortic aneurysm

Palpation of the abdomen is a quick and easy way but not very effective way of detecting an AAA, better in slim patients. Larger aneurysms are more likely to be picked up with abdominal palpation (~75% of >5.0cm). It has moderate sensitivity in picking up AAA that are large enough to require surgery, i.e. it rules in the diagnosis, but cannot completely exclude AAA^[1] IE a normal abdominal examination by a competent clinician does not reliably rule out AAA which may cause trouble in the future.

Ultrasound

This is non-invasive, quick, easy and cheap and allows accurate sizing. It can give limited information on position of AAA in relation to renal arteries, but this can sometimes be obscured by bowel gas.

Computer Tomography

This is the preferred method of investigation in patients that may undergo endovascular repair or in suspected rupture. It gives an accurate size of the aneurysm and allows better definition of the anatomy, particular the tortuosity of the aorta and whether there is a suitable neck for the endovascular graft.

Treatment

• Control risk factors, e.g. smoking, hypertension
• Surgical treatment
  • Open repair. The older procedure. The aneurysm is excised, and a (trouser) graft of Dacron or similar material stitched to arteries remaining above and below.
  • Endovascular aneurysm repair (EVAR). A graft is threaded from distal access, through the aneurysm sac and secured to the arterial wall above and below with an ingenious device. The sac is left and clots up. See main article Endovascular aneurysm repair.

Screening

see Abdominal aortic aneurysm screening

A national screening programme may arise in the next few years. Meanwhile separate efforts proceed to screen men at a suitable age using ultrasound imaging with the reasonably achievable intention of preventing deaths from ruptured unknown abdo. aortic aneurysms.

It seems sensible to measure the aorta in first degree relatives of those who develop an early aneurysm and rupture.

External links

• eMedicine chapter.
• NLH Q&A Service In those with a family history of AAA what age and frequency of screening should be carried out?

References