Editing Aneurysms (section)

== Aortic ==

* Aetiology
** Ascending aorta - typically degenerative or the sequela of prior dissection
** Infra-renal: 
* Distribution:
** Majority in infra-renal segment - 30% of all aortic aneurysms
** 1% of men 55-64 have a AAA > 4cm, which increases with advancing age by 2-4% per decade
* Natural history
** Natural history is of progressive enlargement (2-3mm per year) leading to increased risk of rupture
* Rupture risk:
** Maximal AAA diameter is the standard basis
** RFs for rupture: female, larger initial AAA diameter, smoking, lower FEV1, higher mean BP. Saccular morphology.
** Imaging characteristics for increased risk of rupture: dissection, mural thrombus, dissection of the peripheral calcification of the aneurysm sac.
** Risk of rupture declines when smoking is ceased and HTN is controlled.
**
* Diagnosis
** History
*** Typically asymptomatic
*** Can get NSAP and/or lower back pain
*** Sometimes feel pulsations
*** Can sometimes see a pulsatile mass
** Examination
*** Pulsatile mass, most commonly supra-umbilical and in the midline, but the location is variable
*** Remember to check for POPA and femoral artery too
** Imaging
*** USS has excellent sensitivity and specificity - good for screening and surveillance. Not an ideal method for detecting rupture (sensitivity might be lower than 50%). 
*** CT - better reproducibility of diameter measurements than USS. Best pre-op preparation. 
*** MRI - good, but does not detect aortic wall calcification, which can be important. Only really useful in inflammatory aneurysms where it helps show the extent.
*** Angiography - only used where detailed characterisation of an aneurysm is required or for intervention, or in the case or pre-operative embolisation of an accessory renal artery prior to EVAR.
* Screening:
** See bottom of this page for full table
** Rough consensus:
*** One-off USS screening for all men at age 65
*** Screen first-degree relatives of those with AAA once they reach 50 years old
*** Selective screening for those at high risk (women >65 who smoke, have CVA or FHx
*** Generally, those who screen negative initially are at very low risk of developing a AAA later
* Surveillance
** Those with infra-renal AAA 4-5.4cm should have an USS every 6-12 months
* Medical therapy
** Lots of things (ACE inhibitors, beta blockers, statins, anti-platelets) have slowed AAA growth in mice, but none have worked in humans to date
* Indications for repair
** Consider: operative risk (use VSGNE risk index), rupture risk, morbidity due to rupture
** Symptomatic
*** Thrombosis
*** Embolization of mural debris - lower extremity ischaemia/trash foot syndrome
*** Compression of adjacent organs
*** Aortic dissection
*** Rapid expansion/impending rupture
*** Frank rupture - haemodynamic instability
**** Consider direct to theatre. Alternative is rapid resus with permissive hypotension and rapid CTA
**** CT: heterogeneous mural thrombus, loss of fat planes around aorta, periaortic inflammation, retroperitoneal haematoma
** Asymptomatic
*** Aneurysm diameter >5.5cm in men and 5.0cm in women (UK Small Aneurysm Trial showed very low risk of rupture for <5cm: 2.5% annually)
**** Use risk factors for rupture (above) to personalise decision
**** The real issue is timing rather than eventual necessity of repair - over 80% of patients in the ADAM trial with aneurysms 5-5.4cm EVENTUALLY underwent repair
**** However earlier repair (<5.5cm) provides no survival benefit compared with surveillance and subsequent repair once it gets >5.5cm
*** 12-month growth rate of 10mm or greater in either gender
*** Saccular aneurysms
*** Dissection of mural thrombus
*** Fracture of saccular calcification
* Surgery
** See 'Open AAA repair' page for discussion on choice between open vs EVAR