Abdominal Aortic Aneurysm (AAA)

Last updated 20.09.12

 

Definition

-  Focal dilation of abdominal aorta >3cm

 

AAA

 

Features

-  Most located between renal & iliac a.

-  10-20% have blebs though to increase risk of rupture

-  Incidence 0.5-3%

-  Rupture rate 5 per 100,000 (0.005%)

-  Rupture

-  Rupture at smaller size for women

-  50% ruptured AAAs die pre-hospital

-  35-45% mortality for ruptured AAAs reaching hospital

-   If stable on admission 15-30% mortality

-   If unstable on admission >80% mortality

-  Rupture Risk

-   <4cm 0%

-   4-5cm 0.5-5%/yr

-   5-6cm 3-15%/yr

-   6-7cm 10-20%/yr

-   7-8cm 20-40%/yr

-   >8cm 30-50%/yr

 

Risk Factors

-  Elderly white men most effected

-  Age: peak incidence >70yrs

-  Smoking

-  Family Hx 25%

-  CAD

-  HTN

 

Causes

-  Atherosclerosis

-  Infection

-  Cystic medial necrosis

-  Arteritis

-  Trauma

-  Connective tissue disorders

-  Anastomotic disruption

 

Associated S/S

-  Asymptomatic

-  Sudden onset of severe abdo/lower back pain

-  Somatic pain from retroperitoneum compression

-  Pain may be ongoing (weeks to months)

-  No relief w change of position

-  May radiate to back, flank, umbilicus, pelvis

-  Abdominal mass +/- pulsatile

-  Hypotension: shock: rupture

-  70% normotensive

-  Grey Turners sign: retroperitoneal haemorrhage: rupture

-  Popliteal a. aneurysm 25-50% have AAAs

-  Livedo reticularis (blue toe syndrome): small AAA

-  Atypical

-  Femoral or sciatic n. palsy

-  Thigh, testicular, peroneal pain

-  Groin, scrotal, peroneal echymosis

-  Fistulae: aortocaval, aortoduodenal

 

Ix

-  Group & Hold + 6 units cross matched, FFP & Plts

-  INR & APTT: pre-op

-  FBE: infection, anaemia

-  U&E: operative risk

-  BSL

-  AXR: lateral

-  60% AAA calcified

-  Abdominal Ultrasound

-  Dx aneurysm, size & extent

-  Cannot Dx rupture

-  CT – Abdo

-  Dx aneurysm, size & extent

-  +/- rupture

-  +/- MRA

-  Angiography

-  Gold standard

-  Indicated if renal involvement or pathology

 

AAA CT

 

AAA Angio

 

Mx

-  IV access

-  Maintain BP but avoid HTN

-  Smoking cessation

-  HTN control: Beta blockers

-  If expanding or ruptured

-  Surgical Emergency

-  Only effective Mx is surgery

-  Hypotensive resuscitation w fluids

-  Based on Size

-  <4cm: US every 6/12

-  4-5cm: elective repair

-  >5cm: repair

-   Esp if smoker, HTN, COPD

-  Sx

-  Requires thorough pre-op workup

-  Endoluminal repair vs open

-   Tube graft

-   Aortic iliac bifurcation graft

-   Aortofemoral bypass

 

 

 

References