Overview
The prevalence of AAA sharply increases with age. Rupture is associated with a high mortality. Screening men over the age of 65 years reduces aneurysm related mortality. Patients diagnosed with small AAA should have ongoing surveillance with ultrasound and cardiovascular risk factor modification, and may be referred to a vascular surgeon for counselling about management options. Patients with indications for AAA repair should be referred promptly to a vascular surgeon.
Definition
Aneurysm: an artery that has enlarged to greater than 1.5 times the expected diameter.
True Aneurysm: The aneurysm is bound by all three layers of the vessel wall (intima, media and adventitia). The wall may be attenuated.
False Aneurysm: Occurs when a blood vessel wall is injured, and the blood is contained by the surrounding tissues creating an apparent dilatation of vessel.
Aortic dissection: occurs when a tear in the tunica intima of the aorta causes blood to flow between the layers of the wall of the aorta, forcing the layers apart.
Aetiology and Risk Factors
- Advancing age
- Male gender
- Smoking
- Family history
- Atherosclerosis
- Hypertension
- Hypercholesterolaemia
- Other vascular aneurysm
Clinical Manifestation
Classical Presentation
- Enlarging, painful, palpable, pulsatile, abdominal mass
- Potentially, reduced lower limb pulses, distal limb ischemia and/or vascular bruits audible on auscultation
Asymptomatic – 75%
- Incidental finding or on routine physical examination, AXR or abdominal ultrasound
- Consider for treatment or surveillance
Symptomatic
- Pain in central abdomen, back, loin, iliac fossa or groin
- Thrombus in aneurysmal sac may be a source of emboli to lower limbs
- Inflammation and compression of surrounding structure – ureter or IVC
Rupture
- Usually into retroperitoneum
Remember
75% patients with ruptured AAA do not make it to hospital.
Diagnosis
- Acute Pancreatitis
- Mesenteric Ischaemia
- Ruptured gastrointestinal ulcer
- Appendicitis
- Gallstone Disease
- Nephrolithiasis
- Irritable Bowel Syndrome
Investigation
- Abdominal ultrasound (definitive test)
- ESR/CRP
- FBC
- CT
- MRI
Treatment
Management of AAA is prevention
- Surveillance
- Cardiovascular risk reduction – smoking cessation, lose weight
- Elective surgical repair – Endovascular Aneurysm Repair
| Indications for AAA repair |
| Male with AAA >5.5 cm |
| Female with AAA >5.0 cm |
| Rapid growth >1.0 cm/year |
| Symptomatic AAA (abdominal/back pain/tenderness, distal embolisation) |
Ruptured AAA management
Overall mortality of 80–90%. Rupture into the peritoneal cavity is usually rapidly fatal, whereas retroperitoneal rupture may transiently stabilise, providing a window of opportunity for lifesaving intervention. Patients should be transported to a vascular surgical centre immediately, and hypotensive resuscitation instituted to prevent excessive blood loss. Nevertheless, the majority of patients die before arrival at a surgical centre.
Mortality with open repair for ruptured AAA has stabilised at 30–40%
Clinical Presentation and Examination
- Shock
Management
- Resuscitation
- Urgent Surgical repair
- Open repair
Side note
Open repair involves replacement of the diseased aortic segment with a tube or bifurcated prosthetic graft, through a midline abdominal or retroperitoneal incision.
Prevention
| AAA diameter (cm) | Rupture risk (%/year) |
|---|---|
| 3.0–3.9 | 0% |
| 4.0–4.9 | 1% |
| 5.0–5.9 | 1–10% |
| 6.0–6.9 | 10–22% |
| >7.0 | 30–50% |
| AAA diameter (cm) | Surveillance interval (months) |
|---|---|
| 3.0–3.9 | 24 |
| 4.0–4.5 | 12 |
| 4.6–5.0 | 6 |
| >5.0 | 3 |
Discussion