Atherosclerosis causes weakening of the arterial wall. Due to the high pressures generated in the arterial system, this weakening can lead to dilatation of the vessel. Once the diameter of the vessel has increased by more than 50%, there is an aneurysm. Aneurysms can occur in any artery, but most commonly occurs in the abdominal aorta and the major blood vessels supplying the legs, the iliac arteries. Abdominal aortic aneurysms are mostly asymptomatic when small, but can cause problems in the following ways:
As the size increases, so does the chance that the aneurysm will cause symptoms. The aneurysm can lead to mechanical back pain due to erosion into the vertebrae, but mostly pain is a sign of impending rupture and should be investigated as a matter of urgency.
This is not a common complication, but because of turbulent flow in the aneurysm, there is a risk that the aneurysm will become blocked by blood clots. Depending on the site this will usually lead to a patient presenting with a threatened limb (if blood flow is not promptly restored the limb will need to be amputated).
Because of turbulent flow in the aneurysm blood clot can form in the wall of the aneurysm. If a piece of clot then breaks off, it can cause obstruction further downstream and lead to ischaemia lower down in the limb.
This is the most feared complication. In most cases, the bleeding will be contained by surrounding structures and organs, and the patient will have a 60-80% chance of survival if he seeks prompt medical attention. If the rupture occurs freely into the peritoneal (abdominal) cavity, the chances of survival deteriorate dramatically.
Treatment options for aneurysms include:
Most small aneurysms are detected incidentally and can be observed as they have a low risk of rupture or other complications. In the case of an abdominal aortic aneurysm this would entail 6 monthly ultrasound evaluations. Once the aneurysm becomes symptomatic or a certain size is reached (usually 5.0 - 5.5cm) elective repair should be performed. This can be done by either open repair or endovascular therapy.
- Open abdominal surgery
Open abdominal surgery is a surgical procedure where the surgeon will remove the diseased section of the aorta and replace it with a synthetic tube or graft. This is a major surgery with high rates of complications. Full recovery after this procedure can take as much as 6-8 weeks.
- Endovascular repair
This is a less invasive procedure where the surgeon introduces a collapsed synthetic graft via an artery in the groin inside the aneurysm. Once appropriately positioned the graft is released / deployed and will stent / seal the aneurysm from the inside preventing it from enlarging further and / or rupturing. This a much less invasive procedure and recovery can be as short as 3-5 days. You may however need regular imaging tests to ensure that the repair is not leaking.