This MRCS Part B station is about vascular pathology.
An aneurysm is a focal dilatation in an artery to more than 50% its normal diameter. This equates to 3 cm or larger for the abdominal aorta. An abdominal aortic aneurysm normally results from degeneration of the media of the artery wall, normally secondary to atherosclerosis. The main risk factor is smoking.
Most AAAs are asymptomatic, and screening with ultrasound is being investigated for efficacy. They can also present as a result of pressure on surrounding structures, for instance causing a constant severe lower back pain. The main clinical presentation however is when AAAs rupture, leading to severe hypovolaemic shock and cardiovascular collapse.
A classic clinical OSCE scenario is a patient with illiac fossa pain, who you discover is in shock - always consider a ruptured AAA in your differential and institute urgent investigation and resuscitation,