# Aortic Aneurysm > Abdominal aortic aneurysm for FMGE Surgery: 3 cm definition, 5.5 cm repair threshold, EVAR versus open graft, rupture triad and screening rules. - Canonical URL: https://prepelephant.com/topics/fmge/surgery/aortic-aneurysm-fmge - Exam / course: FMGE · Subject: Surgery - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Aortic Aneurysm", PrepElephant, https://prepelephant.com/topics/fmge/surgery/aortic-aneurysm-fmge ## Direct answer An abdominal aortic aneurysm is a permanent focal dilatation of the aorta to 3 cm or more, typically degenerative, male-predominant, smoking-driven and infrarenal. Repair is advised at 5.5 cm in men, about 5.0 cm in women, with growth beyond 1 cm a year, or with tenderness, because rupture risk climbs steeply with diameter. Open transperitoneal graft replacement remains the durable gold standard, while endovascular repair (EVAR) suits the unfit patient whose anatomy allows it, at the price of lifelong imaging surveillance. Rupture shows the triad of sudden abdominal or back pain, hypotension and a pulsatile mass, kills roughly 80% of patients before hospital, and demands immediate proximal aortic control rather than diagnostics. ## What you must remember - **Definition and thresholds:** permanent dilatation of 3 cm or more (normal aorta about 2 cm); elective repair at 5.5 cm in men, about 5.0 cm in women, expansion over 1 cm per year, or any symptomatic — tender — aneurysm. - **Screening convention:** a one-time abdominal ultrasound for men aged 65-75 who have ever smoked (USPSTF); India runs no national AAA screening programme, so Indian aneurysms usually surface incidentally or at rupture — a quotable contrast for vivas. - **Risk by size:** commonly quoted annual rupture risk runs under 1% below 4 cm, around 5% at 5-6 cm, and above 10% beyond 7 cm; the UK Small Aneurysm Trial is the evidence that let fit men wait until 5.5 cm. - **EVAR requirements:** an infrarenal neck at least 10-15 mm long with under 60 degrees of angulation plus adequate iliac access; type II endoleak (lumbar or inferior mesenteric backflow) is the commonest late complication and the reason surveillance never stops. - **Open repair facts:** Dacron tube or bifurcated graft; the most frequent cause of perioperative death is myocardial infarction, so cardiac risk stratification precedes everything else. - **Rupture disguises:** left loin pain mimicking renal colic in an elderly smoker, and the tamponaded retroperitoneal leak that lets the patient walk in talking, then collapse. - **Inflammatory aneurysm:** younger heavy smoker, thick enhancing wall, retroperitoneal fibrosis with ureteric obstruction, raised ESR and CRP; steroids help the fibrosis and surgery is technically hostile. ## A rupture call, minute by minute A 68-year-old smoker arrives with sudden back pain, blood pressure 84/50 and a pulsatile upper-abdominal mass. Two large-bore cannulae go in, the massive-transfusion protocol activates six units, and the patient moves to theatre — not to the CT scanner, because instability forbids imaging; CT is for the patient who stabilises on resuscitation, and then mainly to choose EVAR versus open. In theatre the classical discipline applies: prep and drape before induction. Muscle relaxation and positive-pressure ventilation collapse the venous return that was tamponading the retroperitoneal haematoma, so the patient is anaesthetised only when the surgeon is gowned, the laparotomy set open, and a supracoeliac clamp ready. Laparotomy follows: clamp the aorta above the coeliac trunk to control, then reassess volume, move the clamp down as far as safe, open the sac between clamps, and graft from infrarenal neck to bifurcation. The postoperative questions are the ones the ICU asks — cardiac ischaemia, renal function (the clamp and the hypotension both tax the kidneys), and colonic ischaemia on day two, which is why lax observations of the stoma or stool matter after an emergency graft. ## How the exam frames it NBE-style one-liners rotate around four facts: the commonest site is infrarenal; the repair threshold is 5.5 cm in men (5.0 cm in women is the discriminator that separates candidates); a tender aneurysm is repaired at any size; and the commonest cause of early death after elective repair is myocardial infarction, not the graft. The favourite distractor is the elderly "first-ever renal colic" — the taught reflex is that new loin pain in a man over 60 with a smoking history earns an aneurysm check before discharge. Expect the EVAR question as anatomy, not opinion: neck length, neck angulation and iliac access decide suitability. ## Frequently asked questions ### At what diameter is elective repair recommended? 5.5 cm in men and about 5.0 cm in women, or growth faster than 1 cm per year, or a symptomatic aneurysm — whichever threshold arrives first. ### Why is EVAR not offered to every patient? It demands suitable neck and access anatomy, commits the patient to lifelong CT surveillance for endoleak and re-intervention, and in fit patients open repair still holds the durability edge. ### What constitutes the classic triad of rupture? Sudden abdominal or back pain, hypotension and a pulsatile abdominal mass — though a substantial minority present with only part of the triad. ### Which patients are screened for abdominal aortic aneurysm? Men aged 65-75 with a smoking history, by a single ultrasound examination, per the USPSTF convention. ### What is the commonest cause of early mortality after elective open repair? Myocardial infarction — which is why cardiac evaluation dominates the preoperative workup of every aneurysm patient.