Abdominal Aortic Aneurysm

Meet the patient

A 72-year-old man, a 50-pack-year smoker, is on the floor of the admissions bay. Twenty minutes ago he was watching television; now he is grey, drenched in sweat, and clutching his left flank and back, begging for something for the pain the triage nurse has labelled renal colic. His blood pressure is 78/50, his pulse 120, and a firm, pulsatile mass fills his epigastrium.[1]

This is a ruptured abdominal aortic aneurysm until someone proves otherwise, and the proof you need is not a scan. The two questions that will decide whether he leaves hospital alive are can I get him to a clamp before he bleeds out? and have I remembered that resuscitating him to a normal blood pressure will kill him? Hold both, and the rest of this page falls into place.[1]

Over 3 cm is AAA, over 5.5 cm is repair — the two numbers that run the whole topic

An AAA is a permanent, localised dilation of the abdominal aorta to 3 cm or more. That 3 cm is 1.5 times the normal infrarenal diameter, which runs 1.7 to 2.2 cm in men and 1.5 to 1.9 cm in women — so 3 cm is a diseased aorta, not a borderline one. It is a true aneurysm: intima, media and adventitia are all involved, which separates it from a pseudoaneurysm where only adventitia holds.[2]

AAA is not simply atherosclerosis. The two share every risk factor and nearly always coexist, but AAA is a degenerative disease of the aortic media — proteolytic destruction of elastin and collagen, chronic inflammation, smooth-muscle apoptosis. That is why some patients with terrible atherosclerosis never dilate, and why the search for medical therapy has chased matrix metalloproteinases and inflammation rather than the lipid pathway alone.[2]

The 5.5 cm threshold is the single most examined number in the topic, and it is not arbitrary. It is the diameter at which annual rupture risk overtakes elective operative mortality in an average-risk patient. The UK Small Aneurysm Trial and its 12-year follow-up fixed it: below 5.5 cm, early surgery offered no survival advantage over surveillance. The fork is real, and it is evidence-based.[8]

Because most aneurysms are silent, the strategy is screening, not waiting. The Multicentre Aneurysm Screening Study (MASS) randomised older men to a single ultrasound and reduced aneurysm-related mortality by 42% at four years — the evidence on which the NHS programme and the USPSTF recommendation (men 65 to 75 who have ever smoked) both stand. One scan at 65 is the intervention that finds the aneurysm before it finds you.[5]

Once an AAA is found, every decision hangs on the anteroposterior diameter, measured outer-to-outer on ultrasound:[1]

[1]

The escalation triggers that override absolute size are a rapid growth rate (over 0.5 cm in 6 months, or over 0.7 cm per year for a 3 to 4 cm AAA) and any new pain attributable to the aneurysm — symptomatic means imminent rupture, and symptomatic is referred within days, not weeks.[3]

Who gets AAA — the older male smoker, and why diabetes is the one risk factor that protects

AAA is a disease of older men of Northern European descent. Community ultrasound surveys put prevalence at 4 to 8% in men over 65 and ten-fold lower, 0.5 to 1.5%, in women — a male-to-female ratio near 6 to 1. Mean age at diagnosis is about 70; AAA is rare before 55. Prevalence is highest in Scandinavian and North American white populations and lower in African, South Asian and East Asian groups, a gap only partly explained by screening intensity.[2]

The risk factors, in the order the viva wants them:[1]

• Smoking — the dominant modifiable risk factor; ever-smoking confers a 3- to 5-fold increase, drives faster growth and higher rupture rates, and accounts for the majority of attributable deaths. Duration matters more than current status.
• Age — prevalence climbs sharply after 55, which is why screening targets the 65 to 75 band.
• Male sex — six times more common, which is why screening is sex-selective.
• Family history — a first-degree relative with AAA doubles to quadruples risk and produces aneurysms a decade earlier; screen male first-degree relatives from age 60, or 10 years younger than the affected relative at diagnosis.
• Hypertension — modest independent contribution, weighted toward rupture rather than growth.
• Caucasian ethnicity, atherosclerosis and its correlates (coronary disease, peripheral arterial disease, a high ABI), and COPD — an independent risk factor, likely shared proteolytic destruction of elastin in lung and aorta.[2]

The viva wrinkle: AAA shares every risk factor with occlusive atherosclerosis except diabetes. Diabetics, paradoxically, develop AAA less often — diabetic arterial stiffening and medial sclerosis appear to limit dilation. It is the one risk factor that runs the wrong way, and examiners love it.[4]

Laplace — the equation that explains why aneurysms grow until they rupture

Wall Tension = Pressure x Radius / Wall Thickness. That single line is the natural history of AAA compressed into physics, and examiners will ask you to write it. As the aneurysm dilates the radius rises and the wall thins — the same tissue lines a larger circumference — so wall tension climbs, which drives further dilation. It is a positive-feedback loop with only one exit, which is rupture. It is also why hypertension accelerates growth (higher P) and why rupture risk bends upward with size rather than tracking it linearly.[3]

The biology underneath the physics runs on four converging mechanisms:[2]

• Matrix degradation — macrophage-driven matrix metalloproteinases, above all MMP-2 and MMP-9, fragment elastin and cleave collagen faster than they can be rebuilt. Elastin bears the load at physiological pressure; once it is lost — elastin content in an aneurysmal wall can fall below 20% of normal — the load shifts to collagen, which fatigues and fails.
• Chronic inflammation — macrophages, T- and B-cells infiltrate the wall and secrete IL-1beta, IL-6, TNF-alpha and MCP-1, recruiting more cells and upregulating the MMPs. When the infiltrate is dense enough to wrap the aorta in a fibrotic rind, it is an inflammatory AAA.
• Smooth-muscle apoptosis — the cells that should resynthesise elastin and collagen die, and the wall loses its capacity to repair itself.
• Biomechanics — Laplace, above — converts each molecular failure into permanent dilation.[2]

[1]

Everyone forgets the mural thrombus paradox. Most large AAAs carry a laminated intraluminal thrombus, and it is tempting to read it as a passive, even protective, layer. It is not. The thrombus is biologically active — it harbours neutrophils and proteases, blocks oxygen diffusion to the inner wall, and weakens the media it sits on. Chunks embolise distally and produce blue toes, livedo and renal infarcts. The thrombus drives both growth and distal embolic disease.[2]

Familial clustering — 15 to 20% of AAA patients have an affected first-degree relative — and the inverse link with diabetes point to extracellular-matrix and insulin-signalling genetics, but no drug has yet prevented growth in a randomised trial.[4]

Classification by status — asymptomatic, symptomatic, ruptured

The classification that drives urgency is clinical, not anatomical. An asymptomatic intact aneurysm is a surveillance problem; a symptomatic intact aneurysm is urgent; a ruptured aneurysm is a surgical emergency with 80 to 90% mortality. Memorise that ordering, because it sets the tempo of every decision below.[1]

The anatomical and morphological axes the viva will probe:[1]

• By extent — infrarenal (commonest, about 95%, the standard anatomy for both repairs); juxtarenal (neck absent or very short — complicates EVAR, often needs suprarenal clamping); suprarenal and pararenal (demand branched or fenestrated endografts, or open repair with renal revascularisation).
• By shape — fusiform (commonest, circumferential) versus saccular (a localised outpouching of one wall, more often mycotic, post-traumatic or from a penetrating atherosclerotic ulcer).[1]

[1]

Read the bedside signs — the expansile mass, and the triad that is only half-complete

The first symptom of AAA is often death. Most aneurysms are found by screening or on incidental imaging — ultrasound, CT or MRI done for something else — or by a hand that happened to feel an epigastric pulsation. The sensitivity of palpation is only moderate (about 40% overall, over 75% for AAAs over 5 cm) and collapses in the obese, so a mass you cannot feel does not exclude an AAA.[1]

The discriminating bedside sign is expansile, not transmitted. A true AAA pushes the examining fingers apart in every direction with each beat, best felt with the hands placed either side of the mass in the epigastrium or periumbilical region, the patient relaxed and the knees flexed to soften the abdominal wall. A mass that merely moves up and down is transmitting a normal aortic pulsation — a gastric tumour overlying the aorta does exactly this. An expansile mass over 4 cm wide in an older man is an ultrasound the same day.[1]

New pain in a known aneurysm is a danger sign. Deep, constant, non-colicky back, abdominal or flank pain — from pressure on the lumbar vertebrae or stretching of the adventitia — or a frankly tender aneurysm on examination is symptomatic non-ruptured AAA, and symptomatic means imminent rupture. Refer within days, not weeks.[3]

The ruptured AAA triad — pain, hypotension, a pulsatile mass — is complete in only about half of cases. The pain is sudden and severe, abdominal, back or flank, often tearing and radiating to the groin or testes, and it mimics renal colic closely enough to fool the front door. Most ruptures track posterolaterally into the retroperitoneum and form a contained haematoma that may tamponade the bleed; free intraperitoneal rupture exsanguinates before arrival. The trap is the lucid interval: the patient transiently stabilises as the retroperitoneal tamponade holds, then collapses again. Do not be reassured.[1]

The atypical presentations the viva sets as traps:[1]

• Aortocaval fistula — erosion into the IVC produces a massive arteriovenous shunt: high-output cardiac failure, a loud continuous machinery abdominal bruit, leg swelling, renal failure.
• Primary aortoenteric fistula — erosion into the duodenum (D3/D4) presents with a small herald upper-GI bleed followed hours later by catastrophic haematemesis. Any AAA with unexplained GI bleeding is a fistula until proven otherwise.
• Distal embolisation — blue toes, livedo, renal infarcts from the mural thrombus, occasionally the first feature.
• Spinal cord ischaemia — rare paraplegia from erosion of segmental supply.
• Inflammatory AAA — chronic dull pain, raised inflammatory markers, ureteric obstruction, and a dense enhancing fibrotic rind on CT.[2]

[1]

The mimic that kills — never call it renal colic in an older smoker

Ruptured AAA is one of medicine's great mimics, and renal colic is the diagnosis that buries patients. In an older male smoker with apparent ureteric colic, the AAA must be excluded before the stones are treated. The discriminator is the haemodynamics: colic hurts but does not drop the blood pressure, and colic does not produce a pulsatile mass. A CT-KUB read only for stones, or one that does not include the aorta, has killed patients by missing the aneurysm behind it.[1]

[1]

The cardinal pitfall, named so you do not forget it: misdiagnosing rupture as renal colic. An older smoker, hypotension disproportionate to the degree of pain, and a palpable mass — that triad buys a bedside ultrasound now, not a urology referral.[1]

Ultrasound to screen and surveille, CT angiogram to plan

Match the investigation to the question being asked. Screening and surveillance ask whether it is there and how big — ultrasound answers. Repair planning asks what the neck, the access and the branches look like — only CT angiography answers.[1]

Ultrasound is the screening and surveillance modality: cheap, non-invasive, repeatable, accurate to within 2 to 3 mm of the maximum anteroposterior diameter measured outer-to-outer. It does not show the proximal neck, iliac involvement or accessory renal arteries reliably, so it cannot plan a repair — but it is the tool of every screening programme and every surveillance interval.[1]

CT angiography with arterial and venous phases is the gold standard for repair planning. It defines the maximum diameter and the fusiform-versus-saccular shape; the proximal neck (length, diameter, angulation, thrombus, calcification — the determinants of EVAR suitability); the distal landing zone and common iliac arteries; the branch vessels (renal, accessory renal, inferior mesenteric, internal iliac); the access vessels (femoral and iliac calibre, calcification, tortuosity); and, in the stable patient with suspected rupture, contrast extravasation or a retroperitoneal haematoma that confirms the diagnosis. A CTA is mandatory before elective EVAR and strongly preferred before complex open repair.[3]

In suspected rupture the rule is absolute: an unstable patient gets no imaging beyond a bedside ultrasound if needed to confirm — straight to theatre. Do not image the unstable patient. A stable patient with suspected rupture gets an urgent CT angiogram to confirm rupture and to select emergency EVAR (rEVAR) versus open repair.[1]

Elective pre-operative work-up is, above all, cardiac work-up, because ischaemic heart disease is the commonest comorbidity and the leading cause of perioperative death: FBC, U and E, coagulation, group and save or crossmatch, LFTs, glucose, HbA1c, lipids, ECG, echocardiogram and cardiopulmonary exercise testing where available, lung function in smokers, and a baseline creatinine and eGFR to predict contrast nephropathy and post-operative AKI.[1]

[1]

Unstable rupture = straight to theatre, no CT — permissive hypotension is the doctrine

Ruptured AAA is a surgical emergency in which every minute matters, and the single most dangerous error is over-resuscitation. The objective is operative control of the aorta as fast as possible while preserving the retroperitoneal tamponade that is the only thing keeping the patient alive. Raising the blood pressure to normal dislodges that tamponade and restarts fatal bleeding — permissive hypotension is not a compromise, it is the doctrine.[1]

[1]

The rupture is managed by emergency open repair or, where anatomy and a rEVAR service allow, emergency EVAR (rEVAR): permissive hypotension until cross-clamping; rapid laparotomy with a supracoeliac clamp for immediate proximal control, then definitive repair once control is secured; or rEVAR in centres with a 24/7 service and a suitable aneurysm — the IMPROVE trial suggested a mortality benefit in women and faster recovery. Alongside the operation, correct coagulopathy, acidosis and hypothermia — the trauma lethal triad — and plan post-operative ITU. Even with all of this, mortality remains 40 to 50% of those who reach theatre, and 80 to 90% overall.[1]

The 5.5 cm fork — best medical therapy for all, repair for the few

Every patient with an AAA, whatever its size, gets best medical therapy; only some get a graft. The decision to repair turns on size, growth rate, symptoms and fitness, and it is made at the multidisciplinary vascular meeting.[3]

Best medical therapy is cardiovascular risk reduction for every AAA patient:[1]

• Smoking cessation — the single most effective intervention; slows growth and lowers rupture risk. Refer to stop-smoking services; offer nicotine replacement, varenicline or bupropion.
• Blood pressure control — target clinic BP under 140/90 mmHg (under 130/80 if high risk); beta-blockers help pre-operatively by lowering both pressure and the rate of pressure rise (dP/dt), the component of wall stress that loads the aneurysm.
• Lipid lowering — a statin for all; lowers cardiovascular events and may slow growth modestly.
• Antiplatelet therapy — aspirin 75 mg once daily for secondary cardiovascular prevention; not proven to affect growth or rupture.
• Lifestyle — regular exercise, weight reduction, and management of diabetes and COPD.[1]

No drug has yet been shown to prevent AAA growth or rupture in a randomised trial. Doxycycline (MMP inhibition), roxithromycin (anti-chlamydial) and angiotensin-receptor blockade have all been studied and all disappointed. Surveillance and risk-factor control remain the cornerstone.[4]

Below 5.5 cm the surveillance pathway is safe — the UK Small Aneurysm Trial showed no survival advantage of early surgery in that range. The intervals are fixed: under 3 cm discharge; 3.0 to 4.4 cm rescan at 12 months (rupture under 1% per year); 4.5 to 5.4 cm rescan at 3 months (rupture 1 to 5% per year); 5.5 cm or more refer for repair, where rupture finally exceeds operative risk.[8]

Repair is offered when the AAA is 5.5 cm or more in an average-risk man, 5.0 cm or more in a woman (whose smaller aorta ruptures at lower diameters) or in a rapidly expanding or symptomatic aneurysm at any size, and the patient is fit enough to benefit — life expectancy over two years and acceptable operative risk.[4]

Open is durable, EVAR needs lifelong surveillance for endoleak

Open repair is the durable, one-off fix; EVAR trades a lower perioperative mortality for lifelong surveillance. Anatomy, fitness and patient preference decide between them at the multidisciplinary vascular meeting.[1]

Open repair is a midline laparotomy (or a left retroperitoneal approach for juxtarenal and suprarenal aneurysms) under general anaesthesia. The steps: mobilise the small bowel and duodenum; gain proximal control by clamping the infrarenal aorta — suprarenal or supracoeliac for juxtarenal aneurysms — and distal control of the common iliacs; give IV heparin 100 units/kg before clamping; open the aorta longitudinally, evacuate the mural thrombus, ligate the lumbar and inferior mesenteric arteries; sew in a Dacron or PTFE tube or bifurcated graft end-to-end proximally and distally; and close the aneurysm sac over the graft. Once healed the graft rarely fails and no lifelong surveillance is needed. Elective 30-day mortality is 4 to 5%; the cost is a major laparotomy, six to twelve weeks of recovery, and significant cardiopulmonary stress.[1]

EVAR delivers a stent-graft — a Dacron graft on a metal skeleton — through the common femoral arteries under fluoroscopy, excluding the aneurysm from the circulation so the sac depressurises and shrinks. No laparotomy, no aortic cross-clamp, shorter stay, faster recovery. It demands suitable anatomy:[3]

• a proximal neck of adequate length (over 10 to 15 mm), diameter (under 32 mm) and angulation (under 60 degrees), free of heavy thrombus and calcification;
• access vessels (common femoral and iliac arteries) of adequate calibre (over 7 mm) and acceptable tortuosity;
• a distal landing zone in the common iliac arteries.[1]

Only about 50 to 60% of infrarenal AAAs meet standard EVAR criteria; the rest need open repair or complex fenestrated and branched endografts.[4]

Two trials fixed the EVAR-versus-open decision. EVAR-1 (fit patients, AAA over 5.5 cm) cut 30-day mortality to 1.7% versus 4.7% for open repair but delivered no long-term survival advantage — late endograft complications eroded the early gain. DREAM (AAA over 5 cm) corroborated it: 1.2% versus 4.6% operative mortality, survival equivalence by two years, more re-interventions in the EVAR arm. Together they say EVAR for the older, less-fit patient with suitable anatomy, open for the young and fit who want one durable operation. EVAR-2, in patients unfit for open repair, showed no overall survival benefit because the patients were too sick for AAA to determine their outcome.[6][7]

[6]

After EVAR, surveillance is lifelong — typically a CT angiogram at one month, then CT and ultrasound alternating annually — to catch endoleak, graft migration, limb occlusion and sac enlargement. Open-repair patients need no such follow-up once recovered. That surveillance burden, and the re-interventions it generates, is the price of the lower perioperative mortality.[4]

The endoleak ladder — I and III urgent, II commonest and watch

An endoleak is persistent flow into the aneurysm sac after EVAR, keeping it pressurised and at risk of rupture. They occur in 10 to 20% of EVARs and sort cleanly by source — and the management ladder is one of the most examinable tables in vascular surgery.[1]

[1]

The rule that earns marks: type I and III threaten rupture and need urgent re-intervention; type II, the commonest, is usually benign and is watched, with intervention only if the sac enlarges.[3]

[3]

The subtypes the viva will probe

• Inflammatory AAA. A dense fibrotic rind invests the wall and encases the ureters (hydronephrosis), duodenum and IVC. Chronic back or abdominal pain, raised CRP and ESR, a characteristically enhancing retroperitoneal mass on CT. Operative risk is higher; steroids or immunosuppression may settle the inflammation first, and most are now treated by EVAR if feasible.[2]
• Mycotic (infected) AAA. Bacterial infection of the wall — Staphylococcus, Salmonella, Streptococcus — with fever, sepsis and back or abdominal pain, often saccular and atypically located. Management is long-term targeted antibiotics plus excision with extra-anatomic bypass or in-situ grafting with antibiotic-impregnated material; EVAR is a bridge or an option in the very unfit.[3]
• Aortoenteric fistula. Primary arises from erosion of an AAA into the duodenum (D3); secondary, far commoner, follows previous aortic grafting. The hallmark is a herald upper-GI bleed — small and self-limiting — followed hours or days later by exsanguination. Any GI bleed in a patient with an AAA or graft needs urgent endoscopy and CT angiography, and the treatment is emergency surgery.[1]
• Juxtarenal and suprarenal AAA. Absent or short necks at the renal level defeat standard EVAR. Options are open repair with suprarenal clamping and renal revascularisation, or fenestrated and branched EVAR in experienced centres, which preserves renal and visceral branches while excluding the aneurysm.[1]
• Symptomatic non-ruptured AAA. Pain or tenderness in a known aneurysm is treated as imminent rupture — urgent repair regardless of absolute size, ideally within days.[1]
• Popliteal aneurysm. Found in up to 40% of men with AAA and bilateral in half — palpate the popliteal pulses in every AAA patient. Asymptomatic popliteal aneurysms over 20 mm are considered for repair to prevent limb-threatening thrombosis or embolism.[3]

The preventable-harm list — five errors that kill AAA patients

These are the failures that turn a survivable disease into a death, and they are all avoidable:[1]

1. Misdiagnosing rupture as renal colic — ultrasound the older smoker before you treat the stone; a CT-KUB read only for stones has missed the AAA and killed the patient.
2. Over-resuscitating the ruptured patient to normotension — you dislodge the retroperitoneal tamponade and restart the fatal bleed. Permissive hypotension, SBP 70 to 80 mmHg, until the clamp is on.
3. Delaying theatre for an unnecessary CT in the unstable patient — the unstable rupture goes straight to theatre; CT is for the stable.
4. Forgetting lifelong surveillance after EVAR — the sac can re-pressurise through an endoleak and rupture years later; the lower perioperative mortality is bought with permanent follow-up.
5. Repairing a small AAA without weighing fitness — in the very frail, operative mortality can exceed the rupture risk you are trying to prevent; screen relatives, do not over-operate.[3]

The complications stack on top of those errors. Of the disease itself: rupture (mortality 80 to 90%), distal embolisation (blue toes, renal infarcts, livedo), aortocaval fistula, aortoenteric fistula, and ureteric obstruction in inflammatory AAA. Of open repair: myocardial infarction — the leading cause of perioperative death — acute kidney injury from clamping, contrast and hypoperfusion, colonic ischaemia from IMA sacrifice (ischaemic colitis of the left colon with bloody diarrhoea), spinal cord ischaemia and paraplegia after suprarenal clamping, respiratory failure in COPD, and bleeding, graft infection and incisional hernia. Of EVAR: endoleak, graft migration and limb thrombosis (acute limb ischaemia), access-vessel injury, contrast nephropathy, post-implantation syndrome (transient fever, raised CRP, back pain in the first week), and rare graft infection that may surface years later as an aortoenteric fistula.[1]

Prognosis — rupture risk by size, and what really kills the survivor

Rupture risk is the core of the prognosis, and it bends upward with diameter:[1]

• under 5 cm — under 1% per year
• 5 to 5.9 cm — 3 to 5% per year
• 6 to 6.9 cm — about 10% per year
• 7 cm or more — over 20 to 25% per year[1]

These are population averages; women rupture at smaller diameters, symptomatic aneurysms at any size, and rapidly expanding aneurysms more readily.[2]

Elective repair mortality is 4 to 5% open and 1.5 to 2% EVAR at 30 days, with five-year survival around 70% — limited not by the graft but by coexisting cardiovascular disease. Ruptured AAA mortality is 80 to 90% overall: about half die before reaching hospital, and of those who reach theatre alive, 40 to 50% die. Five-year survival among rupture survivors is around 60%. For surveillance (under 5.5 cm) the rupture risk is under 1% per year, and the UK Small Aneurysm Trial confirmed that surveillance is safe in that range — early operative mortality exceeded the rupture risk it would have prevented.[8]

The disposition is straightforward: detected AAAs go to a vascular surgeon for counselling and follow-up, surveillance is shared between primary care and the screening service, and after repair the patient stays with the vascular team (lifelong for EVAR) on aggressive cardiovascular risk reduction — because the dominant threat to long-term survival is myocardial infarction, not the aneurysm.[1]

Special populations

• Women. AAA is six times less common in women, but it ruptures at smaller diameters because their aortas are smaller. The ESVS 2024 guidelines suggest considering repair at 5.0 cm rather than 5.5 cm. Screening is not routine because prevalence is low, but a woman with a family history or smoking history warrants individual assessment.[4]
• Elderly and frail. EVAR is preferred where anatomy allows — the lower perioperative mortality matters most when physiological reserve is limited. In the very frail, or with life expectancy under two years, surveillance alone may be the kinder choice.[1]
• Family history. First-degree relatives carry 2- to 4-fold risk and develop AAA a decade earlier; many guidelines advise a one-off screening ultrasound of male first-degree relatives from age 60, or 10 years younger than the affected relative at diagnosis.[1]
• Anticoagulation. Anticoagulation does not increase rupture risk and should be continued for its underlying indication during surveillance; manage it peri-operatively in the usual way.[1]
• Renal impairment. Contrast for CT and the clamp of open repair both threaten the kidney — pre-hydration, nephrotoxin avoidance, and preferential EVAR (no clamp) where feasible.[1]
• Low- and middle-income settings. No national screening programme exists; AAA is under-diagnosed and many patients first present with rupture. Open repair predominates because EVAR infrastructure and lifelong CT follow-up are concentrated in a few centres, and the threshold for repair is often dictated by presentation rather than by screening.[2]

The four trials that fix every threshold

The evidence base is four randomised trials, and every threshold in modern practice traces back to one of them.[1]

[8] [5] [6] [7]

Guideline deltas

The mantra

Carry one line out of this topic and it should be this:[1]

Over 3 cm is AAA. Over 5.5 cm is repair. Unstable rupture is theatre, not CT.[1]

Everything else — Laplace, the endoleak ladder, EVAR-1 and DREAM, the women-at-5.0 correction, the screening scan at 65 — hangs off those three clauses. Say them in that order on the ward round and you have already answered most of the viva.[1]

Ward-round test

1. A 68-year-old smoker arrives with flank pain, BP 76/50, and a pulsatile epigastrium. What is your first action, and what do you explicitly not do?

Straight to theatre — no CT. Two large-bore cannulae, crossmatch 6 to 10 units, activate the massive transfusion protocol, and hold him at permissive hypotension (SBP 70 to 80 mmHg) until cross-clamping. Do not resuscitate to normotension — you will dislodge the retroperitoneal tamponade. Induce only when the surgeon is scrubbed.[1]

2. Why is 5.5 cm the elective repair threshold, and which trial fixed it?

At 5.5 cm the annual rupture risk overtakes elective operative mortality in an average-risk patient. The UK Small Aneurysm Trial — and its 12-year follow-up — fixed it: below 5.5 cm, early surgery offered no survival advantage over surveillance.[8]

3. EVAR cut 30-day mortality in EVAR-1 — by how much, and was there a long-term survival benefit?

1.7% EVAR versus 4.7% open. No long-term survival benefit — late endograft complications and re-interventions eroded the early gain, which is why EVAR demands lifelong surveillance for endoleak. DREAM corroborated it at 1.2% versus 4.6%.[6][7]

4. A routine surveillance CT three years after EVAR shows sac enlargement with no contrast leak. What is this, and what do you do?

Type V endoleak — endotension. Investigate (often a dedicated CTA), and if the sac keeps growing, reline the graft. By contrast, a type I or III endoleak needs urgent repair; a type II (the commonest) is observed and intervened on only if the sac enlarges.[3]

References

1. [1]Isselbacher EM, Preventza O, Hamilton Black J 3rd, et al. 2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines Circulation, 2022.PMID 36322642
2. [2]Kent KC Clinical practice. Abdominal aortic aneurysms N Engl J Med, 2014.PMID 25427112
3. [3]Chaikof EL, Dalman RL, Eskandari MK, et al. The Society for Vascular Surgery practice guidelines on the care of patients with an abdominal aortic aneurysm J Vasc Surg, 2018.PMID 29268916
4. [4]Wanhainen A, Verzini F, Van Herzeele I, et al. Editor's Choice -- European Society for Vascular Surgery (ESVS) 2024 Clinical Practice Guidelines on the Management of Abdominal Aorto-Iliac Artery Aneurysms Eur J Vasc Endovasc Surg, 2024.PMID 38307694
5. [5]Ashton HA, Buxton MJ, Day NE, et al. The Multicentre Aneurysm Screening Study (MASS) into the effect of abdominal aortic aneurysm screening on mortality in men: a randomised controlled trial Lancet, 2002.PMID 12443589
6. [6]Greenhalgh RM, Brown LC, Kwong GP, Powell JT, Thompson SG; EVAR trial participants Comparison of endovascular aneurysm repair with open repair in patients with abdominal aortic aneurysm (EVAR trial 1), 30-day operative mortality results: randomised controlled trial Lancet, 2004.PMID 15351191
7. [7]Prinssen M, Verhoeven EL, Buth J, et al. A randomized trial comparing conventional and endovascular repair of abdominal aortic aneurysms N Engl J Med, 2004.PMID 15483279
8. [8]Powell JT, Brown LC, Forbes JF, et al. Final 12-year follow-up of surgery versus surveillance in the UK Small Aneurysm Trial Br J Surg, 2007.PMID 17514693