Abdominal Aortic Aneurysm Repair
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Direct answer
Elective repair is offered once an abdominal aortic aneurysm reaches 5.5 cm in a man or 5.0 cm in a woman, grows faster than about 1 cm a year, or becomes tender — a symptomatic aneurysm is repaired whatever its diameter. Rupture announces itself with the classical triad of sudden abdominal or back pain, a pulsatile mass and hypotension; about half die before reaching hospital. Open repair replaces the aneurysmal segment with a Dacron tube or bifurcated graft through a transperitoneal or retroperitoneal approach; endovascular repair suits favourable anatomy and is a separate topic. Elective open repair in a fit patient carries mortality of roughly 2–5%, against perhaps a third of those who reach theatre after rupture — the entire rationale for finding these before the catastrophe.
What you must remember
- Thresholds of 5.5 cm in men and 5.0 cm in women come from the UKSAT and ADAM trials; smaller for symptomatic, tender or rapidly growing aneurysms and for familial disease.
- Screening: one-time ultrasound for men aged 65–75 who have ever smoked (USPSTF), or all men at 65 in the UK programme; India has no national screening programme, so diagnosis is usually incidental.
- Small aneurysms grow a few millimetres a year; typical surveillance is roughly annual from 4.0 cm and six-monthly from 4.5 cm.
- Open technique: transperitoneal or left retroperitoneal exposure (the latter for hostile abdomens and reoperations), infrarenal clamping — higher when the neck fails — and tube or bifurcated inlay grafting.
- Clamping raises afterload and can precipitate myocardial ischaemia; declamping causes hypotension and acidotic washout, so the anaesthetist is warned before release.
- Specific complications: renal injury from suprarenal clamping, colonic ischaemia from interruption of inferior mesenteric and internal iliac flow (bloody diarrhoea — assess with flexible sigmoidoscopy), distal embolisation ("trash foot"), and late graft infection or aortoenteric fistula with herald bleeds.
- Inflammatory aneurysms encase the ureters and duodenum; mycotic aneurysms require excision with in situ or extra-anatomic reconstruction plus prolonged antibiotics.
- Rupture management: permissive hypotension (systolic near 90 mmHg), massive transfusion protocol and immediate theatre — no time-consuming CT in an unstable patient with a known aneurysm.
Two patients, one aneurysm
Consider first a fit 70-year-old with a 5.6 cm infrarenal aneurysm found on an ultrasound done for gallstones. The pathway is cardiac risk stratification, lung optimisation, then open versus endovascular decided by neck anatomy and life expectancy; a hostile neck in an unfit patient pushes toward fenestrated technology, not a standard stent graft. Now the second patient: a 75-year-old collapses with back pain, a pulsatile mass and a blood pressure of 80 systolic. Permissive hypotension keeps the fragile retroperitoneal clot intact — vigorous fluid resuscitation can pop it — while blood products are prepared and theatre is activated; if he is stable enough to reach CT quickly, the study confirms rupture and anatomy for a possible endovascular approach. On the table, control comes first with a supracoeliac clamp if needed, dropping to infrarenal once the neck is secured. The two paragraphs together are the screening argument: detection converts a catastrophe with greater than 50% mortality into a planned operation with 2–5%.
How the exam frames it
Examiners love the diameter question: why 5.5? Because UKSAT and ADAM found no survival benefit from repairing smaller aneurysms while operative risk persists — and why lower for women? Because women rupture at smaller diameters in observational datasets. The second favourite is the postoperative patient with bloody diarrhoea on day three: colonic ischaemia until sigmoidoscopy proves otherwise, from loss of inferior mesenteric and internal iliac collaterals. Third, the patient who reports a small volume of fresh rectal bleeding years after grafting: aortoenteric fistula until excluded — CT angiography and a plan for complex revision, not reassurance. Answers built on mechanism separate a pass from a commendation.
Frequently asked questions
At what diameter is elective repair indicated?
5.5 cm in men and 5.0 cm in women per current guidance, earlier for rapid growth beyond about 1 cm a year, tenderness or symptomatic aneurysm.
Which patients should be screened for abdominal aortic aneurysm?
Men aged 65–75 who have ever smoked (or all men at 65 in national programmes); India has no organised screening, so clinicians must image opportunistically in smokers and those with family history.
What physiological consequences follow aortic clamping?
Sudden afterload increase risking myocardial ischaemia, plus altered renal perfusion with high clamps; declamping then produces hypotension from venous pooling and acidotic washout.
What is permissive hypotension in rupture?
Deliberately accepting a systolic pressure near 90 mmHg until control, because over-resuscitation disrupts the contained retroperitoneal haematoma and re-bleeds it.
How does colonic ischaemia present after repair?
Bloody diarrhoea with abdominal distension or leucocytosis in the first days, assessed by flexible sigmoidoscopy; mild cases settle, transmural necrosis demands resection.
When is open repair chosen over endovascular?
When anatomy is hostile to a stent graft, when the patient is young and durable exclusion is valued, or with infective and inflammatory aneurysms where open reconstruction with in situ graft or flap may be preferable.