Abdominal Aortic Aneurysm (AAA)

Related Subjects: Renal Colic | Abdominal Aortic Aneurysm | Acute Abdominal Pain/Peritonitis | Assessing Abdominal Pain | Penetrating Abdominal Trauma | Peripheral Arterial Disease (PAD) |Abdominal Aortic Aneurysm (AAA) | Carotid Endarterectomy | Buerger's disease (Thromboangiitis obliterans ) | Leriche syndrome (aortoiliac occlusive disease) | Vascular Surgery: Introduction | Acute Limb Ischaemia | Ankle-Brachial Pressure Index (ABPI) and Peripheral Vascular Disease | Peripheral Arterial Disease (PAD) | Abdominal Aortic Aneurysm (AAA) | Carotid Endarterectomy | Buerger's disease (Thromboangiitis obliterans) | Leriche syndrome (aortoiliac occlusive disease) |Acute Rhabdomyolysis |Hyperkalaemia |Acute Kidney Injury

🩸 Abdominal Aortic Aneurysm (AAA) → Defined as aortic dilation >3 cm. • Surgery indicated when >5.5 cm, symptomatic, or rapidly expanding. • Mortality: ~6% for elective repair vs up to 50% for emergency repair ⚠️. • Common in >60 yrs, ♂ > ♀, strongly linked to smoking 🚬. Always consider in elderly patients with back or abdominal pain!

ℹ️ About AAA

• 📏 Defined as ≥50% increase in diameter vs normal; abdominal aorta aneurysmal at >3 cm.
• ⚠️ Surgery threshold: >5.5 cm, symptomatic, or rapidly enlarging.
• ⬇️ Most are infra-renal; may extend to iliac arteries.

🧬 Aetiology & Pathophysiology

• 🦠 Chronic inflammation + elastin/collagen degradation → wall weakness.
• 🧬 Genetic predisposition (familial clustering, Marfan, Ehlers-Danlos).
• 📊 Fusiform (diffuse dilation) vs saccular (outpouching).
• 💥 Larger aneurysm → higher wall tension → ↑ rupture risk.
• 🛑 Over-resuscitation can ↑ BP, dilute clotting factors → worsen bleeding.

⚠️ Risk Factors

• 🚬 Smoking (strongest modifiable risk)
• 👴 Age >65, ♂ sex (5–10x risk)
• 🏋️ High BMI, tall stature, COPD
• 🧬 Connective tissue disease (Marfan, EDS)
• 👨‍👩‍👦 Family history of AAA
• Risk of rupture: ♀ sex (3x risk), large size >5.5 cm, smoking, low FEV₁

🩺 Clinical Presentation

• 💥 Sudden severe abdo/back/flank pain ± radiation to groin.
• 📉 Hypotension/shock.
• 🫀 Pulsatile, expansile abdominal mass (classic triad: pain + hypotension + mass → seen in only 25–50%).
• 🛑 Aorto-enteric fistula → GI bleed.
• 🦵 Distal emboli → limb ischaemia.
• 👴 Elderly male with severe back pain → always exclude AAA.

🔎 Investigations

• 🩸 Bloods: FBC, U&E, LFT, lactate, ABG, crossmatch.
• 🖼️ Imaging: • Bedside USS = fast, good for unstable patients. • CT angiogram = gold standard for surgical planning (esp. EVAR). ⚠️ Don’t delay transfer for CT if unstable.
• 📈 ECG, CXR as supportive tests.

🎭 Differential Diagnoses

🛠️ Emergency Management

• 🔄 Resuscitation: ABC, O₂, permissive hypotension (SBP 90–120 mmHg).
• 💉 Blood: 2x IV access, crossmatch, massive transfusion protocol (RBC, FFP, platelets).
• 📞 Immediate vascular surgery referral; transfer if needed.
• ⚠️ Delay anaesthetic induction until knife-to-skin → avoids sudden collapse.

🔪 Surgical Options

• Open Repair: Midline laparotomy, clamp proximal/distal aorta, insert synthetic graft (Dacron/PTFE). High blood loss risk; ICU postop.
• EVAR (Endovascular Aneurysm Repair): Stent graft via femoral arteries. Less invasive, lower immediate mortality, but requires lifelong imaging follow-up (endoleaks).

⚖️ Perioperative Considerations

• 📉 Pre-op: Strict BP control (SBP 90–120).
• 💉 Intra-op: High transfusion requirement (RBC, FFP, platelets).
• 🏥 Post-op: ICU monitoring. Complications: graft infection, AKI, multi-organ failure.

📚 References

• Abdominal Aortic Aneurysm (NICE Guideline)
• RCEM Guideline: Ruptured AAA

Case – Ruptured Abdominal Aortic Aneurysm (AAA)

A 74-year-old man with smoking and hypertension presents with sudden tearing abdominal/back pain, collapse, pallor, and a pulsatile abdominal mass; he is hypotensive and tachycardic with cool peripheries. Bedside POCUS shows a large infrarenal aneurysm with free fluid. Initiate ABCDE, two large-bore cannulas, permissive hypotension (target SBP ~80–90 mmHg) to preserve clot stability, activate major haemorrhage protocol, crossmatch blood, give tranexamic acid per local policy, and avoid unnecessary imaging if unstable. Urgently involve vascular surgery for definitive repair (EVAR if anatomically suitable; open repair if not). Provide broad-spectrum antibiotics if contaminated rupture suspected, correct coagulopathy, and alert theatres/ICU. Post-op, monitor for complications: renal failure, abdominal compartment syndrome, limb ischaemia, and myocardial injury.

Case – Symptomatic (unruptured) Abdominal Aortic Aneurysm

A 69-year-old man with a known 5.6 cm infrarenal AAA attends with new, constant deep abdominal/back pain and tenderness but stable observations. Exam notes a pulsatile mass without peritonism; distal pulses intact. Manage as an impending rupture: ABCDE, IV access, crossmatch, analgesia, cautious BP control (avoid surges), and urgent CT angiography to define anatomy. Early vascular surgery discussion for expedited repair (EVAR if suitable, otherwise open) within hours; keep NBM, avoid heavy anticoagulation unless indicated, and monitor for distal emboli (“blue toe”) or expansion. Educate on risk factors (smoking, HTN) and the UK surveillance/repair thresholds; symptomatic AAAs are treated as emergencies. 🚑