Aortic Aneurysm (Abdominal and Thoracic)

Risk factors

• AAA: smoking (most important), age >65, male sex, family history of AAA, hypertension, atherosclerosis, COPD
• TAA ascending: bicuspid aortic valve, connective tissue disease (Marfan, Loeys-Dietz, vascular Ehlers-Danlos), Turner syndrome, family history
• TAA descending: atherosclerosis, hypertension, prior dissection, vasculitis (Takayasu, giant cell arteritis)
• Infections: syphilis (ascending TAA), mycotic aneurysms
• Trauma (deceleration injury at aortic isthmus)

Pathophysiology

Loss of medial elastin and smooth muscle, with collagen disorganization, weakens the aortic wall. Wall tension increases with diameter (Laplace's law), driving further dilation and eventual rupture. Connective tissue diseases produce structurally abnormal extracellular matrix; atherosclerosis drives the degenerative AAA phenotype.

Clinical presentation

Differential diagnosis

• Aortic dissection — Acute tearing pain with pulse deficit; flap on CT angiography; treat hypertension and consider surgery
• Renal colic — Flank pain radiating to groin with hematuria; CT shows stone, not aneurysm — but always image elderly first-time flank pain to exclude leaking AAA
• Diverticulitis — LLQ pain with fever, CT shows colonic inflammation, not vascular abnormality
• Mesenteric ischemia — Postprandial pain, weight loss; CT angiography of mesenteric vessels
• Acute pancreatitis — Epigastric pain radiating to back with elevated lipase
• MI (inferior wall) — Especially in older patients with epigastric or back pain; ECG and troponin

Diagnostic workup

Diagnostic algorithm

Treatment

Complications

• Rupture and exsanguination (mortality >50% even with surgery)
• Aortic dissection
• Distal embolization, limb ischemia
• Aortoenteric fistula (especially post-graft)
• Endoleak after EVAR (types I-V; surveillance imaging required)
• Renal/spinal cord ischemia from suprarenal or thoracoabdominal repairs

PANCE pearls

• USPSTF recommends one-time AAA screening with abdominal ultrasound in men 65-75 who have ever smoked.
• AAAs grow ~0.3-0.5 cm/year on average; rapid expansion (>1 cm/year) is an indication for repair regardless of absolute diameter.
• Triad of hypotension, back pain, and pulsatile abdominal mass = ruptured AAA — to the OR, not to CT if unstable.
• Marfan syndrome: repair ascending aorta at ≥5.0 cm (or 4.5 cm with high-risk features) — lower threshold than degenerative TAA.
• Always check for an aortoenteric fistula in a patient with prior aortic graft and a herald GI bleed — uncontrolled exsanguination follows.

References

• SVS 2018 AAA — The Society for Vascular Surgery practice guidelines on the care of patients with an abdominal aortic aneurysm (Chaikof et al., J Vasc Surg 2018)
• ACC/AHA 2022 Aortic Disease — 2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease (Isselbacher et al., JACC 2022)
• USPSTF 2019 — Screening for Abdominal Aortic Aneurysm: US Preventive Services Task Force Recommendation Statement (JAMA 2019)
• EVAR-1 — Endovascular versus Open Repair of Abdominal Aortic Aneurysm (United Kingdom EVAR Trial Investigators, NEJM 2010)