View source for Abdominal aortic aneurysm

==Background==
*Focal dilation of the abdominal aorta to >50% of normal diameter (typically >3 cm)
*Most commonly infrarenal (95%)
*'''Ruptured AAA is a surgical emergency''' with overall mortality of '''65-85%''' (including prehospital deaths)
*For those who reach OR, mortality is still 40-50%
*Risk factors:
**Age > 65 years, male sex (6:1 ratio), smoking (strongest modifiable risk)
**[[Hypertension]], family history, [[COPD]], peripheral vascular disease
**Connective tissue disorders (Marfan, Ehlers-Danlos)
*Risk of rupture increases with size:
**<5 cm: ~1%/year
**5-6 cm: ~10%/year
**>7 cm: ~30%/year

==Clinical Features==
===Classic Triad of Ruptured AAA===
*Abdominal/back pain + hypotension + pulsatile abdominal mass
*Present in only ~50% of cases

===Presentations===
*Intact (unruptured) AAA: usually asymptomatic or incidental finding
*Symptomatic unruptured: abdominal/back/flank pain (expanding aneurysm)
*Ruptured AAA:
**Sudden, severe abdominal or back pain (may radiate to groin, flank, or thigh)
**Hypotension / hemorrhagic [[shock]]
**Pulsatile abdominal mass (difficult to palpate in obese or hypotensive patients)
**May present as syncope or [[cardiac arrest]]
*Contained rupture: retroperitoneal hemorrhage may be temporarily tamponaded
**Transient hemodynamic stability — '''do not be falsely reassured'''
*Mimics many conditions: [[renal colic]], [[diverticulitis]], [[MI]], musculoskeletal back pain

==Differential Diagnosis==
{{Abdominal Pain DDX Diffuse}}

==Evaluation==
===Bedside Ultrasound (First-Line in ED)===
*POCUS is the single most important test for unstable patients
*'''Sensitivity ~100%''' for detecting aneurysm >3 cm<ref>Tayal VS, et al. Emergency department sonographic measurement of aortic diameter. ''J Ultrasound Med''. 2003;22(12):1291-1294. PMID 14680900</ref>
*Measure outer wall to outer wall in transverse view
*Cannot reliably detect rupture (free fluid may suggest it but absence does not exclude)
*US identifies the aneurysm; CT identifies the rupture

===CT Angiography===
*Gold standard for defining anatomy and surgical planning
*Identifies rupture, contained leak, extent, relation to renal arteries
*ONLY for hemodynamically STABLE patients
*Sensitivity for rupture approaches 100%

===Labs===
*Type and crossmatch (at least 6 units PRBCs)
*CBC, BMP, coagulation studies, lactate
*'''Do NOT delay resuscitation or imaging for labs'''

==Management==
===Ruptured AAA===
*Activate massive transfusion protocol
*Permissive hypotension: target SBP 70-90 mmHg
*Avoid aggressive crystalloid resuscitation; use blood products
*Emergent vascular surgery consultation
*'''Unstable patients go directly to OR''' (do NOT delay for CT)
**EVAR if anatomy suitable and resources available
**Open surgical repair if EVAR not feasible
*If arrest: consider REBOA or ED thoracotomy with aortic cross-clamp

===Symptomatic Unruptured AAA===
*Urgent vascular surgery consultation
*Blood pressure control: target SBP 100-120 mmHg
*Admit for expedited repair

===Incidental Asymptomatic AAA===
*<4 cm: surveillance US every 12 months
*4-5.4 cm: surveillance US every 6 months; vascular referral
*>=5.5 cm: refer for elective repair
*USPSTF: one-time screening US for men 65-75 who have ever smoked

==Disposition==
*Ruptured: emergent OR / ICU
*Symptomatic unruptured: monitored bed, urgent vascular consult
*Asymptomatic incidental: outpatient vascular referral

==See Also==
*[[Aortic dissection]]
*[[Abdominal pain]]
*[[Shock]]
*[[Ultrasound: Aorta]]

==References==
<references/>
*Chaikof EL, et al. SVS practice guidelines for AAA. ''J Vasc Surg''. 2018;67(1):2-77. PMID 29268916
*Kent KC. Abdominal aortic aneurysms. ''N Engl J Med''. 2014;371(22):2101-2108. PMID 25427112

[[Category:Vascular]]