EM@3AM: Abdominal Aortic Aneurysm

Authors: Dave Ediger, MD (EM Chief Resident; Tacoma, WA), Rachel Bridwell, MD (EM Attending Physician; Tacoma, WA) // Reviewed by: Sophia Görgens, MD (EM Resident Physician, Zucker-Northwell NS/LIJ, NY); Cassandra Mackey, MD (Assistant Professor of Emergency Medicine, UMass Chan Medical School);Brit Long, MD (@long_brit)

Welcome to EM@3AM, an emDOCs series designed to foster your working knowledge by providing an expedited review of clinical basics. We’ll keep it short, while you keep that EM brain sharp.

A 72-year-old male presents with left-sided flank pain for the last two weeks that has worsened over the past several hours. He also feels lightheaded when standing today. Vitals are notable for tachycardia to 124 beats per minute and hypotension of 117/84 mm Hg relative to his chart baseline which has an average systolic in the 160s mmHg. You cannot reproduce his pain on your abdominal exam, but you feel a thrill with deep central abdominal palpation.

What is the likely diagnosis, and what are your initial steps in evaluation and management?

Answer: Abdominal aortic aneurysm (AAA)1-22



  • Focal dilation of the tunica intima, media, and adventitia due to loss of elastin, collagen, and smooth muscle1
  • Anatomically, AAA exists between the diaphragm and aortic bifurcation
  • Most common distal to the renal arteries due to distal aortic narrowing resulting in higher pressures and increased wall stress, poor nutrient supply, and relative lack of elastin and collagen1
  • Aneurysm formation is a complex process driven by inflammation, smooth muscle apoptosis, loss of elastin, and proteolysis1,2
    • Related to, but not directly correlated with, atherosclerotic burden1
    • Immune-mediated destruction of the aortic wall3
    • Patients with AAA have higher incidence of inguinal and incisional hernias and diastasis recti, which may reflect systemic collagen fiber degradation1
  • Mycotic aneurysm
    • Arterial aneurysm due to an infection, though not necessarily fungal
    • Rare; 1% of aortic aneurysms; 50% involve the infrarenal aorta4
    • Most often from infectious emboli from bacteremia (i.e., endocarditis) seeding in diseased, atherosclerotic vessels; less commonly from direct invasion through vasa vasorum or lymphatic penetration from infection (i.e., vertebral osteomyelitis)5
    • Salmonella most common organism; also Streptococcus, Staphylococcus6



  • Increasing prevalence though likely secondary to aging population and increased detection2
  • Non-modifiable risk factors:
    • Male sex: 3-4 times more prevalent2
    • Age: risk increases 40% every 5 years above 652
    • Family history: several associated predisposing genes; family history of AAA increases odds ratio by ~22,7
  • Modifiable risk factors:
    • Smoking: each smoking year increases relative risk by 4%7–9
      • Prevalence of cigarette smoking in the U.S. over time mirrors AAA mortality10
    • Hypertension (OR 1.25-1.5)2,8
    • Coronary artery disease, diabetes mellitus, hyperlipidemia, obesity, chronic alcohol use (>2 drinks/day)1,2,8
  • Risk factors for mycotic aneurysm:4,5,11
    • Recent infection: gastroenteritis, urinary infection, pneumonia, osteomyelitis, endocarditis/bacteremia
    • Immunosuppression: diabetes mellitus, steroid use, cancer, chemotherapy
    • IV drug use
    • The above cardiovascular risk factors for AAA increase risk for mycotic aneurysms



  • The United States Preventive Services Task Force (USPSTF) recommends one-time AAA screening with ultrasound in men 65-75 years old who have ever smoked12
    • Only captures 30% of AAAs in the United States
      • 41% of aortic aneurysm deaths are in women, and 22% in nonsmokers9



  • History
    • Varied presentation; most commonly abdominal or back pain, though could also present with chest, flank, buttock, groin, or upper leg pain6
      • Common associated symptoms: syncope or presyncope, lightheadedness/dizziness, hematuria, nausea
      • Subtle but concerning: lower limb weakness, paresthesias, or paralysis; testicular ecchymosis; radicular pain; GI hemorrhage (indicating aortoenteric fistula)13
    • Cardiovascular history, prior vascular or abdominal surgeries, prior aneurysmal screening
    • Anticoagulation status (in case reversal is necessary), tobacco use14
      • Smokeless tobacco increases overall cardiovascular disease risk, though it is unclear how it affects risk for AAA specifically7,14
    • Family history of AAA or other connective tissue diseases
  • Exam
    • Vital signs
      • Heart rate: tachycardia may reflect ongoing hemorrhage or pain
      • Blood pressure:
        • Hypotension suggests rupture
        • May be normal even in ruptured AAA due to retroperitoneal tamponade
        • Normal blood pressure may also represent relative hypotension in a patient with uncontrolled or poorly controlled hypertension15
      • Fever may suggest a mycotic aneurysm, though this is not sensitive5,6
    • Abdominal exam
      • Palpate just above the umbilicus with both palms for pulsations; may be able to measure the width of the edge of pulsations between your hands (>2.5cm abnormal)6,16
      • Rigidity, guarding, or distension may indicate rupture16
      • Vascular exam: palpate pulses in all four limbs, comparing bilaterally and for pulse delay; evaluate for cyanosis or delayed capillary refill6,17
    • Neurologic exam: evaluate lower extremity strength and sensation; ischemic myelopathy from AAA may cause strength/sensation deficits with intact vibration/position sense6
    • Overall, physical exam is insensitive for ruptured AAA; a pulsatile abdominal mass is 47% sensitive, hypotension 31% sensitive15


Varied presentations

  • Classic: 86-year-old male with coronary artery disease, peripheral vascular disease, hypertension, hyperlipidemia, and a 60 pack-year smoking history with deep abdominal pain radiating into his back, hypotension, and a pulsatile abdominal mass13
    • The classic triad of abdominal pain, hypotension, and a pulsatile abdominal mass is present in only 25-50% of patients13
  • Tricky: 68-year-old male with hypertension and a 30 pack-year history presenting with low back pain not improving with conservative treatment
  • Incredibly challenging: 47-year-old female with a long history of kidney stones with flank pain and hematuria18,19



  • Imaging
    • Ultrasound
      • Preferred imaging modality for aneurysm screening/surveillance17
      • 97.8% sensitivity when performed by trained emergency physicians6,15
      • When compared to radiologists, ED residents were 94% sensitive at finding AAA with ultrasound20
      • Confounded by bowel gas, habitus; must visualize entire abdominal aorta to exclude AAA6
      • Limitation: ultrasound is not sensitive for rupture, as this typically occurs into the retroperitoneum6
    • Computed tomography
      • CTA is the gold standard for AAA diagnosis and the best modality for assessing for rupture in hemodynamically stable patients13,17
      • Typically performed with IV contrast, though AAAs can be seen without contrast
        • Suggestive of rupture: retroperitoneal hematoma, focal discontinuity of aortic calcifications, increased attenuation of crescent shape in peripheral aneurysmal wall6
      • Accurate in assessing AAA size, though it may overestimate if slices are not orthogonal to the course of the aorta17
    • Magnetic Resonance Imaging (MRI) and angiography are alternative modalities, though unlikely to be used for ED evaluation6
  • Labs
    • CBC may show anemia in ruptured AAA, though this is nonspecific and delayed6
    • If aneurysm involves renal arteries, may see decreased renal function (worsened GFR)
    • Coagulation studies may reflect a coagulopathy requiring reversal
    • Include type and crossmatch in case of potential ruptured AAA for large resuscitation requirement
    • If concerned for mycotic aneurysm, may see leukocytosis, elevated CRP; 25% had positive blood cultures5
    • Workup may also include troponin, blood gas, liver function, lactate as indicated
    • Urinalysis: Microscopic or macroscopic hematuria may be present in a AAA, mimicking urolithiasis6,19,21



  • Ruptured:
    • Immediate surgical consult, do not delay definitive surgery for stabilization (goal <90 minutes to intervention)17
      • Endovascular (more common) or open surgical repair2,22
    • Ensure multiple large-bore IV access points and availability of blood products17
    • Consider anticoagulant reversal
    • Control pain while avoiding hypotension
    • Transfusion goal hemoglobin >7, though unstable/ruptured patients may warrant transfusion at a higher Hgb17
    • If vascular surgery not available in-house, consider rapid transfer to capable facility17
    • Blood pressure management
      • Permissive hypotension: reasonable to maintain SBP>70 mm Hg with intact mentation and no evidence of end-organ ischemia2,17
      • Consider arterial line for hemodynamic monitoring
      • No large fluid boluses; hypertension accelerates bleeding, and IV fluids dilute clotting factors2,17
      • If hypertensive, start by controlling heart rate with titratable beta blockers (esmolol, labetalol); go low and slow, as ruptured AAA can quickly progress to hemorrhagic shock6
  • Symptomatic:
    • Repair recommended, though urgency is debated, and generally based on size of aneurysm (>5.5cm portends higher risk of rupture)17
    • Society for Vascular Surgery recommends ICU admission for symptomatic patients if delay necessary to optimize comorbid medical conditions17
    • Anticipate rupture; ensure large bore IV access and blood product availability, and if unstable, treat for presumed rupture6
    • Consider other potential causes of presenting symptoms (renal colic, diverticulitis, gastrointestinal bleed, mesenteric ischemia, testicular torsion, inguinal hernia) simultaneously while engaging surgeon and preparing for rupture6
  • Mycotic aneurysm:
    • Engage vascular surgeon for urgent surgery if surgical candidate; mycotic aneurysms are not appropriate for screening given high rate of progression and risk of rupture4,11
    • Start antibiotics against suspected causative organism (Salmonella, Streptococcus, Staphylococcus/MRSA, syphilis, tuberculosis)6
  • Asymptomatic: refer for outpatient vascular surgery follow-up



  • Rupture: 90% mortality13,20
    • Biggest risk factor for rupture is aneurysm size
      • 1-year risk of rupture by size:1
        • <4cm: <1%
        • 4-5.5cm: 1%
        • 5-6cm: 9%
        • 6-7cm: >10%
        • >7cm: 32%
      • Other risk factors include rate of aneurysm growth, female sex, tobacco use, hypertension1,2
    • 80% of infrarenal aneurysms rupture retroperitoneally; ultrasound is insensitive for retroperitoneal bleeding13
    • Contained rupture may initially be hemodynamically stable due to retroperitoneal tamponade13
  • Aortocaval fistula
    • Peri-aortic inflammation may erode inferior vena cava13
    • May have an abdominal bruit, high-output heart failure, hematuria, renal failure13
    • Can also erode into left renal vein, causing left flank pain and renal dysfunction13
  • Aortoenteric fistula
    • Complication of AAA repair, or less commonly due to inflammation from the aneurysm itself6
    • Consider in any patient with GI bleeding in setting of known abdominal aortic aneurysm or prior aortic repair (graft)
    • Initial “herald” bleed may be small volume, followed by a massive exsanguinating bleed hours to months later6
    • Typically erodes into the duodenum13
  • Limb ischemia: evaluate for pulse deficits or lower extremity neurologic symptoms



  • Ruptured or unstable (presumed ruptured): admit or transfer for immediate surgical repair6,17
  • Symptomatic and stable: generally, admit/transfer for surgical repair, or for pre-operative medical optimization based on risk factors3,6,17
  • Asymptomatic
    • >5cm: immediate referral to vascular surgery for endovascular vs open repair
      • Indicated if >5.5cm (men) or >5cm (women), or saccular aneurysm17
  • 3-5cm: follow up with primary care doctor for regular surveillance17
  • Discharge counseling
    • Smoking cessation
    • Follow up for monitoring
    • Return precautions: abdominal pain, dizziness, lightheadedness, syncope, leg pain, hematuria



  • Consider ruptured AAA in all patients over 50 with truncal pain, syncope / presyncope, or hypotension
  • AAA is a local manifestation of systemic vascular disease
  • A ruptured AAA is a surgical emergency regardless of hemodynamic stability
  • Ultrasound is sensitive for rapid bedside AAA screening, but it cannot exclude rupture, which is typically retroperitoneal
  • Don’t let hematuria anchor you to renal pathology or lumbago (muscular back pain)
  • Magic ultrasound numbers: 3×5 (>3cm defines an aneurysm; >5.5cm at high risk for rupture)

A 65-year-old man with a history of smoking and hypertension presents to the emergency department for back pain after falling. On his computed tomography scan, there are no traumatic injuries, but is an incidentally noted abdominal aortic aneurysm of 4 cm. His back pain resolves with acetaminophen. Which of the following is the most appropriate management of this incidental aortic aneurysm?

A) Admission for blood pressure control and vascular surgery consult in the morning

B) Discharge with outpatient vascular surgery and primary care follow-up

C) Emergent vascular surgery consult in the emergency department

D) Ultrasound of the aorta and vascular surgery follow-up in 24 hours





Answer: B

This patient presents with an incidental asymptomatic abdominal aortic aneurysm (AAA) of 4 centimeters. Older patients, males, and smokers are at increased risk of AAA, and patients with risk factors should be screened by their primary care clinicians. Treatment of an aortic aneurysm in the emergency department depends on its size, rate of increase in size, and whether it is symptomatic (syncope or back, abdominal, or flank pain without other pathology). Patients with symptomatic aneurysms or with rupture should have an emergent vascular surgery evaluation and be resuscitated with fluid and blood products as needed. Esmolol is the preferred agent for blood pressure control in hypertensive patients with expanding aneurysm, due to its short half-life and blunting of the shearing stress on the vasculature. Aneurysms > 5 cm should have follow-up within 1– 2 days for elective repair. Asymptomatic aneurysms between 3 and 5 cm should be discharged with outpatient vascular surgery and primary care follow-up for blood pressure control and periodic screening ultrasounds. Aneurysms of 4 cm have a < 1% risk of rupture per year.

Admission for blood pressure control and vascular surgery consultation in the morning (A) is incorrect for any AAA patient. Emergent vascular surgery consult (C) is indicated for ruptured or symptomatic aneurysms. Ultrasound and vascular surgery follow-up in 24 hours (D) is incorrect. Ultrasound is less sensitive than computed tomography for AAA, and only patients with aneurysms > 5 cm require a 1- to 2-day vascular follow-up.

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