Abdominal aortic aneurysm

Background

• Infrarenal diameter >3cm or >50% increase in size of diameter
  • 85% of cases are infrarenal
• M to F ratio is 4:1
• Rupture Risk
  • <4cm: low risk for rupture
  • 4-5cm: 5 year risk 3-12%
  • >5cm: 25-41%
  • Rupture possible at any size, most commonly >5cm
  • Mortality with rupture: 85-90%

Risk Factors

• Smoking
  • Risk factor most strongly associated with AAA
  • Also promotes the rate of aneurysm growth
• Age (prevalence is negligible in age <50yrs)
• Family history
• Hypertension
• Diabetes mellitus
• Hyperlipidemia

Clinical Features

• Classic triad is pain + hypotension + pulsatile mass
  • Pain often described as sudden, severe, radiating to back
• Syncope (10%)
• Signs of Retroperitoneal hemorrhage
• Massive GI bleed from erosion into intestines
• Pain + AAA = rupture until proven otherwise
• Acute abdomen + hypotension = possible rupture
• Gross Hematuria can be caused by an aortocaval fistula (very rare)

Differential Diagnosis

Diffuse Abdominal pain

• Abdominal aortic aneurysm
  • Aortocaval fistula
• Acute gastroenteritis
• Aortoenteric fisulta
• Appendicitis (early)
• Bowel obstruction
  • Large bowel obstruction
    • Ogilvie's syndrome
  • Small bowel obstruction
• Bowel perforation
• Gastroparesis
• Diabetic ketoacidosis
• Inflammatory bowel disease
• Mesenteric ischemia
• Pancreatitis
• Peritonitis
• Sickle cell crisis
• Spontaneous bacterial peritonitis
• Volvulus

Lower Back Pain

• Spine related
  • Acute ligamentous injury
  • Acute muscle strain
  • Disk herniation (Sciatica)
  • Degenerative joint disease
  • Spondylolithesis
  • Epidural compression syndromes
    • Spinal cord compression (non-traumatic)
    • Cauda equina syndrome
    • Conus medullaris syndrome
    • Epidural abscess (spinal)
    • Epidural hematoma (spinal)
  • Spinal fracture
  • Cancer metastasis
  • Spinal stenosis
  • Transverse myelitis
  • Vertebral osteomyelitis
  • Ankylosing spondylitis
  • Spondylolithesis
  • Discitis
• Renal disease
  • Kidney stone
  • Pyelonephritis
  • Nephrolithiasis
• Intra-abdominal
  • Abdominal aortic aneurysm
  • Ulcer perforation
  • Retrocecal appendicitis
  • Large bowel obstruction
  • Pancreatitis
• Pelvic disease
  • PID
• Other
  • Retroperitoneal hemorrhage/mass
  • Meningitis

Evaluation

AAA

• Ultrasound
  • ~100% sensitive for increased diameter
  • Cannot reliably visualize rupture

• CT
  • ~100% sensitive for increased diameter and rupture
  • IV contrast is preferred but not essential

Management

Rupture

• Do not waste time in ED trying to "stabilize" patient
• Immediate surgery consultation/ go to OR
• Crossmatch 6 units of pRBC
• Pain control (avoid hypotension)
• Antihypertensives (use with caution, goal SBP 110-120 mmHg or MAP 70-80)
  • Labetalol: 20mg IV, then 40-80mg IV q10 min (max 300mg)
  • Esmolol: Bolus 500 mcg/kg, then 50-200 mcg/kg/min
  • Nitroprusside: 0.3 - 0.5 mcg/kg/min, titrate to max 10 mcg/kg/min
• Controversial
  • Too little (ischemia), too much (increased bleeding)
    • Consider allowing for permissive hypotension (SBP 80-100) in conscious patient
  • Pressors
    • Norepinephrine 0.05mcg/kg/min IV; titrate by 0.02mcg/kg/min q5min
    • Phenylephrine 100-180mcg/min; titrate by 25mcg/min q10min
    • Dopamine 5mcg/kg/min; titrate by 5mcg/kg/min q10min

Asymptomatic

• Prompt vascular surgery outpatient follow-up appt
  • Endovascular (75%) vs open repair
• Screening frequency:
  • 3-4 cm diameter: 12 months
  • 4-5 cm diameter: 6 months
  • 5-6 cm diameter: 1 month
• Elective Surgery indicated if:
  • AAA > 5.5 cm in men
  • AAA > 5 cm in women
  • increase in size > 1 cm/year
  • increase in size > 5 mm/6 months

Complications

• Aortoenteric fistula
• Aortocaval fistula
• Inflammatory abdominal aortic aneurysm
• Acute limb ischemia - embolism to lower extremities

Disposition

• Admit to OR in cases of ruptured OR
• Vasc surgery follow up in asymptomatic cases

References

Authors

Jordan Swartz, Ben Isakson, Ross Donaldson, Amanda Alberino, Neil Young, Kevin Lu, Daniel Eggeman, Daniel Ostermayer, Christopher Kim, Michael Holtz, Claire, Lisa Yee