In a 19‑year‑old thin postpartum woman with a pulsatile abdominal mass, vague abdominal pain, nausea, alternating bowel habits, and vertigo, what is the imaging modality of choice and is it normal to palpate the abdominal aorta?

Imaging for Pulsatile Abdominal Mass in a Young Thin Postpartum Woman

Direct Answer

Ultrasound of the abdominal aorta is the definitive first-line imaging test for this patient, and yes, it is completely normal to palpate the abdominal aorta in a thin 19-year-old woman. 1, 2

Why Palpating the Aorta is Normal in This Patient

• In thin, young patients, the abdominal aorta is frequently palpable on routine physical examination and does not indicate pathology. 1
• The normal infrarenal abdominal aorta measures up to 2 cm in anteroposterior diameter, and a pulsatile sensation is expected given the aorta's proximity to the anterior abdominal wall in patients with minimal subcutaneous fat. 3
• An abdominal aortic aneurysm (AAA) is defined as diameter ≥3.0 cm, representing at least a 50% increase from normal. 3, 2
• AAA is exceptionally rare in women under 50 years old, making this clinical scenario highly unlikely to represent true aneurysmal disease. 3

Recommended Imaging Approach

First-Line Test: Ultrasound

Transabdominal ultrasound of the abdominal aorta is the appropriate initial imaging study with the following advantages: 1, 2

• Sensitivity and specificity approaching 100% for detecting AAA 1, 2
• Reliably detects AAA presence in 98-99% of cases 2
• No radiation exposure—critical consideration in a 19-year-old woman of reproductive age 1, 2
• Widely available, low cost, and poses negligible risk 1
• Can be performed portably, including in emergency department settings 1

Ultrasound Technical Considerations

• Pre-examination overnight fasting is recommended to reduce bowel gas interference and optimize visualization. 1, 2
• The American Institute of Ultrasound in Medicine recommends measuring the greatest outer-to-outer (OTO) diameter of the aortic wall. 1, 2
• Scanning should include longitudinal and transverse images from the diaphragm to the aortic bifurcation. 1
• Only 1-2% of ultrasound studies are inadequate due to large body habitus or excessive bowel gas—unlikely in this thin patient. 1, 2

When Ultrasound is Insufficient

If ultrasound cannot adequately visualize the aorta (highly unlikely in a thin patient), non-contrast CT of the abdomen is the next appropriate step. 1, 2

• CT without contrast is diagnostically equivalent to ultrasound for AAA detection. 1
• Avoids contrast exposure while providing definitive assessment of aortic diameter. 1

When CT Angiography Would Be Indicated

CTA is NOT appropriate as the initial test in this asymptomatic young patient, but would be indicated if: 1, 4

• Ultrasound confirms an aneurysm ≥5.5 cm requiring surgical planning 4, 2
• There is clinical suspicion of contained rupture (acute severe pain, hemodynamic instability) 1
• Pre-intervention planning for endovascular or surgical repair is needed 1

Addressing the Other Symptoms

The constellation of generalized abdominal pain, nausea, alternating diarrhea/constipation, and vertigo in a 19-year-old postpartum woman is far more consistent with functional gastrointestinal disorders (such as irritable bowel syndrome) or other non-vascular pathology than with aortic disease. 5, 6

• These symptoms are not typical manifestations of AAA, which usually presents asymptomatically or with acute rupture (severe pain, shock, pulsatile mass). 7
• If ultrasound confirms normal aortic diameter, alternative diagnoses should be pursued for her gastrointestinal and neurological symptoms. 5, 6

Common Pitfalls to Avoid

• Do not proceed directly to CTA in this asymptomatic young patient—this exposes her to unnecessary radiation and contrast when ultrasound provides equivalent diagnostic accuracy. 1, 2
• Do not assume a palpable aortic pulsation equals pathology in a thin patient—this is a normal physical examination finding. 1
• Do not attribute vague gastrointestinal symptoms to aortic pathology without imaging confirmation, as AAA rarely presents with these nonspecific symptoms. 5, 6
• Ensure the ultrasound technician images the entire abdominal aorta from diaphragm to bifurcation, as approximately 5% of AAAs are juxtarenal or suprarenal and may be missed with limited views. 1, 3

Clinical Algorithm

1. Order transabdominal ultrasound of the abdominal aorta with overnight fasting beforehand 1, 2
2. If ultrasound shows normal aortic diameter (<3.0 cm): Reassure the patient that the palpable pulsation is normal anatomy, and pursue alternative diagnoses for her other symptoms 3, 2
3. If ultrasound shows AAA (≥3.0 cm): Implement surveillance protocol based on size, though this would be extraordinarily rare in a 19-year-old woman 3, 2
4. If ultrasound is technically inadequate (unlikely in thin patient): Proceed to non-contrast CT abdomen 1, 2