In a healthy 65‑year‑old woman not on any medications who has a new audible abdominal pulse and new onset abdominal or small‑bowel discomfort that has not improved with over‑the‑counter proton‑pump inhibitor therapy, what is the most appropriate next diagnostic step?

Immediate Ultrasound of the Abdominal Aorta is Required

This patient needs urgent ultrasound imaging of the abdominal aorta to rule out an abdominal aortic aneurysm (AAA), which is the most critical diagnosis to exclude given the audible abdominal pulse and new symptoms. The failure to improve with PPI therapy makes this even more concerning, as it suggests a non-gastrointestinal etiology.

Why This is Urgent

The combination of an audible abdominal pulse in a 65-year-old woman with new abdominal discomfort represents a potential AAA until proven otherwise. Ultrasound is the initial screening test of choice for suspected AAA 1. While AAA screening is typically recommended for men over 65, women can develop AAAs (though at about 10% smaller diameter thresholds than men) 1.

Key Clinical Reasoning

• The audible pulse is the red flag here: While it could represent a tortuous aorta or transmitted pulsations from a non-vascular mass, you cannot afford to miss an AAA 1
• Age 65 is the critical threshold: This is when AAA prevalence increases significantly 1
• PPI failure is informative: The lack of response to OTC PPI therapy over a reasonable trial period effectively rules out acid-related disorders as the primary cause
• Physical examination can be deceptively benign: Even catastrophic conditions like AAA rupture can present with misleadingly normal exams in older patients 2

The Diagnostic Algorithm

1. Order abdominal aortic ultrasound immediately (same day or next available)

   • This is non-invasive, radiation-free, and highly accurate for AAA detection
   • Normal infrarenal aorta diameter is up to 2 cm; ≥3 cm is aneurysmal, 2-3 cm is ectatic 1
   • Remember: threshold is ~10% smaller in women 1

2. If ultrasound shows AAA:

   • 3.0-3.4 cm: Surveillance every 3 years
   • 3.5-4.4 cm: Surveillance every 12 months
   • 4.5-5.4 cm: Surveillance every 6 months
   • ≥5.5 cm: Refer for elective repair consideration 1
   • If AAA found, obtain CT angiography for detailed pre-intervention planning if approaching surgical threshold

3. If ultrasound is normal (aorta <2 cm):

   • Then consider other causes of small bowel discomfort in older adults
   • Evaluate for mesenteric ischemia (especially given age and vascular concern)
   • Consider small bowel obstruction, though less likely given "discomfort" rather than severe pain 2
   • Malignancy screening may be appropriate given age and new symptoms

Critical Pitfalls to Avoid

• Do not dismiss the audible pulse as "normal": This finding demands imaging evaluation
• Do not continue empiric GI therapy without imaging: The PPI trial has already failed; further delay risks missing a life-threatening diagnosis
• Do not assume "healthy and fit" excludes AAA: Aneurysms can occur in otherwise healthy individuals, and rupture carries 50-80% mortality
• Do not order CT first: Ultrasound is the appropriate initial test—reserve CT angiography for characterization if AAA is found 1

Why Not Other Tests First?

The evidence strongly supports ultrasound as the initial screening modality for suspected AAA 1. Other imaging (CT, MRI) is reserved for detailed characterization when intervention is being considered. The audible pulse combined with symptoms makes this a vascular concern first, not a primary gastrointestinal issue requiring endoscopy or additional PPI trials.