What is the best approach to diagnose midline abdominal pain, exacerbated by eating and relieved by recumbency, in a patient with a recent history of aneurysm?

Diagnostic Approach for Midline Abdominal Pain with History of Recent Aneurysm

In a patient with midline abdominal pain that worsens with eating and improves with lying down, with a history of recent aneurysm, computed tomography angiography (CTA) of the abdomen and pelvis should be the initial diagnostic test of choice to rule out mesenteric ischemia or a visceral artery aneurysm.

Initial Assessment

When evaluating midline abdominal pain in a patient with history of aneurysm, several critical considerations must be addressed:

High-Risk Features to Identify

• Pain characteristics: Postprandial exacerbation suggests mesenteric ischemia
• Positional relief: Improvement with recumbency may indicate retroperitoneal involvement
• Absence of nausea/vomiting: May falsely reassure but doesn't rule out serious pathology
• Recent aneurysm history: Significantly increases risk of additional aneurysms or complications

Diagnostic Algorithm

Step 1: Immediate Imaging

• First-line imaging: CTA of abdomen and pelvis
  • Provides detailed visualization of vascular structures
  • Can identify visceral artery aneurysms, dissection, or thrombosis
  • Evaluates for retroperitoneal bleeding or hematoma
  • Assesses bowel viability and perfusion 1

Step 2: Targeted Vascular Assessment

• Evaluate for:
  • Mesenteric artery aneurysms (especially superior mesenteric artery)
  • Dissection of visceral vessels
  • Evidence of bowel ischemia
  • Retroperitoneal bleeding or hematoma
  • Additional aneurysms in other vascular territories 1, 2

Step 3: If CTA is Contraindicated

• MR angiography if patient is stable and has contraindication to CTA
• Ultrasound for initial screening but less sensitive for mesenteric vessels 1

Clinical Reasoning

The symptom pattern strongly suggests mesenteric ischemia or a visceral artery aneurysm:

1. Postprandial pain: Classic for mesenteric ischemia due to increased oxygen demand during digestion
2. Relief with recumbency: May indicate retroperitoneal involvement
3. History of aneurysm: Patients with one aneurysm have significantly higher risk of additional aneurysms

According to ACC/AHA guidelines, patients with one aneurysm have a high likelihood of additional aneurysms in other vascular territories. Up to 85% of patients with femoral aneurysms have coexistent abdominal aortic aneurysms, and patients with one aneurysm should be screened for others 1.

Critical Considerations

Aneurysm-Related Complications

• Visceral artery aneurysms can present with vague abdominal pain before rupture
• Superior mesenteric artery aneurysms can cause postprandial pain due to transient decreases in blood flow 3
• Chronic contained rupture of an aneurysm can present with back or abdominal pain for weeks to months 4

Diagnostic Pitfalls to Avoid

• Don't attribute symptoms to non-specific causes without ruling out vascular pathology
• Don't rely on absence of shock to rule out aneurysm complications - chronic contained ruptures can present with stable hemodynamics 1
• Don't delay imaging in patients with known aneurysm history and new abdominal pain
• Don't miss vertebral body erosion which can occur with chronic contained aneurysm rupture 1

Follow-up Recommendations

If initial CTA is negative but symptoms persist:

• Consider mesenteric duplex ultrasonography to evaluate for dynamic compression
• Evaluate for non-vascular causes (e.g., pancreatic pathology, duodenal perforation) 5
• Consider endoscopic evaluation if pain continues to be associated with eating

Surveillance Recommendations

For patients with known aneurysms:

• Surveillance intervals based on aneurysm size:
  • 3.0-3.4 cm: Every 3 years
  • 3.5-4.4 cm: Every 12 months
  • 4.5-5.4 cm: Every 6 months 2

The diagnostic approach must be aggressive given the potentially catastrophic consequences of missed mesenteric ischemia or aneurysm complications, with mortality rates of 75-90% for ruptured aneurysms 2.