What is the most likely cause of post‑prandial abdominal pain in a 73‑year‑old woman with multiple drug allergies who is taking acetaminophen, tuberculin (twice daily), estrin, fluticasone, fosfomycin, ginger, niacin, prednisone, rosuvastatin, levothyroxine (Synthroid), and tirzepatide (Zepbound)?

Post-Prandial Abdominal Pain: Most Likely Diagnosis

The most likely cause of this patient's post-prandial abdominal pain is mesenteric ischemia, specifically chronic mesenteric ischemia given her age and symptom pattern, though medication-related causes including tirzepatide (Zepbound) gastrointestinal effects warrant consideration.

Primary Differential: Mesenteric Ischemia

Why This Diagnosis Takes Priority

At 73 years old with post-prandial pain, this patient fits the classic demographic for chronic mesenteric ischemia. The condition presents characteristically with post-prandial pain and fear of eating in an indolent pattern 1. Given her statin use (rosuvastatin), she likely has atherosclerotic risk factors that predispose to mesenteric arterial occlusion 1.

Key clinical features to assess:

• Pain timing: occurs 15-30 minutes after eating, lasting 1-3 hours
• Weight loss from food avoidance ("food fear")
• Pain severity disproportionate to physical exam findings
• Absence of peritoneal signs initially

Immediate Diagnostic Approach

Triple-phase CT abdomen/pelvis (non-contrast, arterial, portal venous phases) is the appropriate initial imaging 1. This study:

• Identifies underlying vascular occlusion/stenosis
• Evaluates for bowel complications (pneumatosis, portal venous gas)
• Excludes other acute abdominal pathology
• Assesses vessels for potential revascularization

MR angiography is less useful here as it cannot adequately evaluate ischemic bowel changes 1.

Secondary Consideration: Medication-Related Causes

Tirzepatide (Zepbound) Effects

This GLP-1/GIP dual agonist commonly causes gastrointestinal symptoms including nausea, vomiting, diarrhea, and abdominal pain 2. However, these are typically:

• Present from treatment initiation or dose escalation
• Not specifically post-prandial in timing
• Associated with delayed gastric emptying rather than ischemic-type pain

The anti-inflammatory effects of tirzepatide actually reduce inflammatory markers 3, making inflammatory bowel pathology less likely.

Drug Interaction Concerns

Critical medication review needed:

• Rosuvastatin: Can cause abdominal pain, nausea, vomiting, and diarrhea as adverse effects 4. However, these are not characteristically post-prandial.

• Niacin + Rosuvastatin combination: This combination increases myopathy risk 4, but gastrointestinal symptoms are not the primary concern.

• Synthroid (levothyroxine): Can cause abdominal cramps, diarrhea, and vomiting when overdosed 5, but again not specifically post-prandial.

Important Caveat: ACE Inhibitor History

While this patient is not currently on ACE inhibitors (she's allergic to multiple drug classes), ACE inhibitor-induced small bowel angioedema presents with abdominal pain, nausea, vomiting, and can occur years after therapy initiation 6, 7. Given her extensive allergy history, previous exposure cannot be ruled out. However, this typically causes:

• Episodic rather than consistently post-prandial pain
• CT findings of small bowel wall thickening and ascites
• Resolution within days of drug cessation

Clinical Algorithm

Step 1: Urgent vascular assessment

• Order triple-phase CT abdomen/pelvis immediately
• Look for: SMA/celiac artery stenosis, bowel wall thickening, pneumatosis

Step 2: If CT shows vascular compromise

• Vascular surgery consultation for revascularization
• NPO status, IV fluids, empiric antibiotics
• Anticoagulation if embolic source suspected

Step 3: If CT negative for ischemia

• Consider medication-related causes
• Trial discontinuation of tirzepatide (most recent addition likely)
• Evaluate for other causes: peptic ulcer disease, biliary pathology, pancreatic disease

Step 4: Consider rare diagnoses if above negative

• Median arcuate ligament syndrome (MALS): requires angiography with breathing maneuvers 8
• Functional dyspepsia
• Small bowel pathology requiring endoscopy

Critical Pitfalls to Avoid

1. Delaying imaging in elderly patients with post-prandial pain: Mesenteric ischemia mortality approaches 60% when diagnosis is delayed 1.

2. Attributing symptoms solely to new medications: While tirzepatide causes GI symptoms, missing mesenteric ischemia in a 73-year-old would be catastrophic.

3. Ordering wrong imaging: Single-phase CT or ultrasound will miss vascular pathology. Triple-phase CT is essential 1.

4. Assuming multiple drug allergies indicate functional disorder: Her allergy history is extensive but doesn't exclude organic pathology.