What are the differential diagnoses for a patient with abdominal pain triggered by eating, without nausea, vomiting, or diarrhea?

Differential Diagnoses for Postprandial Abdominal Pain Without Nausea, Vomiting, or Diarrhea

The most critical differential to exclude immediately is chronic mesenteric ischemia, which presents with postprandial pain 15-30 minutes after eating, food avoidance, and weight loss—this requires urgent CT angiography as it carries the highest mortality risk. 1

Life-Threatening Diagnoses to Exclude First

Chronic Mesenteric Ischemia

• Pain occurs 30-60 minutes after eating and lasts 1-3 hours, developing insidiously over months 1
• Patients develop food avoidance and weight loss due to "intestinal angina" 1
• CT angiography is the first-line diagnostic test with 95-100% sensitivity and specificity 1
• The American College of Cardiology recommends prioritizing treatment of the Superior Mesenteric Artery with covered balloon-expandable stents 1

Internal Herniation (Post-Bariatric Surgery)

• Occurs in 2.5% of gastric bypass patients, 90% within 20 months postoperatively 2
• Presents with cramping epigastric pain after eating in 80% of cases 2
• Critical pitfall: Normal labs do NOT exclude this—white blood count was normal in 68.75% and lactate normal in 90% of cases 2
• CT abdomen/pelvis with IV contrast is mandatory if prior bariatric surgery 2

Common Biliary and Pancreatic Causes

Biliary Colic/Chronic Cholecystitis

• Most common in obese females, presents with postprandial right upper quadrant or epigastric pain 2
• Right upper quadrant ultrasound is the initial test of choice 2
• If ultrasound is negative or equivocal, proceed to CT abdomen/pelvis with IV contrast 2
• Liver function tests should be ordered to evaluate biliary pathology 2

Chronic Pancreatitis

• Postprandial pain due to increased pancreatic secretory demand
• May present without classic features of nausea/vomiting in chronic stages
• Lipase levels and CT imaging guide diagnosis 2

Emerging and Often-Missed Diagnosis

Alpha-Gal Syndrome

• The AGA recommends considering this in patients with unexplained abdominal pain in alpha-gal prevalent areas (Southeast, mid-Atlantic, Midwest, East Central US) 3
• Abdominal pain occurred in 71% of oral food challenge-proven alpha-gal allergic patients 3
• 40.7% of patients developed GI symptoms alone without skin findings or anaphylaxis 3
• Pain occurs 2-5 hours after eating mammalian meat (delayed IgE-mediated reaction) 3
• History of awakening at night with GI distress suggests alpha-gal given the typical delay from ingestion to reaction 3
• History of tick bites or outdoor pursuits increases risk 3
• Diagnosis requires serum testing for alpha-gal IgE antibodies 3
• These patients are often misdiagnosed with irritable bowel syndrome 3

Functional and Structural GI Causes

Peptic Ulcer Disease

• Postprandial pain without nausea/vomiting can occur, especially with gastric ulcers
• Upper endoscopy is required to exclude structural disease before diagnosing functional dyspepsia 2

Abdominal Wall Pain

• Pain elicited by physical movement and localized to circumscribed sites in the abdominal wall 4
• Pain increases when abdominal muscles are tensed (Carnett's sign) 4
• Most commonly located in the semilunar line (39/55 patients in one study) 4
• Correct diagnosis avoids repeated costly investigations 4

Irritable Bowel Syndrome

• Should only be diagnosed after organic pathology has been confidently excluded 5
• Repetitive testing is not recommended once functional diagnosis is established 5

Diagnostic Algorithm

Immediate Assessment:

• Check vital signs for tachycardia, hypotension, or fever to predict serious complications 2
• Assess for peritoneal signs indicating perforation or necrosis 2
• Critical pitfall: In obese patients, physical examination is unreliable—serious pathology may present with minimal findings 2

Essential History:

• Prior bariatric surgery (15-30% present to emergency rooms within 3 years) 2
• Timing of pain relative to meals (30-60 minutes suggests mesenteric ischemia; 2-5 hours suggests alpha-gal) 1, 3
• Food avoidance and weight loss (suggests mesenteric ischemia) 1
• Geographic location and tick exposure (suggests alpha-gal) 3
• Medication history including NSAIDs, opioids, and GLP-1 agonists 2

Laboratory Evaluation:

• Complete blood count, comprehensive metabolic panel, lactate 2
• Liver function tests 2
• C-reactive protein 6
• Alpha-gal IgE antibodies if in endemic area with appropriate history 3
• Do NOT exclude serious pathology based on normal labs alone 2

Imaging Strategy:

• Right upper quadrant ultrasound if biliary colic suspected 2
• CT abdomen/pelvis with IV contrast is the definitive test for most causes 2
• CT angiography if mesenteric ischemia suspected 1
• Serial abdominal exams every 4-6 hours to detect developing peritonitis 2