What are the differential diagnoses and treatment options for a patient presenting with stomach pain?

Differential Diagnoses and Treatment for Stomach Pain

Approach to Differential Diagnosis

The most common causes of abdominal pain presenting to emergency departments are appendicitis (one-third), no established diagnosis (one-third), and other documented pathology including acute cholecystitis, small-bowel obstruction, pancreatitis, renal colic, perforated peptic ulcer, cancer, and diverticulitis (one-third). 1

Upper Abdominal/Epigastric Pain Differentials

Gastroesophageal Reflux Disease (GERD)

• Presentation: Epigastric pain with heartburn and regurgitation, affecting 7% of Americans daily and 42% monthly 2
• Treatment: High-dose proton pump inhibitor (PPI) therapy with omeprazole 20-40 mg once daily before meals 2. Full-dose PPI achieves 80-90% healing rate for duodenal ulcers and 70-80% for gastric ulcers 2

Peptic Ulcer Disease

• Presentation: Duodenal ulcers cause epigastric pain several hours after eating, often at night, relieved by food; gastric ulcers cause pain immediately after eating, worsened by food 3, 2
• Treatment: PPI therapy as above 2. If H. pylori positive, triple therapy with omeprazole 20 mg twice daily, clarithromycin 500 mg twice daily, and amoxicillin 1 g twice daily for 10 days 4
• Complications: Perforation (mortality up to 30%) presents with sudden severe pain, fever, and abdominal rigidity requiring immediate surgical intervention 2

Functional Dyspepsia (FD)

• Presentation: Bothersome epigastric pain and/or burning for >8 weeks, unrelated to defecation, may occur fasting or with meals 1
• Diagnosis: Requires exclusion of organic disease; coexists with IBS in up to 50% of patients 1
• Treatment:
  • Low-dose tricyclic antidepressants (TCAs) starting at 10-25 mg at bedtime, titrating slowly 5
  • SNRIs like duloxetine if TCAs not tolerated 5
  • Cognitive behavioral therapy (CBT) and gut-directed hypnotherapy 5
  • Avoid opioids completely due to risk of narcotic bowel syndrome 5

Acute Pancreatitis

• Presentation: Epigastric pain radiating to the back 3
• Diagnosis: Serum amylase ≥4x normal or lipase ≥2x normal (sensitivity/specificity 80-90%) 2
• Treatment: Supportive care; mortality <10% overall but 30-40% in necrotizing pancreatitis 2

Acute Cholecystitis

• Presentation: Right upper quadrant pain with characteristics of biliary colic (pain 30-90 minutes postprandially) 1, 5
• Diagnosis: Ultrasound is initial imaging modality of choice 6
• Treatment: Surgical cholecystectomy

Lower Abdominal Pain Differentials

Appendicitis

• Presentation: Right lower quadrant pain, most critical diagnosis to exclude 6
• Diagnosis: CT abdomen/pelvis with contrast is initial imaging of choice 6
• Treatment: Surgical appendectomy

Diverticulitis

• Presentation: Left lower quadrant pain, especially in older adults 6
• Diagnosis: CT abdomen/pelvis with contrast 6
• Treatment: Antibiotics for uncomplicated cases; surgical intervention for perforation or abscess

Irritable Bowel Syndrome (IBS)

• Presentation: Abdominal pain related to defecation, with altered bowel habits 1, 3
• Treatment:
  • Dietary modifications tailored to symptoms 7
  • Antispasmodics for pain 7
  • Laxatives for constipation-predominant IBS 7
  • Antidiarrheals for diarrhea-predominant IBS 7
  • CBT and gut-directed hypnotherapy for refractory cases 5
  • Never use opioids 7

Small Bowel Obstruction

• Presentation: Abdominal distension with vomiting 6
• Causes: Adhesions (55-75%), hernias (15-25%) 6
• Diagnosis: CT abdomen/pelvis with contrast 6
• Treatment: Surgical intervention for complete obstruction

Life-Threatening Causes Requiring Immediate Exclusion

Myocardial Infarction

• Presentation: Epigastric pain with risk factors and exertional symptoms 2
• Diagnosis: ECG immediately, especially in women, diabetics, and elderly 2
• Treatment: Acute coronary syndrome protocols; mortality 10-20% if missed 2

Mesenteric Ischemia

• Presentation: Pain out of proportion to physical findings, especially in elderly with vascular risk factors 2, 6
• Treatment: Emergent vascular surgery consultation

Perforated Viscus

• Presentation: Sudden severe pain with peritoneal signs (rigid abdomen, rebound tenderness) 6
• Diagnosis: CT showing extraluminal gas (97% sensitivity), fluid/fat stranding (89%), ascites (89%) 2
• Treatment: Emergent surgical repair

Ruptured Abdominal Aortic Aneurysm

• Presentation: Sudden severe pain in patients >50 years with vascular risk factors 2
• Treatment: Emergent vascular surgery

Critical Red Flags Requiring Urgent Evaluation

• Hemodynamic instability (tachycardia ≥110 bpm, fever ≥38°C, hypotension) suggests bleeding or sepsis 2
• Peritoneal signs indicate perforation or ischemia 6
• Persistent vomiting excludes functional dyspepsia and mandates investigation 2
• Weight loss, anemia, dysphagia require urgent endoscopy 1, 2
• Age >40 years with new-onset dyspepsia from high gastric cancer risk area requires 2-week wait endoscopy 1

Diagnostic Algorithm

1. Obtain vital signs immediately to identify hemodynamic instability 2
2. ECG for all patients with epigastric pain to exclude MI 2
3. β-hCG in all women of reproductive age before imaging to exclude ectopic pregnancy 6
4. Laboratory workup: CBC, CRP, serum lactate, liver/renal function, amylase/lipase 2
5. Imaging based on presentation:
   • Non-localized/diffuse pain: CT abdomen/pelvis with IV contrast (changes diagnosis in 51% of cases) 1, 6
   • Right upper quadrant: Ultrasound first 6
   • Right lower quadrant: CT abdomen/pelvis with contrast 6
6. Endoscopy indications: Alarm features (weight loss, anemia, dysphagia, persistent vomiting), age >40 with new dyspepsia from high-risk area, treatment-resistant dyspepsia age ≥55 1, 2

Common Pitfalls to Avoid

• Missing cardiac causes in patients presenting with epigastric pain (obtain ECG on all patients) 2
• Failing to obtain β-hCG before imaging in reproductive-age women 6
• Overlooking hernia orifices and surgical scars during examination 6
• Dismissing atypical presentations in elderly patients (laboratory tests may be normal despite serious infection) 1, 6
• Prescribing opioids for functional gastrointestinal disorders (worsens outcomes and risks narcotic bowel syndrome) 5, 7
• Performing unnecessary cholecystectomy for functional dyspepsia misattributed to gallstones 5
• Repetitive testing once functional diagnosis is established 8