Initial Approach - First Look, First Clues
- Vitals & ABCs: First, rule out shock (hypotension, tachycardia). Is the patient stable? If not, resuscitate immediately (IV fluids, O₂, monitor).
- Focused History & Physical:
- Use 📌 "OPQRST" for pain analysis.
- Ask about prior surgeries, comorbidities, and last menstrual period.
- Examine for peritoneal signs: guarding, rigidity, rebound tenderness.
⭐ In elderly, obese, or immunocompromised patients, peritoneal signs may be subtle or absent despite serious pathology like perforation.
Pain Localization - Where It Hurts Matters
Pain location narrows the differential diagnosis. Visceral pain is often midline (periumbilical) initially, becoming localized as the parietal peritoneum gets irritated.
| Region/Quadrant | Common Causes |
|---|---|
| Right Upper (RUQ) | Cholecystitis, Biliary colic, Hepatitis, Fitz-Hugh-Curtis |
| Epigastric | PUD, Gastritis, Pancreatitis, MI, Aortic Aneurysm (AAA) |
| Left Upper (LUQ) | Splenic infarct/rupture, Pancreatitis, Gastritis |
| Periumbilical | Early Appendicitis, Small Bowel Obstruction (SBO), Ischemia |
| Right Lower (RLQ) | Appendicitis, Ectopic Pregnancy, Ovarian Torsion, IBD |
| Left Lower (LLQ) | Diverticulitis, Ectopic Pregnancy, Ovarian Torsion, IBD |
Lab Investigations - Blood, Guts, & Glory
- Initial Screen:
- CBC: ↑WBC suggests infection; ↓Hct indicates bleed.
- CMP: Evaluates LFTs for biliary pathology, BUN/Cr for hydration status.
- Key Diagnostic Markers:
- Lipase & Amylase: ↑ in pancreatitis (lipase is more specific).
- Lactate: Critical marker for mesenteric ischemia/sepsis.
- Urinalysis: Screens for UTI or nephrolithiasis.
- Urine β-hCG: Mandatory for all females of childbearing age.
- Pre-Surgical: Type & screen, PT/INR.
⭐ A serum lactate >2 mmol/L is a red flag for mesenteric ischemia, even with a normal WBC count.
Diagnostic Imaging - A Picture's Worth
*Initial choice depends on patient stability and suspected diagnosis. Unstable? Straight to OR!
⭐ In stable patients with undifferentiated abdominal pain, an IV-contrast CT scan is the diagnostic workhorse, boasting >95% sensitivity for common urgent causes like appendicitis, diverticulitis, and bowel obstruction.
High‑Yield Points - ⚡ Biggest Takeaways
- The history and physical exam are the cornerstone of diagnosis, guiding all subsequent steps.
- Hemodynamic instability (hypotension, tachycardia) signals urgent conditions like sepsis or hemorrhage.
- Initial labs include CBC, CMP, lipase, and lactate to assess for inflammation, organ damage, and ischemia.
- CT of the abdomen/pelvis with IV contrast is the primary imaging for undifferentiated abdominal pain.
- Ultrasound is preferred for suspected biliary or gynecologic pathology.
- Peritoneal signs (rigidity, rebound tenderness) strongly suggest a need for surgical intervention.
- Consider extra-abdominal mimics like MI or DKA.
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