A 41-year-old woman is brought to the emergency department with the acute-onset of severe abdominal pain for the past 2 hours. She has a history of frequent episodes of vague abdominal pain, but they have never been this severe. Every time she has had pain, it would resolve after eating a meal. Her past medical history is otherwise insignificant. Her vital signs include: blood pressure 121/77 mm Hg, pulse 91/min, respiratory rate 21/min, and temperature 37°C (98.6°F). On examination, her abdomen is flat and rigid. Which of the following is the next best step in evaluating this patient’s discomfort and stomach pain by physical exam?

Elicit shifting dullness of the abdomen

Perform light palpation at the point of maximal pain

Attempt to perform a deep, slow palpation with quick release

Percuss the point of maximal pain

A 27-year-old woman presents with acute abdominal pain in her right upper quadrant. The pain came on suddenly while she was eating dinner. After this pain she began feeling dizzy and came to the emergency department. In the ED, her blood pressure is 75/40 mmHg, pulse is 100/minute, and she is afebrile. On physical exam, she feels too light-headed to ambulate. She demonstrates normal bowel sounds with tenderness upon palpation in the right upper quadrant. The patient is deemed too unstable for imaging. An abdominal radiograph and CT are reviewed from a recent previous visit to the ED for mild abdominal pain, and are shown in Figures A and B, respectively. Which of the following specific additional findings in her history supports the most likely diagnosis?

Use of oral contraceptives (OCPs) for birth control

Symptoms that began after a fatty meal

A 15 pack/year history of smoking

A history of Epstein-Barr virus and participation in rugby

An extensive history of sexually transmitted diseases (STDs) and pelvic inflammatory disease (PID)

Diagnostic approach to acute abdomen for USMLE Step 3: High-Yield Surgery Lessons

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

Abdominal Pain: Location and Potential Causes

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!

CT scan: Acute appendicitis with appendicolith

⭐ 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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