USMLE Prep - Medical Reference Library

Appendicitis — Adult

System: General Surgery • Reviewed: Aug 31, 2025 • Step 1Step 2Step 3

Synopsis:

Suspect with migratory RLQ pain, anorexia, and tenderness; CT with IV contrast is preferred imaging in adults; laparoscopic appendectomy is standard; selected uncomplicated cases may be treated nonoperatively.

Key Points

  • Stabilize ABCs; begin targeted evaluation without delaying life-saving therapy.
  • Use system-specific risk tools to guide testing and disposition.
  • Order high-yield tests first; escalate imaging when indicated.
  • Start evidence-based initial therapy and reassess frequently.

Algorithm

  1. Primary survey and vitals; IV access and monitors.
  2. Focused history/physical; identify red flags and likely etiologies.
  3. Order system-appropriate labs and imaging (see Investigations).
  4. Initiate guideline-based empiric therapy (see Pharmacology).
  5. Reassess response; arrange consultation and definitive management.

Clinical Synopsis & Reasoning

Appendicitis typically presents with periumbilical pain migrating to the RLQ, anorexia, and fever, with leukocytosis; ultrasound or CT confirms diagnosis. Consider mimics (gastroenteritis, ovarian torsion, mesenteric adenitis) and perforation risk when symptoms are prolonged or systemic toxicity is present. Risk scores (Alvarado, AIR) support decision‑making and imaging selection, particularly in pregnancy and pediatrics.


Treatment Strategy & Disposition

Uncomplicated disease is treated with early appendectomy or, in selected cases, antibiotics with shared decision‑making about recurrence risk. Perforation with abscess may warrant antibiotics and interval appendectomy after drainage. Provide peri‑operative antibiotics, analgesia, and VTE prophylaxis per risk. Most patients go to surgical service; admit when complicated or with comorbidities requiring monitoring.


Epidemiology / Risk Factors

  • Risk factors vary by condition and patient profile

Investigations

TestRole / RationaleTypical FindingsNotes
CBCBaseline hematologyAbnormal counts
BMPElectrolytes/renalDerangements

Alvarado Score (Abbrev.)

FeaturePoints
Migration to RLQ1
Anorexia1
Rebound tenderness1
Fever1
Leukocytosis2
Neutrophilia1

Pharmacology

MedicationMechanismOnsetRole in TherapyLimitations
Ceftriaxone + metronidazoleCephalosporin + nitroimidazoleHoursPeri-op/complicated casesAllergy; disulfiram-like (metro)

Prognosis / Complications

  • Prognosis depends on severity, comorbidities, and timeliness of care

Patient Education / Counseling

  • Explain red flags and when to seek emergent care.
  • Reinforce medication adherence and follow-up plan.

Notes

Discuss recurrence risk with nonoperative approach. Consider perforation/gangrene if toxic or with mass—manage with source control and antibiotics.


References

  1. WSES Appendicitis Guidelines — Link
  2. SAGES — Acute Care Surgery — Link