Acute Appendicitis
General Surgery
Illness script · General Surgery
Acute Appendicitis
Acute inflammation of the vermiform appendix, most commonly from luminal obstruction, causing right lower quadrant pain and peritoneal signs.
This illness script for Acute Appendicitis covers predisposing factors, classic presentation, mechanism, workup, management, and the clinical pivots that separate it from look-alikes—written for USMLE Step 1 and clerkship reasoning.
01
Predisposing factors
- Peak incidence ages 10–30; lifetime risk ~7%
- Fecalith or lymphoid hyperplasia causes luminal obstruction
- Low-fiber diet associated; slight male predominance
- Rare in infants; perforation risk highest in elderly and young children
02
Presentation
- Classic: periumbilical pain migrating to RLQ over 12–24 hrs
- Anorexia, nausea/vomiting follow pain onset (pain first distinguishes from gastroenteritis)
- Low-grade fever (high fever suggests perforation/abscess)
- McBurney's point tenderness (1/3 from ASIS to umbilicus)
- Rovsing's sign (LLQ pressure → RLQ pain), psoas sign, obturator sign
- Rebound tenderness and guarding indicate peritoneal irritation
03
Pathophysiology
- Obstruction → luminal distension → venous congestion → bacterial overgrowth
- Mucosal ischemia → transmural inflammation → risk of perforation (24–72 hrs)
- Visceral pain (periumbilical) precedes somatic RLQ pain as parietal peritoneum involved
- Perforation leads to localized abscess or diffuse peritonitis
04
Diagnostics
- CBC: leukocytosis (WBC 10,000–18,000); >18,000 suggests perforation
- CT abdomen/pelvis with IV contrast: gold standard (sensitivity ~94–98%)
- Ultrasound first-line in children and pregnant women (avoids radiation)
- Alvarado score combines clinical + lab findings to risk-stratify
- Pregnancy: MRI if ultrasound inconclusive; never delay for labs if classic presentation
05
Management
- NPO, IV fluids, analgesia (opioids do NOT mask diagnosis — give them)
- Appendectomy (laparoscopic preferred) is definitive treatment
- Pre-op IV antibiotics (cefoxitin or pip-tazo) to reduce wound infection
- Uncomplicated appendicitis: antibiotics-first is an alternative in selected adults
- Perforated with abscess: percutaneous drainage + antibiotics → interval appendectomy in 6–8 weeks
06
Clinical pivots
How to separate this script from the look-alikes that show up on exams and on the wards.
Ovarian torsion
Sudden-onset severe unilateral pain without classic pain migration; adnexal mass on ultrasound
Mesenteric adenitis
Preceded by URI/viral illness; no peritoneal signs; CT shows enlarged nodes without appendiceal thickening
Ectopic pregnancy
βhCG positive; pain with vaginal bleeding; no fever or leukocytosis early — always check βhCG in reproductive-age females
Meckel's diverticulitis
Clinically indistinguishable preoperatively; Meckel's scan or found intraoperatively near terminal ileum
Keep reading
Full libraryEducational use only. This illness script is a study framework, not medical advice. Confirm decisions with current guidelines and your clinical supervisors.