Appendicitis

Background

• Most common surgical emergency worldwide
• Lifetime risk: ~7-8% (peak incidence ages 10-30)
• Pathophysiology: luminal obstruction (fecalith, lymphoid hyperplasia, rarely tumor) → bacterial overgrowth → wall inflammation → ischemia → perforation
• Perforation risk increases with time: ~2% at 24 hours, increasing to ~50% by 72 hours
• Atypical presentations common in: children, elderly, pregnant women, immunocompromised

Clinical Features

Classic Presentation

• Periumbilical pain migrating to RLQ over 12-24 hours (migration is most specific historical feature)
• Anorexia (nearly universal; absence should raise doubt)
• Nausea, vomiting (usually after onset of pain)
• Low-grade fever (high fever suggests perforation/abscess)

Physical Exam

• McBurney point tenderness (1/3 distance from ASIS to umbilicus)
• Rovsing sign: RLQ pain with LLQ palpation
• Psoas sign: RLQ pain with right hip extension (retrocecal appendix)
• Obturator sign: RLQ pain with internal rotation of flexed right hip (pelvic appendix)
• Rebound tenderness and guarding (peritoneal irritation)
• Dunphy sign: increased pain with coughing

Atypical Presentations

• Retrocecal appendix (~30%): flank or back pain, positive psoas sign, less peritoneal irritation
• Pelvic appendix: suprapubic pain, urinary symptoms, diarrhea
• Pregnant women: RUQ pain (displaced appendix); less peritoneal signs; higher perforation rate
• Elderly: delayed presentation, less fever, higher perforation rate (~50%)
• Children <5: nonspecific symptoms; perforation common by presentation

Differential Diagnosis

• Mesenteric adenitis (children — viral)
• Ovarian torsion, ruptured ovarian cyst, ectopic pregnancy
• Crohn's disease (terminal ileitis)
• Diverticulitis (right-sided in Asian patients, cecal)
• Cholecystitis, nephrolithiasis, UTI
• Pelvic inflammatory disease
• Epiploic appendagitis, omental infarction
• Testicular torsion

Evaluation

Labs

• WBC: elevated in ~80% (but normal WBC does NOT exclude appendicitis)
• CRP: elevated; combined normal WBC + normal CRP has high NPV
• Urinalysis: mild pyuria/hematuria may occur (inflammation adjacent to ureter) — does not exclude appendicitis
• Pregnancy test in all reproductive-age women
• Lipase if epigastric component

Clinical Decision Rules

• Alvarado Score (MANTRELS): Migration, Anorexia, Nausea, Tenderness RLQ, Rebound, Elevation of temp, Leukocytosis, Shift to left
  • Score ≤3: low risk; 4-6: moderate; ≥7: high probability
• AIR Score (Appendicitis Inflammatory Response): incorporates CRP
• These scores help risk-stratify but do NOT replace clinical judgment

Imaging

CT Abdomen/Pelvis with IV Contrast (Test of Choice in Adults)

• Sensitivity 94-98%, specificity 95%
• Findings: enlarged appendix > 6 mm diameter, periappendiceal fat stranding, appendicolith, wall enhancement
• Signs of perforation: abscess, extraluminal air, phlegmon
• Oral contrast generally NOT needed

Ultrasound (First-line in Pediatrics and Pregnancy)

• Sensitivity 86%, specificity 81% (operator dependent)
• Findings: non-compressible appendix > 6 mm, target sign, periappendiceal fluid
• If US equivocal in pediatrics: MRI preferred over CT to avoid radiation

MRI (Alternative in Pregnancy)

• Sensitivity 94%, specificity 97%
• Preferred over CT in pregnancy (no radiation)

Management

Uncomplicated Appendicitis

• NPO, IV fluids, pain control (analgesics do NOT mask peritoneal signs)
• Pre-operative antibiotics: cefoxitin 2g IV or ceftriaxone + metronidazole
• Laparoscopic appendectomy (standard of care)
• Antibiotics-first approach: emerging evidence supports nonoperative management with antibiotics alone for selected uncomplicated appendicitis (CODA trial)
  • ~30% failure/recurrence rate at 1 year
  • Shared decision-making with patient and surgeon

Complicated Appendicitis (Perforated/Abscess)

• Broad-spectrum antibiotics: piperacillin-tazobactam 3.375-4.5g IV OR ceftriaxone + metronidazole
• Small phlegmon/abscess (<3 cm): antibiotics + interval appendectomy in 6-8 weeks
• Large abscess (>3 cm): CT-guided percutaneous drainage + antibiotics + interval appendectomy
• Peritonitis/sepsis: emergent appendectomy

Disposition

• Surgical consultation for all confirmed or highly suspected appendicitis
• Admit for surgical management
• If appendicitis suspected but imaging equivocal: observation with serial exams or repeat imaging in 6-12 hours
• Discharge with close follow-up only if alternative diagnosis confirmed and appendicitis reliably excluded

Calculators

Alvarado Score

Alvarado Score (MANTRELS)

Criteria	Points	No	Yes
Symptoms
Migration of pain to RLQ	+1	1
Anorexia	+1	1
Nausea/vomiting	+1	1
Signs
Tenderness in RLQ	+2	1
Rebound pain	+1	1
Elevated temperature (≥37.3°C / 99.1°F)	+1	1
Labs
Leukocytosis (WBC >10,000/μL)	+2	1
Left shift (>75% neutrophils)	+1	1
Alvarado Score	/ 10

Interpretation
0–4	Low risk — Appendicitis unlikely. Consider other diagnoses.
5–6	Equivocal — Consider CT imaging or observation with serial exams.
7–8	Probable appendicitis — Surgical consultation recommended.
9–10	Very probable appendicitis — Operative management almost certain.

See Also

• Abdominal pain
• Appendicitis (peds)
• Abdominal pain (peds)
• Surgical abdomen

References

• Di Saverio S, et al. Diagnosis and treatment of acute appendicitis: 2020 update of the WSES Jerusalem guidelines. World J Emerg Surg. 2020;15:27. PMID 32295644
• Bhangu A, et al. Acute appendicitis: modern understanding of pathogenesis, diagnosis, and management. Lancet. 2015;386(10000):1278-1287. PMID 26460662
• Alvarado A. A practical score for the early diagnosis of acute appendicitis. Ann Emerg Med. 1986;15(5):557-564. PMID 3963537