What assessments are used to diagnose appendicitis?

Diagnostic Assessments for Appendicitis

For diagnosing appendicitis, a combination of clinical evaluation, laboratory testing, and appropriate imaging studies is recommended, with CT scan being the preferred initial imaging modality for non-pregnant adults and ultrasound for pregnant women and children. 1

Clinical Assessment

History and Physical Examination

• Key clinical findings:
  • Characteristic abdominal pain (initially periumbilical, migrating to right lower quadrant)
  • Localized abdominal tenderness in right lower quadrant
  • Anorexia, nausea, and/or vomiting
  • Low-grade fever 2

Physical Examination Signs

• Adults: Right lower quadrant pain and abdominal rigidity are the most reliable signs 3
• Children: Absent/decreased bowel sounds, positive psoas sign, positive obturator sign, and positive Rovsing sign 3

Risk Stratification Using Clinical Scores

• Recommended scoring systems:
  • AIR (Appendicitis Inflammatory Response) score and AAS (Adult Appendicitis Score) - highest discriminating power in adults 1
  • Alvarado score - useful for excluding appendicitis but not sufficient for confirming diagnosis 1
  • Pediatric Appendicitis Score - useful tool in excluding appendicitis in children 1

These scores help identify:

• Low-risk patients (who may not need imaging)
• Intermediate-risk patients (who benefit from imaging)
• High-risk patients (who may proceed directly to surgical consultation) 1

Laboratory Testing

• White blood cell count (WBC) - elevated (>10,000/mm³) but has limited specificity when used alone 1
• C-reactive protein (CRP) - particularly useful when combined with WBC 1
  • Combination of WBC >10,000/mm³ and CRP >8 mg/L has high positive likelihood ratio (23.32) 1
• For children: WBC count, absolute neutrophil count, and CRP should be routinely requested
  • CRP ≥10 mg/L and WBC ≥16,000/mL are strong predictive factors 1
• For pregnant patients: Laboratory tests and inflammatory markers should always be requested 1

Imaging Studies

Non-pregnant Adults

• CT scan with IV contrast is the recommended initial imaging modality 1
  • Helical CT of abdomen and pelvis with IV contrast (oral or rectal contrast not necessary) 1
  • Low-dose CT is preferred over standard-dose CT for young adults 1
  • CT findings to assess: appendiceal dilation (≥7 mm), presence of appendicoliths, mass effect 2

Pregnant Women

• Ultrasound is recommended as the initial imaging modality 1
• If ultrasound is equivocal, MRI should be considered next 1
• Limited CT may be considered if other imaging is inconclusive 1

Children

• Ultrasound is recommended as the initial imaging modality 1
• If ultrasound is equivocal and clinical suspicion persists, CT may be considered 1
• Point-of-care ultrasound (POCUS) is appropriate as a first-line diagnostic tool 1

Follow-up for Negative or Equivocal Imaging

• For patients with negative imaging but persistent symptoms, follow-up at 24 hours is recommended 1
• For patients with equivocal imaging and persistent clinical suspicion, consider:
  • Observation and supportive care
  • Additional imaging
  • Surgical consultation if clinical suspicion remains high 1

Important Caveats

• No single clinical finding is definitive for diagnosing appendicitis
• Diagnostic accuracy improves when combining clinical scores with imaging
• Imaging requirements differ based on patient population (adults vs. children vs. pregnant women)
• Delayed diagnosis increases risk of perforation (occurs in 17-32% of cases) 3
• In high-risk patients under 40 years with high clinical scores, imaging may not be necessary before surgical consultation 1

By following this structured diagnostic approach, clinicians can efficiently diagnose appendicitis while minimizing unnecessary radiation exposure and optimizing patient outcomes.