What are the diagnostic criteria and treatment for appendicitis?

Diagnosing Acute Appendicitis

Acute appendicitis should be diagnosed using a combination of clinical evaluation with validated scoring systems and appropriate imaging studies, with ultrasound as first-line and CT as second-line imaging. 1

Clinical Assessment

Key Symptoms and Signs to Look For

• Classic presentation (present in ~50% of patients):

  • Periumbilical pain migrating to right lower quadrant (RLQ)
  • Anorexia
  • Nausea/vomiting
  • Fever
  • Leukocytosis 2, 3

• Physical examination findings:

  • RLQ tenderness (most reliable sign in adults)
  • Abdominal rigidity
  • Rebound tenderness
  • Positive psoas sign (pain with extension of right hip)
  • Positive obturator sign (pain with internal rotation of flexed right hip)
  • Positive Rovsing sign (pain in RLQ when pressing left lower quadrant) 4

Validated Clinical Scoring Systems

1. Alvarado Score components:

   • Migration of pain (1 point)
   • Anorexia (1 point)
   • Nausea/vomiting (1 point)
   • RLQ tenderness (2 points)
   • Rebound tenderness (1 point)
   • Fever (1 point)
   • Leukocytosis (2 points)
   • Left shift (1 point)

   Risk stratification:

   • <5: Low risk
   • 5-6: Intermediate risk
   • 7-10: High risk 1

2. AIR Score components:

   • Vomiting (1 point)
   • RLQ pain (1 point)
   • Rebound tenderness (mild=1, moderate=2, severe=3 points)
   • Fever ≥38.5°C (1 point)
   • Leukocytosis (1-2 points)
   • Neutrophilia (1-2 points)
   • CRP (1-2 points)

   Risk stratification:

   • <5: Low risk
   • 5-8: Intermediate risk
   • 9-12: High risk 1

Imaging Studies

Ultrasound (First-Line)

• Sensitivity: 83.1%, Specificity: 93.6%
• Preferred first-line imaging, especially for children and pregnant women
• Look for:
  • Non-compressible appendix >6mm in diameter
  • Wall thickening
  • Periappendiceal fluid 1, 2

CT Scan (Second-Line)

• Sensitivity: >95%, Specificity: >95%
• Indicated when ultrasound is inconclusive or unavailable
• Look for:
  • Appendiceal dilatation (≥7mm)
  • Appendiceal wall enhancement defect
  • Periappendiceal fat stranding
  • Extraluminal air (indicates perforation)
  • Appendicolith (increases risk of perforation)
  • Abscess formation 2, 3

MRI

• Recommended for pregnant women with inconclusive ultrasound
• Sensitivity: >90%, Specificity: >95% 1

Diagnostic Algorithm

1. Initial risk stratification using clinical scoring systems (Alvarado, AIR, or AAS)

2. Low-risk patients (Alvarado <5, AIR <5, AAS <11):

   • Consider observation and reassessment

3. Intermediate-risk patients (Alvarado 5-6, AIR 5-8, AAS 11-15):

   • Proceed with imaging
   • Start with ultrasound
   • If ultrasound is inconclusive, proceed to CT scan (or MRI in pregnant women)

4. High-risk patients (Alvarado 7-10, AIR 9-12, AAS ≥16):

   • Young patients (<40 years) with strong clinical signs may proceed directly to diagnostic laparoscopy without pre-operative imaging
   • Older patients (>40 years) should undergo CT scan to rule out other pathologies 2, 1

Special Considerations

Elderly Patients

• Often present with atypical symptoms
• Higher risk of perforation and complications
• CT scan with IV contrast recommended for patients >60 years with Alvarado score ≥5 and negative ultrasound 2

Children

• Ultrasound is first-line imaging
• Clinical scoring systems (Pediatric Appendicitis Score) are particularly helpful 2, 5

Pregnant Women

• Ultrasound is first-line imaging
• MRI recommended if ultrasound is inconclusive
• Avoid CT scan when possible 1

Complications to Watch For

• Perforation (occurs in 17-32% of cases)

  • Risk increases with prolonged symptoms before intervention
  • CT findings: extraluminal air, abscess, phlegmon 4

• Abscess formation

  • CT findings: fluid collection with rim enhancement 2

Common Pitfalls

• Atypical presentations are common, especially in elderly and very young patients
• Negative appendectomy rates have decreased from 15-25% to 1-3% with appropriate imaging 2
• Delayed diagnosis increases risk of perforation and sepsis 4
• Appendicitis following trauma is rare but should be considered in patients with RLQ pain after blunt abdominal trauma 6

Remember that timely diagnosis is crucial to prevent complications. When in doubt, surgical consultation should be obtained promptly, especially in moderate to high-risk patients.