Appendicitis criteria
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Finding Sources
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Here is a comprehensive overview of the diagnostic criteria and scoring systems for appendicitis, drawn from multiple surgical and emergency medicine textbooks.
Appendicitis: Diagnostic Criteria
Classic Clinical Presentation
Symptoms (in typical sequence):
- Vague periumbilical/visceral pain → migrates to the right lower quadrant (RLQ) within 6–8 hours
- Anorexia
- Nausea ± vomiting
- Low-grade fever (usually <38.5°C in uncomplicated disease; higher suggests perforation)
Signs:
- McBurney's point tenderness — 1/3 the distance from the anterior superior iliac spine to the umbilicus
- Rebound tenderness (localized peritonitis)
- Guarding / involuntary rigidity (suggests perforation if diffuse)
- Rovsing's sign — RLQ pain on palpation of the LLQ
- Psoas sign — pain with extension of the ipsilateral hip (retroperitoneal appendix)
- Obturator sign — RLQ pain on internal rotation of the hip (pelvic appendix)
Atypical presentations:
- Retroperitoneal appendix → flank/back pain
- Pelvic appendix → suprapubic pain, may mimic UTI
- Cervical motion tenderness can occur from adjacent inflammation (mimics PID)
Laboratory Findings
| Test | Finding |
|---|---|
| WBC | Leukocytosis (10,000–14,000) in ~90% of cases; normal in 10% — cannot exclude alone |
| Differential | Neutrophilia ± bandemia |
| CRP | >10 mg/mL: suggestive; >50 mg/mL: suggests complicated appendicitis |
| Urinalysis | Trace pyuria/hematuria possible (from adjacent inflammation); >30 RBCs or >20 WBCs/HPF suggests urologic cause |
| Pregnancy test | Mandatory in all females of childbearing age |
Combined normal WBC + CRP has NPV of 88% for excluding appendicitis.
Clinical Scoring Systems
1. Alvarado Score (MANTRELS) — Adults & Children
Score out of 10. The most widely validated tool.
| Feature | Points |
|---|---|
| Migration of pain to RLQ | 1 |
| Anorexia | 1 |
| Nausea / vomiting | 1 |
| Tenderness in RLQ | 2 |
| Rebound tenderness | 1 |
| Elevated temperature (≥37.3°C) | 1 |
| Leukocytosis (WBC ≥10,000) | 2 |
| Shift to left (≥75% PMNs) | 1 |
| Total | 10 |
Interpretation:
- 1–4: Appendicitis unlikely (score ≤4 reliably excludes in men)
- 5–6: Compatible with appendicitis → observation/imaging
- 7–8: Probable appendicitis
- 9–10: Appendicitis highly likely → surgical consultation
Note: Less discriminating in women and children.
2. Pediatric Appendicitis Score (PAS) — Children
| Feature | Points |
|---|---|
| Migration of pain | 1 |
| Anorexia | 1 |
| Nausea/vomiting | 1 |
| RLQ tenderness | 2 |
| Cough/hopping/percussion tenderness in RLQ | 2 |
| Elevated temperature ≥37.3°C | 1 |
| WBC ≥10,000 | 2 |
| PMNs ≥75% | 1 |
Interpretation:
- ≤5: Not appendicitis → observation
- ≥6: Appendicitis → surgery
3. Appendicitis Inflammatory Response (AIR) Score — Adults & Children
Currently recommended over Alvarado in recent consensus guidelines (AUC 0.90 vs 0.87).
| Feature | Points |
|---|---|
| Nausea/vomiting | 1 |
| RLQ tenderness | 1 |
| Rebound tenderness (mild/moderate/severe) | 1 / 2 / 3 |
| Elevated temperature ≥38.5°C | 1 |
| WBC 10,000–14,999 / ≥15,000 | 1 / 2 |
| PMNs 70–84% / ≥85% | 1 / 2 |
| CRP 10–49 mg/L / ≥50 mg/L | 1 / 2 |
Interpretation:
- 0–4: Low probability → discharge/outpatient follow-up
- 5–8: Intermediate → in-hospital observation ± imaging or diagnostic laparoscopy
- 9–12: High probability → surgery
Score Comparison
| Score | Best Population | AUC |
|---|---|---|
| AIR | Adults & children | 0.90 |
| Alvarado | Adults & children | 0.87 |
| PAS | Children | 0.82 |
Current consensus guidelines recommend AIR or Adult Appendicitis Score (AAS) over Alvarado, as the Alvarado is useful for rule-out but lacks specificity.
Imaging
| Modality | Notes |
|---|---|
| CT (gold standard) | Sensitivity 95%, specificity 94%. Appendix diameter >10 mm diagnostic; periappendiceal fat stranding, RLQ fluid, failure of contrast to fill appendix |
| Ultrasound | Sensitivity 71–94%, specificity 81–98%; operator dependent. Preferred in children and pregnant patients to avoid radiation |
| MRI | Sensitivity/specificity approaching CT; preferred in pregnancy |
| Plain radiograph | No diagnostic value; rarely shows fecalith (~5%); useful only if pneumoperitoneum suspected |
Sources: Sabiston Textbook of Surgery 21e; Sleisenger & Fordtran's GI and Liver Disease; Mulholland & Greenfield's Surgery 7e; Rosen's Emergency Medicine; Tintinalli's Emergency Medicine
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