Pediatric Appendicitis Risk Calculator (pARC)

Estimates the probability of appendicitis in children and adolescents 5–18.9 years with acute abdominal pain up to 96 hours, to guide imaging versus observation — a risk aid, not a rule-in/rule-out diagnosis.

Sex

Age (years, 5–18.9)

Duration of pain

Pain with walking

Migration of pain to right lower quadrant

Maximal tenderness in right lower quadrant

Abdominal guarding

Neutrophil entry mode

ANC value (x10³/µL) — only if mode = ANC

WBC count (x10³/µL) — only if mode = WBC only or WBC + neut%

Neutrophil percent (0–100) — only if mode = WBC + neut%