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    Patent Pending

    Pediatric Appendicitis Risk Calculator (pARC)

    Quantifies appendicitis risk in pediatric patients with abdominal pain, possibly better than the Pediatric Appendicitis Score.


    Use in children ≥5 years old presenting to the emergency department or outpatient setting with acute abdominal pain (duration <96 hours).

    When to Use
    Why Use

    • Children ≥5 years old presenting to the emergency department or outpatient setting with acute abdominal pain (duration <96 hours).

    • Patients with the following conditions were excluded from the study:
      • Pregnancy.
      • Previous abdominal surgery.
      • Inflammatory bowel disease.
      • Chronic pancreatitis.
      • Sickle cell anemia.
      • Cystic fibrosis.
      • Any medical condition affecting the ability to obtain an accurate history.
      • History of abdominal trauma within the previous 7 days.

    • The age range of patients included in the study was 5-18 years. Appendicitis is relatively rare in children <5 years old, and is more likely to present with atypical features not captured by this calculator.

    • Cases of appendicitis among the lowest risk groups (<5% or 5-14% risk as determined by the calculator) were missed only 0.4% of the time in each. The sensitivity of this calculator in children with <5% risk was 100%; the sensitivity was 97.2% in children determined to have a 5-14% risk of acute appendicitis.

    • May help determine need for advanced imaging such as formal ultrasound or CT.

    • Can identify low risk patients who can be observed in or discharged from the ED with follow up or return precautions.

    • In the validation study, Kharbanda et al found that the formula performed better than the Pediatric Appendicitis Score (sorts fewer patients into equivocal risk categories), making it more useful in aiding clinical decisionmaking.

    Pediatric ED
    24 to <48
    48 to 96
    Unknown (defaults to <24 hrs)
    × 10³ cells/µL


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    Next Steps
    Creator Insights


    Specificity of this calculator for cases determined to be at highest risk of appendicitis (pARC Score >85%) was 99.7%; specificity was 97.5% for cases in the high-intermediate range (pARC Score 75-84%).


    • Children determined by the calculator to be low risk for appendicitis can be considered candidates for safe discharge or observation in the emergency room without advanced imaging such as ultrasound or CT, depending upon provider discretion and family comfort.

    • Given the specificity of the calculator, children classified as high or high-intermediate risk for appendicitis may not need advanced imaging. 1.2% of appendectomy specimens in the high risk group were negative for appendicitis on pathology analysis. In the high-intermediate risk group, 2.6% of specimens were pathology-negative.

    Critical Actions

    Critically ill children, or children with emergent “surgical abdomens” (rigidity, visible ecchymosis or hematoma, etc) should not be considered for delayed surgical consultation or imaging. Those children will likely benefit from early involvement of pediatric surgeons as well as imaging when able to be transported to radiology.

    Content Contributors
    Reviewed By
    • Hector Vazquez, MD
    About the Creator
    Dr. Anupam B. Kharbanda
    Partner Content
    Content Contributors
    Reviewed By
    • Hector Vazquez, MD