Pediatric Appendicitis Risk Calculator (pARC) in Children With Appendix Ultrasounds

Background Acute appendicitis (AA) is the most common condition requiring emergency surgery
in children. The potential for morbidity and mortality from perforation of the appendix
necessitates prompt diagnosis.2 Acute appendicitis scoring systems such as pediatric
appendicitis score (PAS) use elements of history, exam findings, and lab tests to identify
patients at high risk of having acute appendicitis.3 Despite having limited use for this
intent 4,5 these scores are often used to stratify patients by risk for continued
observation, imaging or operative care. 6 While CT scans may have higher diagnostic yield,
its use is not without risk. CT- related radiation exposure has been shown to increase cancer
risk. There have been US first strategies published by the American College of Radiology7 and
the American College of Emergency Physicians.8 However, nearly 50% of appendix US
examinations are equivocal, which poses a dilemma for EM physicians and results in variation
in clinical care.

Various strategies exist for the diagnostic approach to the patient after equivocal US with
symptoms of AA. While select patients may be safely discharged based on clinical judgment,9
emergency providers often obtain CT or admit patients for clinical observation. In a study
conducted by Garcia et al., they concluded that a protocol of US followed by CT in children
with negative or equivocal US exam results in beneficial management as well as cost
savings.10 In a study by Gregory et al., they concluded that a clinical decision rule
followed by staged imaging was found to be the most cost-effective approach for diagnosis of
AA in children.11 Bachur et al. integrated PAS score with US findings and concluded that
patients with high risk (PAS 7-10) but negative US or low risk (PAS 0-3) benefit from serial
exam or further work up. 12 The addition of US to the strategy reduced CT utilization.11
Standardized radiology reports have also been shown to reduce CT scans and admissions for
observation.13 At a network of institutions nationwide a tool called the pediatric
appendicitis risk calculator (pARC)1 is being studied to assess patient's true risk of
appendicitis and provide guidance for clinical management to ER physicians. Preliminary
studies have found the pARC to be more accurate at predicting risk of appendicitis in
children when compared to PAS score.

The study objective is to assess acute care charges and clinical outcomes among children with
appendix US and pARC < 25%. To the investigator's knowledge, this is the first study to do so
in a tertiary care pediatric hospital.

Inclusion Criteria:

- Patients between 5-18 years

- Patients who had an appendix ultrasound in one of our EDs

Exclusion Criteria:

- Outside appendix ultrasound or abdominal CT obtained

- Previous significant abdominal surgery (for example appendectomy, short gut,
ileostomy, Hirschsprungs with pull through)

- No CBC obtained (i.e. cannot determine pARC)

- Developmental or cognitive delay that impedes communication

- If there is suspected abuse