Acute appendicitis (AA) is the most common condition requiring emergency surgery in children. 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 other scoring systems. The study objective is to assess acute care charges and clinical outcomes among children with an appendix ultrasound and a pARC score of less than < 25% risk.

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

We will collect data on all patients presenting to the emergency departments of Children's Minnesota between the ages of 5-18 years old who have a US of the appendix performed in the ED over 12 month period from September 23, 2017 to October 1, 2018.