To determine the association of emergency department (ED) volume of children and delayed diagnosis of appendicitis.

Delayed diagnosis of appendicitis is common in children. The association between ED volume and delayed diagnosis is uncertain, but diagnosis-specific experience might improve diagnostic timeliness.

Using Healthcare Cost and Utilization Project 8-state data from 2014 to 2019, we studied all children with appendicitis <18 years old in all EDs. The main outcome was probable delayed diagnosis: >75% likelihood that a delay occurred based on a previously validated measure. Hierarchical models tested associations between ED volumes and delay, adjusting for age, sex, and chronic conditions. We compared complication rates by delayed diagnosis occurrence.

Among 93,136 children with appendicitis, 3,293 (3.5%) had delayed diagnosis. Each 2-fold increase in ED volume was associated with a 6.9% (95% CI: 2.2, 11.3) decreased odds of delayed diagnosis. Each 2-fold increase in appendicitis volume was associated with a 24.1% (95% CI: 21.0, 27.0) decreased odds of delay. Those with delayed diagnosis were more likely to receive intensive care [odds ratio (OR): 1.81, 95% CI: 1.48, 2.21], have perforated appendicitis (OR: 2.81, 95% CI: 2.62, 3.02), undergo abdominal abscess drainage (OR: 2.49, 95% CI: 2.16, 2.88), have multiple abdominal surgeries (OR: 2.56, 95% CI: 2.13, 3.07), or develop sepsis (OR: 2.02, 95% CI: 1.61, 2.54).

Higher ED volumes were associated with a lower risk of delayed diagnosis of pediatric appendicitis. Delay was associated with complications.