To define and measure complications across a broad set of acute pediatric conditions in emergency departments using administrative data, and to assess the validity of these definitions by comparing resource utilization between children with and without complications.

Using local consensus, we predefined complications for 16 acute conditions including appendicitis, diabetic ketoacidosis, ovarian torsion, stroke, testicular torsion, and 11 others. We studied patients under age 18 years using 3 data years from the Healthcare Cost and Utilization Project Statewide Databases of Maryland and New York. We measured complications by condition. Resource utilization was compared between patients with and without complications, including hospital length of stay, and charges.

We analyzed 27 087 emergency department visits for a serious condition. The most common was appendicitis (n = 16 794), with 24.3% of cases complicated by 1 or more of perforation (24.1%), abscess drainage (2.8%), bowel resection (0.3%), or sepsis (0.9%). Sepsis had the highest mortality (5.0%). Children with complications had higher resource utilization: condition-specific length of stay was longer when complications were present, except ovarian and testicular torsion. Hospital charges were higher among children with complications (P < .05) for 15 of 16 conditions, with a difference in medians from $3108 (testicular torsion) to $13 7694 (stroke).

Clinically meaningful complications were measurable and were associated with increased resource utilization. Complication rates determined using administrative data may be used to compare outcomes and improve healthcare delivery for children.