Objective: To characterize the influence of intraoperative findings on complications and resource utilization as a means to establish an evidence-based and public health-relevant definition for complicated appendicitis. Summary of Background Data: Consensus is lacking surrounding the definition of complicated appendicitis in children. Establishment of a consensus definition may have implications for standardizing the reporting of clinical research data and for refining reimbursement guidelines. Methods: This was a retrospective cohort study of patients ages 3 to 18 years who underwent appendectomy from January 1, 2013 to December 31, 2014 across 22 children's hospitals (n = 5002). Intraoperative findings and clinical data from the National Surgical Quality Improvement Program-Pediatric Appendectomy Pilot Database were merged with cost data from the Pediatric Health Information System Database. Multivariable regression was used to examine the influence of 4 intraoperative findings [visible hole (VH), diffuse fibrinopurulent exudate (DFE) extending outside the right lower quadrant (RLQ)/pelvis, abscess, and extra-luminal fecalith] on complication rates and resource utilization after controlling for patient and hospital-level characteristics. Results: At least 1 of the 4 intraoperative findings was reported in 26.6% (1333/5002) of all cases. Following adjustment, each of the 4 findings was independently associated with higher rates of adverse events compared with cases where the findings were absent (VH: OR 5.57 [95% CI 3.48–8.93], DFE: OR 4.65[95% CI 2.91–7.42], abscess: OR 8.96[95% CI 5.33–15.08], P < 0.0001, fecalith: OR 5.01[95% CI 2.02–12.43], P = 0.001), and higher rates of revisits (VH: OR 2.02 [95% CI 1.34–3.04], P = 0.001, DFE: OR 1.59[95% CI 1.07–2.37], P = 0.02, abscess: OR 2.04[95% CI 1.2–3.49], P = 0.01, fecalith: OR 2.31[95% CI 1.06–5.02], P = 0.04). Each of the 4 findings was also independently associated with increased resource utilization, including longer cumulative length of stay (VH: Rate ratio [RR] 3.15[95% CI 2.86–3.46], DFE: RR 3.06 [95% CI 2.83–3.13], abscess: RR 3.94 [95% CI 3.55–4.37], fecalith: RR 2.35 [95% CI 1.87–2.96], P =  < 0.0001) and higher cumulative hospital cost (VH: RR 1.97[95% CI 1.64–2.37], P < 0.0001, DFE: RR 1.8[95% CI 1.55–2.08], P =  < 0.0001, abscess: RR 2.02[95% CI 1.61–2.53], P < 0.0001, fecalith: RR 1.49[95% CI 0.98–2.28], P = 0.06) compared with cases where the findings were absent. Conclusion and Relevance: The presence of a visible hole, diffuse fibrinopurulent exudate, intra-abdominal abscess, and extraluminal fecalith were independently associated with markedly worse outcomes and higher cost in children with appendicitis. The results of this study provide an evidence-based and public health-relevant framework for defining complicated appendicitis in children.

More severe presentations of complicated appendicitis are associated with worse outcomes and greater resource use. Severity adjustment may be needed to ensure fair reimbursement and comparative performance reporting, particularly at hospitals treating underserved populations where more severe presentations are common.

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