Collection of data

The CAMIN (Surgical Working Group for Military and Emergency Surgery) Study Group of the German Society for General and Visceral Surgery (DGAV) prepared an anonymized database (Excel 2016, Microsoft, USA) containing various perioperative variables without allowing patient identification. The following variables were recorded as follows: age, gender, comorbidity (including the American Association of Anesthesiologists ASA score [23] and the Charlson comorbidity index [24]), symptoms of appendicitis (including the duration of symptoms prior to medical consultation, clinical signs, biochemical inflammation parameters, modified Alvarado score (MASS) [25]), intraoperative findings (including peritonitis, perforation, abscess and the Mannheimer Peritonitis Index [26]), a histopathological evaluation of appendicitis, and postoperative outcome (including length of stay (LOS), intensive-care-unit (ICU) utilization, and postoperative complications graded according to Clavien-Dindo [27]).

Data were collected from hospital information systems, internally validated, and transferred to a database. They were imported to IBM SPSS Statistics, Version 26, for statistical analysis. All variables were checked in detail for plausibility. Plausible entry errors were corrected; implausible data values were deleted.