MAPS — Protocol Outline (v1.0): Multicenter study on Appendix Presentation and neoplasmS

Background. Acute appendicitis is a common emergency with heterogeneous diagnostic pathways (clinical scores and imaging) and variable adoption of non-operative management (NOM). Appendiceal neoplasms (NET, LAMN/HAMN, adenocarcinoma, goblet cell) are rare and often incidental, raising questions on staging, right hemicolectomy, HIPEC, and follow-up.

Objective. To establish a pragmatic multicenter observational patient registry (MAPS) that (1) estimates the rate of appendiceal neoplasms among appendectomy specimens; (2) describes real-world diagnostic-therapeutic patterns across centers; (3) reports outcomes and short-term oncologic management.

Design. Prospective observational patient registry (with optional retrospective backfill per site). Consecutive ED patients with suspected acute appendicitis and/or patients undergoing appendectomy with available pathology are included. Core variables: demographics; clinical presentation; AIR/Alvarado/RIPASA; labs; imaging (US/CT/MRI); management (NOM vs surgery; timing); intra-operative findings; pathology (NET, LAMN/HAMN, adenocarcinoma, goblet cell); complications (Clavien–Dindo); length of stay; 30/90-day readmission and mortality; oncologic referral, right hemicolectomy, HIPEC; follow-up to 12 months where applicable.

Governance & ethics. IRB/EC approval per site; minimal-risk observational design; de-identified centralized dataset; data-sharing upon reasonable request after primary publication. Steering Committee with one representative per participating center.

Planned registrations and links. This protocol will be linked to the ClinicalTrials.gov record (Observational [Patient Registry]) when available (NCT identifier to be added after PRS release). This Zenodo record serves as the citable, time-stamped “frozen” version (v1.0); subsequent amendments will be versioned (v1.1, v2.0).