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

MAPS – Multicenter study on Appendix Presentation and neoplasmS Background & Rationale Acute appendicitis is a common emergency with heterogeneous diagnostic pathways (clinical scores, imaging) and variable use of non-operative management (NOM). Appendiceal neoplasms (NET, LAMN/HAMN, adenocarcinoma, goblet cell) are rare, frequently incidental at appendectomy, and raise questions on staging, right hemicolectomy, HIPEC, and follow-up. A pragmatic multicenter registry is needed to quantify neoplasm rates and describe real-world diagnostic-therapeutic patterns. Objectives Primary: Estimate the rate of appendiceal neoplasms among appendectomy specimens. Secondary: (1) Describe diagnostic performance of AIR/Alvarado/RIPASA; (2) quantify imaging utilization and accuracy; (3) describe adoption and failure of NOM vs surgery; (4) report complications (Clavien–Dindo), LOS, readmission, short-term mortality; (5) describe oncologic management (right hemicolectomy, HIPEC) and short-term outcomes. Design Retrospective, Prospective, multicenter, observational patient registry (with optional retrospective backfill per site). Consecutive ED patients with suspected acute appendicitis are recorded using a standardized eCRF. Setting Emergency Departments/General Surgery Units at participating centers (lead: Sapienza University of Rome / Policlinico Umberto I). Participants Inclusion: consecutive ED patients with suspected acute appendicitis; and/or patients undergoing appendectomy with available pathology; consent per local regulations. Exclusion: incomplete core data; prior appendectomy; refusal of consent; pregnancy optional per local policy. Variables & Data Collection - Demographics; clinical presentation; AIR/Alvarado/RIPASA scores; labs. - Imaging (US/CT/MRI), findings, timing. - Management: NOM vs surgery, timing, intraoperative findings. - Pathology: NET, LAMN/HAMN, adenocarcinoma, goblet cell, margins. - Outcomes: complications (Clavien–Dindo), LOS, 30/90-day readmission and mortality; oncologic referral, right hemicolectomy, HIPEC; follow-up to 12 months when applicable. Sample Size & Duration Pragmatic target ≥1500 patients across centers over ~24 months; no formal hypothesis testing required for registry objectives. Analysis Plan Descriptive statistics with center-level summaries; diagnostic accuracy metrics for scores/imaging; exploratory multivariable models (e.g., NOM failure) if data quality permits. Pre-specified data dictionary and handling of missingness. Ethics IRB/EC approval obtained per site. Minimal-risk observational design; de-identified centralized dataset. Data sharing plan: de-identified data available on request after primary publication. Governance PI/Steering Committee (one representative per site); core dataset mandatory; periodic data quality checks; publication policy acknowledging participating centers. Timeline & Milestones Site initiation → first patient in → 12-month interim → database lock → primary manuscript. Intended registrations: ClinicalTrials.gov (Observational Patient Registry) and protocol DOI via Zenodo.