The CAMUS Initiative: A Multiphase, Multicentre International Collaboration to Redefine Risk Stratification,...

Surgical complications remain a major source of preventable morbidity, mortality, and health care expenditure, but existing frameworks such as the Clavien-Dindo classification and Comprehensive Complication Index are clinician-centred and intervention-focused and fail to capture cumulative patient-centred outcomes. This protocol outlines the Complications After Major and Minor Urological Surgery (CAMUS) initiative, a global, multiphase effort to redefine complication reporting, risk stratification, and outcome measurement in urological surgery. CAMUS aims to address these limitations via an integrated, seven-arm programme combining retrospective and prospective data analysis, consensus development, and digital infrastructure design. Arm 1 has assembled a retrospective data set of 130 034 major urological procedures from 180 centres across 33 countries, the largest of its kind. Arms 2 and 3 have completed Delphi surveys with physicians ( n  = 1113) and pilot nursing participants ( n  = 20) and has generated consensus on novel grading domains and highlighted the importance of multidisciplinary perspectives. Arm 4 will incorporate patient-reported outcomes and behavioural economics methods to quantify subjective burdens, while arm 5 will develop the CAMUS Intraoperative and Postoperative Risk and Difficulty Estimation Index (IPRADES) for surgical risk and difficulty prediction. Arms 6 and 7 will build a secure e-database and dictionary and prospectively validate the system using >2000 new cases. Statistical methods include multivariable regression, meta-analysis of individual patient data, and machine-learning approaches to model predictors of morbidity and mortality. Outputs will be benchmarked internationally to facilitate both clinician- and patient-driven definitions of complication severity. Ultimately, CAMUS will deliver a reproducible, patient-inclusive classification system with broad applicability to clinical practice, audits, education, and policy. By integrating more than 130 000 procedures with global Delphi consensus, CAMUS represents the most comprehensive complication classification initiative undertaken in surgery. Its outputs are expected to improve transparency, standardise reporting, and inform patient-centred risk stratification worldwide.