Management of cryptoglandular anal fistula is characterised by wide variation in diagnostic strategies, surgical techniques and outcome reporting, limiting comparison between studies and hindering evidence-based guideline development. This study aims to implement a standardised core outcome measurement set within a large international observational framework and to evaluate the feasibility of a scalable digitally supported model for global collaborative surgical research.

Cryptoglandular anal fistula treatment is a prospective, international, multicentre observational study comprising two components: a short-term audit capturing clinician-reported outcomes at 3 months and a long-term cohort capturing clinician- and patient-reported outcomes over twelve months. Adults undergoing surgery for primary or recurrent cryptoglandular anal fistula are eligible, excluding non-cryptoglandular aetiologies. Data are collected using secure electronic case report forms and digitally administered patient-reported outcome measures, with paper alternatives available where required. Outcomes are defined according to the Anal Fistula Core Outcome Measurement Set and include clinical and radiological healing, recurrence, complications, reintervention, development of additional fistulas, symptoms, psychological impact of treatment, continence, quality of life and additionally work productivity. The study was designed around a predefined nine-step framework, including multidisciplinary coordination, central ethical approval to support local submissions, artificial intelligence-assisted translation of study materials with native review and implementation of secure digital data capture systems. Based on previous European Society of Coloproctology studies and expected centre volumes, the audit arm aims to include approximately 1000 patients and the cohort arm 500 to 750 patients.

Central ethical approval has been obtained from the Medical Ethics Review Committee of the Maastricht University Medical Centre+ under METC 2024-0374 (audit arm) and METC 2024-0361 (cohort arm) with local approvals or waivers secured in participating countries according to national regulations. Written informed consent is obtained for cohort participation. Results will be disseminated through peer-reviewed publications and international conferences, with the aim of informing future guideline development and supporting patient-centred care in cryptoglandular anal fistula management.