PURPOSE: Pouch-related fistulae are devastating complications of ileoanal pouch surgery, which is performed to improve the quality of life (QoL) for patients who have had a proctocolectomy. Their management is limited by inconsistent evidence, including using poorly and heterogeneously defined outcomes. This study aims to identify all Outcome Measurement Instruments (OMIs) used in pouch fistula research, including Patient-Reported Outcome Measures (PROMs) and Clinician-Reported Outcome Measures (ClinROMs) and evaluate their quality using COSMIN guidelines to help select the best tool for a standardised core outcome measurement set in a future consensus study. METHODS: A systematic review was conducted to identify all OMIs used in ileo-anal pouch fistulae studies, from MEDLINE, Embase, and the Cochrane Library. We evaluated existing OMIs based on COSMIN guidelines and used the GRADE approach to assess evidence quality. Results were synthesized narratively. RESULTS: Among 91 studies, 13 OMIs were reviewed. Pouch-specific instruments performed poorly in key domains of reliability, validity, and responsiveness. Only 17.6% of studies assessed QoL using PROMs. The best-performing instruments were the SF-36 and IBDQ. The Ileoanal Pouch Syndrome Severity Score was the only pouch-specific instrument that involved patients in its development and although useful for pouch dysfunction, it lacks specific QoL assessment and was not validated in pouch-fistulae patients. CONCLUSION: Existing OMIs for pouch-related fistulae lack adequate measurement properties, with no PROMs specifically validated for QoL in this population and very few instruments involving patients in their development. There is an unmet need for a validated PROM specifically for QoL in pouch-related fistulae.