VALIDATE-PERIANAL: an international real-world multi-centre exploratory validation of the TOpClass definition of a radiologically healed fistula in perianal fistulising Crohn’s disease

The TOpClass definition provides an internationally agreed and standardised MRI-based criteria for identifying a radiologically healed fistula in perianal Crohn's disease. 93% of patients who met the TOpClass criteria for a radiologically healed fistula achieved sustained clinical remission, with excellent inter-rater reliability. The TOpClass criteria offer a potential benchmark for clinical trials, where a radiologically healed fistula represents the aspirational gold standard, associated with long-term remission in perianal fistulising Crohn's disease.