Collagen Paste Injection in Crohn's Disease Perianal Fistula: Long-term Outcomes of a Pilot, Prospective Cohort Study.

Objectives: Crohn's perianal fistula represents a challenging condition to treat. Sphincters-preserving surgical techniques are increasingly being adopted as repeated surgical procedures may lead to various degrees of incontinence. This prospective study aims to assess the long-term efficacy of collagen paste application in patients with simple and complex Crohn's perianal fistulas. Methods: Patients with Crohn's perianal fistula (simple or complex) and inactive luminal disease were enrolled. The fistula tract was treated by curettage and injection of acellular, porcine dermal collagen paste between 2019 and 2021. The primary endpoint was the clinical healing of the fistula at 12 and 24 months, defined as the absence of suppuration on clinical examination. The trial was preregistered on a public repository (ClinicalTrials.gov; NCT03776825). Results: Fourteen patients were included in the study, ten patients (71%) had complex perianal fistula. All patients underwent previous fistula operations. Nine patients (64%) reached complete clinical remission at 12 months, two patients (14%) had a clinical recurrence six months after surgery, and three patients (21%) at 12 months follow-up. Three relapsed patients presented postoperative abscesses. Twelve patients (86%) were followed up at 24 months, no further clinical recurrences or complications were observed and the complete healing rate was 58%. No continence disturbances were recorded after collagen paste injection. Conclusions: The results suggest that collagen paste injection may represent a safe and effective option for Crohn's perianal fistulas, worth further investigation in larger trials.