Efficacy and safety of freshly collected autologous adipose tissue for complex anal fistulas in non-IBD patients: a prospective cohort study

BACKGROUND: Complex cryptoglandular anal fistulas present a treatment challenge, with many surgical options associated with recurrence, variable healing rates, and risk of incontinence. Freshly collected autologous adipose tissue (FCAAT) has been proposed as a minimally invasive, one-step alternative. This study aimed to assess clinical healing and clinical improvement and to evaluate the safety of the procedure. METHODS: This prospective cohort study included 31 patients without inflammatory bowel disease (IBD) with complex single-tract cryptoglandular anal fistulas treated with FCAAT between May 2019 and December 2023 and followed until August 2024. The surgical procedure involved liposuction, processing of adipose tissue, closure of the internal opening, and local injection along the fistula tract in a one-step procedure. Primary outcomes were clinical healing and clinical improvement; secondary outcomes were adverse events. RESULTS: The patient cohort presented with advanced disease. Median disease duration was 20 months, and one-third of patients had undergone previous attempts at surgical closure. Clinical healing was achieved in 23 patients (74%), with an additional four patients (13%) demonstrating clinical improvement. Five of 27 responders (19%) healed more than 3 months post-procedure. Common adverse events included proctalgia in 8 patients (22%), donor site pain 5 (14%), and minor graft site hematomas in 4 (11%). One Clavien-Dindo IIIa event (graft site bleeding) was managed with a single suture; all other complications were minor and resolved conservatively. CONCLUSION: FCAAT is a safe and effective one-step treatment for complex anal fistulas in non-IBD patients, offering a high healing rate with predominantly minor complications. A delayed effect was observed in some patients.