Additional Intraoperative Autologous-Derived Platelet-Rich Stroma to Transanal Flap Repair for the Treatment of Cryptoglandular Transsphincteric Fistulas in a Tertiary Referral Center: Long-Term Outcomes of a Prospective Pilot Study.

Transanal advancement flap repair (TAFR) fails in approximately 30-40% of patients with a cryptoglandular transsphincteric fistula. An additional intraoperative injection of autologous platelet-rich stroma (PRS) with TAFR proved to be safe, feasible, and effective in the short term for the treatment of cryptoglandular transsphincteric fistula in a tertiary referral center. In this study, we assessed the long-term outcomes in patients with a cryptoglandular transsphincteric fistula who were treated with an additional intraoperative autologous PRS injection with TAFR (n = 43). The majority of the patients (88%) had a complex transsphincteric fistula (high transsphincteric and/or multiple side tracts) and underwent (one or more) fistula procedure(s) aimed at fistula repair (56%) before study inclusion. At a median follow-up time of 4.2 years [IQR 3.5-5.1], long-term primary clinical closure (i.e., clinical closure of the treated external fistula opening(s) after TAFR with additional PRS injection without the need for any re-interventions during long-term follow-up) was observed in 77% of the patients. Subsequently, 94% of these patients also reached radiological healing (i.e., fibrotic fistula tract on MRI). Recurrence after clinical closure or radiological healing was observed in 9% and 5%. Unplanned re-interventions were performed in 12% of the patients for recurrent or residual fistulizing disease. In this uncontrolled pilot study, additional autologous PRS injection with TAFR showed promising outcomes, as long-term primary clinical closure and, subsequently, radiological healing was reached in the vast majority of tertiary referral patients with a (complex) cryptoglandular transsphincteric fistula at long-term follow-up. In addition, recurrence rates were low. Future randomized research is warranted to study the effects of PRS.