Complete Healing After Umbilical Mesenchymal Stem Cell-Derived Exosome Therapy For a Refractory Complex Anal Fistula

Complex anal fistulas pose a persistent challenge due to high recurrence and the risk of continence impairment. While sphincter-sparing techniques exist, outcomes are variable in refractory disease. Mesenchymal stromal cell (MSC) therapies show promise but face logistical barriers, prompting interest in acellular exosome-based approaches.  We report a 45-year-old woman with a complex anterior anal fistula refractory to multiple surgeries, including two endoanal advancement flaps, complicated by new-onset flatus incontinence. Following the second endoanal advancement flap, the patient's Cleveland Clinic Continence Score (CCIS) was 10, and the Quality of Life in Patients with Anal Fistula Questionnaire (QoLAF-Q) score was 51. A two-stage salvage strategy was undertaken: meticulous curettage and closure of the internal opening, followed by local administration of MSC-derived exosomes at baseline and three weeks. Significant wound reduction was observed, progressing to complete epithelialization within two weeks after the second exosome application. At six months after combined surgical intervention and exosome therapy, CCIS and QoLAF-Q scores improved to 0 and 28, respectively, indicating full restoration of continence and a marked improvement in quality of life. This case suggests that local exosome therapy, used as an adjunct to careful surgical preparation, may support healing and functional recovery in refractory complex anal fistulas. Controlled studies with standardized protocols are warranted to define efficacy, dosing, and durability.