Microvascular Free Flap Transfer for the Closure of Recalcitrant Digestive Fistulas: A Systematic Review of Surgical Success, Definitive Closure, and Clinical Outcomes

Recalcitrant digestive fistulas are difficult to manage when local tissues are irradiated, infected, scarred, or depleted. Because pharyngocutaneous, enterocutaneous, esophageal, colorectal/perineal, and pancreatic fistulas are anatomically and biologically distinct, they were evaluated as site-stratified evidence rather than as a single pooled clinical entity. This review aimed to assess definitive fistula closure, flap survival, recurrence, complications, reoperation, mortality, and functional recovery after microvascular free flap transfer for established recalcitrant digestive fistulas. This Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020-informed qualitative systematic review searched PubMed/MEDLINE, Embase, Scopus, Web of Science Core Collection, the Cochrane Library, Google Scholar, and reference lists. Heterogeneity in fistula anatomy, timing, flap selection, adjunctive procedures, and outcome definitions precluded a pooled meta-analysis. The review included 15 studies, including seven case series, six case reports, one retrospective cohort, and one technical clinical report, with sample sizes ranging from 1 to 50. Direct evidence was concentrated in post-laryngectomy pharyngocutaneous or pharyngostome fistulas. In studies with explicit extractable numerators, 25/25 flaps survived, but this figure derived from three small series and six case reports and excludes larger cohorts with incomplete or nonseparable reporting. Larger series reported substantial complications, revisions, and adjunctive procedures. Abdominal enterocutaneous evidence was limited to isolated salvage cases. Microvascular free flap transfer is a plausible salvage option for selected recalcitrant digestive fistulas, particularly in irradiated or surgically depleted head and neck fields. The evidence remains very low in certainty and does not support a single pooled closure estimate across fistula sites.