EP1083 - A Systematic Review and Meta-analysis of the Efficacy and Safety of Hyperbaric Oxygen in Anal Fistulas in the Crohn’s Population

Purpose/Background: The treatment of perianal fistulizing Crohn’s disease (pCD) is challenging with different therapeutic options and high rates of recurrence. Hyperbaric oxygen therapy (HBOT) is a potential adjunctive treatment of unknown efficacy and safety. Therefore, this meta-analysis assessed the efficacy and safety of hyperbaric oxygen in anal fistula in the Crohn’s population.

Methods/Interventions: This PRISMA-compliant systematic review and meta-analysis searched PubMed up to September 2025 for studies that assessed the outcomes of HBOT in adult patients of either sex with Crohn’s disease-associated perineal fistulas. The primary outcome was healing, clinically defined as closure of the external opening with epithelialization with absence of drainage. In some studies, closure was confirmed by MRI, colonoscopy, or activity indices (PDAI, CDAI). Complications and adverse events of therapy were secondary outcomes. Random-effect proportional meta-analyses and meta-regression analyses were undertaken to estimate the pooled rates of healing and complications and factors associated with each outcome.

Results/Outcomes: Seven studies, 5 case series and 2 clinical trials, comprising 92 patients were included. The median age was 34 (range, 30–43.6) years with 52.2% males and a median Crohn’s disease duration of 11.2 (range, 3–16) years. Patients underwent a median of 21.8 HBOT (range, 20–40) sessions and had a median follow-up of 39 (range, 5.5–78) weeks. HBOT was consistently used as an adjunct to standard treatment, including seton placement, fistulotomy, or LIFT, in addition to medical treatments such as immunosuppressants, biologics, antibiotics, and anti-inflammatory agents. Most patients had refractory or recurrent complex fistulas, including high trans-sphincteric, and multi-tracts. The pooled healing rate was 73.2% (95% CI: 58.5–87.9; I² = 70%). The number of HBOT sessions (SE: -0.017, 95%CI: -0.028, -0.006, p= 0.002) and follow-up duration (SE: 0.005, 95%CI: 0.0001, 0.010, p=0.045) were significantly associated with healing. The pooled complication rate was 12.9% (95% CI: 13–24.5; I² = 82.4%), primarily mild reversible events such as ear barotrauma, sinus discomfort, and transient hearing or visual changes. No major complications were reported.

Conclusion/Discussion: HBOT may potentially be a useful adjunctive therapy for perianal fistulizing Crohn’s disease. However, the few available studies have poorly defined inclusion criteria, variable patient demographics, and heterogenous methods of assessing healing. Thus, more data is required prior to including HBOT in the standard therapeutic algorithm.