Endoanal ultrasound-measured internal anal sphincter changes after nonablative 1470-nm diode laser therapy for anal incontinence: a prospective single-arm pilot study

BACKGROUND: Fecal incontinence (FI) is a debilitating condition that may be associated with structural abnormalities of the anal sphincter complex. Nonablative anal laser therapy has been proposed as a minimally invasive treatment option; however, its anatomical correlates remain insufficiently defined. OBJECTIVES: The objectives of this study were to evaluate endoanal ultrasound (EAUS)-detected changes in internal anal sphincter (IAS) morphology after nonablative 1470-nm diode laser therapy and to explore their association with clinical outcomes. METHODS: In this prospective single-arm pilot study, 30 patients with mild-to-moderate FI and IAS defects or atrophy underwent up to six sessions of nonablative 1470-nm diode laser therapy. EAUS was performed before and after treatment to assess IAS thickness, IAS length, and defect length. Clinical response was assessed using the Wexner score, and anorectal manometry and Fecal Incontinence Quality of Life (FIQL) scores were evaluated. RESULTS: A total of 24 patients completed treatment and post-treatment reassessment. EAUS demonstrated small but statistically significant increases in IAS thickness and length, with a concomitant reduction in IAS defect length (p < 0.05). Symptomatic improvement was observed in 17/24 completing patients (70.8%) and was more frequent among patients with isolated IAS defects than among those with combined IAS and external anal sphincter defects. Greater reduction in IAS defect length was associated with clinical improvement (p = 0.015). Adverse events were generally transient; however, six patients discontinued treatment, including four owing to pain or burning sensation. CONCLUSIONS: In this uncontrolled pilot study, nonablative 1470-nm diode laser therapy was associated with EAUS-detected IAS changes and symptomatic improvement in selected patients with FI. Because of the absence of a control group, small absolute sonographic changes, and limited follow-up, these findings should be interpreted as preliminary and require confirmation in controlled studies with standardized imaging and functional assessment.