Background: Obstetric anal sphincter injuries (OASIs) occur during childbirth, affecting up to 11.0% of women. Three-Dimensional High-Resolution Anorectal Manometry (3D-HR-ARM) provides an advanced evaluation of pathophysiological anorectal abnormalities and allows identification of potential lesions. The aim of the study was to evaluate the diagnostic accuracy and inter-rater reliability of (3D-HR-ARM) in identifying OASIs compared to ultrasound assessment.
Methods: A retrospective cohort study was conducted at a tertiary referral center from January 2021 to June 2023. Women with anal incontinence (AI) following a vaginal delivery underwent assessment with both 3D-HR-ARM and endoanal ultrasound (3D-EAUS). Diagnostic accuracy in identifying anal sphincter defects was determined using 3D-EAUS as the gold standard, and inter-rater reliability was assessed among multiple observers.
Key results: Among 35 women, 19 had OASIs. For identifying severe residual defects (global Starck score ≥ 8), 3D-HR-ARM demonstrated an accuracy of 95.7% (95% CI 79.0-99.2), sensitivity of 100% (95% CI 64.6-100), specificity of 93.8% (95% CI 71.7-98.9), positive predictive value (PPV) of 87.5% (95% CI 52.9-97.8), and negative predictive value of 100% (95% CI 79.6-100). However, its accuracy decreased to 68.6% (95% CI 52.0-81.4) for detecting any sphincter defect. Inter-rater agreement varied from good (κ = 0.60) to mild (κ = 0.27), depending on the observer pair.
Conclusions: 3D-HR-ARM shows potential for the identification of severe OASIs in women with AI symptoms. However, its moderate accuracy for mild defects and significant inter-rater variability underscore the need for standardized protocols and additional training to improve reliability.
Keywords: 3D high resolution anorectal manometry; endoanal ultrasound; fecal incontinence; obstetric anal sphincter injuries.
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