Grading of obstetric anal sphincter injury: endoanal or transperineal ultrasound?

Background Obstetric Anal Sphincter Injury (OASI) occurs in up to 5% of vaginal deliveries and is associated with significant maternal morbidity. 3D endoanal ultrasound (EAUS) is considered the gold standard for imaging anal sphincter pathology. 3D/4D transperineal ultrasound (TPUS) is a less invasive alternative that is more widely available. Aims To evaluate agreement between EAUS and TPUS in detecting anal sphincter defects after primary repair of OASI and to assess the correlation between the degree of anal sphincter defect on ultrasound and anal incontinence symptom severity. Methods Twenty-seven primiparous women, after primary OASI repair, underwent clinical examination, EAUS, and TPUS at a median of 6 months post-delivery. Agreement between clinical grading, EAUS, and TPUS was assessed using weighted kappa statistics. Anal incontinence symptoms were evaluated using the St. Mark’s Incontinence Score (SMIS). Results Moderate agreement was found between clinical grading and both EAUS (κ = 0.713) and TPUS (κ = 0.594). Agreement between EAUS and TPUS grading was also moderate (κ = 0.593). No significant association was found between ultrasound findings and anal incontinence symptoms at 6-month follow-up. Conclusion TPUS demonstrates promise as an alternative to EAUS for evaluating anal sphincter injuries after OASI repair, showing moderate agreement. Further research is needed to refine diagnostic criteria and establish the relationship between imaging findings and long-term functional outcomes.