Reliability of endoanal ultrasound interpretation following Obstetric Anal Sphincter Injury (OASI) with and without patients’ clinical data

Obstetric anal sphincter injury (OASI) occurs in approximately 3% of vaginal births. OASI can cause long-term sequelae, such as dyspareunia, perineal pain, and incontinence to gas and stool. Endoanal ultrasound (EAUS) is the gold standard for diagnosing OASI. The first aim of this study is to compare the accuracy of the interpretation of EAUS without knowledge of the clinical context (EchoA), with the interpretation of EAUS with knowledge of the clinical context (such as the grade of OASI observed immediately after delivery and the symptoms presented by the patient) (EchoC). The second aim of this study is to describe the different characteristics of the patients and patients’ delivery and compare them to the existing literature. The third objective of this study focuses on comparing interpretations from clinical ultrasound and anonymized ultrasound with the anorectal symptoms reported by patients during the postpartum consultation, during which the ultrasounds were performed. We included 165 patients, reviewed postpartum several weeks after delivery at the urogynecology unit of the Centre universitaire Vaudois (CHUV) between January 1, 2014, and December 31, 2019, who experienced an OASI following childbirth at CHUV and the same examiner interpreted the printed ultrasound with clinical context (EchoC) and without clinical context (EchoA), in two different times. A high level of agreement was observed in the assessment of the internal anal sphincter (IAS), with 90% concordance between the two interpretations. However, for the evaluation of the external anal sphincter (EAS), particularly in identifying the presence of an injury, agreement between the two interpretations was notably lower (<50%). Clinical context remains necessary for accurately interpreting EAS injuries, but not necessarily for IAS evaluation. We note the presence of several biases that limit the interpretation of the results, such as the possibility of over diagnosis of OASI at the time of delivery, undetected lesions on EAUS because of healing, or the involvement of only one examiner. We need new studies to confirm our results. Brief Summary Endoanal ultrasounds show more accurate interpretation after an obstetric anal sphincter injury when the clinical context is known.