How comparable is the clinical grading of obstetric anal sphincter injury with that determined by four-dimensional translabial ultrasound?

Objectives To evaluate the agreement between grading of obstetric anal sphincter injuries (OASI) on translabial ultrasound (TLUS), using a newly developed algorithm and on examination, using the current clinical classification. A secondary aim was to assess correlation of tear severity, as defined on ultrasound, with symptoms of anal incontinence and/or fecal urgency. Methods A retrospective study on 260 patients seen at a perineal clinic between 2012 and 2018 after recent primary repair of OASI. All patients underwent a standardized interview including the St. Mark's anal incontinence score (SMIS) and four‐dimensional (4D) TLUS. Post processing of ultrasound volume data was performed blinded against all other data. Using tomographic ultrasound imaging (TUI) a set of eight slices was obtained and the central six slices were evaluated for sphincter abnormalities. Slices with distortion, thinning or defects were rated abnormal. The following algorithm was used to grade OASI: 3a tear was diagnosed if