Transperineal Ultrasonography in the Assessment of Anal Incontinence and Obstetric Anal Sphincter Injuries

Three-dimensional endoanal ultrasound (3D-EAUS) has been defined as the gold standard imaging technique for the evaluation of anal sphincter defects. However, it is an intrusive technique, not universally available to urogynaecologists and may distend the anal canal. Therefore, several exoanal approaches, such as transperineal (TPUS) and endovaginal ultrasound (EVUS), have been evaluated for the assessment of anal sphincter integrity. The correlation of EVUS and 2D-TPUS with EAUS are not good enough, making images and volumes difficult to interpret. Nevertheless, the 3D-TPUS technique has shown better correlation with clinical manifestations and EAUS, having an acceptable sensitivity and specificity for the detection of sphincter defects. Unfortunately, there is currently no valid system to classify sphincter defects observed by TPUS. Therefore, 3D-TPUS could be proposed as a tool for the initial evaluation or screening of women with symptoms of faecal incontinence (FI) or to identify residual defects following primary repair of an obstetric anal sphincter injury (OASI), to thereby decide which women have indications to undergo an endoanal study to more clearly define the characteristics of the lesion.