Fig. 1From: Obstetric anal sphincter injuries (OASIS): using transperineal ultrasound (TPUS) for detecting, visualizing and monitoring the healing processTransperineal ultrasound of the anal sphincter. a Intact anal sphincter EAS IAS lumen b positive contraction effect—the sphincter disappears c complete tear of the EAS 3 days after delivery d scar of the EAS after 6 monthsBack to article page