EP31.16: The “Triangle Sign”: a novel dynamic ultrasound technique for identifying an obliterated cul‐de‐sac in patients with a retroverted uterus

The identification of an obliterated cul-de-sac in patients with a retroverted uterus due to endometriosis is crucial for proper evaluation of the complexity of surgery for patients with advanced disease. However, the traditional sliding sign on ultrasound may be limited in cases where the uterus is retroverted as the majority of the posterior uterine serosa and the retrocervix are not in contact with bowel. Instead, the uterus lies on the back of the vagina and the bowel often stays out of this space. We propose a novel dynamic transvaginal ultrasound technique, implementing the new terminology, “Triangle Sign,” for identifying cul-de-sac obliteration in these cases. We present a case series of videos depicting the “Triangle Sign,” both when present (i.e. positive) and absent (i.e. negative), that were also surgically confirmed. Our case series also depicts cases where we attempt to use the original sliding sign without success in eliciting sliding in the location of the true obliteration. The technique is based on the observation that with a release of pressure with the transvaginal probe, we visualise a triangle appearance comprised of peritoneal fluid filling the space between the retroverted uterus, cul-de-sac, and rectum. In the abnormal setting when there is obliteration, we cannot elicit the triangle sign as fluid does not fill the densely adherent space. By evaluating the separation between the uterus and posterior structures and identifying the presence of fluid within the cul-de-sac, the “Triangle Sign” technique could improve the accuracy of diagnosis and guide surgical management.