The sliding sign is a dynamic sonographic sign performed during transvaginal ultrasound (TVS) of women with suspected pelvic endometriosis. The loss of the normal sliding sign indicates pouch of Douglas (POD) obliteration due to adhesions and is suggestive of deep infiltrating endometriosis (DIE). It is important to note that although endometriosis is the leading cause of POD obliteration, adhesions can be due to other causes (such as pelvic infections).
This technique involves using gentle probe pressure to assess whether the anterior rectum and sigmoid colon glides freely across the posterior aspect of the upper uterus, cervix and vaginal wall.
Normal sliding motion of the uterus is regarded as a “positive” sliding sign.
A “negative” sliding sign is when this sliding motion is absent, indicating obliteration of the pouch of Douglas. Studies have shown that in women with suspected endometriosis undergoing laparoscopy, this sign has greater than 90% accuracy in predicting the likelihood of POD obliteration 1. A sensitivity of 88% and specificity of 94% has been demonstrated in a meta-analysis 2.
The sliding sign is also a highly valuable marker for rectosigmoid endometriosis with a meta-analysis showing is has a sensitivity of 81% and specificity of 95% for detecting rectosigmoid lesions 2.
Given the complexity of the surgery and prolonged operating times associated with POD obliteration, it is highly valuable for the laparoscopic surgeon to know the status of the POD preoperatively. An obliterated POD not discovered until the time of surgery may result in surgery needing to abandoned.
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