What is a Positive Sliding Sign on Pelvic Ultrasound
A positive sliding sign on pelvic ultrasound indicates normal mobility between pelvic structures—specifically, free gliding movement of the uterus relative to surrounding structures (rectum, bladder, ovaries) during real-time dynamic assessment, which effectively rules out adhesions or deep infiltrating endometriosis in that anatomic location. 1
Technical Definition and Performance
The sliding sign is assessed during transvaginal ultrasound by applying gentle pressure with the probe while observing real-time movement of pelvic structures during respiration or manual manipulation. 2
A positive (normal) sliding sign demonstrates free cephalad and caudad gliding of the uterus under the abdominal wall during deep inhalation and exhalation, suggesting absence of adhesions or endometriotic involvement. 3
A negative (abnormal) sliding sign indicates absence of this free movement, suggesting the presence of adhesions, obliteration of the pouch of Douglas, or deep infiltrating endometriosis. 3
Clinical Applications and Diagnostic Performance
Endometriosis Detection
The sliding sign has robust diagnostic performance for detecting deep infiltrating endometriosis involving the bowel and pouch of Douglas. 1
The American College of Radiology advocates including the sliding sign assessment with routine pelvic ultrasound to help diagnose endometriosis, as it provides good diagnostic performance for detecting disease in the posterior compartment. 1
The technique is part of the standardized 4-step dynamic ultrasound approach recommended by the International Deep Endometriosis Analysis (IDEA) group for evaluating endometriosis during routine pelvic ultrasound. 2
Assessment of pouch of Douglas status using the real-time ultrasound-based sliding sign is a critical component of the expanded transvaginal ultrasound protocols that have shown excellent performance for detection of deep endometriosis. 1, 2
Adhesion Prediction
The sliding sign can predict intra-abdominal adhesions in surgical planning contexts:
In women undergoing repeat cesarean section, a negative paraumbilical sliding sign showed 94.6% sensitivity and 93.3% specificity for predicting dense intra-abdominal adhesions. 3
A negative suprapubic sliding sign demonstrated 95.2% sensitivity and 91.7% specificity for the same purpose. 3
When both paraumbilical and suprapubic sliding signs are negative in the same patient, the sensitivity is 90.2% and specificity is 96.3% for predicting dense adhesions. 3
Anatomic Locations Assessed
The sliding sign should be evaluated at multiple pelvic locations:
Pouch of Douglas: Assessment of uterine mobility relative to the rectum to detect posterior compartment endometriosis or adhesions. 1, 2
Paraumbilical region: Evaluation of anterior abdominal wall mobility relative to underlying structures. 3
Suprapubic region: Assessment of bladder and anterior uterine mobility. 3
Ovarian mobility: Evaluation of ovarian movement relative to surrounding structures, which is considered a "soft marker" for endometriosis. 2
Clinical Significance and Pitfalls
A positive sliding sign is reassuring and suggests absence of significant adhesive disease or deep endometriosis at the assessed location. 1, 3
The technique requires real-time dynamic assessment and cannot be adequately evaluated on static images alone. 2
Operator experience matters significantly—studies demonstrating high accuracy were performed by trained operators in specialized endometriosis centers. 4, 2
The sliding sign has good interobserver reproducibility for detecting pouch of Douglas obliteration when performed by experienced operators. 4
A negative sliding sign warrants further investigation with expanded ultrasound protocols or MRI for surgical planning, particularly when deep endometriosis is suspected. 1