What is the significance of the Slidell sign in pregnancy?

The Sliding Sign in Pregnancy: Diagnostic Utility for Ectopic Pregnancy

The sliding sign in pregnancy is a crucial ultrasound finding used to differentiate between normal intrauterine pregnancies and ectopic pregnancies, particularly helping to identify tubal ectopic pregnancies by demonstrating movement between structures during transvaginal ultrasound examination.

Definition and Technique

• The sliding sign refers to the movement or "sliding" observed between structures during ultrasound examination, particularly with transvaginal ultrasound probe pressure 1
• In early pregnancy evaluation, the sliding sign helps determine if a gestational sac or mass moves separately from the ovary, which is important for diagnosing ectopic pregnancies 1
• The technique involves applying gentle pressure with the transvaginal probe to observe if structures move independently of each other 1

Clinical Significance in Pregnancy

Ectopic Pregnancy Diagnosis

• The sliding sign is particularly valuable in differentiating between tubal ectopic pregnancies and corpus luteum cysts 1
• When no intrauterine pregnancy is visualized, the sliding sign can help confirm if an adnexal mass is separate from the ovary, suggesting a tubal ectopic pregnancy 1
• A positive sliding sign (where structures move independently) helps confirm that a mass or tubal ring moves separately from the ovary, increasing suspicion for ectopic pregnancy 1

Early Pregnancy Loss in Progress

• The sliding sign is also useful in diagnosing early pregnancy loss (EPL) in progress 1
• Movement of a gestational sac, either spontaneously or with uterine pressure from the ultrasound probe, can confirm that it is not implanted but transiently located in the lower uterus, favoring an EPL in progress 1
• If cardiac activity is present in a lower uterine segment or cervical gestational sac that doesn't slide, cervical or cesarean scar ectopic pregnancy should be considered instead of EPL in progress 1

Differential Diagnosis Applications

• Helps differentiate between:
  • Tubal ectopic pregnancy vs. corpus luteum cyst 1
  • Early pregnancy loss in progress vs. cervical ectopic pregnancy 1
  • Intrauterine pregnancy with eccentric implantation vs. interstitial ectopic pregnancy 1

Diagnostic Accuracy and Limitations

• The sliding sign should be used in conjunction with other ultrasound findings and clinical context 1
• While highly useful, it should not be the sole criterion for diagnosis 1
• Short-interval follow-up imaging is recommended in indeterminate cases 1
• The sliding sign is one of several tools to help establish pregnancy location when findings are ambiguous 1

Importance for Patient Outcomes

• Early and accurate diagnosis of ectopic pregnancy is critical as untreated ectopic pregnancies carry significant risk of maternal morbidity and mortality 1
• Proper application of the sliding sign can help avoid diagnostic errors and inappropriate management in pregnancy location assessment 1
• Timely identification of ectopic pregnancies allows for appropriate intervention before rupture occurs, potentially preserving fertility and reducing complications 1

Common Pitfalls and Caveats

• The sliding sign should be interpreted in the context of other clinical and sonographic findings 1
• Absence of sliding between the uterus and a gestational sac doesn't always indicate abnormal implantation; additional imaging features should be considered 1
• In cases where the sliding sign is difficult to elicit or interpret, additional imaging modalities or follow-up ultrasound may be necessary 2
• The term "sliding sign" is also used in different contexts in obstetrics, such as for detecting intra-abdominal adhesions in women with previous cesarean sections, which is a different application 3, 4